Simple wiring diagram for small craft

[CDK]

Regularly I've seen questions on this forum about electrical wiring because that is still a mystery for many boat owners.
Here is a simple wiring diagram for motor- and sailing boats with one engine and just the basic equipment. There are only 7 wires shown that connect the engine bay; I omitted temp. gauges, rev counters etc. which all have their own wires or cables. The ignition wire is not used for diesels, but there it can be used for the fuel valve.

A friendly reader in the US is invited to translate my wire sizes from mm2 to AWG numbers. Parts like the diode bridge and 4-way battery switch are available from Vetus in Europe, I did not look for US suppliers.

Drawings are shown as .JPG, but also available as .CDR (Corel draw).
Boat owners who have no idea what this all means should of course hire a qualified technician!

[apex1]

COMPACT
DUTCH
KNOWLEDGE

as usual......................

[Knut Sand]

Pretty.;)

I once, somewhere suggested automatic 12 vdc diode light in the engine compartment, biwired together with the bilge pump. Also on the same biwire an alarm/ buzzer located at the steering position (with on/ off switch, normally set at "on") telling the driver that something is going on down under..... In case, it can cive you a few extra minutes....:?: For a low cost....:)

[BillyDoc]

Nice, Knut, very useful!

BillyDoc

[Delane]

Re-wired my J-24. Basically pulled everything and started over. The goal was simplicity in design and to not use one of those typical switch panels. I used a 100 volt A/C switches. Have any questions, please ask.

[BeauVrolyk]

Re-wired my J-24. Basically pulled everything and started over. The goal was simplicity in design and to not use one of those typical switch panels. I used a 100 volt A/C switches. Have any questions, please ask.

I am looking at a rewire on my boat as well, similar size and complexity. I was wondering why you didn't use one of the plastic boxes with the clear lid to contain all the junctions? I get a fair amount of water aboard, probably a lot like a J24 when races, and the last junction strip just turned into a ball of salty corrosion.

Beau

[Delane]

My wiring is inside of a closed compartment and the boat is very dry. Tabernacle mast set up and everything has been re-beaded. Bone dry and I have a solar vent to circulate air.

[BeauVrolyk]

My wiring is inside of a closed compartment and the boat is very dry. Tabernacle mast set up and everything has been re-beaded. Bone dry and I have a solar vent to circulate air.

You're lucky. The water in my boat doesn't leak in, it's carried in by the soaking wet spinnaker and headsails during sail changes in heavy seas. That and the sopping foul weather gear etc... We typically sail in 20 to 30 knots of breeze and big waves - it's wet. It must be nice to have a dry boat, none of the J24s around here are dry if they're raced.

B

[BeauVrolyk]

Regularly I've seen questions on this forum about electrical wiring because that is still a mystery for many boat owners.
Here is a simple wiring diagram for motor- and sailing boats with one engine and just the basic equipment. There are only 7 wires shown that connect the engine bay; I omitted temp. gauges, rev counters etc. which all have their own wires or cables. The ignition wire is not used for diesels, but there it can be used for the fuel valve.

A friendly reader in the US is invited to translate my wire sizes from mm2 to AWG numbers. Parts like the diode bridge and 4-way battery switch are available from Vetus in Europe, I did not look for US suppliers.

Drawings are shown as .JPG, but also available as .CDR (Corel draw).
Boat owners who have no idea what this all means should of course hire a qualified technician!

I am curious why you've used both circuit breakers and fuses. Is there a specific reason? I have had great luck with waterproof circuit breakers and pretty bad luck with the contacts on fuses.

Beau

[Delane]

The switches are not the breaker type. That little fuse box was the most expensive part of the whole panel at $40 by the time it arrived.

[CDK]

I am curious why you've used both circuit breakers and fuses. Is there a specific reason? I have had great luck with waterproof circuit breakers and pretty bad luck with the contacts on fuses.

Beau

No, I used switches and fuses, but of course you could also take automatic circuit breakers if you don't mind the extra cost.
Because this post was only meant to help people getting started, I did not supply detailed info. Perhaps I should have.

Fuses are absolutely necessary to protect your safety, but with proper, careful wiring they should never do what they are designed for: blow. So the should cost as little as possible. The automotive type with knife contacts costs only a few cents and makes reliable contact with a socket or crimp terminal. Glass fuses in a fuse holder are very unreliable in a marine environment but you already found that out. Some grease or Vaseline prevents corrosion of fuse contacts but is seldom used.

[zamgod]

CDK, can I ask what the box at the bottom left of your drawing is?
The one where most of the wires feed into.
Thanks.

[CDK]

That box is the engine compartment.
There are only 7 wires connecting it to the rest of electrical parts that is located elsewhere on board, i.e. under the steering console or in the cabin.

[TollyWally]

Very nice basic set up to get people started.

I've wondered about taking common cheap ac switches like Delane used and attaching pigtails potting them with epoxy.

[gonzo]

If you have fuel onboard, those switches are not spark protected. That means the possibility of fire or explosion.

[TollyWally]

Gonzo,
Are the common everyday switches on pleasure boats spark protected? I feel a little foolish not to have thought of that. I've bought "marine" switches on more than a few occasions and didn't give it a second thought. The ones I like best are epoxy potted with leads that I solder to.

[Delane]

Gonzo is so right, and to cover that base one should only place spark proof switches in a location wear fuel vapor may exit due to a leak or venting.

Otherwise if vapor safe, think out of the box and try something cheap and effective.

[CDK]

Gonzo,
Are the common everyday switches on pleasure boats spark protected? I feel a little foolish not to have thought of that. I've bought "marine" switches on more than a few occasions and didn't give it a second thought. The ones I like best are epoxy potted with leads that I solder to.

The switch panels you but in boat shops have very cheap, poor switches. Not spark protected, which is not a requirement for normal pleasure boats, but not sealed against moisture and without adequate contact material.
Finding something reliable that isn't overly expensive (like mil spec or aviation grade) is not easy.
I use C&K switches, with potted terminals if I can find them. It is one of the few manufacturers who specify in detail what their products can do in term of current, voltage and life expectancy. If the load to be switched requires more current than a C&K switch can handle, I use automotive relays. They are very inexpensive and can carry at least 25 Amps.

[TollyWally]

I didn't think those switches looked very high class that I've seen on pleasure boats. I'll try sourcing this C&K brand. The internet is my friend (I hope)

[Tim B]

The switches I've seen on small craft have been very pretty unimpressive. However, they are easily replaceable. Personally, I'm all in favour of using MOSFETs (Effectively solid-state switches) and controlling them through a microprocessor and serial interface. This has a few advantages:

1. The high-power system is spark-proof by definition.
2. The user to keeps all the large switching loads and cables in the engine bay (for example).
3. The "Human Interface Panel" then only needs to handle very small switching currents (which means small, light, reliable switches, though it does require a microprocessor). Potentially, it could even be a mini touch panel, NavPC etc.
4. MOSFETs are capable of handling upto 400A (check your current rating) without welding themselves together.
5. It could even be made ethernet (or USB) capable, depending on how you wanted to integrate the system.

For cases where 8 lines or fewer are required, the system could be setup following the PC parallel port guidelines, which would negate the need for uPs. Indeed, multiples of 8 could be wired on separate ports to negate the need for uPs on larger systems, though this may risk running out of parallel ports in future interfacing.

Tim B.

[Landlubber]

Try looking here

http://www.bepmarine.com/

good quality work.

[zamgod]

Hi CDK,
The battery isolator switch that I purchased has four positions; off, 1, 2 and both. But on the reverse side it only has 3 connectors; 1, 2 and common.
Does the common on my switch correspond to the '0' on your BS switch?
Which connector(s) do I use for my main feed to the circuit breaker (and then on to the fuses)?
Thanks.

Regards,
Alasdair

[CDK]

Yes, I labeled the positions (P)ort, (S)tarboard, (B)oth and (O)ff. Common connects to the engine, 1 and 2 to the batteries.
If you don't have a solar controller, engine bay terminal 5 is the main feed.

[Bglad]

Regarding the diagram and notes in the absence of an RCD or ELCI type of breaker on the AC inlet how is it wise to leave the green ground on the AC off the battery charger and the DC negative? Bad for swimmers in the water and a potential hazard if the boat is on a trailer plugged in and the charger is putting AC current on the DC system.

I am assuming this being a minimum system the inlet is not a full blown 30 or 50 amp but more along the lines of a 15 or 20 you might use with an extension cord. If that is the case I don't see why the green ground would not at least be connected to the charger...

[CDK]

There is a heated discussion about the ground lead here: http://www.boatdesign.net/forums/metal-boat-building/welding-steel-craft-whilst-afloat-electrolysis-32665.html.

A ground fault interrupter device is normally behind the marina power socket, but it cannot do harm to have one in your boat as well (I also have one).
As for connecting the green wire to the charger: that depends on how the charger is wired. I've seen chargers where the ground wire is connected to the transformer core only, with the DC output floating. In that case there is no objection to a ground connection. But others have the negative output tied to it as well, that might cause galvanic corrosion.

The danger for swimmers is non-existent, the boat on a trailer connected to shore power could be a potential hazard if the charger isolation (2500 V breakdown) fails. You should add a ground switch or a galvanic isolator for that situation, I could also imagine a circuit that would audibly warn in such a case.
Please bear in mind that this post was meant as a guideline for small craft that normally stay in the water during the season, have a single engine and only basic equipment.

[Bglad]

I get that it is a basic diagram and I will say right up front your knowledge way exceeds mine in the technical aspects of the various systems aboard. I'm a bit of a lug trying to learn enough to keep myself out of trouble doing my surveying business.

Check out electric shock drowning at this site to see how swimmers are at risk although primarily in freshwater http://qualitymarineservices.net/ when a vessel is plugged into AC power.

My basic idea is to think of the boat hull as a refrigerator frame. The green ground needs to be connected to the hull or in the case of wood or plastic hulls the DC (-) and bonding system to protect you in the event the AC current runs amok. The metal parts touching the water are a path to ground when plugged into dock power it would be no fun to make the connection while rummaging around while aboard!

I have been lurking for a couple of weeks doing a lot of reading seeing if might add anything here or there but mostly just trying to catch up and take notes. Maybe this discussion can help someone out...

[CDK]

The qualitymarineservices link provides some interesting items. Some seem to contradict my assessment of an ungrounded hull, but if you read carefully nearly all cases where the cause of electrocution was established, there was a small current carrying object like a cable or submerged socket in the water. Only in such cases a voltage gradient steep enough to paralyze a swimmer can exist.

The guy leaving his berth without removing the cable is a striking example. Wiring or not wiring ground shore in the boat wouldn't have made a difference.

Exactly for cases like this it is of paramount importance to have a ground fault interrupter installed near every waterfront socket. Such a device measures the current flowing through the two power leads and trips whenever there is an unbalance of more than 5 milli-amps, cutting off the power to the socket immediately. This threshold is reached even when rain gets inside a socket or plug. The device is normally behind a panel, so a technician must be called and the reason of the ground fault explained.

Such devices are mandatory in all European countries, even in the not-quite-up-to-standards country I live in.

[Bglad]

One of those instances was aboard an IO boat that did not have the AC green ground DC negative connected. A DC wire burned through a AC wire in the harness and sent the outdrive up to 80 or 90 volts. It killed a young child floating by in a lifejacket (freshwater). Not likely in a simple system but not beyond possibility. Had the AC green ground and DC negative been connected the circuit breaker would have tripped eliminating the fault. Most boats have this connection somewhere unentionally if they have a generator, inverter or even a battery charger that is grounded properly.

Saltwater is not nearly so hazardous since it is a better path than the human body.

Here in the US ELCI circuit breakers are going to be required soon on new boats. If current is leaking off the boat they will trip requiring a visit from an electrician.

[patrick1973]

WOW !!!!!!! Tank YOu for these simple print outs... You saved my life. I bought the 12v bible and big book of marine electronics. There's some nice lesson plans in there and basic science. BUT NOT very good diagrams or photo's These 2 pieces of paper are helping me more than both books.. So Tanks YOU!

By the way, the black 6 switch panel with rubbers over the switches and round fuse holders next to switches.... Is that panel "SPARK RESISTANT" ???? Just spent 60 bucks one. Also how much ventilation do you suggest on a console. I have four slots on the panel door. But I feel like I should have more air ? It;s my 1st boat rebuild. Should I add a few clam shell vents? Fog humidity VS fumes. I like humidity more than fumes.

Anyways, great website here. Thank you.
Pat

[Tim B]

It's more important to make sure that any fuel tank vents are routed properly, so that no fuel fumes end up in the "living quarters". The switch panel is generally going to be on a cupboard or some form of facing board, which probably has a direct route from bilge to deck behind it anyway. Ventilating said cupboard is only important if you expect to generate heat in it (eg. running a PC or possibly a NAV console).

Is your console spark resistant? Probably not. But it's probably not an issue as long as you have adequate ventilation in the living quarters.

Tim B.

[DaveJ]

I agree with Tim B with the use of MOSFET's over relays for the following reasons.

1. 9 times out of 10 they are cheaper
2. More reliable
3. Are enviromental sealed (execpt for the leads, but your going to have the same problem with a relay)
4. You don't get contact bounce
5. With a small RC (resistor and capacitor, also know as a time delay) curcuit attached across the gate and drain you can achieve a soft on/soft off flow of current. ie. You can have a long time delay to faid lights on and off.

[CDK]

I've nothing against MOSFET's but for most boaters even a relay is a mystery.

A disadvantage is that the rugged and cheap ones are N-Channel, so you switch the ground lead. Not a problem but you must get used to it.
For the soft turn-on the dissipation needs some consideration, a heavy load will heat up a Mosfet very quickly.

[Ike]

I agree with Gonzo. Those knife switches may be cheap and simple, but is it worth saving a few bucks and losing your boat or your life?

Ignition protected switches are readily available, but they do cost a little more.

[Dean Smith]

Regularly I've seen questions on this forum about electrical wiring because that is still a mystery for many boat owners.
Here is a simple wiring diagram for motor- and sailing boats with one engine and just the basic equipment. There are only 7 wires shown that connect the engine bay; I omitted temp. gauges, rev counters etc. which all have their own wires or cables. The ignition wire is not used for diesels, but there it can be used for the fuel valve.
A friendly reader in the US is invited to translate my wire sizes from mm2 to AWG numbers. Parts like the diode bridge and 4-way battery switch are available from Vetus in Europe, I did not look for US suppliers.

Drawings are shown as .JPG, but also available as .CDR (Corel draw).
Boat owners who have no idea what this all means should of course hire a qualified technician!

cdk, nice but surely folk want it simple, here is one I did so the owner can read it:) all boards supplied BEP marine NZ Was told other day that can only buy black tinned due to new fire regs re coatings for wire

[whitepointer23]

hi everyone. i have an electrical question. my boat has a seperate house battery and 1 starter battery for each engine, at the moment the house battery is wired to the starboard starter battery and it also runs through a solenoid which all the lights and accessorys are connected to. what i want to do is isolate the house battery from the start batterys like it is supposed to be. can i just hook up another solenoid that engages with the ignition so the house batt gets charge while the engines are running. also in referance to knuts idea about the diode for bilge alarm, a very simple bilge alarm is a float switch hooked to a light or horn, simple and works well.

[Bglad]

Check out voltage sensing relays on Blue Seas Systems web site:)

[CDK]

can i just hook up another solenoid that engages with the ignition so the house batt gets charge while the engines are running.

That is not a good idea. You can only start the engine when the ignition is powered. Your solenoid is also powered at that moment and you'll draw starter current from the house battery.

Bglad's suggestion is a good solution. Cheaper, but less efficient is the use of (Schottky) diodes. The voltage drop causes a lower charging current for the house battery.

[bernd1972]

By the way, for do-it-yourself guys try the freeware-program TiniCAD for documenting your wiring. It helps if you have to find out later what you did a few years ago.

[BertKu]

Bglad's suggestion is a good solution. Cheaper, but less efficient is the use of (Schottky) diodes. The voltage drop causes a lower charging current for the house battery.

Morning CDK, I am often wondering whether the use of Schottky diodes are really that much inefficient, versus the advantage of using them. A generator charges at 14,4 Volt (depending on ambient temperature) and the extra loss over the Schottky diode is 0.1 - 0.13 Volt. Depending where the current usage is on the curve. As soon the Lead acid batteries are charged, the voltage will be 13.8 Volt maximum. In my view all what happens is that it takes a few seconds longer to fully charge a battery.
But for me personnally, two batteries parallel is a no go for me. Even only during charging.
Bert

[CDK]

Schottky diodes have more fwd voltage drop Bert, 0.3 V as a rule of thumb. Look at the application sheet here:
http://www.st.com/stonline/books/pdf/docs/4354.pdf

These 0.3 V doesn't seem much, but because the charging current is determined by Vch - Vbatt and the internal resistance, it reduces charging current with approx. 50% at the end of the cycle.

[BertKu]

Schottky diodes have more fwd voltage drop Bert, 0.3 V as a rule of thumb. Look at the application sheet here:
http://www.st.com/stonline/books/pdf/docs/4354.pdf

These 0.3 V doesn't seem much, but because the charging current is determined by Vch - Vbatt and the internal resistance, it reduces charging current with approx. 50% at the end of the cycle.

Yes, I had a look at it. Still better than silicon diodes, but indeed for higher currents still too much of a loss. 380 mVolt to 0.4 Volt is too high. In that case I would use 2 x MosFets IRFP064N and put a small 12 Volt battery on the VGS and when the big battery has to be replaced, change the little battery at the same time. Tonight I will measure the leakage current and see whether I am talking crap or that it is a good solution. The loss Forward Voltage is then only about 160 mV at 60 Ampere ( 2 in parallel).
With all the hunderds of batteries I supplied with our battery charger and Schottky diodes for the Horsy People, I never had any problems. I had to charge up to 10 batteries of 12 Volt at the same time parallel and used schotky diodes.
Bert

[BertKu]

Yes, I made a little test circuit.
I used a 12 Volt penlite remote control Alekeline battery and a 1 MegaOhm resistor.
I would make a little box with two stainless steel bolts. connect 3 or 4 (cheap ) Mosfets IRFP064N and connect them parallel. Then with the 12 Volt small battery permanently connected in this box via a 1 MegaOhm resistor between VGs (gate)and Source and leave it permanently in the box for 5 years. It may be better to avoid possible oscillation, to place a 180 Ohm 1/4 watt rsistor in each gate of each parallel placed MOSFET. The otherside is then soldered to the 1 MegaOhm resistor. The 1 MegaOhm resistor is connected to the plus of this small alkaline battery. The minus of this alkaline battery is to the source of all MOSFET's paralleled

You have then a diode which can handle 60 Ampere at only 110 mV loss or 450 Ampere at a loss of only 180 milliVolt or pulsed maximum 1500 Ampere.
I do not believe that the 110 milliVolt is a problem for charging a large battery bank.
Bert

[CDK]

You have then a diode which can handle 60 Ampere at only 110 mV loss or 450 Ampere at a loss of only 180 milliVolt or pulsed maximum 1500 Ampere.


I'm sorry, but no you don't.
the IRFP064N with a positive gate conducts almost as good as a copper wire, but it cannot be reversed beyond 1.3 VDC, so it is not a really a diode.....

[BertKu]

I'm sorry, but no you don't.
the IRFP064N with a positive gate conducts almost as good as a copper wire, but it cannot be reversed beyond 1.3 VDC, so it is not a really a diode.....

I am to differ from you CDK. Maybe with Vgs = 0 volt, but not at + 12 Volt Vgs. (which is the case, because we have a battery 24/7 connected . The reverse voltage is at least 10 Volt.
Also I do not expect a 11 Volt batteriy to be swichted parallel to a 13.8 Volt fully charged battery. Even then the voltage is still acceptable. Therefore you need diodes to prevent this. Or otherwise said, you could do so if you use diodes.
Were did you see reverse voltage is only 1,3 Volt??
Bert

Note: indeed it does not work refer reply # 46

[BertKu]

CDK, let me test this. I have enough batteries to have a reverse voltage of 12 Volt. Will let you know.
bert

[BertKu]

I took one 6 Volt battery, a MOSFET as "diode" and a globe of 12 Volt/60 Watt. This I connected to a second MOSFET which acted as a "diode" and again a 12 Volt globe. I connected the globe to a 12 Volt battery.

Guess what. ??? CDK You flipping right. Both globes burned as hell on 12 Volt , also the 6 Volt battery got a knock and moved up to over 8 Volt.
Proving that the reverse voltage is not allowed to be greater than 1,3 Volt. The reason is that Vgs = > 0 Volt (12 Volt) At Vgs = 0 volt, the reverse voltage was > 6 Volt and the MOSFET acted as a "diode".

That is flipping sad. I have to remove the replies , to avoid somebody having a mishaps. It still works on two batteries, provided the voltage difference is not more than 1,3 Volt. But that is crammy solution.

Well one can only learn from errors.
Thanks CDK

[BertKu]

I am still of the opinion that more than one Lead Acid battery parallel is a no go. Maybe when they are brand new, but certainly not when they are used and varies from each other.

Back to the schottky diodes. I like to do a test and see what the real difference is, charging with or without schottky diodes.

1) I will take a battery, charged it to 13,6 - 13,8 Volt
2) load it with a load for 1/2 hour until battery is 1/2 discharged
3) charge the battery without diode and take the time with a stopwatch how long it takes.
4) load the same battery and discharge for exactly 1/2 hour again
5) charge the battery with a schottky diode and see how much longer it takes to charge the same battery to the same 13,6 - 13,8 Volt

But there are some other solutions.
1) Find a voltage regulator, which is adjustable or could be modified from 14,4 Volt to 14,8 Volt to compensate for the schottky diode of 0.4 Volt
2) Have the MOSFETS alternating if one has more than 2 batteries parallel by stepping mode the VGS from + to 0 and only have one charging a battery for a short period.
3) The full voltage of different makes varies slightly per cell and select the lower voltage type per cell required to charge the cell fully. This depends on the chemical composition and metals used in the battery.
i.e. if one select a cell with 2.3 Volt required x 6 = 13.8 Volt. or a cell which requires 2.4 Volt per cell x 6 = 14.4 Volt. If one uses Schottky diodes on the latter one, the battery will only be fully charged after a long time. If one uses the 13.8 Volt one, with schottky diodes the battery will be fully charged.
(I phoned the battery manufacturer and put my questions to the lab)
Bert

[BertKu]

Now I understand why my battery packed up when I drove 1200 km to Johannesburg. I have a diesel engine and if the battery only require 13.8 Volt,
while being charged at 14.4 Volt, no wonder the battery got overcharged and packed up.
Today , I am driving long distances with my bright lights on. Just to avoid that the battery gets overcharged. A gasoline/petrol engine allways uses some current, which avoid overcharge, but not a diesel engine.

Thanks CDK for pointing this hiccup with a Mosfet out.
Bert

[CDK]

There is a protection diode on the MOSFET chip to prevent reverse biasing.
For this particular one the border between life and death is given in the datasheet of Int'l Rectifier as 1.3 V. From my own experience I know that even a short negative spike turns a MOSFET into a normal FET with quite different parameters.

[BertKu]

There is a protection diode on the MOSFET chip to prevent reverse biasing.
For this particular one the border between life and death is given in the datasheet of Int'l Rectifier as 1.3 V. From my own experience I know that even a short negative spike turns a MOSFET into a normal FET with quite different parameters.

Hold it, hold it, Hold it, you are right. It does mean then that it still could work with normal FET's. But where the hick do I get cheap 115 Ampere normal FET's ? Do they still make them?
Bert

p.s. what about 2 zenerdiodes in opposite direction, over such a normal FET, that should work then.

[BertKu]

There is a protection diode on the MOSFET chip to prevent reverse biasing.
For this particular one the border between life and death is given in the datasheet of Int'l Rectifier as 1.3 V. From my own experience I know that even a short negative spike turns a MOSFET into a normal FET with quite different parameters.

You are clever CDK. It took me two IRFP064N to blow the reverse zenerdiode without blowing the chip itself also.
Yes, it probably would work in that case.

But I am not too sure to promote this route as the ideal solution.

I must have been in wonderland, that I forgot about the reverse zenerdiode, which is a pure short circuit, if the voltage is reversed. I wonder why they do not place 2 zenerdiodes in opposite direction.

Thanks CDK for the discussion. Great to discuss some topic, without being bashed by some rude person. Lucky he is no longer on the net.
Bert

[BertKu]

Well, we all have sometimes egg on the face, this round, it is my turn. Sorry CDK, I misinterpreted your reply and blew 3 Mosfets, then to realize that even normal Fet’s has only a reverse voltage of 1,5 Volt. I always used Mosfets in resistive mode and with the Source to ground and Drain to the resistive side. Never had to bother about reverse polarity.

Thus using Mosfets or Fets is indeed out of the question, like you said.

However I am the opinion, rather to use Schottky diodes if batteries are used parallel with the consequence, that it will only be recharged to 95% and never fully charged. Then having a number of different make batteries or new and old batteries mixed, switched parallel. It is just an opinion which has worked for me. I believe and have proven to myself, that the batteries last longer.
I did do the test to see how it actual performs.

The same battery used for both test., just to make it accurate. Each having the same load for an half hour discharging the battery.

Battery without Schottky diode-------------- Battery charging with Schottky diode
Date----- Time---- Voltage ---------------------Date ------Time ------Voltage
26/3 -----19h38---13.60 Volt -----------------28/3 ------15h25 ----13.60 Volt
26/3 -----20h08 ---12.25 Volt---discharged----28/3 ------15h55-----12.17 Volt

27/3------20h09 ---12.25 Volt—charging -----28/3 -------15h56-----12.20 Volt
27/3------20h45---13.05 Volt-------------------28/3 -------16h30-----12.60 Volt
27/3------21h17---13.10 Volt ------------------28/3 --------18h00----12.96 Volt
27/3------22h40---13.20 Volt-------------------28/3---------20h20----13.05-Volt
28/3------06h50---13.50 Volt-------------------28/3---------22h35----13.10 Volt
28/3------10h40---13.59 Volt-------------------28/3 --------23h35----13.12 Volt
28/3------1oh45---13.60 Volt------------------- 29/3--------06h55----13.21 Volt
-------------------------------------------------29/3--------08h35----13.23 Volt
In conclusion:
1) It took 14hours 13 minutes to recharge the battery to the same level as it was original without diode
2) It took 1 hour 8 minutes to charge to 13.10 Volt, which is about 95% without diode
3) Versus, with diode , it took 7 hours 19 minutes also to charge to 13.10 Volt

The test was done not with an alternator, but with an exponential charger. i.e. above 13 Volt it supplies lower charging current then an alternator.

Why the discharged voltage was lower the second round , may have to do with ambient temperature
Bert

[Joakim]

2) It took 1 hour 8 minutes to charge to 13.10 Volt, which is about 95% without diode
3) Versus, with diode , it took 7 hours 19 minutes also to charge to 13.10 Volt

The test was done not with an alternator, but with an exponential charger. i.e. above 13 Volt it supplies lower charging current then an alternator.


What are you trying to measure/prove? The battery voltage during charging is very hard to convert to actual state of charge. Does your charger regulate voltage? The type of the charger is very important factor on how a diode affects charging.

[BertKu]

What are you trying to measure/prove? The battery voltage during charging is very hard to convert to actual state of charge. Does your charger regulate voltage? The type of the charger is very important factor on how a diode affects charging.

Thank you Joakim,
I trying to prove to myself that if you have a number of different make and age Lead Acid batteries parallel, it is better to use some schottky diodes.
The first test I did was with a kind of smart Lead Acid Battery charger. Now I am testing various Car Alternators out and have already noticed that it varies from 14.25 Volt to 14,65 Volt regulating . The charging with an alternator is different then with a smart charger. I will do that test now also with a normal car alternator and voltage regulator. Just to see what bubbles.
Too many people state "Don't use diodes" , while I am of the opinion that it is better practice.
Bert

[BertKu]

The battery voltage during charging is very hard to convert to actual state of charge.
Hi Joakim,

I forgot to mention. When I wrote down the Voltage, I took the charging clamps off. Therefore the battery voltage does tell me something about the condition of the battery, nearly full or still a long way to go.
bert

[DaveJ]

@BertKu: the only real way to tell how charged or uncharged (condition) a lead acid battery is to detect how saturated the solution is. If the solution has no more lead to put back into the plates then it is fully charged, if the solution can't take any more lead then the battery is fully discharged (this is a simplistic point of view). You need an analyser in the solution to tell you this, otherwise your guessing just using the voltage level of the battery or the voltage your charging at (your plates could be saturated with lead and the solution can be at 80% saturated, so your voltage level will indicate high but the battery will not take long to be discharged). Different battery at different state of age will have different rates of acceptance and voltage required for that acceptance. Have you looked at diacs or triacs, a triac will block current in both directions until triggered.

For everyone, if you want to see how bad having two or more static (by this i mean not being kept charge in one way or anyother) batteries in parallel without some isolation, stick a sensative current meter between the two posative terminals and over time watch it swing back and forth as the batteries discharge each other in an attempt to get to a equal state.

[BertKu]

@BertKu: the only real way to tell how charged or uncharged (condition) a lead acid battery is to detect how saturated the solution is. If the solution has no more lead to put back into the plates then it is fully charged, if the solution can't take any more lead then the battery is fully discharged (this is a simplistic point of view). You need an analyser in the solution to tell you this, otherwise your guessing just using the voltage level of the battery or the voltage your charging at (your plates could be saturated with lead and the solution can be at 80% saturated, so your voltage level will indicate high but the battery will not take long to be discharged). Different battery at different state of age will have different rates of acceptance and voltage required for that acceptance. Have you looked at diacs or triacs, a triac will block current in both directions until triggered.

For everyone, if you want to see how bad having two or more static (by this i mean not being kept charge in one way or anyother) batteries in parallel without some isolation, stick a sensative current meter between the two posative terminals and over time watch it swing back and forth as the batteries discharge each other in an attempt to get to a equal state.
Hi Dave,

Thank you Dave, your last paragraph confirms the problem. Maybe a few batteries parallel of the same make and brand new, you may get away with murder, but not when they get older and one of them is being replaced.

With regards to your first paragraph. That may well be the case with a liquid Lead Acid Battery, but not for gell batteries. Most modern batteries are today in solid form. Even my KIA diesel has no longer liquid, but gell.
Thus the best way is to measure the voltage over the battery terminals, with the one side not connected and a few minutes after the charger is disconnected. I guarantee you that if the meter shows 13,4 Volt, your battery is pritty full.

The problem with Triacs and silicon diodes, the Forward Voltage drop is too high to my likings, between 0.5 and up to 1,5 volt, while Schottky is between 0,3 and 0,45 Volt. Depending on temperature and current.

bert

[CDK]

.... the only real way to tell how charged or uncharged (condition) a lead acid battery is to detect how saturated the solution is......

That was once true but nowadays very impractical. Without drilling a hole you can get a pretty good indication using a high current shunt for a few seconds and watching the voltage drop. Smart chargers gather their display information that way.

...... Have you looked at diacs or triacs, a triac will block current in both directions until triggered......



Not a very smart remark. Diacs in a 12V system are as useful as a piece of rope: they do not conduct below 28V. A triac doesn't revert to a non-conductive state in a DC circuit.

[BertKu]

Not a very smart remark. Diacs in a 12V system are as useful as a piece of rope: they do not conduct below 28V. A triac doesn't revert to a non-conductive state in a DC circuit.
Dave, it is now your turn to have egg on your face. Don't worry I had my turn. We all do have at one stage of another. CDK is a sharp engineer and I appreciate his straightforward remarks. Have a good grin.
Bert

[Joakim]

I forgot to mention. When I wrote down the Voltage, I took the charging clamps off.

That doesn't really help much, which can easily be seen from your measured voltages. A full lead acid battery is only about 12.7 depending on type, condition and temperature, never over 13 V. It takes hours after charging for the voltage to stabilize unless some load is used.

[Joakim]

For everyone, if you want to see how bad having two or more static (by this i mean not being kept charge in one way or anyother) batteries in parallel without some isolation, stick a sensative current meter between the two posative terminals and over time watch it swing back and forth as the batteries discharge each other in an attempt to get to a equal state.

Well I have done this and seen only very small currents. There are plenty of examples of such parallel connection used without problems for several years. This is standard in many new boats and in some new cars as well.

[BertKu]

That doesn't really help much, which can easily be seen from your measured voltages. A full lead acid battery is only about 12.7 depending on type, condition and temperature, never over 13 V. It takes hours after charging for the voltage to stabilize unless some load is used.

It differs for Sealed Lead Acid Batteries (SLABS) the modern battery today used in most new cars. It is much better to use such a SLAB in the marine environment
bert

[Joakim]

It differs for Sealed Lead Acid Batteries (SLABS) the modern battery today used in most new cars.

As I said there are differences between different types of lead acid batteries, but still all are well below 13.0 V:

http://jgdarden.com/batteryfaq/carfaq4.htm#ocv_soc
http://jgdarden.com/batteryfaq/carfaq4.htm#mf_soc

[BertKu]

As I said there are differences between different types of lead acid batteries, but still all are well below 13.0 V:

http://jgdarden.com/batteryfaq/carfaq4.htm#ocv_soc
http://jgdarden.com/batteryfaq/carfaq4.htm#mf_soc

Have a good look at http://www.powerstream.com/SLA.htm , it will give you all answers.
Bert

[DaveJ]

Not a very smart remark. Diacs in a 12V system are as useful as a piece of rope: they do not conduct below 28V. A triac doesn't revert to a non-conductive state in a DC circuit.

http://www.jaycar.com.au/products_uploaded/sc151.pdf

@CDK can you please show me where in the above that this particular triac will not conduct below 28vdc. From what i can see for the triac to tigger, the gate voltage needs to be between 2.5 to 3.5 vdc (depending on the model number) and the on state are all below 1 vdc. The braw back of this triac is its voltage drop between 1.52 to 1.85 vdc, or am i reading it wrong.

Yes the triac will stay trigged until a reverse potential is placed apon it and will turn off and not be trigger until the gate is triggered again for either direction. So in a charging cct if you want the triac to turn off you momentaryly apply a reversed voltage, this can be achieve through a small volatge doubling cct.

[BertKu]

http://www.jaycar.com.au/products_uploaded/sc151.pdf

@CDK can you please show me where in the above that this particular triac will not conduct below 28vdc. From what i can see for the triac to tigger, the gate voltage needs to be between 2.5 to 3.5 vdc (depending on the model number) and the on state are all below 1 vdc. The braw back of this triac is its voltage drop between 1.52 to 1.85 vdc, or am i reading it wrong.

Yes the triac will stay trigged until a reverse potential is placed apon it and will turn off and not be trigger until the gate is triggered again for either direction. So in a charging cct if you want the triac to turn off you momentaryly apply a reversed voltage, this can be achieve through a small volatge doubling cct.

Yes Dave, it will work. However not with a diac. A diac needs first at all +/- 32 Volt to reach the Voltage whereby it "collapses" and supply the current to the Triac to conduct. A diac only revert to its original state if the current falls below a certain value. Thus you need a normal DC Voltage via a resistor to conduct the Triac. But it is indeed not advisable to use a triac due to the high Forward Voltage. The debate was to create a system whereby 2 large batteries with high current capabilites can be professional connected parallel. Regardless whether you have a liquid Acid battery of 12,7 Volt switched parallel to a modern Sealed Lead Acid battery of 13,4 - 13,6 Volt, or a brand new and an at the end of its lifetime battery.

Diacs are similar in behaviour as lightning arrestors. It conduct as long the current flowing through the device is enough to keep it conducting.
Bert

[DaveJ]

But it is indeed not advisable to use a triac due to the high Forward Voltage.

Why, the triac i quoted could handle voltage up to 400V before its turned to toast, unless the rise was higher then 30v/usec, since the system will not get above 15v that parameter will not be reached.

The debate was to create a system whereby 2 large batteries with high current capabilites can be professional connected parallel. Regardless whether you have a liquid Acid battery of 12,7 Volt switched parallel to a modern Sealed Lead Acid battery of 13,4 - 13,6 Volt, or a brand new and an at the end of its lifetime battery.

Oh, ok, i missed the point, what you want is load sharing. How i would try to achive this is to have a voltage/current regulation cct just after each positive terminal of each battery that has a sense line to the other cct of each battery, the lowest battery dictates the supply of voltage until it reaches a level that is too low is dropped out of the cct (and a charge can be placed) and the next lowest battery takes over. This would allow different types of batteries to be used in conjunction with each other. Does that sound like what your looking for.

[CDK]

http://www.jaycar.com.au/products_uploaded/sc151.pdf

@CDK can you please show me where in the above that this particular triac will not conduct below 28vdc.

No I cannot, I never said so.

And before you start drawing circuits: to let a conducting triac revert to off-state, the current trough the device must be reduced below the holding current or reversed. In a low resistance circuit with LA batteries that can only be achieved with inductance and a short command pulse.

[BertKu]

No I cannot, I never said so.

And before you start drawing circuits: to let a conducting triac revert to off-state, the current trough the device must be reduced below the holding current or reversed. In a low resistance circuit with LA batteries that can only be achieved with inductance and a short command pulse.

Dave, CDK is correct in both paragrahs. It is only wise to use electronics in the marine environment, if it can be substantial better or it cannot be done otherwise. With forward Voltage we mean, the voltage drop over the "contact" of the device i.e. if you have a 100 Ampere load and your Forward Voltage is 2,35 Volt, you have lost 235 Watt in the "contact". Not very efficient. With a Diode this means between Anode and Cathode, with a transistor this means between Collector and Emitter etc.

The ideal situation is a device which has at 100 Ampere only a loss of 0.1 Volt , thus 0.001 Ohm. Thus during the conducting stage you loss is only 100 Ampere x 0.001 Ohm = 10 watt at a usage at 1200 Watt, this is acceptable. A relay contact is such an example with paladium as contact material.
Bert

[DaveJ]

You got me, i don't know what i'm talking about

[boattech2]

Hi, I'm a newbie on this forum! Hello all!
I'm not trying to hijack the post to another subject but this may be a worthy comment:

Re: Simple wiring diagram for small craft;

Per the diagram posted, I thought the SHP Shore Power Charger Green wire Must be connected to the chargers A.C. input. To omit it may become a hazard, I think. Possibly this is an automotive type charger? I was taught never use an "automotive" battery charger for permanent installation on boats because a charger made for Marine use safely Isolates the A.C. Ground & D.C Negative internally.

[BertKu]

Hi, I'm a newbie on this forum! Hello all!
I'm not trying to hijack the post to another subject but this may be a worthy comment:

Re: Simple wiring diagram for small craft;

Per the diagram posted, I thought the SHP Shore Power Charger Green wire Must be connected to the chargers A.C. input. To omit it may become a hazard, I think. Possibly this is an automotive type charger? I was taught never use an "automotive" battery charger for permanent installation on boats because a charger made for Marine use safely Isolates the A.C. Ground & D.C Negative internally.
No we hijacked the thread and now we are back to the original schematic.
If you earth the boat's earth to the offshore earth and should the offshore earth have a voltage potential, your boat becomes a nice "Magnet" . Your stray currents will eat your metal up like the most delicious pudding on earth.
Well that is what I guess.Therefore you notice the warning "Note the green earth is not connected". In principle you could use any charger, provided you know what you are doing concerning the earth and as long your boat has its own earth properly connected.
Bert

[CDK]

Boattech2, I answered that question in post #13 here:

http://www.boatdesign.net/forums/electrical-systems/grounding-37360.html?highlight=grounding

[BertKu]

Hi Boatech2,

Maybe we should discuss the shorepower. Somewhere there is agenerator in an electricity company which generates via transformers stepped down 220 Volt/380Volt to the the harbour. The generators are normally configured in star mode, whereby the center of the star is earthed. via all the transformers between phase and this star centerpoint it is 220 Volt and between two phases 380 Volt.
If the earth is a mile away from your boat and at the same time also used by other users, not nesseccary boat users, you build up a Voltage potential between your earth of your boat and the earth on this "cheap automotive " transformer. For that reason the earth must be taken off. The question then remains "what quality transformers is used in the cheap automotive charger" and that maybe a problem. Although my experience is that as long the casing of the cheap automotive charger is earthed to the offshore, but not to your boat. It is as safe as any charger, provided your boat is earthed to the water.
Bert
Sorry CDK, this reply crossed yours.

[BertKu]

You got me, i don't know what i'm talking about

Dave as long you don't stop asking questions. You know probably more about another subject ,you are an expert on, then us. We all have sometimes made a wrong conclusion. Nothing wrong with that. Even people like Pistbroke are sometimes wrong. I have here 40 Ah / 12 Volt SLABS which are charged to 13.7 Volt (just below the gasdsing voltage) and when the charging leads are taken off, the Voltage drop to 13.6 Volt and after days and days the Voltage is still above 13 Volt ( 13.2) @ 25 degrees Celcius.
Thus statements like all Lead Acid Batteries are less then 13 Volt is incorrect.
Don't feel bad about it.
Bert