Parallel Alterntors for faster charge. [Archive]

pistnbroke

08-20-2009, 02:30 AM

I contribute to a british canal boat forum and they have gone to 26 pages on how to paralled alternators .

What they do is use 50 mm2 cable between the batteries and the alternator to up the baulk current and when the starting battery is charged they connect it and its alternator to the bank . Charge currents are generally doubled ( but be aware that over 25 A per 100AH will heat the batteries ) These boats typically have a 100ah starting and 4x 100ah for the house battery ..

The problem that has taken 26 pages to NOT sort out is that when the start battery is joined to the house battery its voltage drops and the contactor chatters ..In this circuit when the start battery reaches say 14.2v set by the vr the zener conducts and charges the capacitor .this then discharges through the Unijunction and triggers the SCR which switches the contactor .The SCR will not switch off until the ignition is turned off ...and that was another of their problems making it auto reset . If you are clever enough to make it you are clever enough to make some mods.....have fun. Yes I know I missed the earth off the central block of electronics ....yes and alternators has 2 As

DaveJ

08-20-2009, 11:15 PM

WotEver

08-21-2009, 12:02 PM

Seeing as you invited me over here to continue this discussion...

The problem that has taken 26 pages to NOT sort out is that when the start battery is joined to the house battery its voltage drops and the contactor chatters

Nope, that's wrong. The problem that has taken 26 pages to not sort out (whilst veering off into all sorts of wonderful diversions) is how to stop the parallelling once the domestic batteries have reached acceptance stage in order to avoid excessive gassing of the start battery.

..In this circuit when the start battery reaches say 14.2v set by the vr the zener conducts and charges the capacitor...

Once again, no. In this circuit the contactor will close almost instantaneously and might just as well be connected directly to the engine electrics - it serves no purpose and won't disconnect the engine start battery when it needs to be disconnected.

Regards,
Tony

pistnbroke

08-21-2009, 05:51 PM

So what your are saying it has taken 26 pages because the peole do not know there batteries properly. Perhaps you do not understand your Unijunctions. Certainly the circuit does what it claims to do ..fires a SCR when start battery reaches a pre determined voltage ..ie is charged
The starting battery will not gas if its voltage is not allowed to go over 14.7v . so there is no point in disconnecting it from a gassing point of view . However when the start battery connects to the well discharged house bank it will discharge into it as the housebank is at a lower voltage.....you just need two solenoids one to disconnect the start and one to connect the house ....but watch how you do your switching it as alterntors should not be run disconnected .

In my experience the start battery takes only a few seconds to replenish the 0.008 AH (100a for 10 sec) used for starting ...the system will not parallel until the start battery reaches the voltage that has been set by VR

Perhaps the attached photo is the real solution ..!!

Fanie

08-21-2009, 07:08 PM

There is a relationship between the size alternator (in this case alternatorS) that is required to charge a specific size battery (or batteries in parallel).

To be honest, any specific battery can only charge so fast up to it's regulating voltage which is usually fairly quick since an alternator can pump quite a bit of amps, from there on the battery will draw the current it requires depending on how much charge it needs.

The only reason I can think of for using so many alternators in parallel (good grief) is if you have some application that does require continuous big currents, like a big beer fridge or something sensable...

pistnbroke

08-21-2009, 07:22 PM

I only put the 4 alternator on as a joke ..but these canal boat guys have to run the engine 6-8 hrs a day even if tied up as the 400ah of battery does take time to charge after a night watching the telly running pumps etc..if they can reduce this time it saves on engine and diesel fuel

Fanie

08-21-2009, 07:29 PM

Expensive Tv ! For a moment there I was wondering what people did before Tv but it occured to me back then they all had anything from 6 to 27 kids, so yes the canal boat guys save a fortune running those alternators. Just thinking about it, if I was a canal boat guy I'd run that telly 24/7 :D

Frosty

08-21-2009, 08:55 PM

If you have a automatic regulator then when it sees 13.8 it will tail off the charge as it is supposed to do. It doe'snt matter if you got 6 alternators they will all see13.8.

The current from an alternator is exited by the current crossing the slip rings. This can be controlled manually to boost the charge output regardless.

On some auto regs there is a sensing wire that senses the voltage , I have cut his and fitted a rehostat that fooled the reg in to thinking the batt voltage was low. I was then in charge of the output without the heavier gear required directly controlling to current across the slip rings exiter circuit.

Is'nt that right Pistn?

WotEver

08-22-2009, 02:31 AM

Certainly the circuit does what it claims to do ..fires a SCR when start battery reaches a pre determined voltage ..ie is charged

Which would be pretty much instantaneous as I've already stated. Just replace your circuit with a switch.

The starting battery will not gas if its voltage is not allowed to go over 14.7v

You show not only a stunning lack of reading ability but also a staggering ignorance of battery technology. If you want to boil your batteries then fine, go ahead - why don't you rename your circuit "Battery Boiler".

It's probably a waste of time, because you've already demonstrated that you can't read a thread, but if by some chance you do want to fully understand why you are wrong you might want to take some time to read the technical sections of this site (http://www.smartgauge.co.uk/technical1.html).

Regards,
Tony

TerryKing

08-22-2009, 09:14 AM

I did it differently, by use of a comparator and using a zener to set the referance voltage, out of comparator to an opto coupler which turned on hard to drive the relay. I like your way though, it is simpler and less components.
Davej, please put up your circuit, in the spirit of "more ideas is better"!

With a comparator, you can add some positive feed back to create some 'hysteresis' or 'different thresholds for on and off', and solve the 'chatter' problem with the relay ...

WotEver

08-22-2009, 01:44 PM

Davej, please put up your circuit, in the spirit of "more ideas is better"!

Hi terry. Here's a simple circuit that should work fine, PLUS incorporate the most important feature of un-parallelling once the domestic batteries get into acceptance to avoid excessive gassing of the engine start battery.

34271

Note that this circuit is currently untested but there's no reason to believe it won't work as required.

Note also that the only purpose for doing this is to enable the domestic bank to get up to acceptance voltage faster; once they're into acceptance then you only need a comparatively small charge current (for a long period of time) to fully charge them. Most folks never achieve full charge because it takes several hours on a large bank.

Switching the parallelling ON at a certain voltage isn't important in the application this is designed for (narrow boats), it can switch on instantaneously if you wish (which is what Pistn's circuit would do). It's switching OFF when required that's important.

Oh, and there was no problem with "chatter from the relay" in this application - that quote was another result of Pistn's inability to read a thread. Also, 50mm sq cable from alternator to battery would only be on a relatively small installation. Larger boats would have more like 120mm cable.

Regards,
Tony

WotEver

08-23-2009, 03:52 PM

The starting battery will not gas if its voltage is not allowed to go over 14.7v

There is a lot of disinformation and old wives tales on the net about battery charging, and this is a good example.

It's absolute rubbish to state that a (12V) battery will not gas if kept 14.7 volts and it is the kind of comment that could only be made by someone who's never actually studied the subject. It doesn't matter if 1000 web sources state the same, all it would mean is that 1000 web sources are all wrong.

The gassing voltage of a wet cell battery is an inverse function of the state of charge. The average gassing voltage of a 12V battery throughout the range 50% to 100% is 14.4 volts. That is a FACT, not an opinion.

I came to this forum at Pistnbroke's invitation partly in an attempt to help clear up such fallacies.

Regards,
Tony

pistnbroke

08-23-2009, 05:12 PM

As to never studying the subject I use to lecture a 30 hr course on battery testing , maintanence and charging ...alslo lectured on canal boat wiring to the employees of some of the companies who now produce fancy chargers ....as for qualifications both practical and technical I got shedloads .

In the old days of dynamos you raised the battery volts to 15.3v but had to top up the battery every week as it gassed . With increasing maintanence intervals the makers reduced this voltage to 14.4v (14.7 in japan) to prevent gassing and hence loss of water . This resulted in the battery only being 80% charged relative to the old dynamo 15.3v days.

Sure the start battey will be charged fast its only supplied 0.008 ah to start the engine ....(100A for 10 sec )

Sorry dont see what D1 is for as the output from W is half wave recifed AC anyway (relative to earth )and a reverse current cannot flow back into the alternator ..or maybe you did not know that ....ha ha... are you trying to say the voltage at W falls when the start battery is charged and the relay drops out ...??? dont think so ..1watt thin filament bulb ,thats a reliable component ...perhaps if we could see the alternators /contactor connections and the batteries is might make some sense ......????

An explanation of the circuit is required with a fuller diagram ...

DaveJ

08-23-2009, 07:31 PM

Attached is the circuit, as i'm writing this from work, i trying to remember the circuit from memory, and thus no resistor values.

This idea of the circuit is to sence the charging voltage on the battery. The zener is used to set the referance voltage for the comparator, if the charge voltage rises above the referance voltage it start to provide current to the optic relay, which turns on hard when enough current to turn it on.

The Variable resistor on top of the comparator are your offset, your adjustment to how much of a difference between the two voltages to when to turns on the optic relay. You could also add a time cct between the optic relay and the comparator to build in a time delay to stop relay chatter, most likely a 1-2 sec delay.

I used a 5v regualtor to power the comparator, but i believe it can work up to 16V or maybe more so is not realy required.

I had this device working great on the breadboard hooked up to me desktop power supply, but when i soldered onto a board and put it into the car it would turn on all the time, quick testing showed that the zener referance voltage was at 11.90 V when i needed it to be around 12 V, the offset didn't have enough adjustment to compensate, i could shove a normal diode under the zener to bring up the voltage, or change the resistors value for the offset.

The capacitors are just for filtering any spikes, these IC's are analog devices so can handle noisey power supplies, but it is good practise to always filter them.

The Comparator is a LM311 and the optic relay is HFS2A213DN, both from jaycar. I haven't done anymore work on this device as i've been too busy so will be interested if anyone can clean the design up some. I'm not sold on the use of voltage refeance and will look at current sensing in the future, as i would like to control the current and direct it where i want it to go.

Dave

pistnbroke

08-23-2009, 08:26 PM

I think you picked too high a voltage for the Zenner dave...you dont want the have a 14v zenner but a lower say 4.7v and a potential divider....what you have done dave is produce a VSR voltage sensitive relay without the capacitors timing to stop the chatter ...VSR often lock on for 20 sec once activated to stop cycling chatter...If you want to stop chatter there can be no substitute for an SCR..if its on it stays on ..

What some of these canal boys are doing is fitting an external regulator set higher than 14.4 ..if its connected too long the battery gasses and the plates get blown apart by the gas ..bad idea .acid goes pink with bits of disintegrated plate material...what they forget is below 14.4v the switching transistor in the Alt Volt reg is on so you have full rotor current ...Alternator output current is determined by cables and state of battery....current drops as battery voltage rises and then at 14.4v the reg prevents furthur rise in output voltage to prevent gassing

Used one of your comparitor chips a long time ago to clean up signals from the first Russian Satellites ..worked great until they coded it !!! Great weather for us dave ..not rained for 5 weeks now ....

DaveJ

08-23-2009, 09:31 PM

Pisnbroke:

Like i said, i like your idea, the SCR once turned on is on. If i had to gripe about anything is the fact that you have the variable resistor across the battery which will constantly drain the battery, but the current draw when i calulated was so low it would take about a month to drain, and since this is for a system that is used constantly it has very little bearing on the system.

As for the weather, yer its great but i wish i was out on the bay sailing instead of working.

For everyone:

As for the gassing, i think there might be some missunderstanding on what some people determine what gassing is. Bubbles forming on the plates and slowing rising can be called gassing, but this is normal, this is the byproduct of the electrolysis which is required to put the lead back into the plates, which is what charging is. Now if it looks like water boil in a pot on the stove, that is bad, the electrolysis is happening too fast and heat will build up and can cause the battery to explode.

Picture this, you have accidently left your headlights on in your car, your battery is dead flat, you jump start your car to go to work in the morning, now while your driving to work does your battery explode under the bonnet, well of course it doesn't, the system is design not to.

Dave,

WotEver

08-24-2009, 01:33 AM

I use to lecture a 30 hr course on battery testing , maintanence and charging ...alslo lectured on canal boat wiring to the employees of some of the companies who now produce fancy chargers ....

That explains a lot. You probably also believe that adaptive charging from these fancy chargers works then... (to save you thinking about it, no it doesn't).

"An explanation of the circuit is required"

I thought it was simple enough to be self explanatory.

W connection is from the engine start battery alternator.
D1 is to prevent the start push button from connecting +ve directly to the W terminal.
D2 is a snubber.
The lamp is to cause the latch relay to drop out as soon as the signal from W starts to collapse. It might need to be 2W, but looking at the hot resistance coupled with the hold-on voltage of a typical 12V 'car-type' relay suggests that 1W will work.
The contactor parallells the batteries.

Well designed NB installations have a higher voltage regulation on the domestic alternator than the engine start alternator for what should be obvious reasons.

When the higher voltage alternator exceeds the lower voltage one the reg on the lower voltage one will shut down completely, collapsing the signal from the W output (albeit briefly).

Ergo, parallelling self-disconnects when engine start battery is fully charged, thereby avoiding excessive gassing.

As I've repeated several times, parallelling the two alternators is the easy bit and doesn't really need to be automated; it's DISCONNECTING the parallelling that's important.

Regards,
Tony

WotEver

08-24-2009, 01:48 AM

As for the gassing, i think there might be some missunderstanding on what some people determine what gassing is. Bubbles forming on the plates and slowing rising can be called gassing, but this is normal, this is the byproduct of the electrolysis which is required to put the lead back into the plates, which is what charging is. Now if it looks like water boil in a pot on the stove, that is bad, the electrolysis is happening too fast and heat will build up and can cause the battery to explode.

Picture this, you have accidently left your headlights on in your car, your battery is dead flat, you jump start your car to go to work in the morning, now while your driving to work does your battery explode under the bonnet, well of course it doesn't, the system is design not to.

I think you've missed the point entirely, Dave. Firstly, no-one has mentioned exploding batteries, I'm only concerned about battery life, and having to top up the electrolyte more often than would otherwise be necessary.

The system you've described above is quite naturally designed for purpose - an alternator matched to the battery and car electrical systems. The alternator will power all of the car's electrical systems and will also push a charge back into the battery if required. It's a reverse system to that on a narrowboat, where the system is designed for recharging as its main purpose and powering systems as a secondary function. However, that's not why you're wrong in your assumption.

In the example we're describing, we have a fully charged engine start battery being parallelled with deeply discharged leisure batteries. The leisure batteries will require a long charge at elevated voltages. The engine start battery does not need that charge, and the only result of feeding it that voltage will be excessive gassing and loss of electrolyte. Hence, we parallel the two alternators to get the leisure batteries into acceptance as fast as possible without damaging them, then disconnect that parallelling for two reasons: 1) it's no longer required, the leisure alternator can easily supply all the charge required, and 2) because we don't want to cause the engine start battery to gas for no reason.

I've repeated again and again that the parallelling is the easy bit - it's disconnecting that parallelling when it no longer serves any useful purpose that's the harder part.

Regards,
Tony

pistnbroke

08-24-2009, 02:04 AM

so we have new informaton here ...the starting battery must be connected to the alternator with the lower volt reg setting .....ahhh

the W signal collapses ......the alternator is still producing 14.4v and the W is only a rectified output from the stator so its voltge will not collapse ...or your rev counter stops ?????
..you dont need the diode if you study the circuitry of the alternator ...

If you want to know if the starter alternator has stopped charging why not pass the rotor current ( max 4A ) around a reed relay so it drops out and disconnects the solenoid .. or bypass some of the charge current via a coil on a reed relay ....cable in parallel with the 50 mm 2 .....only giveing you ideas that you clearly need ..
PS I dont believe in adaptive charging and when I lectured on canal boat wiring things were basic ....rotary converters one alternator .. about 1980s but it set those people thinking/gave them the basics and off they went when the techonology was available ...
dont assume what you have not been told ..this is a site for highy qualified boat designers and interlectuals with brains (95%) on one side and idiots on the other unlike uk canal world...........

WotEver

08-24-2009, 03:39 AM

so we have new informaton here ...the starting battery must be connected to the alternator with the lower volt reg setting .....ahhh

New? I thought you knew everything about narrowboat electrics. Oh, that's right, you don't actually know as much as you think you do.

the W signal collapses ......the alternator is still producing 14.4v and the W is only a rectified output from the stator so its voltge will not collapse ...or your rev counter stops ?????

Correct. If the rev counter is connected to the engine start alt and the two alts are parallelled the rev counter does indeed stop. The charge warning light also comes on. That's why rev counters are generally connected to the domestic alt. Something else you didn't know?

D1 quite possibly isn't required, but it doesn't hurt, and only costs a few pence.

this is a site for highy qualified boat designers and interlectuals with brains

This from the man who told me that 200A alternators are connected with max 8mm cable and I must be on tablets if I thought otherwise.

I suggest that before you continue with any further disinformation about narrowboat electrics you actually spend some time to learn your subject.

Regards,
Tony

Edit to avoid any confusion here that we're referring to wet lead-acid batteries. If sealed gel batteries are used with their lower charging voltages the subject is irrelevant.

WotEver

08-24-2009, 03:48 AM

If you want to know if the starter alternator has stopped charging why not pass the rotor current ( max 4A ) around a reed relay so it drops out and disconnects the solenoid ..

Because the whole point of the thread which you didn't read properly was to avoid any tampering with / modification of the alternator.

Regards,
Tony

Frosty

08-24-2009, 04:03 AM

Tony chill out mate, you are obviously a talented young man that knows his stuff but calm down mate. you are making Brits look like twats here.

Im the biggest Pomy twat here and there isnt room for another.

WotEver

08-24-2009, 04:19 AM

Im the biggest Pomy twat here and there isnt room for another.

You can never have too many :D

WotEver

08-24-2009, 04:23 AM

To all those whom I have offended with my jibes at one particular member I apologise.

I believe that I've now said all that can be said on the subject so you probably won't see me on this thread again.

Regards,
Tony :)

pistnbroke

08-24-2009, 05:38 AM

so lets make it simple .....give us the circuit that solves all the problems ....

and if thats not possible lets know what needs solving ..many very clever people on his forum ..well qualified and willing to help

Stay cool but not Frosty ...ha ha

WotEver

08-24-2009, 06:14 AM

so lets make it simple .....give us the circuit that solves all the problems ....

I believe Post #11 does that. It's simple, cheap and (hopefully although untested) effective.

The requirements are simple:
1. Parallell the two alternators for long enough to accomplish bulk charge on the domestic battery bank.

2. Disconnect the parallelling once the domestics are into acceptance phase so as to mimimise gassing of the start batt.

3. K.I.S.S. so that anyone can build it (that means no tampering with alternators or breaking charging cables).

It's virtually a redundant circuit anyhow, because if the narrowboat already has a Smart Gauge fitted (and most well-specc'd ones do - how else do you know how charged your batteries truly are?) then the facility is already there for the user to hang a contactor off it for the above purpose.

Regards,
Tony

pistnbroke

08-30-2009, 05:49 PM

One comment by Whatever made me think...the problem is disconnecting the starter battery ( because the volt regs are set too high and it gasses)

so applying reverse logic I thought why disconnect it ..just make sure it does not get excessive voltage ....

The circuit below is based on Two Bosch RE55 regulators which have a loop that can be cut to raise the output voltage 1v ..Ideal for the baulk phase of the 400AH House battery. the starter battery is kept below gassing by being fed via a 50 A diode .

By switching the loops on the RE55s The voltage can be brought to normal when the bulk phase is over . I am not convinced you need a solenoid at all but if you think it essential then the SCR circuit posted before is fine...OR use a unijunction timer to fire the SCR say 10 min after the engine starts ..power from the WL terminal ....

WotEver

09-01-2009, 04:37 AM

I am not convinced you need a solenoid at all ....

Me neither - that circuit is elegant in its simplicity and fulfills the requirements with off-the-peg components.

Nice one :)

T.

pistnbroke

09-04-2009, 01:52 AM

Well the 26 pages on the british canal boat forum has finally come up with a workable circuit ..

You need to disconnect the cable to the voltage regulator that normally goes to the field diodes and bring it out to go the " the third diode" ( or put a 6A diode in series with it inside the alternator and use 2 external diodes)

I am not totally convinced that it gives priority to the starting battery but a heavy duty switch in the line from the top diode to the house battery should do the trick ..throw it after 10 min of running .....

you can still of course use the Bosch RE55 regulators if you want to up the voltage easily ...

WotEver

09-04-2009, 02:36 AM

Well the 26 pages on the british canal boat forum has finally come up with a workable circuit ..

The explanation of that solution from the guy who came up with the circuit (after 28 pages of digression and discussion) is as follows:

The output from the engine alternator connects to 3 diodes, one is backfed to the field +ve on the regulator and thence to + brush. The alternator senses on this and therefore the diode voltage drop is compensated for. The other 2 diodes are connected each to one of the batteries.

Turn on, warning lamp current flows to the field and alternators excite and cut in. The domestic alternator begins to charge the domestic battery. Voltage is say 13.5 and alternator is delivering full whack to try and drive it higher.

Engine alternator is regulated at 14.2 but is also unable to drive the domestic voltage (Via the diode) that high and so is delivering full whack to try to do so. Engine battery is also recieving a small charge.

Domestic battery voltage slowly rises until it reaches 14.2 and engine alternator begins to regulate. Domestic alternator is set at say 14.6 for the sake of argument regulated by a sterling pdar, and so until voltage reaches this level it continues to run flat out. Output from engine alternator slowly falls until voltage on domestics reaches 14.3 at which point all the engine alternator output is flowing to the engine battery alone and the domestic alternator is working flat out until 14.6 is reached and the acceptance phase begins.

I'd add that under most circumstances the engine (start) battery needs very little charge because all it's had to do is crank the engine for a second or two, hence it will go into acceptance phase within a very few minutes.

Also, the 3 diodes can be purchased as a diode triple, designed just for this sort of purpose (CARGO part number 160343 up to 70A, 160399 to 120A).

Great, simple solution that requires no mechanical parts and minimal wiring.

Tony :)

MattZ

09-06-2009, 07:01 PM

The forward conduction voltage of an SCR at rated current is about 1.8V. For this reason I would not recommend it for the application being discussed.

DaveJ

09-06-2009, 07:31 PM

As i have no idea whats inside an ALT's, can some one please send me a schmatic of a typical alt system.

pistnbroke

09-07-2009, 03:19 AM

MATTS ...I think you lost the plot those are a tripple diode pack not SCR ...the only scr used was in the locked on VSR

DAVE J its called Google

WotEver

09-07-2009, 03:24 AM

As i have no idea whats inside an ALT's, can some one please send me a schmatic of a typical alt system.

Below is a block diagram of an alt internal workings:

A pretty good if basic description of their function in a vehicle context can be found here (http://www.bcae1.com/charging.htm).

On the subject of SCRs, I've never seen one used in a charging application. The most common component used for parallelling batteries is a Duralit relay if you want cheap, or an Albright contactor if you want good and reliable.

Regards,
Tony