Anybody in the UK willing to do 18650 discharge tests?

Batteries and Chargers Rechargeable Batteries
1

Hi All,

I recently got a 6 pack of protected Panasonic 3100 mAh 18650 batteries from HKEquipment.net. These are the clear wrapped ones that are showing up in a few places. Great price ($66 delivered) and incredibly fast shipping (7 days to the UK!). So far, so good.

All of them shipped around 3.6 volts. Still good.

I gave them an initial charge on my Pila IBC, and here's where it gets troubling. After resting for a few hours, each pair showed the same result: battery A was around 4.13v and battery B was around 4.18v. (So the score is 3 low, 3 normal.)

Thinking that my Pila is charging differently in each bay, I discharged a pair of older Xtar 2600s and charged them up. Both are 4.18v.

I'll note that my DMM is a cheapy, but it's very consistent in these numbers.

So, is there anyone in the UK (or even HKJ, if I could be so bold as to ask) who would be willing to put these batteries through a discharge cycle to see how they compare to each other (and possibly extrapolate to how they compare with other Panasonic 3100s)?

I'm willing to pay shipping both ways of course, with a pint or two thrown in for good measure.

If the clear-wrapped Panasonic 3100s are a low-quality bin, I think I'll still be content. If they test really badly, then I'd like to be able to warn the group.

Thanks in advance.

2

I could do them mate, subject to how busy I am at work it may take a while. I can only do a 1amp discharge so each test takes around 3 hours. HKJ will do a better job if he offers.

3

Are you totally sure that the Pilla charge didn't miss one or two times (4.13v) and other times you didn't bother to check the termination voltage on the cells?

As for some do to any discharge on those cells, the ones with lower voltage will result in a lower capacity, because they simply aren't charged enough. But of course HKJ for example could measure the internal resistance and how the Mos or ICs affect the cells.

4

Jeansy, I'll take you up on that unless HKJ is interested. I'm not in any rush to put them into service... I've got a few others kicking around already.

Hikelite, I see your point about the capacity appearing to be lower simply because of the lower voltage. I'm not sure what to say or do about that one.

But I'm not sure I completely understand your comment, "Are you totally sure that the Pilla charge didn't miss one or two times (4.13v) and other times you didn't bother to check the termination voltage on the cells?"

I don't think the Pila missed anything, as I pulled the batteries off sometime after the lights turned green. Plus, the low/high voltage ones were together in the charger -- it wasn't that there was one pair charged together that was low and another pair together that was charged high.

I think I'll discharge the cells and re-charge them, paying closer attention to which battery went in which bay. If anyone has any other suggestions or ideas, I'm listening.

5

ruffles I mean are you sure that 4.13v hasn't happened by chance. Have you always check the Pilla and it was always 4.18V?

You should try to measure the termination voltage at least 2 times on the same cell before get worried.

6

I have a v3 eSevens single bay charger that charges all my Panasonic 18650 (eagleTac, Intl. Outdoors and now some Keeppower) to 4.12v (at 1A). If I use a Xtar MP1, I get 4.20v. Keep meaning to try at 0.5a.

Not overly concerned, and as someone here helpfully mentioned, handy to charge to 4.12v if I don't need to use them immediately.

7

Aaaah, I understand now. I have to admit that I'm not as thorough as I should be at checking cells off the charger. But when I do check them (AW 2900, Xtar 2600) they seem to be around 4.17/4.18v.

Running down two that ended up at 4.12v right now and will charge as soon as I can.

8

I do not have time to check them, I do still have over a months work for my testing stations.

This does include some of these batteries, but from DX.

9

Not being funny, but measuring to 0.00V and comparing results with what you admit is a cheap DMM could be a issue.

If you take into consideration Amb temp changes, measurement uncertainty and you'll seI would say e there's not much between the results.

10

Fair point about the DMM, Essexman... I'll try and lay hands on a nice DMM and compare numbers.

And HKJ, thanks for checking in. I completely understand that you've got a lot on the go. (Your review output proves it!)

11

My protected DX ones do give around 300mAh lower capacity on my tests iirc. I need to grab my impedance tester again and see what impedance they give. I'm almost tempted to then cut off the protection and see the difference.

Edit, i was out, its less than that, i have added some results at the bottom of my thread in the battery sub-forum

12

Just an update, for anyone interested... it appears that my Pila IBC is sometimes charging low in one of its bays. All six of the HKE batteries have charged up to 4.18v, which makes me perfectly happy.

I'll try doing some discharge tests in a flashlight to double-check, but first I need to get over to buddy-with-a-Fluke's place, to get some accurate tailcap readings. (My cheapy DMMs results were justifiably called into question above, and I fear that tailcap readings would definitely be inaccurate.)

So, these batteries are back to "rufflesApproved". (Sorry, Foy.)

13

I’ve just charged 2 new(ish) ultrafire 18650’s 3000mAh protected 3.7V, on a DMM check they’re showing 5.20V.
Having just read about exploding 18650’s, and not knowing anything about batts, should I be worried??

14

Replace the battery in your DMM and try measuring again.

15

Good thinking HKJ, just tried them with a AMM, and it’s giving 4.25 on each.

16

I'm going to have to check my Pila IBC the next time I charge any of my li-ion's. But then again charging a bit low is better than over charging right?

17

Agree that a bit undercharged is not too bad… you get a little less burn time, but it is supposedly better for the battery. I’m mostly uppity about it because I’ve got one light that uses batteries in series and I’m trying to play as nice as possible with matching them up.

As for the Pila, a bit of research on the other forum (that I probably should have done before I opened my mouth!) suggests that it’s somewhat common for the charger to terminate a bit early. Causes might include jostling the charger before it’s done, or tiny buildups on the contacts. One good bit of advice seems to be to put the batteries in and then give them a quarter twist to help with contact.

18

I usually hit the recharge/reset button on my IBC just to make sure they are fully charged. I haven't checked any after charge voltages since I bought it last year so I guess it's about time I do check.