diy solar

diy solar

Old new CALB cells !

benja.min47

New Member
Joined
Oct 25, 2020
Messages
50
Hello,

I found a person in my country who sells CALB 40Ah (lifepo4) cells, following the abandonment of his project. The cells are new but they are 3 years old and have never been recharged. Do you think there is a risk in buying these cells?

thank you,
Ben
 
Yes. There is always a risk to purchasing used cells, unless you know and trust the seller to provide a truthful accounting of their source and history.
 
Yes. There is always a risk to purchasing used cells, unless you know and trust the seller to provide a truthful accounting of their source and history.
The cells are new (they have never been fitted). On the other hand, they remained stored for 3 years without charge. Is this a problem for this technology?
 
The cells are new (they have never been fitted). On the other hand, they remained stored for 3 years without charge. Is this a problem for this technology?

New? Sounds like they are 3 years old to me. I would say they are "unused."

Clarify "without charge" - are they in the as-received condition, or were they depleted and placed into storage?

LFP cells deteriorate in storage. The conditions of storage (state of charge and temperature) dictates the severity of the deterioration.
 
I am sorry i am french and i use a translator. You are right, the exact term is not used. The seller says the voltage is at 3.23v and the internal resistance at 86 miliOhm.
 
If the information from the seller is truthful i would treat the cells as if they were new.
 
Si les informations du vendeur sont véridiques, je traiterais les cellules comme si elles étaient neuves.
Okay. thank you. the fact that they have remained 3 years without load does not pose a problem then?
 
Are those measurements recent? I would ask for proof that those measurements have been made recently.
 
If they measure between 3.20 and 3.29V, they should suffer from negligible deterioration from storage for 3 years if they weren't stored in a hot environment (35°C+).

86mΩ is concerning. That's very high for this type of cell, but it depends how it was measured. If all of them have a similar internal resistance, then that is a good sign.

I would confirm all voltage and IR measurements on each cell prior to purchase.
 
86mΩ is concerning. That's very high for this type of cell, but it depends how it was measured. If all of them have a similar internal resistance, then that is a good sign.
Well worth asking what kind of instrument was used to make that measurement.
 
It's a matter of trust as pointed out by others. In my day, it was not uncommon for those selling used A123's to give them a charge prior to shipping so that when they arrived at your door, they were at 3.2v.

But then later only discovered that they had a very high self-discharge rate.

Used or even new-old-stock is always a gamble. Like using someone else's toothbrush. :)
 
Like using someone else's toothbrush.
I used to work some as a Iron Worker...Sometimes a coworker would ask to borrow my welding helmet, I would always say, that would be like reusing someone else's condom....

Batteries are a little different though if you have the time/tools/skill to test I believe.
 
I used to work some as a Iron Worker...Sometimes a coworker would ask to borrow my welding helmet, I would always say, that would be like reusing someone else's condom....

That’s just silly - you can’t put a welding helmet on inside-out.
 
Okay. thank you. the fact that they have remained 3 years without load does not pose a problem then?

No - 3 years unused isn’t a significant issue. As others have said, you are relying on the seller being truthful, that is the only issue.
 
Hi,

I don't know which tool the seller used to measure but here is the datasheet.
How many Ah do you think the cell can provide?
 

Attachments

  • 7e137cbf041ffd5e7f3b27e237501dd21efc02dc.jpg
    7e137cbf041ffd5e7f3b27e237501dd21efc02dc.jpg
    121.6 KB · Views: 8
Back
Top