IMPORTANT: Does pumping 4.5 volts into a Lithium Ion Cell constitute abuse?
SOLICITING OPINIONS – Should the seller be considered responsible?
I was told that I had shipped 3 defective batteries to a fellow BLF member that used a hobby charger to charge ONLY ONE cell in “balance mode” and the user admitted to pumping at least 4.5 volts into the cell. He claimed that we had sent him defective cells and asked/demanded a refund.
I responded that setting that hobby charge to 4.5 (or higher) voltage constituted overcharging and abuse of the cell and, even more important, that doing so is a very dangerous practice. I also pointed out that Balance Charging is a process that involves more than one battery and asked him why he was trying to balance charge a single cell.
Note that (within reason) we try to take the attitude that “the customer is always right” and we quickly offered to refund the entire purchase price. I still think we did the “right thing” in this case but must confess to feeling that we were “taken advantage of” to some extent.
Almost all Lithium Ion batteries that I’m aware of should be charged at no more than 4.17 to 4.22volts (at most!).** Any voltage higher than that and there is the chance you may damage the cell, or even cause a cell to self-destruct. Even if you don’t damage the cell, HKJ has pointed out that charging to 4.17 rather than 4.22 will greatly increase the useful life of a cell. 4.5 volts IMHO is dangerous and abusive to these cells.
The buyer suggested that the protection circuit in these cells was defective because, as he said, it did not stop the charger from pumping more current into the protected cells.
WHAT SORT OF PROTECTION SHOULD PROTECTED CELLS PROVIDE?
I believe that protection circuits should cut off current drain from a given cell at a certain minimum (trigger point) voltage. These cells will undergo unwelcome chemical reactions if drained too low. I am told that crystallization forms and the cell can be destroyed, diminished in capacity, or made to be dangerous.
I also believe that the protection circuits should cut off the current drain from a protected cell if it is allowed to go higher than specific trigger amperage (a short circuit being the extreme). Asking a cell that was designed to provide a maximum of xx.xx amps to produce more than that is also asking for problems.
I have 7 or 8 chargers and none of them (even the “$4 generic” units from China) charge higher than 4.21volts. I occasionally send these out to neophytes on a budget but I will not send them out without testing them overnight to make sure they don’t overcharge cells and that they charge both bays to the same voltage.
**Note that the Samsung 2800 and 3000mAh batteries are exceptions (as may be some of the LG cells) in that they can accept 4.3 and 4.35 volts respectively – and there are some special chargers (like the “CottonPickers”) that are designed for them. (We may bring in the Samsung cells and the LG cells because they both have very good reputations – but people would have to settle for less than their design capacity or buy a new dedicated charger.)
The other main type of Li-ion battery is LiFePo4 and as most people are aware, they operate at even lower voltages – roughly 3.2 volts while operating and up to 3.5 volts when fully charged.
PLEASE “CHIME IN” WITH YOUR OPINIONS!
We’d very much appreciate your opinion on the situation described above. We’d also appreciate your comments about our take on protection circuits and what they are meant to do.
THANK YOU VERY MUCH.
Best Regards,
KumaBear Bob