PowerBoost 500 + Charger Doubt/Problem when fully discharged

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lasbainas
 
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PowerBoost 500 + Charger Doubt/Problem when fully discharged

Post by lasbainas »

Hello,
I have been using a PowerBoost 500 + Charger with no problem until today. The battery was fully discharged for the first time, and then I plugged in the the USB cable. The leds would then switch very fast and the battery would not be charged, neither the load would be supplied with enough voltage.
I noticed I could solve the problem by connecting the EN pin to ground. The charging starts fine after that.
Is this a normal behaviour? If so, what is the reason for it, and is there any way I can avoid it?
I can give more details on this issued if needed.
Thank you very much!!

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adafruit_support_mike
 
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Re: PowerBoost 500 + Charger Doubt/Problem when fully discha

Post by adafruit_support_mike »

Fully depleted LiPos have a tendency to plate metallic lithium out of the polymer if you apply full charging current to them. That produces low-resistance paths through the battery which can short and catch fire.

To prevent that, the chip that manages the charging process drops to a low-current preconditioning mode when the LiPo voltage is too low. For the PowerBoost 500C, that's about 20mA.

The boost circuit pulls its supply power from the LiPo charger, so a significant amount of that 20mA gets pulled away from the LiPo and boosted to about 10mA @ 5v, which probably isn't enough to power the load. The LiPo doesn't get enough preconditioning current to bring its voltage up, so the system sits in a "trying to do too much with too little" state until something changes.

Pulling the EN pin low for a few seconds is enough to precondition the LiPo, and allow the charger to kick the current up to the regular charging level.

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