Issue with AW LifePO4 in series

[cland72]

Hi all,

I've been using my AW lifepo4 batteries for a few weeks now, and in my single cell lights they work great. However, I've been using them in series in my Surefire A2L-RD and have noticed that it went into dim mode very quickly. I removed the batteries and put them on my multimeter, and one read 3.2v, the other read 1.6v.

Any idea what's happening here? Shouldn't the voltage drop be equal across both batteries?

 

[Robin24k]

If both batteries had been fully charged, then the cell with the lower voltage is weak/defective and will need to be replaced.

 

[cland72]

If both batteries had been fully charged, then the cell with the lower voltage is weak/defective and will need to be replaced.

Thank you. I'm going to run them down again today and see if I can duplicate the problem. I'll contact AW if it happens again. I appreciate the info!

 

[Robin24k]

What charger are you using with the batteryes? Make sure that you're using a charger that's designed specifically for 3.2V lithium phosphate batteries. Although nothing bad will immediately happen if you use 3.7V lithium-ion battery chargers, it will overcharge and damage the battery.

 

[BVH]

Also, are the channels separate so that when one finishes, the other is still independent to do whatever it needs?

 

[cland72]

What charger are you using with the batteryes? Make sure that you're using a charger that's designed specifically for 3.2V lithium phosphate batteries. Although nothing bad will immediately happen if you use 3.7V lithium-ion battery chargers, it will overcharge and damage the battery.

Ultrafire WF-138 on the 3.0v setting

Also, are the channels separate so that when one finishes, the other is still independent to do whatever it needs?

Not sure, can you speak to that now that you know which charger I'm using?

 

[Robin24k]

You need to get a 3.2V lithium-phosphate charger, it's not going to charge the batteries correctly with the 3.0V setting.

 

[cland72]

What would you recommend that is inexpensive but works well?


Sent from my iPhone using Tapatalk

 

[donn_]

I have an older Tenergy 2-bay charger made for LiFePO4 123 cells, and it works just fine, although a little slow. You can get them at Amazon, Battery Junction, etc.. I also have a faster set-up (these cells can take fast charges with no ill effects) I put together with parts from BatterySpace.

 

[Robin24k]

I'm using the K2 Energy kit from SureFire:

http://www.surefire.com/sf2r-kit01-charger-kit.html

Another choice is Tenergy, but I'm not convinced about the quality of their cells (I doubt they are really 750mAh). K2 Energy has better batteries, but the Tenergy charger may be better.

I have an older Tenergy 2-bay charger made for LiFePO4 123 cells, and it works just fine, although a little slow.

How slow is it? K2's charger isn't fast either, but it only has one channel, which charges two cells in parallel. Does the Tenergy charger have two channels?

EDIT: Found a link to the Tenergy charger only, but the kit with 2 x 123A is only $4 more...

http://www.ebay.com/itm/390404922359

http://www.ebay.com/itm/330434752963

 

[Viking]

LifePO4 cells are named 3.0 volt as well as 3.2 volt. There seems to be a little confusion about that some times


I'm almost certain the 3.0 volt setting is meant for LifePO4 cells , though theoretically it could be for 3.0 volt Li-ION. But I don't think that's the case.

 

[donn_]

How slow is it? K2's charger isn't fast either, but it only has one channel, which charges two cells in parallel. Does the Tenergy charger have two channels?

I think it's only 1 channel. It's model # PH-123A-3.0, 360mA output. It takes 3-4 hours to do 2 cells. The batteryspace charger puts out 750mA. It charges 1 cell in less than 45 minutes.

 

[Robin24k]

LifePO4 cells are named 3.0 volt as well as 3.2 volt. There seems to be a little confusion about that some times

Lithium-phosphate does not have a nominal voltage of 3.0V, so it would be incorrect to call them 3.0V. By the time lithium-phosphate cells discharge to 3.0V, there's not much capacity remaining.

I'm almost certain the 3.0 volt setting is meant for LifePO4 cells , though theoretically it could be for 3.0 volt Li-ION. But I don't think that's the case.

It looks like the 3.0V setting is intended for lithium-phosphate, but it does not look good. Charge should be terminated around 3.6V to 3.65V, but the WF-138 overcharges to 3.8V.

http://www.candlepowerforums.com/vb...sting-of-Ultrafire-WF-138-and-WF-139-chargers

I'm not sure about how the Tenergy charger performs, but K2 Energy's charger will not overcharge the batteries. They come off the charger around 3.65V.

 

[Robert_M]

I use the Tenergy model 01207 charger; technical info is here. The charger spec claims 500mA charging current; however, it is actually 250mA per channel (250mA x2) which is printed on the bottom of the charger. It has two independent channels. Output is 3.65V at 250mA per channel. It typically takes 2 hours to charge the Tenergy 750mAh LiFePO4 batteries which are actually closer to the minimum spec of 450mAh shown here. I also use this charger to charge my AW LiFePO4 cells.

 

[Viking]

Robin24k

It's like Li-ion cells. Some are named 3.6 volt , others are named 3.7 volt depending on the brand.

Same voltage confusion goes around for lifepo4 cells (3.0/3.2 volt).
The question of the most correct term for LiFePO4 cells , is a thread worthy of it self

 

[Robin24k]

It's like Li-ion cells. Some are named 3.6 volt , others are named 3.7 volt depending on the brand.

There are both 3.6V and 3.7V lithium-ion cells because nominal voltage is different. Sometimes, this is because of how nominal voltage is calculated, but that's not always the case. For example, the Panasonic NCR18650 is a 3.6V lithium-ion cell that operates at slightly lower voltages than 3.7V lithium-ion cells.

Unless there are lithium-phosphate cells that are 3.0V nominal, calling it a 3.0V cell is incorrect. As for what they are called, I got into the habit of calling them "lithium-phosphate" because LiFePO4 is too technical for most people...

 

[BenChiew]

From my observations, assuming both cells starts off equally charged, the cell closer to the head will deplete more than the one on the tail.

But in your case, there is a problem. The variance should not be so big.

 

[JCD]

Ultrafire WF-138 on the 3.0v setting

I've been using that charger to charge my LiFePO4 cells for about 4 years, with excellent results.

 

[cland72]

I've been using that charger to charge my LiFePO4 cells for about 4 years, with excellent results.

Then I wonder, am I using it wrong? Should I put it on the 3.6v setting instead of the 3.0v setting?

Everyone else, thank you for the replies.

 

[Robin24k]

What voltage does the charger output on the 3.0V setting (look on the bottom of the charger for output voltage and current)? Also, check the voltage of fully charged batteries.

You shouldn't use 3.6V or 3.7V lithium-ion charging settings to charge lithium-phosphate batteries, it will overcharge the lithium-phosphate.