Eagletac 3400mah protected - questions

One missed call

Newly Enlightened
Joined
Jul 26, 2013
Messages
92
Hi all

I am hoping I can get some feedback on a couple issues I have with Eagletac 3400mah batteries:

Some background:
- Batteries are new and part of a larger batch
- Only used 1-2 times
- checked voltage before/after use and charge
- charged using a VP1
- stored in a Pelican case

This morning I checked all of my Eagletacs which have been stored for the past 5 months. When I stored them, they were all charged to 4.0V. Now 3 of them read 2.8V, 2.9V and 0.0V. The other cells read 3.7-3.8v.


Bad cells?
 

Tachead

Flashlight Enthusiast
Joined
Jan 3, 2015
Messages
3,872
Location
Northwestern Ontario, Canada
Hi all

I am hoping I can get some feedback on a couple issues I have with Eagletac 3400mah batteries:

Some background:
- Batteries are new and part of a larger batch
- Only used 1-2 times
- checked voltage before/after use and charge
- charged using a VP1
- stored in a Pelican case

This morning I checked all of my Eagletacs which have been stored for the past 5 months. When I stored them, they were all charged to 4.0V. Now 3 of them read 2.8V, 2.9V and 0.0V. The other cells read 3.7-3.8v.


Bad cells?

All cells have a certain amount of self discharge. If you are going to be storing them for that long, you need to check on them periodically(I recommend once a month) and cycle them as needed. Also, a lot of lithium chemistries should be stored at around 50% capacity when stored for long periods of time as storing at full voltage can be harder on them.
 
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tandem

Enlightened
Joined
Aug 5, 2010
Messages
874
Location
Vancouver, BC
4.0V is closer to 80%.

I've had cells stored at 80% exhibit very low self discharge over similar periods of time. Something is wrong with this picture.
 

One missed call

Newly Enlightened
Joined
Jul 26, 2013
Messages
92
All cells have a certain amount of self discharge. If you are going to be storing them for that long, you need to check on them periodically(I recommend once a month) and cycle them as needed. Also, a lot of lithium chemistries should be stored at around 50% capacity when stored for long periods of time as storing at full voltage can be harder on them.

Yes, I know storing fully charged isn't good for overall life of the cell. However, storing at 4.0v and finding 3 out of 20 cells at 0 - 2.9v is surprising. Especially when the others are all 3.7-3.8v. How does a cell show 0.0v? Could the protection circuit have been tripped while in storage???
 
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tandem

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Joined
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Messages
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Location
Vancouver, BC
How does a cell show 0.0v? Could the protection circuit have been tripped while in storage???

That does seem to be the case. It may come back; decent chargers will make an attempt to bring voltage over the trigger point but will give up if the cell doesn't respond within T time. If it does come back you'll want to keep a close eye on that cell, make sure it's marked.

Maybe we should ask about it's life history - what sort of lights were the cells used in? Single cell lights or multi-cell lights?
 

One missed call

Newly Enlightened
Joined
Jul 26, 2013
Messages
92
That does seem to be the case. It may come back; decent chargers will make an attempt to bring voltage over the trigger point but will give up if the cell doesn't respond within T time. If it does come back you'll want to keep a close eye on that cell, make sure it's marked.

Maybe we should ask about it's life history - what sort of lights were the cells used in? Single cell lights or multi-cell lights?

I have already decided to scrap that cell. In fact all 3 will have to be disposed of. I am not going to take any chances. That being said, I don't understand how this could happen while in storage, especially the one reading 0.0v. When it was stored the charge was ~4.0v. How could protection circuit have been triggered while in a Pelican case with the ends of the battery only touching the rubber insert and the battery being snug inside.

History of the cells...used once at most (some were never used) in multi cell HQ torches. Checked before and after use (nothing unusual noted) and then again after charge/before storage.
 
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