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Old Jan 29, 2002, 10:56 AM
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The Other Dave's Avatar
Colorado Front Range, USA, EARTH, Sol system, Milkyway Galaxy
Joined Nov 2001
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Question
When you got your Qualcom 830's did some of them read < .5 volts out?

I got my 10 qualcom li-ions last night.

In my preparation for electron extasy I checked
the output voltage on all of them.

5 read > 6 volts.

4 read < .5

1 read 5.5 volts.

I tried charging one of the ones that read < .5 volts
and it seemed to charge up ok. It charged up to 8.2
volts.

Now a few hours after charging it reads 8.053 volts.

My sony li-ions (10 hours after charging) read 8.153 volts.

Is any or part of this normal?

T O D
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Old Jan 29, 2002, 11:32 AM
Quacker's Avatar
United States, CO, Longmont
Joined Jul 2001
2,836 Posts
If you were measuring the pack voltage before disassembly, the low voltage may have been due to a low voltage cutoff inside. The batteries are likely low, but not that low. When you open these packs, initially charge them at c/10 until the voltage comes up to 2.9 v/cell.

The top charging voltage is 8.4V. Some drop after charging is normal. You have not yet completed the charge on these cells at 8.2 volts. You will need to cycle the packs 2 or 3 times to get back all the capacity lost during storage.

Regards,
Q
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Old Jan 29, 2002, 01:03 PM
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Colorado Front Range, USA, EARTH, Sol system, Milkyway Galaxy
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Quacker

I was measuring these packs before disasembly.

I am going to use the protection circuit and delivered
charger to charge them.

It just worries me that "UNUSED" cells would be below the
protection circuit point since one of the problems with
these cells is that you don't want to get them below
3 volts per cell.

I thought li-ions had very little storage leakage loss (unlike NIMH's which lose 1% per day).

T O D
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Old Jan 29, 2002, 01:11 PM
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Colorado Front Range, USA, EARTH, Sol system, Milkyway Galaxy
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Quacker one other question.

I charged the first pack up (which started out dead at the terminals) using the charger and
it seemed to charge ok.

When you say charge at c/10 have you done this
with a current supply or a series resistor in the
charging circuit.

If you wanted to limit the current to c/10 then a
~50 ohm resistor would limit the current to c/10
assuming the packs were at 4 volts or somthing
like that and that the charger would limit to 8.4 volts
out.
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Old Jan 29, 2002, 02:11 PM
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United States, CO, Longmont
Joined Jul 2001
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You should be a little worried about unused cells with low voltage. The leakage is very low, so the implication is that they have been hanging around for a long time. Perhaps a somewhat shorter time if the packs were not fully charged before storage. Such is the world of surplus.

The c/10 current is about the max that Panasonic recommends for getting the voltage up into the fast charge range. It's not a very important number as long as the current is kept low. Your resistor ideas sound good as long as the charger does not have some sort of circuit that gets unhappy and shuts off. Because of the possibility that one cell could be bad, and one good, I would observe the mid voltage while charging. I believe the safety circuit watches voltage this too, so an imbalance may terminate the charge.

Q
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Old Jan 29, 2002, 03:49 PM
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Berkeley, CA USA
Joined Apr 2001
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I got a couple of 'duds'. i will deal with them .
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