Strange power bank behavior

[Timothybil]

I have a couple of Attom Tech 2500 mAh power banks. They aren't much [two of them sandwiched together would be about the same size as a cigarette pack,] but they are small enough to slip into a shirt or pant pocket and carry in case a little extra power is needed. They have a single LED indicator that blinks red while charging, and turns blue when fully charged. I make it a policy of charging them every couple of months just to make sure they are fully charged if needed. I put one on charge this afternoon and nothing. No indication whatsoever. I left it thinking that maybe it had self-discharged to the point the LED didn't display. I checked it a little while ago [about three hours after starting to charge] and still no LED. So I left it plugged in, and plugged its charging cable into my phone, which was at 86% Well, the phone just indicated full charge so I went to unplug the Attom from the phone, and lo and behold there was the blue LED. My only theory is that the battery was so far down that it when it had recharged, for some reason that didn't trigger the signal circuitry. but the pass-thru charging of the phone triggered it. I'm going to keep an eye on the Attom, but am glad that so far it appears to still work.

 

[Lynx_Arc]

Some of the cheap power banks don't show a red LED if they are too deeply discharged until they are charged for awhile sometimes it takes a few hours and I've had one or two with bad red LEDs that didn't light up at all. I've bought several of them when I was getting them off Ebay for dirt cheap and with free shipping a few cost me a little over $1 to my house for plastic single cell varieties. I've managed to get a few of them that work with very low current drain devices and I've found some dimmable USB LED light modules that take super low current such that a single 18650 power bank can run for weeks without recharging.