i charged up a lipo (unbalanced) and the readings said one cell was a little over 4.26v and the other cell was about 3.88v. the automatic shut off on the passport ultra is 4.26v. the total of the two cells was about 8.4v, which i'm assuming it cut off at. however, i thought the charger would have cut off at the 4.26v the one cell had reached, preventing damage to that cell.

The question that begs to be asked is: Why are you not balancing this battery? With it being that far out of balance it's only going to get worse. You are asking for a fire.

Edit: Check your math again. 4.26 + 3.88 = 8.14 So, lucky for you it appears the charger did cut off on the high cell reading.

Your results illustrate exactly why you need to balance lipos when they're charged. You've overcharged one cell and have undercharged the other, yet the total voltage is about where it's supposed to be. Cells are diff and have diff internal resistance that cause them to charge at diff rates unless they've been matched, which yours have not been. This is the reason you balance charge - the balancer keeps them within a tolerable difference voltage wise.

Does this charge sound right? No, its not right. How can the charger tell the voltage for an individual cell when the balance wires are not hooked up? That's what the balance wires provide - they're there so the charger can read the voltage in the individual cells. the charger would have either maintained the high voltage cell at 4.2v while still charging thr other cell, or would have shut the charge down. Lipo cells shouldn't be charged any higher than 4.2v/cell.

Discharge the lipo until the overcharged cell is back below 4.2v before its damaged. Then connect the balance wires and let the charger balance charge back to full voltage or some storage vslue like 3.85v or 65% if you're not going to be using it for a while.

lol. i have tried to balance this battery. both cells continue to rise, unfortunately the cell with the higher cell volt continues to rise faster then the other one. in fact the gap increased between the two cells. i have also tried to discharge, but they discharged completely uneven and made balancing more difficult. i had someone put it on a venom charger and it would not do anything with the battery

You must ALWAYS use balance charge with this pack, else you risk a fire. If you have the option to exchange the pack you should do that right away. If not, you might be able to make it work for you.

What is your charge rate? Most balancers have a 0.2A discharge on the higher cell. For packs like yours this is not enough to overcome anything over 0.2A charge rate. Even if you are only charging at 1A, the higher cell is getting 0.8A, while the lower gets the full 1A. If the cells are anywhere close then this will be plenty to balance the pack, but yours does not sound very close.

Try charging the pack at 0.1A or 0.2A. This will take forever, and you will have to check on it often.

OK, I remember this now - you had a post thinking it was maybe a prob with the charger a few days ago. Now it looks like its a bad lipo. If another charger doesn't do any better or any diff with this, then I'd suspect its the the lipo. Do you have another lipo you can try with your Passport charger - it it balance charges another lipo, then you'd at least know there is nothing wrong with your charger.

Can you rig up a two prong connector that you could use to charge just the low voltage cell thru the balance connector at low rate like 0.2 - 0.5amp? You can make one from deans mini plug and using a DVM you could tell which pair to connect with on the balance connector. I have a charger that's made just for this and use it in cases like this where a cell won't come into line with the others. Its usually a last ditch effort to save a lipo.


But, it sounds like you may have a cell thats going/gone bad.