Battery types & distribution, over time [RE-wrenches]

Wed Jun 26 16:51:57 PDT 2002

Andrew:

My experience is:

Remote Home - Surrette or Trojan flooded batteries - 2 Volt Cells,
L16's, or T105's 
All are Lead antimony which is what you want for deep cycling.
The down side of Lead antimony is:
The self discharge is much higher and it INCREASES dramatically (10
times +/-) over time. This means more watering and more energy lost to
self discharge.  The also require periodic equalization to get the best
performance.  IMHO, you want to charge them harder than most people
think.
Run the bulk set point way up there and then back it off when the
watering becomes excessive.

Backup power - Sealed Gell Cells or AGM.  Lead calcium, Lead selenium,
or a hybrid with different alloys on the different plates. These
batteries have much lower self discharge and do not require periodic
equalization. With a Lead calcium battery the self discharge stays
almost constant over time so the system performance remains pretty
stable over the life of the battery.

Between the AGM and Gells, I prefer gells.  AGM is hard to do right and
they tend to be very picky about overcharge.  If they are over charged
they dry out and you see open cells and dead batteries.   The backup
power application is almost a UPS application but the discharge rates
will be slower than UPS.  A UPS battery uses lots of thin plates to
increase the surface area for high rate discharge.  For backup power you
want a little thicker plates for longer life and better cycling
performance.  In my experience the batteries in backup systems fail
because they are not properly maintained.  They just sit there and are
easy to forget.  The downside of the sealed batteries is higher initial
cost and they do not tolerate severe deep cycling the way lead Antimony
will. 

If you have any questions, or if I can be of any further assistance,
please do not hesitate to contact me.

Best Regards,

John Berdner

SMA America, Inc.
20830 Red Dog Road
Grass Valley, CA  95945
530.273.4595 (voice)
530.274.7271 (fax) 

-----Original Message-----
From: Andrew Bortz [mailto:solarman2 at attbi.com] 
Sent: Wednesday, June 26, 2002 2:29 PM
To: RE-wrenches at topica.com
Subject: Battery types & distribution, over time [RE-wrenches]

Wrenches,

Not surprisingly my clients have had a lot of questions about the best
type of batteries to use in their PV systems.  While I realize this is a
complex issue (affected by system configuration, on or off grid etc.),
answers to the following question would help greatly in advising them
intelligently!

Is there any comprehensive info. out there on the distribution of
battery types (& possibly brands also) in PV systems (residential &
commercial) over time?  In other words where (not so much geographically
as what system configs.) have the different types been used in the past
and what are the trends in use?

I beg enlightenment!

Thanks,
Andrew Bortz
Solar Design & Construction
Corvallis, OR
[Non-text portions of this message have been removed]

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