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Author Topic: Charging a set of 20 dead batteries  (Read 2400 times)

Offline DROdio

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Charging a set of 20 dead batteries
« on: June 20, 2006, 09:59:00 PM »
OK Nick Badame was kind enough to help me get my new inverter installed, and when I got home I started charging my battery bank of 20 deep cycle batteries (yes save me the grief, i know 20 batteries is a LOT!)

the batteries were super low when we hooked them up to the charger.  they basically hadn't been charged in over a year because they were just sitting there as I set my electrical system up.

so, the batteries had been charging for about 24 hours when i noticed some of them were gassing.  i checked the water level and it was low in most of the batteries, and very low in about 20% of the batteries.  so i re-filled them with distilled water.  Now, here are my questions:

1) when a battery is gassing during recharging, is this a bad sign?  i was NOt equalizing them, but there was about 130 amps being put into the batteries. (they were on "float"  status)

2) some of the batteries were starting to get very hot.  how big a deal is this?

I just had these visions of my battery bank exploding, so i shut the batteries off and decided i'd let them cool overnight and start the recharging tomorrow.   I'm really not sure how much danger the batteries were in, so any advice would be appreciated!
1989 VanHool T-815


Offline boogiethecat

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Re: Charging a set of 20 dead batteries
« Reply #1 on: June 20, 2006, 10:28:34 PM »
Quite often if the battery gets hot during charging, if its old, it could be  because it's sulfated and somewhat shorted.  Then when you take the charger off, it will stay warm for a day or two, and be dead.
Sorry, bad battery!
Bubbling while charging is an ok thing. It's just some water being turned into hydrogen and oxygen (a nice explosive mixture so make sure you're vented!!) and is a normal part of the process.

Oh... DON"T let your batteries get too hot. If you can't touch them for a long time, you may be killing them.  If they are getting too hot, back off on the charging current or turn them off until they cool down before proceeding.

Here's an excellent webpage (actually quite a few pages) that covers more than everything you'd like to know about batteries.  You'll find all your answers and probably more than one sorrow there...
This guy has written an amazing tome on batteries...

« Last Edit: June 20, 2006, 10:31:48 PM by boogiethecat »
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Offline Nick Badame Refrig/ACC

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Re: Charging a set of 20 dead batteries
« Reply #2 on: June 21, 2006, 06:06:34 AM »

boogiethecat Gives you some good advice, I think you should individually check each battery with a hydrometer too.

Having 20, 115 amp Hr. batteries, you may of even purchaced a couple of bad one's from new!!  If so bring them back.

Whatever it takes!-GITIT DONE! 
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Offline TomC

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Re: Charging a set of 20 dead batteries
« Reply #3 on: June 21, 2006, 09:00:42 AM »
DROdio- Personally, I would consider buying a complete set of new matched batteries made from the same batch.  And while I was at it, change to a larger battery.  For instance, Trojan makes the popular T105 6 volt that has 225 amp hr that has a dimension of 10 3/8"L x 7 1/4" W x 10 7/8" H that weighs 62lb.  Also made is the L16H at 420 amp hr that  has a dimension of 11 5/8" L x 7" W x 16 3/4" H that weighs 121lb-or vertually twice the battery.  My point, you can always have better battery balance with fewer batteries, and there are the batteries that you can maintain the amp hour rating you want, but with fewer batteries.
The batteries I have settled on are Lifeline AGM (Absorbed Glass Mat) batteries.  They are sealed, can operate in any position (they prefer you not to operate them upside down, but they will), never need watering, do need a three stage charger, can be charged much faster than a normal watered battery since there is less resistance in the battery, and have a 5 year prorated warranty, but are about twice the money of a watered battery.  Because of my space limitations on my transit bus, I only use 2- 8D's for a total of 510 amp hrs, which is enough for my purposes.  If I need serious electricity, I just start my generator.  When boon docking, I run the gen for two hours in the morning and evening.  Then I don't have to carry around all that extra weight of multiple batteries.  But-you'll do it your way.  Good Luck, TomC
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Offline Jerry Liebler

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Re: Charging a set of 20 dead batteries
« Reply #4 on: June 21, 2006, 10:29:40 AM »
   With 20 batteries you have both series and parallel groups of batteries.  The batteries that are getting hot definitely indicate you have some batteries with shorted cells. The shorted cel is either in the battery getting hot or another connected in series with it. You'll need to identify the batteries that have shorted cells and remove them. then reconnect as a smaller pack and recharge.  I'd suggest removing all the intertie connections then measuring the voltage of each battery.  Reconnect only those that show a voltage near 2 volts per cell and try charging again.  A little gasing during charging is normal, but violent gasing, at float voltage, indicates that a cell in that series string of batteries is shorted & the battery  with the shorted cell needs to be scrapped.
Jerry 4107 1120