Pismo battery "successfully" revived

[Dennis Nedry]

I have a Pismo battery that went one day from holding a charge for an hour to not taking a charge, the light would not even blink on it. I took it apart and manually (eek!) charged the thing up to 12V using a very low amount of current. But yes it was normal DC, which may not have been the best method.

Anyway, it was flat so I didn't have any reason not to try. I charged it at only 200 mA for a LONG time and kept monitoring the temperature and voltage, and finally it got up to 12V. I stuffed it into my Pismo, and BEHOLD, the Pismo ran for over an hour with the processor maxed out and screen all the way bright.

There are some interesting things that happened, though:

-Before doing this, the battery reported a charge capacity of 2 mAh, and would not take a charge.

-After manually charging, capacity report jumped to 401 mAh (strange).

-In an attempt to initialize this, I ran the Pismo for a long time, and the % charge went down to zero within 15 minutes. Pismo continued to run for another 45 minutes at 0% reported charge.

-Further attempts to charge the battery from inside the laptop are successful, but battery light always blinks, even at 100%, and it will only charge to 401 mAh. It stops charging at this point when it obviously can hold much more.

It would be awesome to reset this little mAh capacity meter, maybe this battery can continue working normally then. I don't know why that reading went UP after manually charging, it would be nice if I could make it go up again. I don't think anybody really knows how to reset this though, I've never heard of anybody doing it.

It must be able to reset when you bring in a laptop battery to be professionally repacked, though! Otherwise none of those would take a charge. Should I try disconnecting the cells for a while and see what happens when I hook them back up?

 

[Bunsen]

Have you tried Battery Reset?

 

[Dennis Nedry]

I have not tried that yet. I'll see what happens later tonight.

I have been using Battery Health Monitor in Mac OS X to see the mAh values.

 

[Dennis Nedry]

It appears that Battery Reset is not compatible with Pismos unfortunately, but good try.

I wish I could just figure out what causes the mAh number to go up and do it.

 

[tomlee59]

With most lithium-ion packs, the fuel gauge software is adaptive. It needs a training period to get properly calibrated for a given set of cells. During that training period, the battery needs to be fully charged, then discharged to shutdown, a couple of times. Until it gets calibrated, expect odd behaviors, inaccurate capacity indications, etc. Although this chemistry does not suffer from the memory effect that NiCds, eg., are famous for, the digital fuel gauge can introduce artificial capacity reductions that behave much the same way. Running the pack through a full charge/discharge cycle from time to time helps keep the fuel gauge calibrated as the cells age.

 

[Dennis Nedry]

the battery needs to be fully charged, then discharged to shutdown, a couple of times.

I have done this once, but I'll try it a couple more times. It seems it won't charge to full capacity, at this point, but maybe a few charge cycles will help.

 

[Bunsen]

Good info there tomlee59. I got two hours of solid websurfing out of my $20 as-is Lombard battery last night on my first test run, but it went dead with no warning and the battery meter still reading about 25%. I guess that's the reason.