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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