1100mAh 3.2V LIFePO4 rescue if there stored to 0V (selfdischarge new cells)

5 replies [Last post]
terramir
Offline
Joined: 07/21/2008
Points: 33

Question here is the follwoing I can get my hands on many LiFePO4 cells HW 18650P 3.2V 1100mA GD25 Anyway I can get some dirtcheap as in for next to nothing one catch they were not charged during storage and self discharged to 0V the people told me I should be able to rescue about 15% of the cells with a capacity of maybe 600 to 800 mAh.

Any rescue techniques/ experiances with 0V LiFePO4's of the cheaper variety, I know the 123 system batteries have survived that (at least from posts on RC forums).
Please let me know what you know, and what recommendations you have for rescue attempts like for example: charging at like 5mA till it reaches a certain voltage etc.

terramir

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.
reikiman
reikiman's picture
Offline
Joined: 11/19/2006
Points: 8456
Re: 1100mAh 3.2V LIFePO4 rescue if there stored to 0V ...

0v is way far below the low voltage cutoff of LiFePO4 cells. As I understand it when the voltage falls below the low voltage cutoff the chemicals change state to where they cannot be recharged.

I would suppose you could charge those cells and if some hold a charge then they are okay at diminished capacity, as you say. But I doubt you'll get many usable cells and they won't behave as well as usual.

I tried this recently with the Headway battery pack I have. Two of the cells arrived reading at 0 volts. I took one of the spare wallwarts lying around, it was one that produced 5v at 100mA or so and hooked it up to the battery. Over a few hours the voltage rose to a reasonable level and then the regular pack charger and BMS began to work. It managed to hold a charge for a short time but within a couple hours of removing the charger the cells read 0v again.

__________________

- David Herron, Green Transportation Examiner, Green Transportation Info, The Long Tail Pipe, Electric Race News, davidherron.com, 7gen.com, What is Reiki
- Charger bike (rebuilt), Electrified Electra Townie, 1971 Karmann Ghia

terramir
Offline
Joined: 07/21/2008
Points: 33
Re: 1100mAh 3.2V LIFePO4 rescue if there stored to 0V ...

well investing 40 bucks for 200 cells is not much and it will be worth it if I only get like 30 usable cells but it definetly be worth it just for the learning experiance. I wonder if methods would have any influance on the cells
terramir

terramir
Offline
Joined: 07/21/2008
Points: 33
Re: 1100mAh 3.2V LIFePO4 rescue if there stored to 0V ...

ended up buying 100 cells I have some wierd issues some of em had a voltage level above 2V but even the ones below seem to have the same issue they seem to not charge above 3.3V but for 24 hours so far they are seemingly holding a charge(staying at 3.3V) I have to experiment with the ones that are totally at 0V but it seems like I got about 17 out of 100 that are working just that the voltage doesn't rise to 3.65 anymore which is strange.
I'll have to do some experiments with them before I can really say what is truely going on but seeing your post at least gives me hope for the ones that weren't 0V updates later

Iccarus
Iccarus's picture
Offline
Joined: 12/20/2008
Points: 347
Re: 1100mAh 3.2V LIFePO4 rescue if there stored to 0V ...

I had a mishap with a couple of my thundersky 40ah cells. They got shorted briefly and when I checked the voltage they were at 1.15v and 1.1v. I trickle charged them with a hobby charger till I got them to about 2.5v then I put them back in the pack (which I discharged first) and then charged them with my Thundersky charger. They have been behaving fine so far but I'll keep an eye on them.

__________________

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycle Analyst mounted in 48v Lipo 30AH battery Box. 16kw in an 89lb. Trike! O-54mph/5sec

terramir
Offline
Joined: 07/21/2008
Points: 33
Re: 1100mAh 3.2V LIFePO4 rescue if there stored to 0V ...

hmmm gotten almost all of the ones charged that were above 0V although it seems like with my manual charging method 3.3 something Volts is the cut off point, I also think because of the long storage time some of these cells will have to be cycled with slight discharges till there completly back in shape as far as they can be. I am right now charging 5 0V and 5 .4 and below cells. it's taking a long time considering the max I'm feeding the cells till they reach 2V is like 30 to 45 mA and once they reach about 2V I start feeding them 90mA and then a max of 160mA from around 2.5V on. Seems like these very low voltage and 0V cells have quite the hard time charging but it seems different for every cell. Some of the 0V cells are up to over 2.5V while others are still below 1.5V in good time I suspect I will be able to revive some of the 0V cells, however some probably will be a lost cause. the true test will be of those cells that Have charged keep a voltage lever around 3.3 to 3.2V for at least a week and then the cycling tests will begin.
keep you guys posted
terramir

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.
Motenergy ME-0907 Brushless DC Permanent Magnet Motor 3-Phase Permanent Magnet Brushless Motor equivalent to the ETEK
Customize This