Marine Wire

Fanne,

I was looking at Bat Isolators and bat switches. I appears that the isolator is an auto switching and the bat switch looks like a manual 4 place switch.

Is that what you are talking about drawing current with the islolator but the bat switch turned to the off position will not draw current?

Mark

 

Well I am new to the board but can't resist to put in my two cents. My only comment is that the electricity goes through wire differently with DC current than it does with AC. Yet 99% of the wire for sale is for AC. With DC the electrons tend to stay on the outside of the strand instead of going through the strand evenly. I doubt this would have much effect on wire heating up from more resistance or voltage drop on small loads. If you take this into effect though on large loads in can make a big difference. That is why wire with large DC loads have many more strand in in. For example leads on your welder or your jumper cables. (Unless you have one of those $10.00 pair.)

Might want to keep that in mind when installing the larger wire for batteries and starter motors on the engine. Its been a long time since I opened a electrical theory book but, I if I remember, it is called an eddy current.

I wonder if the wire labeled marine has more strands in it than wire without the marine label???

 

Hi Mark,
The problem with manual switches is you can create arcs and sparks because they do not switch as fast as the electrical ones. The solenoid switches works electrical. They have a coil you apply 12V to that smacks the contacts close, when 12V to the coil is removed usually a spring pulls it open. It is this 12V coil drawing the current, can be 2A to 12A depending on the solenoid you use. They are made for switching high amps, and most motors use them in various models for the starter motors also.

I don't know what a 'bat' switch / isolator is.

It is not the amount of strands that is important, but the sq surface of the conductor. If the wire is installed and doesn't have to bend or flex you can even use a solid wire. The thinner (finer) wire strands are the more they can flex or bend without beginning to break. Sharp bending of wires is never a good idea. The more gradual it bends and the longer the flexing piece the longer the wire will last.

 

Thanks Fanie,

Ok here are some questions.

Wholesale marine has a Battery isolator that will handle 70 amps. What I am trying to do on a 20 pontoon boat is have a bat for the engine start and one for the lights, trolling motor, nav lights, etc.

I want to run a 10 gage wire 7 feet from the engine to where the 2 bats will be. At that point I want to attach the bat isolator to the 10 gage wire. Then attach the 2 battery wires to the other ends of the bat isolator.

Does this sound like the right idea?

I will also have a 2 gauge wire running from the engine bat to the starter.

Mark

 

DC electrical is actually quite simple compared to AC (and it won't kill you if you make a mistake). I'd recommend that you go to your local library and ask for the following book.

Boat Owners Mechanical and Electrical Manual by Nigel Calder.

http://www.amazon.com/Boatowners-Me...=sr_1_1?ie=UTF8&s=books&qid=1255557102&sr=8-1

You can buy it from Amazon but hey, we're in a recession!

Study the chapter on designing a balanced electrical system. All the information you need is contained in this text and Mr. Calder is a recognized authority in the field.

For what it's worth I buy my wire from an internet retailer called genuinedealz.

www.genuinedealz.com

and believe it or not you can get some good pricing on electrical assessories at:

www.dogbytecomputer.com

Blue sea systems also has a good site. You can use the DC circuit wizard to determine the size wiring you need and then order it from genuinedealz.

www.bluesea.com

Really though, if you take the time to read Mr. Calders book you'll not only learn much that applies to your boat you'll also gain knowledge that will help you with all kinds of electrical diagnosis and repair.

Regarding the type of wire to use......I'd always use marine rated wire. For reliability, for insurance purposes and because it's better quality and therefore less likely to fail out there. Just MHO. Besides, how much are you going to use? Are you really going to save much?

MIA

 

In my mind marine-grade wire meets the following criteria:

Type 3 Stranded Tinned Copper Conductors.

Water, chemical, and heat resistant (105C) insulation. Most is PVC but a couple other compounds are used by companies such as Ancor.

Rated for 600V

Sized according to American Wire Gage, not SAE.

Manufacturers of Marine-Grade wire are Ancor, Cobra, Pacer, and Berkshire.

Keep in mind that from a regulatory standpoint, the USCG (and similar agencys in other countries) do have requirements for wire being used on boats regarding construction, size, and insulation. Make sure that any wiring job you undertake is in accordance with the regulations at the least, and industry best-practices at best.

 

Mark,
I will run one wire to the starter and another to the accessories. The starter motor will cause a voltage drop over the wire, so to minimise the effect on the accessories they should not share the same supply cable.

In fact, I would highly recommend that you use two batteries, one for the starter motor and another for the accessories.

To charge both batteries from the same source you need a high current schotkey diode and a relay. The charge supply should go to the starter motor battery, from the starter motor battery the pos is fed through the high current schotkey diode and a NO relay contact to the pos of the accessories battery. The relay coil gets connected to the ignition of the motor that generates the power, so whenever the power generator feeds to the starter battery, it will at the same time charge the accessories battery.

The high power schotkey diode has very little foreward drop over it allowing the accessories battery to charge to the same level as the starter battery, while also preventing the accessories battery to supply power to the starter battery. Iow the accessories battery is isolated from the starter when you start, when the motor has started however the accessories battery is also charged. When the power generator is switched off, the relay opens and the two batteries are isolated from each other. This means lengthy use of the accessories battery will not drain the starter battery and you always have a fresh starter battery.

You cannot use common si diodes, the voltage drop over then is too much (0.8V)

 

The starter battery pos can be taken directly to the solenoid that feeds the starter motor.

The accessories should go through a fuse box so that a problem on any wire will open the fuse and the rest of the accessories doesn't get affected.

You also get mutifuses or polly fuses. I have used these extensively in various apps and they are marvelous. A short on a fuse's output will cause the fuse to heat up and it goes 'open circuit', although drawing very little current to maintain the heat to remain open circuit. As soon as you remove the short and draws no current, the fuse cools down and you can use the circuit as before at it's rated current. It sure beats finding the spare fuses and they work over and over and over... you get the idea.

Multi fuses are available in small (50mA) to 9A ratings. If you cannot find a higher rating one then you can parallel equal sized ones but you have to thermally join them with heat transfer paste (the white stuff you saw on power transistors and their heatsink) so they would react simultaniously.

Remember a fuse rating should be higher than the current drawed, ie a spot light drawing 5A should get a 9A fuse.

 

The starter cable should be either crimped professionally with a decent crimping tool, or better still it should be soldered in a solder bath, or both. Don't go skimpy on the quality here, a loose or poorly connected wire can cause one endless problems, and can be a real pain to identify.

 

Mark,

I will echo Fanie's Two-battery approach. It has a few pluses, one being that your accessories don't drain your starting battery and the other is that you can select batteries that have the optimum construction for the application (means longer life).

As for joining the two systems for charging, I would go with an Automatic Charging relay from Blue Sea Systems or similar device over a traditional battery isolator. The main advantages of the ACRs are they are disconnected during starting (no spike to sensitive electronics), the starting battery will recharge before the house battery (voltage sensing relay only closes after starting battery reaches around 80%, which means that you won't turn off the engine and find the starting battery dead because the alternator was charging all batteries simultaneously), and in the event of failure the relay defaults to open (isiloators are just diodes witha heatsink, so when the diode fails, and they all do, there is nothing preventing the battery from trying to turn the alternator or charge the other battery, niether of which are good things).

As for the crimping, most West Marines have rigging crimpers in the store available for customer use (in store of course). While they are not designed for electrical connections and will not meet ABYC certification, they do make an excellent crimp connection for battery lugs (I've tested the connection both electrically and mechanically and it is equal to the $500 AMP Box crimpers I use). Also, Battery Lugs are the only terminals able to be affixed solely by soldering (per ABYC) so if you did want to solder them feel free. I prefer crimping and use the following method: I fill the lug (they are closed on the ring end) about halfway with dielectric grease, insert the stripped cable into the lug, crimp the barrel, and the put heavy-duty heat shrink over the entire connection. It's kind of a belt & braces approach but I have yet to have any corrosion even when the insulation is compromised.

 

Home > Products by Vendor > Guest > Guest 70 Amp Battery Isolator - 1 Alternator, 2 Batteries Guest 70 Amp Battery Isolator - 1 Alternator, 2 Batteries


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Product Description:

Battery Isolators
Optimized heat sink design for maximum performance
Minimized voltage drop across isolation barrier using Schotky type diodes
Each output individually capable of carrying the full alternator load
Fixed cable posts for secure connections
Waterproof components for harsh environment performance - year after year
NOTE: If used on a 24V system, boat must be equipped with 24VDC alternator
Guest Battery Isolators Feature:
Solid state design
Rubber wire caps
Marine grade construction
Two-year warranty -Through Guest
70 Amp Battery Isolator
Usage: 1 Alternator / 2 Batteries
Max. Output per Alternator: 70 Amps
Operation: 12V to 48V
Dimensions: 5.4” x 4.5” x 2.6”

Fanie,

this is what i was talking about. is this what you are calling a schotkey diode?
If not, will this work?
Mark

 

Not exactly what he was talking about (diode yes, but no relay on an isolator), yes it will work, see my response above regarding relays vs isolators.

 

You guys have been to much! Thank you for the help. Who in the U.S. carries the Blue Seas Systems ACRs?

 

Retailers would be West Marine, Defender, BoatersWorld.com (still in business ironically), and most regional and local marine suppliers. Bass Pro Shops and Cabela may also be able to get them for you as well, but I am unsure.

 

Thanks Pa,

I just looked on west marine and they have a 120 amp acr. Do you think I need something that big for nav lights, trolling motor, flood lights, and fish finders?

Mark