RE: [PSUBS-MAILIST] uneven charging

[irox <irox@ix.netcom.com>]

Has anybody compared forklift batteries to 12V deep cycle batteries
as far as cost and capacity?

I've been looking around for a battery solution for my sub.  I've got
plenty of volume, so space isn't really an issue.  I would like as
much capacity as I can afford - I like the figure "3tons".

I figure I'll probably kill my first set of batteries through improper
use (although I do plan to try my best to not damage them).  So I
thinking going with a number of smaller isolated battery banks, these
should provide at least several hours of operation time, before they
get drain to the point that I have to switch to the next bank.  This
way I can start with one or two banks, and once I'm happy I've got a
solution that works reliably, build out the rest of battery banks.

Cheers,
  Ian.

-----Original Message-----
>From: "Jay K. Jeffries" <bottomgun@mindspring.com>
>Sent: May 9, 2008 6:44 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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