Parallel Alterntors for faster charge.

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,

 

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).

"

"

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

 

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

 

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...........

 

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.

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 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.

 

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

 

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 **** here and there isnt room for another.

 

You can never have too many

 

Apologies

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

 

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

 

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

 

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 ....

 

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

Nice one

T.

 

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 ...

 

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