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Old 11-11-2013, 02:08   #1
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200 Ah => 300 Ah with same alternator?

Hi,

Most likely there is a old thread for this somewhere but being a newcomer could not find it so apologies in advance.

My question is this: I want to add 100 Ah to existing leasure battery bank of 2 x 100 Ah. What are the consequences
a) to the alternator (standard alternator of VP MD2040 from 2004)
b) to the shore power charger
c) to the batteries?

Some preliminary answers in my mind: most likely the situation where the batteries are at 30% is the worst scenario. In this scenario,
a) the alternator must work with 1.5 times the current that the 200 Ah bank drew and possibly a longer time. For electric parts perhaps ok (is it?), but do I see a broken belt more often?
b) If the maximum current for the shore power charger is exceeded in the beginning, some safeguard will snap in the charger? Or are they usually built so that they can restrict the current automatically?
c) charge current will be some 10% of the total capacity. Will this cause some sulphate forming in the lead batteries in the long run, or other problems? (In any case the average life span of a cheap battery is about 6 years so is this really a problem?)

Please comment, Tuomas
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Old 11-11-2013, 02:31   #2
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Re: 200 Ah => 300 Ah with same alternator?

Tuomas,

I could be reading this incorrect but you are adding 100ah to an already existing 200ah bank? If that is the case there won't be a problem and I think you are over thinking it. Adding AH to your bank isn't going to affect your alternator or your shore power charger, they will continue to charge at their rated power, adding AH to your bank doesn't make them stress at all you'll be fine.

I would be more concerned with mixing different aged batteries together, that could be a problem depending on the age of the current 200ah bank. Also making sure they are the same chemistry is quite important. Remember your bank is only as strong as your weakest battery.. Hope this helps.
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Old 11-11-2013, 02:36   #3
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Re: 200 Ah => 300 Ah with same alternator?

Oh to answer question C.. If you have sufficient charging adding to the bank will actually reduce the amount of cycle, potentially increasing your overall battery life.. For example a 200ah battery bank that uses 100ah has consumed and cycled to 50%, where that same usage with a 400ah battery bank will have only consumed 25% with 100ah usage. As long as you can effectively keep your bank charged in between those with solar,wind, alternator, generator etc you will have more usable.
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Old 11-11-2013, 07:31   #4
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Re: 200 Ah => 300 Ah with same alternator?

Greetings and welcome aboard the CF, Tuomas.
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Old 11-11-2013, 07:47   #5
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Re: 200 Ah => 300 Ah with same alternator?

You can add a new battery to an old bank if you isolate it and use a seclector switch.
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Old 11-11-2013, 08:18   #6
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Re: 200 Ah => 300 Ah with same alternator?

A and B are non issues, C is the charger out put generally should be 25-35% of total bank amperage. May want to upgrade the charger however it shouldn't hurt anything it just will take longer to charge back up to full
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Old 12-11-2013, 03:56   #7
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Re: 200 Ah => 300 Ah with same alternator?

Ok, thanks for replies.

The older I get the more I suspect that things looking self-evident might not be that

I will then just go for it.
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