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Re: [PSUBS-MAILIST] Battery charging
Partial discharges are definitely an issue. We built simple light panels (say, 20X500 watt bulbs) or you could use heater coils, etc., to discharge the batteries when doing specific gravity testing. We'd get them all the way down to 1.75 volts unloaded, check for out of spec cells, then belt 'em up to max and do it all again, maintaining a log on every cell to monitor trending (a 0.01 volt drop this month in one cell might be a 0.02 volt drop next month, showing some kind of short or calcification, and suggesting a need to change that particular battery before it got to be a bigger problem).
In long term-storage (say over the winter for an inactive sub) battery maintenance was a monthly ordeal, along with the weekly tailing charge to keep them hot. Today's battery tenders could probably simplify this (never leave home on the bike without one). At any rate, by doing the relatively simple maintenance, the battery banks were always hot and ready, so when it was time to go, we'd just button up and go.
Keep in mind, this was usually four banks X 120 vols each, plus two banks at 12/24 volts--the better part of two tons--too big an investment in time and money to allow failure due to neglect. Moreover, gel cells and the like don't really let you do this kind of thing. You check the overall pole voltage and take your best guess with those. Phil Nuytten runs his per season and replaces both strings during every winter overhaul. That takes care of the problem except for sudden internal failures, which you would detect during charge/discharge cycles. In that case, you'd just haul out the bank on deck, find the culprit and replace it. Simple, eh? (That's Canadian. Told you I was bilingual).
Vance
-----Original Message-----
From: Dan H. <Jumachine@comcast.net>
To: personal_submersibles@psubs.org
Sent: Thu, Sep 17, 2009 8:37 am
Subject: Re: [PSUBS-MAILIST] Battery charging
Frank,
From my experience, I'd be more concerned with how deeply you can discharge before recharging again and their shelf life rather then how many cycles the batteries can take. Most P subs won't see 700 cycles in fifty years.
What you need is, as much power as you get get out of a charge. It's hard to beet lead acid for the price.
Dan H.
----- Original Message -----
Sent: Wednesday, September 16, 2009 10:39 PM
Subject: Re: [PSUBS-MAILIST] Battery charging
I saw this on Ebay while researching what's out there for chargers.
An American made charger for 36 volt/20 amp runs about $260 new.
Anyway, there was also this little gage for a golf cart.
I'm wondering what it measures. Probably volts because it only has two wires but it brought to mind the next phase of my project which will be batteries.
Everybody has their own idea of what's best for them, and right now I'm leaning toward the Trojan golf cart ones. They have a good track record and are pretty affordable. The plates are thicker so can take more cycles than a basic marine deep cell.
Would be nice to get a set of Li-ion but they're still pretty pricey.
The Trojans advertise 700 cycles and I've used the same ones on a solar system to run my cabin. They were still working after 13 years. Of course, the application is different. These were kept charged usually where a sub or golf cart will pull them down regularly but golf carts are made to do this.
Anyway....my question is, anybody got any new info on batteries ? I know there's been a lot of new developments lately. Frank D.