batery banks

 hello,
If I want to use a bank of car batteries to hold my load from a solar
bank or a wind generator, a bank of four batteries, do I connect them
in series or parallel?  Thanks for any help carjo@nethere.com

  from carjo@nethere.com contains these words:


 I wouldn't recommend car batteries for this service. They don't take
kindly to what, on the face of it, is a very controlled and tightly
regulated float charging regime (as I've discovered at least three times
over the past 15 years [1]).

 The charging current from a car alternator has a high ripple content
(not as extreme as in the case of a full wave rectified single phase
battery charger, but still sufficient to avoid the crystal growth
between and within the plates when a pure DC current is used to float
them at 13.8 volts per 6 cell battery).

 Unless your charge controller emulates a 'Dirty DC' charging current,
you're likely to find the batteries totally buggered within 12 months of
being put into such service regardless of whether they frequently get
used in anger or just sit there waiting to be called into action.

[1] The first time I had a brand new car battery 'prematurely fail'
after less than 6 months of service harks back to my days of CB radio
and the use of the classic 13.8 volt CB power pack supplemented by a
float charged car battery to provide the extra oomph lacking in the CB
power pack on its own. Unfortunately, I didn't realise the true nature
of the problem at the time, putting it down to being a case of 'Bad
Luck'.

 The later events involved a 48 volt battery bank using four 36AH car
batteries on a 2KVA UPS which only lasted 12 months at the most before I
replaced them with yet another four 42AH batteries which also failed
within 12 months of being put into service :-(

 Since all four batteries were exhibiting the same symptoms (low resting
voltage of 6 to 10 volts and an inability to charge to the float voltage
end point of 13.8), the penny finally dropped and the truth of the fact
that a gentle charge current with almost zero ripple was definitely not
good for car batteries, finally became proved beyond any doubt.

 The more usual 'Dryfit'(tm) type of battery used for this service are
designed to cope with this (seemingly non) abuse charging regime. There
are two types of 'Dryfit' (or sealed spill-proof) design, gel
electrolyte and absorbent glass matting (AGM) which retains a liquid
electrolyte. Of the two, I believe the AGM type has the edge in
performance when used in such float charged service.

HTH

--
Regards, John.

 Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

 On Sat, 2 Aug 2008 04:00:46 +0100, Johnny B Good


tnanks much for the info  carjo

 For a 12 volt solar or windcharger, wire your battery bank in parallel.

 


thanks a lot,   carjo