Large Alternator Control

[davidb]

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On our barge we have a 6 HP Lister CS stationary engine which drives a very big ( I think it is 180 A at 24v ) alternator like this:

 

 

I like to run the engine at reduced revs which means that it is well underpowered to drive this alternator at its full output.

 

in order to reduce the load on the engine, I have the alternator field current running through a variable (in parallel) bank of resistors.

 

For 8 years or so this setup has been fine, but I would like to automate the switching of the resistors in and out to optimise the load on the engine.

 

As it is at present, I have to keep reducing the field current as the domestic battery voltage increases ( V x I = W ) or the engine really starts to smoke when the battery is getting full.

 

Any ideas for an uncomplicated DIY solution please?

 

thanks, David

[Sir Nibble]

Fit a smaller cheaper alternator and e-bay the monster.

[davidb]

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Thanks Sir,

 

I didn't explain fully.

 

When the battery is flat and the engine is at full revs, it can cope and deliver loads of charge in short time - ideal for bulk charging.

 

This takes about 10 minutes, then we switch to tickover ( a pleasant sound to certain ears-_- )

 

It is the trickle charging at the end which is the problem, this often takes 2 hours of running a day, like it does for many boats without shore power.

 

I suppose I could fit another smaller one, but that would still require manual switch - over.

 

Cheers, David

[Timleech]

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Thanks Sir,

 

I didn't explain fully.

 

When the battery is flat and the engine is at full revs, it can cope and deliver loads of charge in short time - ideal for bulk charging.

 

This takes about 10 minutes, then we switch to tickover ( a pleasant sound to certain ears-_- )

 

It is the trickle charging at the end which is the problem, this often takes 2 hours of running a day, like it does for many boats without shore power.

 

I suppose I could fit another smaller one, but that would still require manual switch - over.

 

Cheers, David

 

I suppose you've tried adjusting the tickover speed up a bit?

 

Tim

[Gibbo]

Cheap and cheerful method (read rough-arse):-

 

Put a microswitch on the throttle control to operate a relay to switch the resistors in and out of circuit.

 

Slightly less rough-arse:-

 

Use a voltage controlled relay to switch the resistors.

[john4647]

I think what you have is a Lucas designed AB172RL alternator originally intended for military use.

 

Although I can't help with your opening question, I do have a full workshop manual for this unit, with internal wiring diagrams etc.

 

You may be able to work something out from that.

 

If you want a copy let me know and I will scan it and e-mail to you but as it is 40 pages, it may get after the weekend.

[davidb]

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Thanks a lot for your offer, John, but I don't need to open it up, i already have fly leads coming out for reducing the field.

 

"

Put a microswitch on the throttle control to operate a relay to switch the resistors in and out of circuit."

 

excellent idea, thanks, just my style of job, but I would prefer a voltage controlled relay to switch the resistors especialy if it could be solid state,

 

But how to achieve voltage control? I don't mind using automotive relays, I have a shed full of those.

 

D

[Nickhlx]

How about incorporating (any) alternator onto the engine and use the resulting electricity to heat ? Great in winter !

 

Nick