[RE-wrenches] unique battery bank design question

[R Ray Walters]

Both cases started with new batteries: Trojan L16s. One was a 24 v system that tapped for 12 v lighting, the other was a 48 v system that charged with a 24 v Bergey added later. The problem seems to come up when you have more than one parallel string. I could see the Vanner working on a single string. The imbalance showed up just barely at first, and got much worse with time. In the end, the L16s died in less than 5 years, and never provided their full rated amp hours even the first year.
DC to DC converters from Solar Converters, Inc. seem to work pretty well, but I always under load them (maybe 5 to 10 amp load on a 20 amp rated unit)
THese days I just go all AC and avoid multiple DC voltages in the first place. There is almost always another solution.
A fair bit of our rewire work these days involves converting DC circuits (lighting, etc.) to AC under the K.I.S.S. principle.

R. Walters
ray at solarray.com
Solar Engineer




On Sep 3, 2011, at 9:10 PM, boB Gudgel wrote:

> On 9/3/2011 7:57 PM, Darryl Thayer wrote:
>> 
>> I have had one experiance with equalizers, the batteries be came very unequal.  (over time of course)
>> 
>> From: R Ray Walters <ray at solarray.com>
>> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
>> Sent: Saturday, September 3, 2011 5:55 PM
>> Subject: Re: [RE-wrenches] unique battery bank design question
>> 
>> Systems I tried years ago with Vanner equalizers, still ended up being unequal. I pulled them all years ago. It seems to be about as much a problem as not balancing your battery cables so each battery string has the same wire resistance,
>> I know that you couldn't imagine a few amps on 12" of 2/0 making a difference, but after 5 years the battery damage is very consistent and identifiable.
>> The only load I would consider tapping would be metering, or maybe a low milliamp relay. I wouldn't go over 100 mA, and even then I bet you would see some long term imbalance. I've seen imbalances due  to some batteries just being closer to a cold outside wall.
>> 
>> R. Walters
>> ray at solarray.com
>> Solar Engineer
> 
> 
> Has anyone that has used battery balancers checked the individual battery voltages or SG during charge and/or discharge to
> see how well the balancers worked ??
> 
> Could it be that the batteries themselves were just not quite the same age at the start ??
> 
> I would think that a decent balancer system that makes things share should work pretty well.  Maybe the balancer
> itself does a bit of unbalaced charge/discharge ?
> 
> boB
> 
> 
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