On 2/12/2019 7:26 PM, malua mada! wrote:
On Tuesday, February 12, 2019 at 3:21:32 PM UTC-8, Mike wrote:


I can't think of any place a jumper will be useful.
Don't even think about shorting the BMS chip.

blush... isn't a bare metal battery better than a dead one?

No, it isn't. Lithium batteries need a lot of care.

The cells are protected against under/over voltage. You need all that.
My limited experience with this battery is that it shuts off charge
when either cell reaches 4.2V.
I prefer to quit before that, around 4-4.1V/cell

I have a little 9V charger, blissfully ignorant of balancing acts.
"Little charger" is too vague to be helpful.
If it's a little charger designed to charge these EBL batteries,
you're good to go. If it ain't, don't use it.

The battery protection circuit seems to be reasonably good at shutting
off the charge at 8.4V, but that's the protection circuit, not normal
operation.


https://imgur.com/pAjauT7

I poked a tiny hole in the side of the package so I could poke a probe in
and access the point where two batteries connect in series.

Mine looks the same. I totally missed the tap to the series connection there.

If I ever need it again, I can use that and the two 9V terminals
to charge each cell individually to 4V. I'm hoping that the
battery will shutdown output at a voltage higher than the voltage
that prevents charging. Not had to test that yet.

Maintaining balance is a proactive activity.
(swaying precariously) tisn't what happy consumers sposed to have to do?
No, it's not. But that's the price we pay for the other benefits of the
technology.
If you keep the battery voltage within the shutdown limits, I expect it
works pretty well.
It's when you go beyond the safe limits that cell differences start
to manifest more visibly as imbalance.

It's been three years. Probably should open up all the meters
and recharge 'em.

amen! and get rid of the devices that just stay on to the last millivolt.
Meanwhile, I appreciate the knowledge that allows me to wake these (still costly) batteries from their self induced coma... wish it were easier.

It's not rocket science. Set your bench supply to 4.0V. Put a 1K
resistor in series with it and charge one cell at a time. When the
voltage across the resistor gets to about zero, do the other one.
I typically let the battery sit for a day after and check the balance again.
Tweak it till they're within a few millivolts after a rest.
That's overkill, but why not...

Note that I did NOT say take any random usb 5V charger and use it.
MUST stay below 4.2V.
If you don't have a way to generate 4ish volts, throw the batteries away.