Brian,
Your local distributor vice the manufacturer would probably be the best
choice. We use specialized silver-iodine batteries here and match them
ourselves. These are high energy density batteries with a limited number of
recharges...very expensive. They were used (and still be) in some of the
early research submersibles.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
Vive vt vivas
- Live that you may live
_____________________________________________
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brian Cox
Sent: Friday, May 09, 2008 20:02
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] uneven charging
Jay,
I was thinking of getting AGM deep cycle marine batteries 12V 210
amp hour , 8 of them. Are you saying I should contact the manufactureer and
request a matched set? Don't they just produce the batteries on an assembly
line so that they are all basically the same?
Brian
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Jay K. Jeffries
Sent: Friday, May 09, 2008 3:44 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] uneven charging
Forklifts and large submarines have a luxury that unfortunately we
cannot afford in PSUBS and that is the use of large volume batteries. An
application closer to us is the scooters used in tech diving that are used
to explore miles of underwater caves in a given dive. They test their
batteries by measuring the various discharge rates of batteries and group
similar discharge rated batteries together as they have the same charging
rate and do not display the issues described in previous posts. They are
tested regularly over their lifetime to insure matched service. When you
purchase batteries, you can request that the battery firm provide you with a
matched set for a small premium and thus save buying a bunch of batteries
and matching them yourself. If you replace one, you have to replace all to
keep matched service.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
Vive vt vivas
- Live that you may live
_____________________________________________
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Hugh Fulton
Sent: Friday, May 09, 2008 18:07
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] uneven charging
The best solution, I have been told, is to use 2 volt cells in
series. This is how forklifts etc do it as it is very hard to get the
internal resistance of batteries to be the same. Forklift batteries
generally have 2 volt cells that are up to 2000 Amp-hours per cell. This is
why you should always recharge batteries, that are in parallel, in
isolation. Also batteries left in parallel can discharge themselves through
this unevenness. All this was explained to me by a battery importer. Makes
sense to me but I am still going for parallel as the 2volt cells with high
amp hours are a crazy size physically. This probably explains some of the
problems I have in my boat which has 3 batteries in parallel. It is very
common advice in the marine industry that id you are using batteries in
parallel you should use the same manufacturer, size and model of battery.
Hugh
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