Topband Navitas Prismatic Cells - Voltage (and uAmp current) between case and terminals???

[mhdgraphics]

I posted this on the Facebook group for BatteryHookup but I am not getting the info I need.

Just got my case of Navitas batteries and took one out to look it over.
The terminals look good though I dont see how they are insulated from the case.
So I took voltage readings relative to the case metal... Positive post to case is 0.46v Negative post to case is -2.70 v
Pos to Neg is 3.30v. (Just out of box)
Now - I also checked current (case to terminal) and got 150 uA at first and it started dropping down to 70uA.
Is this normal? Or is there a electrochemical reaction between the case and the rest of the battery?

 

[Horsefly]

Just FYI, I guess these are back in stock. I just went to the website and the description still said they were sold out, but the button no longer said sold out. It let me put in a quantity 8, so I went ahead and placed the order. I'll update here if the order eventually gets bounced or delivered.

 

[Luthj]

Is this normal?

Yes, the metal case is in contact with the electrolyte, and thus forms a pseudo cathode. So it will show a voltage differential to the terminals based on their chemical potential. This is why the case must be insulated from nearby batteries and grounded metal. A short here could cause the cause to slowly electrolysize into the electrolyte.

 

[michael d]

I posted this on the Facebook group for BatteryHookup but I am not getting the info I need.

Just got my case of Navitas batteries and took one out to look it over.
The terminals look good though I dont see how they are insulated from the case.
So I took voltage readings relative to the case metal... Positive post to case is 0.46v Negative post to case is -2.70 v
Pos to Neg is 3.30v. (Just out of box)
Now - I also checked current (case to terminal) and got 150 uA at first and it started dropping down to 70uA.
Is this normal? Or is there a electrochemical reaction between the case and the rest of the battery?

are you really trying to report milliamps? is uA 1 million for 1 amp? u stands for micron ?? correct? a micron is 1 million of a whole amp. I think.
in scientific measures that is a terribly small number.

Full name: microampere

Plural form: microamperes

Symbol: uA

Alternate spelling: microamps

Category type: electric current

but still, the best bet is to put nonconductive sheets between the cells.
i bought plastic chopping mats that are 11 inches by 14 inches in a pack of 2 for a dollar at the dollar store. that will make 4 plastic spacers when cut to size.
this was what I saw from my second vendor of Lishen 272Ah aluminum cased cells but his picture had some type of yellow plastic between the individual cells.
the plastic shrink wrap is a good start, but a better insulator between the cells is a good precautionary measure.
I also have them on top of a slick particleboard (not sure of what its coating is) for the base of the compression jig... to hopefully have the longest safe lifespan for the new LiFePO4 battery cells.

 

[mhdgraphics]

are you really trying to report milliamps? is uA 1 million for 1 amp? u stands for micron ?? correct? a micron is 1 million of a whole amp. I think.
in scientific measures that is a terribly small number.

No, I'm reporting uA microAmps...

 

[Horsefly]

No, I'm reporting uA microAmps...

So then, I think what everyone is saying is, you don't need to worry about it. Microamps is millionths of an Amp, so the 150 microamps or 70 microamps are so small that it doesn't mean anything for the lifespan of the cell or anything else. Don't worry, be happy!

 

[Gazoo]

So then, I think what everyone is saying is, you don't need to worry about it. Microamps is millionths of an Amp, so the 150 microamps or 70 microamps are so small that it doesn't mean anything for the lifespan of the cell or anything else. Don't worry, be happy!

The voltage and current measurements mhdgraphics posted are not a concern. It is concerning if compressing larger cells to make a pack and the PVC the cell is wrapped in wears to the point the cells make electrical contact with each other.

Since these cells are 25ah I don't think compression is necessary. But, for example, if I was going to tape them together, I would still put an insulator between the cells as a precautionary measure. IMO the plastic chopping mats michael d is referring to are perfect. Cheap but effective and gives one a little extra peace of mind.

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