Typically, a bank of 18650 Li-ion batteries is used in laptop power packs.
Each cell is nominally 3.7 V when fully charged. Circuitry in the cells puts
them into "sleep" mode at about 2 V. This can happen with any Li-ion battery
not used for a long time. All that is needed is a "kick start" at about 2 A
for a few seconds to get them above the threshold and wake them up. Some
battery chargers will do this, most won't. One needs to be cautious - if it
is overdone, there is a risk of explosion. I have done this with 18650 cells
from a "defunct" laptop power pack & used them in emergency lights. Also
with mobile batteries.
Alan C
-----Original Message-----
From: mike wilson
Sent: 26 December, 2017 1:26 AM
To: Pentax-Discuss Mail List
Subject: Re: Hint on reviving old rechargable batteries
I had a netbook, about four years old at the time, running on XP, that had a
"dead" battery. No problem, as I would just run it on the charger. I
changed
the OS to UBUNTU and !suddenly! the battery could charge. Checking the
charge
history (which I could not do in XP) I found that the OS had checked the
battery, found nothing wrong with it and proceeded to charge it.
Clearly, there was something in XP preventing the charge sequence. You
could
argue that there was something going on to protect the computer but Occam's
Razor suggests to me that it merely counted out time or number of charges
and
decided at that point that the battery was toast and refused to play.
I think a truly dead battery is a very rare occurrence.
On 25 December 2017 at 10:51 Alex Sarbu <[email protected]> wrote:
Indeed, "intelligent" chargers would detect "bad" batteries and refuse
to charge them; and often you can jump-start them in a "dummy"
charger. Apparently that's a feature.
You could use the BC 900 to test or refresh the batteries (don't leave
the charger unsupervised! - nor near flammable materials). I assume
the old batteries had no signs of physical damage/leaks/corrosion.
Alex
On Tue, Dec 19, 2017 at 8:00 PM, Igor PDML-StR <[email protected]> wrote:
>
>
> I've discovered that NiMH AA batteries that were in the old Pentax DS
> body
> (remember those?) were completely dead.
> I tried to put them in renown La Crosse charger (BC-900), and that
> refused
> to charge them.
>
> I was able to resuscitate them by putting them into a "fast" Duracell
> charger, and then trying to start charging a few times by plugging that
> charger into the power outlet. At first, that charger also refused to
> charge
> them, but after 3-4 attempts, the first pair started charging, and then
> (after that pair was somewhat charged, so that I can put them in
> BC-900), I
> did 2-3 more attempts with the second pair, and it worked.
>
> I suspect BC-900 was a bit too gentle with the initial charge attempt.
> But it is also possible that it could have worked if I tried a few more
> times.
>
> I am not sure how well these batteries will work, the time will show.
> But at least this allowed to charge them up.
>
> An alternative would be to use a 1.5 V power supply, but this trick was
> simple enough.
>
> I thought this might be useful to somebody.
>
>
> Igor
>
>
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