Help identifying 240mm x 160mm pouch chemistry

[RC_guy]

Hi all,

I'm trying to identify the chemistry of a 3-4 year old prismatic pouch that measures 240mm*160mm*7mm
I'm pretty familiar with most common chemistries from being in the RC hobby for over 20 years and buildding my own packs of LIPO, LIFE, etc.

I would have assumed they were LiFePO4 but what has me puzzled is that after this time, the voltage of all cells is between 3.5 to 3.6V
The cells have never been used and never connected together.
I thought that charging LIFE packs was done to 3.6V but then the voltage should settle at 3.3V

This is from someone who passed away and could these be a LIPO battery? I don't think they make them that big?

Thanks for the help

 

[amberwolf]

There's plenty of various chemistries in large pouches. Attach a picture of the pouch to your post using the attachements tab. Include both sides, and if possible closeups of every marking on it, as they may help us help you find the origin.

 

[RC_guy]

There are no markings of any kind.

Could I just charge in lipo mode (to 4.2V) while monitoring temperature and if they don't start heating up, all is good?

Thanks,

 

[Hillhater]

There are no markings of any kind.

Could I just charge in lipo mode (to 4.2V) while monitoring temperature and if they don't start heating up, all is good?

Thanks,

It would be safer and more revealing to monitor and plot a discharge curve (from their current voltage point) and use it to identify both the state of charge, possible chemistry, and the capacity of the cells...which may ultimately help identify the source manufacturer.

 

[RC_guy]

There are no markings of any kind.

Could I just charge in lipo mode (to 4.2V) while monitoring temperature and if they don't start heating up, all is good?

Thanks,

It would be safer and more revealing to monitor and plot a discharge curve (from their current voltage point) and use it to identify both the state of charge, possible chemistry, and the capacity of the cells...which may ultimately help identify the source manufacturer.

 

[amberwolf]

Well, one thing to consider is taht the one(s) with an X on them might be bad, if they were marked by the previous owner during their testing of them. (which you may not know about).

IF you're going to charge one up to see what it goes to, I'd recommend doing it while monitoring current and voltage over time, so that you can see when voltage rapidly climbs while current drops that that is the end of their "real" charge curve, most likely.

Probably a safer sign than heat.

EDIT: the other twp posts above showed up after I hit submit, so basically show the same thing I mean, I think.

 

[Hillhater]

Re the discharge plot ...very unusual profile ?
What is the time base ?..mins ?
What discharge rate ?
DIscharged capacity ?

 

[john61ct]

I reckon early LFP, they used to say go higher than nowadays.

Do a precise capacity test at 0.1C and calculate energy densities to confirm.

Might even be A123 fresh out of MIT

3.45Vpc termination at a low C-rate, say under 0.4C would be my 100%

Likely to settle at 3.33-3.35Vpc after resting isolated.

Fast charging up to 1C maybe stop at 3.50V, but less conducive for longevity.

Low C-rate discharging, stopping well before say 3.1V

you might get 5000+ cycles and 15-20 more years.

 

[RC_guy]

Sorry all, the discharge graph had explanations but I screwed up something on my phone and they did not appear.

Discharge rate was 5.6 amps.
Time was in minutes.

I'm curious if these are LIPO because after 5 years of inactivity, from new condition, they were at 3.5 to 3.7.
With this much IR, I charge to 3.60 in 300mha but at discharge, it took 3500mah to go from 3.7 to 3.05 at 5.6 amp discharge rate.

I do not understand how to do a more accurate IR test?

Thanks

 

[john61ct]

Just realize "LiPo" is just packaging technology in get better density, gelified electrolyte, no hard casing.

Over the years there have been radical shifts in chemistries used, and even now there can be lots of variations.

The V vs SoC mapping would be radically different after many years.

Was that graph at real CC?

 

[RC_guy]

Just realize "LiPo" is just packaging technology in get better density, gelified electrolyte, no hard casing.

Over the years there have been radical shifts in chemistries used, and even now there can be lots of variations.

The V vs SoC mapping would be radically different after many years.

Was that graph at real CC?

From my understanding a LIPO can be charged to 4.2V and without strain, discharged to 3.6-3.8V.
a LIFE will be charged to 3.6V and after a few hours of not being charged any more will settle around 3.3-3.4V.
They can then be discharged to around 2.6V and 2V being the absolute minimum.

I'm thinking these are LIPOs because they rest (after isolating for many years) at 3.5-3.7 not at 3.3

This discharge was constant at 5.6 amps. And my Milliamp readings from the charger are consistent with this:

5 minutes = 460mah
10 = 920mah
20=1860mah
30= 2780mah

 

[john61ct]

I am not saying LFP for sure, just consider the possibility.

I have seen quality LFP cells sit untouched for over ten years did not lose one iota of capacity nor any decline in sitting voltage, at. all.

And as I said in early days they spec'd high voltages, so even if just a "surface charge" (no significant capacity represented by the higher voltage) it is possible they just held it stored after being fully (over fully) charged.

Other LI chemistries nominal 3.6-3.7V were not nearly as well developed back then

still don't hold voltage and capacity as well just sitting in storage in warm temperatures

and do not show a smooth curve like that all the way to 3.0Vpc

In fact you may find there is another 20% of mAh capacity going from 3.0 down to say 2.6V.

Another test would be, added mAh discharge capacity from a termination charge at

3.45, 3.50, 3.55 and 3.60Vpc

If it is more than say 15-20% of the total then keep going up to 4.05 or so

and if that does add real mAh capacity then yes I doubt it is LFP.

And then just treat them as regular LI nominal 3.6-3.7V, charge to 4.15V stop discharge before 3V, as if NMC or LMO, LCO whatever does not matter.

 

[Hillhater]

There is a spreadsheet listing most of the EV type cells on this thread .
https://endless-sphere.com/forums/viewtopic.php?f=14&t=89680&p=1570834#p1570834
Its in a Jan 2020 post .
If you can weigh the cell it may help you identify it on that list.