"DEAD" Battery Charging

[paragon]

Lady Ada was discussing a charger that works for the batteries that will not charge if the voltage goes too low.
This particular charger will charge these batteries back up.
I went thru month's of "New Product" Videos but, I can't find it.
Can you help?

Thanks,

[adafruit_support_mike]

The MCP73831 and MCP73833 LiPo charge controllers have a 'preconditioning trickle charge' option that will bring deeply depleted cells up to a level where it's safe to charge them normally.

These chargers from our shop use one of those two chips:

https://www.adafruit.com/products/259
https://www.adafruit.com/products/1304
https://www.adafruit.com/products/1904
https://www.adafruit.com/products/1905

[stevenrice]

When the charger trickle charges what do the lights do? I have a 1200 mah battery that when its connected to the charger the red light is solid then the green light kicks on after a minute.

[adafruit_support_mike]

Officially there's no difference in the LED state between precharge current and regular charging. You just get the yellow "charging" LED. In practice, when I've charged deeply depleted LiPos I've seen the LED flicker as the current jumps up from a few microamps to 100mA. That usually happens within a few seconds, because LiPos are ridiculously good at developing voltage from stored charge.

The pattern you're seeing means the LiPo is probably dead. The red LED means the cell isn't accepting current the way the charger thinks it should, and the green LED means the charger has basically given up.

Most LiPo cells contain a built-in protection circuit that prevents them from charging once the cell has been discharged too far. Without some kind of charge the lithium polymer can crystallize, which creates low-resistance paths through the cell. If the paths get too long they can short the cell and set it on fire. The protection circuits keep that from happening.

The LiPo charging cycle has several "something's wrong here" points, and the charger control chips will stop trying to send power to a cell that doesn't behave as expected. The protection circuits deliberately feed the charger bad information to make the charger shut off the current.

The first step is to make the charger announce an error if it's capable of doing so. Usually that involves shorting the precharge current to GND (or some fixed voltage) so the charger sees a battery that isn't responding to current (red LED). Some chargers don't have status LED outputs though, so the second step is to pretend the cell is fully charged and doesn't need any more power from the charger (green LED).

[stevenrice]

Thank you for the very informative information I figured the battery died but now I have an extra JST connector :)