another battery question

I appreciate the comments posted under the "batteries" thread, and I
learned some things.

I have a different type of battery, and a different question.

The battery is a 55 amp-hour 12 volt gel-cel from Globe that has not
been used for a few years; my voltmeter reads 1.6 volts.

I would like to bring this battery back from the dead, if possible. I
have an automotive battery charger that will charge a 6-volt battery and
will charge a 12 volt battery at either 2 amps or 6 amps.

But first, I clipped a Deltran Battery Tender Plus to the gel-cel, and
the red light continued to flash, indicating that the Battery Tender did
not recognize that a battery was even hooked up, so it won't charge.

Two friends have suggested slightly different methods of charging the
battery.

One said that I could use the automotive charger in the 6 volt position,
then after a while, switch to 12 volts at 2 amps. The idea being not to
hit the discharged battery with too much amperage in a short time.

Another said that I could use any "wall blob" (transformer) for a few
days to slowly recharge the battery, then use the automotive charger
when the battery approached 12 volts.

I would like to request a krusty opinion and an opinion of the pooder
variety, and any others who might have experience with this type of
battery, because I have a few others of the same type that will need the
same treatment.

I would ultimately like to use these batteries to operate ham radio
equipment while being periodically hooked to the Battery Tender Plus to
keep them in good shape.


Dave S.

1996 FLHR-I Road King

BS#146, DOF#181, NEWT#4, KOTOR#1, SENS, CVNS G&W, DOF # 6021, ARSE

 

Dave, You might as well toss 'em. I use Gel Batteries on a daily basis
and if you let them sit without keeping them charged, they go dead. You
might be able to get them to take a charge but they won't have any
capacity. That 55 AH may give you 10-15 AH capacity when charged. To try
to bring it back. Start with 2 amps at 13-14V for several hours. Reduce
current if the battery gets above 130F. Then charge at reduced rate
500ma for 24hrs and float charge after that. (Your tender should be able
to take over after the initial 2 hours with the other charger)
Gel batteries to run radios is not the best application for them. The
discharge rate is murder on a gel battery. Car batteries work better and
are less expensive. (They are meant to survive high current discharge in
short burst (Transmitting is like starting))
Good luck

--
Gopher 33 28 19N 112 01 49W
'77 CB750K (Street) '78 CB750K (Cafe)
'79 FLHassle (Gone) '00 ZG1000 (Sarge)
'97 Ducati M750 (horse with no name, yet)
'96 Ducati 900SS (Trackstar)
Pull 'mychain' to reply

 

been used for a few years; my voltmeter reads 1.6 volts.

I have an automotive battery charger that will charge a 6-volt battery
and will charge a 12 volt battery at either 2 amps or 6 amps.

It doesn't sound like it's totally dead and sulfated. Gel keeps the
electrolyte in contact with the plates, the water can't get out...

I would just go ahead and charge it on the automotive charger for two
days, and check the battery voltage half an hour after taking the
battery off the charger to see if it's still up around 13.5 volts.
That's a good sign that it's healthy...

Then do a capacity test while monitoring the voltage. A 55-ampere hour
battery should supply 1 amp for 55 hours, or 55 amps for an hour. You
can easily make up a capacity tester with a 55 watt automotive
headlight bulb, which will draw 4.6 amps at 12 volts...

The battery voltage should never drop below 12 volts during the
capacity test which should last for 12 hours...

position, then after a while, switch to 12 volts at 2 amps. The idea
being not to hit the discharged battery with too much amperage in a
short time.

I wouldn't worry about that. If I had the kind of charger that service
stations use to "quick charge" a battery, I would definitely start at a
low rate, and then switch to a higher rate, but your 2-amp 12-volt
charger won't hurt your gel cell...

days to slowly recharge the battery, then use the automotive charger
when the battery approached 12 volts.

I have one of those, a 600 milliamp job that I use to "top up" my 14
ampere hour motorcycle batteries in 12 hours or so. Amazingly, it puts
out about 15 volts when connected to a battery that isn't dead, and
which still indicates about 12.6 volts after the bike has sat unridden
for a few months...

It would probably take about three days to see any results from your
"blob"...

equipment while being periodically hooked to the Battery Tender Plus to
keep them in good shape.

Well, you'll get clean DC from a battery, that's for sure. I used a
motorcycle battery to power a home-brewed shortwave receiver that I
built from plans in the Radio Amateur's Handbook many years ago...

 

That's awfully dead

Aha! the Tender agrees with me!

The "soft start" is certainly a good idea, the 6 volt setting should be
needed for only a matter of minutes.

Best to make sure the wallwart is protected against overheating on a
dead short, as that's what the battery will look like initially.

Ok, here's an unsolicited $.02

Find a small (5-10 watt) incandescent light bulb. Wire it in series
with the standard battery charger set to 12 volts, 2 amps. Wire a
voltmeter to the battery and watch the voltage over a period of days.

Ideally it'll quickly (hours) come up to about 13.5 volts, the minimum
needed to store energy in a lead-acid cell. It should stay below 14 for
some extended time, ideally 55 hours for a 55 amp-hour battery with a
one-amp bulb, but that never happens in practice.

Record the voltage every so often and try to establish a voltage trend.
A perfect battery will promptly jump to 13.5 volts on slow charge and
very slowly ramp up to about 14.5, a battery with bad cells will change
voltage in a staircase fashion as the mismatched cells charge.

If the battery gets to 14.5 volts, disconnect it, let it sit for a few
hours and measure the voltage at no load; should be at least 12.5, ideally
more like 13.

Next, put the bulb on the battery as a load and record the voltage.
Batteries are rated for amp-hours at a fixed discharge rate, and
you have to know what the rate is; car batteries (at one time) used
a 20 hour rate, I understand motorcycle batteries presently use a 10
hour rate, ie, the test load should discharge a 10 amp-hour battery
in ten hours, thus one amp. You have to know the manufacturer's intent
when checking a battery. Watch the battery voltage as it discharges.
When the weakest cell discharges the other cells will drive it into
reverse, taking about four volts away. When that happens the battery
is discharged. Take care to charge it back up promptly if it's not junk.

Amp-hours are not entirely linear; energy storage in a battery is partly
in the plates and partly in the acid, so diffusion of acid (which takes hours)
plays a part and a high current draw will result in a low measured amp-hour
rating. A valid test must be done at the manufacturer's rate.

The use of a light bulb to limit charging current and as a test load is
motivated by the temperature coefficient of resistance for tungsten; it
causes light bulbs to be approximately constant current limiters. A cold
12 watt 12 volt bulb has a resistance of only about an ohm, hot it's
closer to the 12 ohms one would expect (no, it's not perfect, but better
than a dumb charger's current limit).

Given the initial condition of the batteries it's hard to believe
they'll ever be in good shape! But, a sick battery sufficiently
oversized might do the job for you. Probably best to float charge.

Good luck,

bob prohaska

 

You might want to take a look at
http://www.windsun.com/Batteries/Battery_FAQ.htm

***SNIP****