IMPORTANT: Does pumping 4.5 volts into a Lithium Ion Cell constitute abuse?

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.


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.


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.


Best Regards,

KumaBear Bob

Were the cells in question protected ?

Basically, it's completely intentional abuse outside the product's design specs.

If a cell's protection circuit was absolute, then I'd be hooking up a simple bridge rectifier directly into 240V mains through to the battery's terminals to charge me batts.

If deliberately applying an overvoltage to a cell, who's to say what's the reasonable limit? 4.3V? 5V? 10V? 10,000V? Enough EMF to rip electrons from the outer shell of the molecules that make up the insulation, converting into an electrical conductor?

I wouldn't have refunded them, and I wouldn't expect a refund either. (Good thing I'm not a seller then, huh?)

Hope you don't ever sell to them again, and their hobby charger explodes and burns their whole house down. Without them or their family inside of course. Okay, maybe just half their face burns off.

Seriously, hope the rest of your buyers are a lot better.

Without wanting to comment on the situation, my opinion is yes, charging a cell up to 4.5V is “abuse” and very foolish.

Also though, a protected cell’s circuit should cut out well before that - around 4.35V is a figure I’ve seen quoted. I’ve never tried it on any of mine though! (Not that stupid)

Not only abuse but dangerous. Whether it’s intentional or ignorance it’s sort of like ramming my car through the garage door and then complaining about paint scratching and body damage.

Mixed opinions. I think refunding him was the right choice. I also think you should test your protection circuits.

Is the buyer a moron who shouldn’t be trusted with Lithium Ion batteries? yes.

Did the protection work as it should? no.

Most of the ‘reasonable cost’ protection circuits that I’ve seen are based on the Silan SC451 IC. This chip should provide absolute over-voltage charge protection at around 4.325V (the absolute range is 4.275 to 4.375). If the buyer was really able to charge up to >4.5V then the protection circuit is not working properly.

I understand your cells use a slightly different controller IC, but I would expect it functions much the same.

Protection circuits are not designed to be the charge controller, and that is why the buyer is tempting fate and risking his own safety. Still, The protection circuit should be able to be relied upon to contain an over-charge condition.


No way in hell you should have refunded them, you should have said that’s abuse, pure and simple, and to pound sand. You took the high road and I applaud you, but if I were you I would NEVER do business with them again.

I’m glad my charger only charges to 4.2V

I have seen some horror stories with ppl trying to be slick with there hobby chargers.

It is abuse and they should be charged with battery
(overused i know)

Bob, you stated that the cells were protected, and as you had pointed out, protection circuits are supposed to protect cells from 1. undervoltage and 2. overcurrent/shorts.

However, I’m not sure if you’re forgot or intentionally didn’t say that they also should protect the cell from being overcharged.

I’m curious whether the member was testing out the circuit or just being foolish with the hobby charger.

Here are the facts:
-that the circuit had failed
-consequently, the cell was overcharged to a dangerously high voltage.

Here are the pieces of information we should have:
-was the user intentionally overcharging the cells to test out the circuit?
-or was he/she doing so out of ignorance?

It’s be nice if HKJ would chime in too.

Hi Pilot!

Thanks very much for your input.

With your very impressive background, you’re keenly aware of what I’m about to say (and much more) but it bears repeating – particularly some comments about Keeppower that may be new to many people.

It turns out that the protection circuit in the Keeppower Brand cells has at least 2 high quality Japanese ICs. It’s been made clear to me that the circuit was designed for two primary purposes:

1) It was designed to act as a “circuit breaker” when the voltage dips below a trigger point. Many people don’t understand why you shouldn’t run a Lithium Ion cell until its “empty” – something that can be done with a Sanyo Eneloop NiMh, but never a Lithium Ion. Nevertheless, anyone who uses properly protected cells or has been around the BLF long enough to know about the proper “care and feeding” of Lithium Ion cells will not make that mistake.

2) The other task that a good battery protection circuit is called upon to perform is to break the circuit if and when the amperage exceeds a predetermined limit – a short-circuit being the extreme.

There is a difference of opinion regarding which device has the task of limiting the charging voltage – the charger or the battery’s protection circuit or both.

IMHO, ALL properly functioning chargers for Lithium Ion batteries should be self-limited to no more than 4.22 volts (at least as the battery is reaching its maximum capacity). Some people will argue that it is permissible to charge at higher voltages when the battery is close to empty but that is a debatable point.

Before considering the other two options – the one where the battery is responsible for protecting itself from abusively high charging voltages and the one where both the charger and the battery are supposed to share the burden – please allow me to point out some “facts of life” in the protected Lithium Ion battery business.”

I would love to provide the list (that I promised to keep secret) of battery brands and so-called manufacturers that don’t even touch their own batteries, let alone have anything to do with their manufacture or assembly. The list is rather long and it includes several battery brands that have that “aura” of super high quality and are certainly sold for super high prices. Most of them have been tested by HKJ and others. As would be expected, they test equivalently to the Keeppower Brand Protected cells.

Why do they test the same? They test the same because they are IDENTICAL – with the possible exception of a button top vs. a broader top and the difference between one or two layers of PVC. (Note: Keeppower may also undertake a little better QC to protect their own brand – something for which there is empirical evidence, but that I can’t claim for certain.)

By the way, we were given the option to choose in those two areas and after consulting several people including HKJ, the best choices became very clear. We chose the button top because the larger top is not compatible with several high-end flashlights and we chose a single layer of PVC because some battery carriers are not able to accommodate the extra diameter added by the second layer of PVC. (Some people are not aware that the bare cell can have the original layer of PVC followed by the ribbon wire, then the second layer of PVC and finally, the label. All of this makes it impossible to use some batteries in certain battery carriers and narrow tube flashlights.)

Thank you for listening.

Best Regards,

KumaBear Bob


I’ve heard nothing but good about you and your batteries - I’m not at all surprised that you did the honorable thing even with a moron at the other end of the transaction. It bodes well for your company, and it further sways me toward ordering your cells the next time I need to stock up.

A few quick questions…

First, are you willing to share the part numbers of the ICs in the protection circuit? I don’t see why they should be a trade secret, but if they are, I do understand. My wild guess is that you’re using a Seiko chip…

Second, from your above response:

Do your protection circuits not have a third task - Preventing Battery Over-Voltage? Even the ‘cheap’ Silan SC451 has that function. It provides Over-Voltage, Under-Voltage and Over-Current protection. Do your IC’s provide that same protection?


I don’t think there’s a difference of opinion about what protection circuits should do - for instance, the NCP800 protection chip has functions of overvoltage (4.35V typ.), undervoltage (2.5V typ.) and overcurrent sensing (value set by appropriate resistor - sensing voltage is 200mV typ.).

If the protection circuits on your cells are different, it wouldn’t hurt to advertise that fact, because most protected cells provide the three functions described above.

Was it the charger or the battery that read 4.5 volts???

I forgot to mention that the user admitted to being a neophyte – particularly regarding hobby chargers. The sole fact that he was attempting to “balance charge” a single battery would point to that reality. The other obvious mistake was to set the hobby charger at 4.5 volts (or higher!).

About the 4.5 volt reading, he never did make it clear whether the battery was charged to that level or whether the charger was putting out that voltage. He did mention that a TrustFire 26650 did not go beyond exactly 4.2 volts. This claim prompts more questions to me than it does answers. I am somewhat familiar with the TrustFire protection circuit and it does not stop a charger from applying voltage at exactly 4.2 volts. I know that from experience. For reference, I have at least 5 or 6 different 26650 batteries for test – both with and without protection. There is a very broad spectrum of performance among them.

So – there are still questions to be answered and frankly, I’m a little unsure how to answer them all. Some depend on an already embarrassed user. Others seem to present a dangerous situation that I personally don’t want to risk. By that I mean that I don’t want to take one of the batteries he has already returned and duplicate the 4.5 volt charge level to see what happens. It seems to me he may just have been lucky not to have hurt himself.

I think I’ll contact HKJ and Keeppower and see what they recommend.

Best Regards,

KumaBear Bob

I wonder how the batteries are defective, just charging them from 4.5 volt will not do be a huge problem, because the protection will stop the charger.

Here is an example of a battery where it happens:

I charger with 4.35 volt (Any higher voltage would give exactly same result), because the charge process is still in the CC phase, there will be a significant voltage drop when the charge stops. It might not be obvious from the above chart that the charger stops immediately when the protection kicks in, i.e. it turns off the voltage.

There might be protection circuits that works different, i.e. does not reconnect the battery after the overcharge. Using a low charge current might also be a problem.

And as has already been said, the function of the protection circuit is not to control charge, but to prevent a dangerous situation.

If your contacting keeppower find out what its over-voltage limits are. They should have over-voltage protection.

It seems this has already been covered but I will add this, don't sell that person any more batteries. They are a danger to themselves and a potential liability for you.

First and foremost, I think you did the right thing to issue a refund. I don’t think it was your responsibility at all, but you’ve enhanced your brand at relatively low cost. And I doubt that you’ll get many more of those sorts of returns.

With that in mind, can I suggest that you send out a data sheet, preferably written by the manufacturer, to shelter you from liability? I imagine it would be pretty simple:

- use a charger designed for li-ion that tops out at 4.2v, +/- 5%

- don’t overcharge

- don’t drain below xx volts (whatever xx is for a given battery)

- don’t cut open

- don’t burn

  • and a few other obvious things I can’t think of right now…

Dont put in the microwave like some people did with their pets? :P

I’m still wondering what brand of hobby charger can be set to charge at 4.5V.

Or was it set to NiMH?

I don’t know what to comment. The story is too incomplete to piece together.