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Tony75
Tony75

Posted: Mon Mar 05, 2012 6:42pm

Post Subject: Alternator

I have a 14hp Lister SR2. I want to fit a 90 amp alternator to charge 3 120ah leisure batteries. Will the engine provide enough power to sevice this. I also have a Sterling Batterie management system to boost the charge

Tony-B
Tony-B

Posted: Mon Mar 05, 2012 8:33pm

Post Subject: Alternator

At full output that alternator will require over 4hp. (assuming a 33% efficiency which is probably not far out)so as long as at whatever speed the engine is turning at to produce the full output (this depends upon the pulley ratio - and just to complicate things I think the alternator drive pulley might be off the camshaft which turns at half engine speed, so check) has a power output of (say) over 6hp then it should be OK. However it is not unknown for these older slow revving engines to be pullied up for maximum alternator output only to find the engine will not rev up because the alternator is demanding more power than the engine can produce at low revs. Before you spend any money I would advise you to consult someone who really knows Listers like Marine Engine Services at Uxbridge. There are way of overcoming such problems by altering the pulley ratio, which might result is lower output, or wiring the warning lamp/energisation onto a push switch so you only energise the alternator when the engine is revving above a certain speed. After half an hour or so the charging current will drop so the engine probably would then be producing enough power at low speed. If your charging system wiring is updated for optimum performance and the alternator has a regulated voltage of 14.4 volts + the Sterling unit may have very little effect. If you are driving the alternator slowly the action of the Sterling (and any other advanced controller) may help the alternator to burn out because of lack of fan speed and thus cooling air flow. Sorry not to give a direct answer but I have not done this and I fear you may run into problems. Tony Brooks

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