Date:         Wed, 21 Nov 2012 10:43:29 -0500
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Help with sealed lead batteries
Comments: To: Harry Hoffman <hhoffman@IP-SOLUTIONS.NET>
In-Reply-To:  <50AC28C0.9020804@ip-solutions.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 08:05 PM 11/20/2012, Harry Hoffman wrote:
>http://bit.ly/QtprbR

Interesting...those batteries are rated to deliver 23 watts per cell
for fifteen minutes.  Using the nominal 2V/cell...
23W x 1/4h = 5.75 Wh per cell x 6 cells = 34.5 Wh per battery / 12V
~= 3Ah per battery x 8 batteries ~= 24Ah for all eight.  The actual
number is no doubt somewhat larger (for new batteries, of course)
because the watt-hour rating takes the changing discharge voltage
into account and amp-hours don't.

Note that maximum starting charge current is listed at about 1.25
amps for cyclic use.  If you connect all eight in parallel you could
charge them with a ten-amp charger.  However the no-maximum specified
for float use implies that you can get away with higher charging
currents once in a while (since batteries on float service only get
charged from scratch after the emergency they're guarding against,
hopefully never).

To charge them in series you'd have to use the UPS internal charger
if it's working, but of course you'd have to hook it up to 220V.  And
you'd be working with 100VDC which could get exciting.

Yrs,
d