Battery Life in Grid-Tie Systems [RE-wrenches]

[Scott: Backwoods Solar]

Todd and Richard,

I have a 24v Harris hydro system which generates between 19 and 25 amps
depending on the number of nozzles open. It charges 8 Trojan L16HC batteries
which are four years old. These batteries have been faithfully monitored
with an hydrometer and watered as needed with plates never being exposed. I
have gradually lowered my bulk volt setting as regulated by a temperature
compensated Trace C40 from 29.6 to 29.0 volts in order to reduce water
consumed. Hydrometer readings on a daily basis reach 1275+ in all batteries.
Depth of discharge is typically 10% with a 30% discharge having occurred
perhaps 6 times in 4 years. Perhaps twice a year I have applied an equalize
charge. A year ago, I rotated batteries in response to the battery from
which all (-) leads originated using more water than the balance of
batteries.

Last weekend, one cell in the battery which is now my main (-), not the one
using extra water, died. It would not respond to any charging input from the
hydro nor a backup generator while the other two cells in this battery
quickly attained a 1275 + hydrometer reading as did the other batteries in
the bank. I spoke with a Trojan engineer at great length about this
situation and after a careful review of my entire system's parameters, he
concluded that I did not cycle my batteries deep enough.

In summary, he said:

Minimum 20% - 30% discharge on a regular basis;
Equalize once a year if hydrometer readings don't indicate to do it more
often;
The main (-) battery will use more water; and
Rotate battery positions once a year.


So do I believe him?? and does anyone have other comments on my battery
situation?

Thanks

Scott

Backwoods Solar Electric Systems www.backwoodssolar.com


----- Original Message -----
From: "Todd Cory, Mt. Shasta Energy Services" <toddcory at finestplanet.com>
To: <RE-wrenches at topica.com>
Sent: Thursday, November 20, 2003 6:34 AM
Subject: Re: Battery Life in Grid-Tie Systems [RE-wrenches]


> Richard Perez in a recent post about this said there is no reason to cycle
a
> floated, wet cell battery in a grid tie system. Equalizing is still
> something worthwhile to do occasionally. Run the voltage up until all the
> hydrocaps get the same (warm) temperature and you are done.

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