"empty" battery voltage for IMR cells?

[Mjolnir]

I have a pair of the 4000 Mah IMR 26650's from BatterySpace. Since they don't have protection, I was wondering if there is any general consensus on what voltage (without load) to recharge the cells at. I know that for LiCo cells it is about 3.6 Volts, but I have been unable to find any agreed upon numbers for IMR cells.

 

[LuxLuthor]

I have a pair of the 4000 Mah IMR 26650's from BatterySpace. Since they don't have protection, I was wondering if there is any general consensus on what voltage (without load) to recharge the cells at. I know that for LiCo cells it is about 3.6 Volts, but I have been unable to find any agreed upon numbers for IMR cells.

My personal guideline with an average quality cell.....from reading various Lithium Manganese guidelines are when it has a resting voltage of about 3.4 to 3.5Volts. While under load these go well below 3.0, once they start dropping, you should err on the side of being conservative to avoid damage.

When I use them in AlanB or JimmyM's regulators, I set the low voltage protection at 3.1V, knowing that will catch it on a fast dropping, nearly empty curve. When the load is removed, voltage will bounce back up to 3.4+

If you are seeing the cell in the 3.2-3.3V range, by the time you removed the load and tested it, you can be pretty sure it has been sucked of life. This is more of a concern with low amp loads (<1.0 A) which drains so slowly you may not notice the dimming until it is below 2.5Volts. Note the curves we did here of these C & D IMR cells.

 

[VidPro]

yo lux, i am confused here, which isnt a hard thing for me

Isnt an IMR cell a Lithium magnesium? and a li-Fe a lithium iron cell?
and dont they both have different voltage specs?

and the 4000ma battery space li-mn cell here
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=5161
with the data sheet here
http://www.batteryspace.com/prod-specs/5161.pdf


and the li-fe version only gets to some 3400 ?
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2385

and then you list rates and specs for a li_fe, under a IMR link. mabey the link points to the wrong post? even though the info in This above post still sounds all correct for the IMR

so many abreviations, so many chemistries, so many numbers, so little time :shrug:

 

[LuxLuthor]

yo lux, i am confused here, which isnt a hard thing for me

Isnt an IMR cell a Lithium magnesium? and a li-Fe a lithium iron cell?
and dont they both have different voltage specs?

and the 4000ma battery space li-mn cell here
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=5161
with the data sheet here
http://www.batteryspace.com/prod-specs/5161.pdf


and the li-fe version only gets to some 3400 ?
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2385

and then you list rates and specs for a li_fe, under a IMR link.

so many abreviations, so many chemistries, so little time :shrug:

IMR is Lithium Manganese (not Magnesium). LiFeP04 (Lithium Iron Phosphate) are indeed totally different safe chemistries.

Nominal of each is 3.7 & 3.3V respectively. However, I was answering OP question on how low before recharging the IMR. It would be even lower if he was using LiFePO4 before needing to recharge. I gave the wrong link as you noticed.

The link I should have given is here. Sorry.

 

[VidPro]

cool, now i have both links