[RE-wrenches] unique battery bank design question

[Rob Shappell]

I never, never recommend taps of any sort, but sometimes we have to satisfy
the needs of the customer. If any taps are done in any manner I would
recommend AT LEAST an annual reconfig of the taps.

To reduce and/or eliminate the imbalance of the 12 volt and 24 volt taps,
you could install a 12 volt charging source to the 12 volt tap, a 24 volt
charging source to the 24 volt tap and the 48 volt loads get a 48 volt
charging source. The array is still calculated the same, just distributed
different through different controllers. Is this bullet proof or perfect?
Nope, but neither are DC/DC converters and the system is much more efficient
too. 

Rob Shappell

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Hugh
Sent: Friday, September 02, 2011 4:51 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] unique battery bank design question

At 19:39 -0400 1/9/11, Jason Szumlanski wrote:
>Sorry - I missed the 4 days part of your post. I'm not sure where you 
>came up with 4 days - sounds kind of arbitrary.

Any chosen time is arbitrary.  Maybe I should have chosen a month. 
700 amphours.  Dead flat 12 volt battery.  I often use 4 days in the design
of stand alone battery systems.

>
>I'd be interested to know if it makes any difference at all if you tap 
>a 12V load only when there is a 48V charging source present (assuming 
>the charging source current is significantly greater than the load).

Not really because the other batteries get 1 amp more charge, and will reach
the point where the current is limited by the 48 volt controller, whereas
the one that is on load will not get properly charged up.

>  Assume you want to run a small 12V fan only when batteries are charging.

Then it's maybe only on for 25% of the time and it takes 4 times longer for
everything to go pear shaped.
>
>Another option I've been reading up on is a Battery Equalizer/Battery 
>Balancer.

This seems like a valid solution, yes.

best wishes,
--
Hugh Piggott

Scoraig
http://www.scoraigwind.co.uk
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