Alternator upgrade

[Sybarite]

I recently posted on this subject. Having moved up to two batteries I was advised to get a larger alternator from 35ah to something like 55ah.

I gave the job to a specialist marine electrical firm in Lorient and they upgraded the present 13 volt alternator to 15 volts and told me that this would do. The job was done in my absence and I have not yet spoken to them but I noticed that they have also removed the TWC regulator that I used when I had the single battery.

The logic for having the TWC seemed good and I wonder whether, with the two batteries, it could still be useful.

I would appreciate some knowledgeable advice before discussing this with the firm.

Many thanks,

John



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[john_morris_uk]

How big are your new batteries? I assume that you mean 35 Amp and not Ah (Amp hour) for your alternator?

Normally a car (or standard boat) alternator has a regulator that charges the battery at between 13.8 and 14.5 volts and as the voltage rises, the alternator controller slows down the charge rate to a level that cannot damage your battery. The problem with this system for the average yachtsman who charges his batteries for a period and then runs all the electronics lights etc is that the batteries never (or very very rarely get fully charged. For this reason various alternator 'boosters' are sold and I assume that your TWC was one such device. I do not know the TWC device personally (we have a Sterling one on our boat) but the problem with altering the output of your alternator to 15 Volts permamently is that you are very likely to damage your batteries! No altering the regulator will make your alternator produce more amps than it was designed for (he internal resistance of the windings and the design will see to that). If you need to charge bigger batteries in less time the only way to do it is with a more powerful (higher rated current in amps) alternator with a smart regulator... Recomendations vary, but many people suggest about three times your alternator in amps should be the same as your amp hour capacity in amp hours. Hence my initial question, 'How big are your new batteries?' If you have a powerboat and run everywhere on engines and normally plug into a shore power when you are alongside, then the answer is different!

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[Heckler]

just by chance was speaking to sterling power today about basically the same thing.
when you fit the sterling alternator regulater it makes the alternator put out a bigger voltage which charges the battery faster to a cetain point and then it controls the voltage at an optimum point so that the battery doesnt cook but recieves the optimum voltage to ensure a fast charge, i asked the question "how many amps does my VP valeo nominal 60 amp alternator put out" i mean i had always been led to believe that the alternators would only put out a lot less than the rated value, his answer was that with the sterling making the alternator put out a larger voltage that they actually had a bosch 75 amp one putting out a measured 90 amps !!
so the answer to my question was that my 60 amp valeo was probably putting out at least 60 amps.
the story about a 15volt alternator is a bit fishy, alternators put out what ever the regulator tells it to so an alternator is sold as a nominal voltage ie 12v or 24 v etc
and the regulator will fine tune the voltage output to whatever is desired by the designer or in the case of someone fitting a sterling or twc the owner.
s

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[dickh]

The TWC is the predecessor of ADVERC and is good. Speak to Adverc - <A target="_blank" HREF=http://www.adverc.com>http://www.adverc.com</A> who will give good advise.
I have the TWC and it seems to work OK - my advise is to refit it.

<hr width=100% size=1>dickh
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