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Old 17-09-2009, 20:09   #1
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Recharging GEL Batteries After Total Discharge

Hi folks

I have a double bank (2 x 3) 105 a/h 12 Volt GEL type batteries
that were left on a boat on the hard, the batteries were "in circuit"
being charged/topped up by a 110 W Solar panel
protected by a solar panel regulator to prevent "over-charging"

This system had been working for nearly two years
while the boat was in storage,
just operating a small 12 V fan to ensure air circulation
and a bilge pump to take out any rainwater that managed to get in

not sure yet what happened,
maybe a lightning strike knocking out some fuses
maybe the solar panels or the regulator faulty - not sure
but leaving me with 6 x 105 A/hrs batteries totally discharged

My first concern is getting these batteries recharged
which I intend to do with an industrial
heavy duty battery charger on shore power

Has anyone had experience of doing this
is there a particular procedure to follow to minimise possible damage
to the GEL batteries, ?

from what I gather
they have been discharged or discharging
for maybe 5-6 weeks ...

Thanks - John
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Old 17-09-2009, 21:34   #2
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Charge them normally. If they're lazy and don't hold much of a charge, kick their butts with a heavy load like an inverter with a microwave on high until the inverter won't run.
Recharge and discharge them a few times with heavy current loads.
Tell 'em who's boss.
Worked for us back in the '90's with a couple of Prevailer 8D's.

Steve B.
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Old 17-09-2009, 21:45   #3
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Hi

just a bit more information to my original post
the batteries are on my boat in the tropics

ambient temps of around 30 deg C most of the time
with high Relative Humidity

battery compartment well vented
Batteries are approximately 4.5 years old

Reading up on the Google links
gives a slightly confused feedback
most of the posts there
seem to be in support of a particular charger or manufacturer
Appreciate any "hands on" recommendations

John
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Old 17-09-2009, 21:49   #4
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Quote:
Originally Posted by senormechanico View Post
Charge them normally. If they're lazy and don't hold much of a charge, kick their butts with a heavy load like an inverter with a microwave on high until the inverter won't run.
Recharge and discharge them a few times with heavy current loads.
Tell 'em who's boss.
Worked for us back in the '90's with a couple of Prevailer 8D's.

Steve B.
Hi Steve

so just charge on boost or normal charge (slow) ?
I was going to basically trickle charge over 24/48 hours ?

The heavy load cycle to clean up the plates
makes sense to me - good point

John
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Old 17-09-2009, 21:59   #5
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Well, first thing to do is finding a suitable charger for gel cells and then just try to charge them first. Only when that fails you go into "all or nothing" experiments like waking them up with high voltages etc. I think you'll find info in books from Nigel Caulder and Steve Dashew.

cheers,
Nick.
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Old 18-09-2009, 12:45   #6
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I didn't do anything out of the ordinary to charge mine when they "went to sleep" during the summer storage in Mexico. The boat had a 100 amp Balmar alternator and a smart regulator set to bulk charge at 14.1 v and float at 13.8.

During the whole time we were on the hook in Guaymas, Sonora Mexico.

After charging until the regulator went to float, I used a power sander, drill and the microwave to discharge them. (I was doing a lot of boat work while restoring the batteries). We did at least 4 charge/discharges the first day, and a couple of cycles the next couple of days.

After 3 days, the batteries were back to normal function.

Steve B.
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Old 18-09-2009, 13:12   #7
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Agreed, exercise them for a day or 2, but charge normally UNLESS they refuse to take a charge. Only then, kick them. At 4.5 years old maybe look at replacement? But I'm not that familiar with gel cells (life expectancy), I mostly work with wet and flooded cell....

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