INR18650-30Q severely overcharged by MiBoxer C4-12 charger -- is it now bad?

Batteries and Chargers Rechargeable Batteries
1

I was testing the new MiBoxer C4-12 charger with some of my batteries (18650s, AAA, AA).

I was VERY SURPRISED when I noticed the charger indicated 4.48v "Full" reading on my precious INR18650-30Q (as this is the only 18650 that Banggood ever shipped to me -- it was bought with the BLF A6 -- I pay the BLF A6 to get the battery shipped to my country, bare batteries cannot be shipped). Fortunately, I think it was only about 30 minutes or so when I placed the INR18650-30Q (the 30Q was around 4.10v or so when I placed in the charger -- I was testing the new charger).

At first, I thought maybe it's just the display malfunctioning for the MiBoxer C4-12, but then I tested with my multi-meter and got surprised (the MiBoxer C4-12 display is reading the voltage correctly!), my MS8229 multi-meter reads 4.52v (based on comparing with other meters, I've noted that my MS8229 multi-meter tends to have a higher reading of around 0.02-0.03v for batteries DC voltage range). In any case, the INR18650-30Q had been severely overcharged (the battery was not hot or anything though, when I touched it).

My immediate thought was to discharge the battery first to safe levels, I don't think my other analyzng chargers can discharge this severely-overcharged battery ("check battery voltage"), so I got my EBD-USB+ and connected to a battery holder and used that to discharge the battery, at first I used a 0.30A discharge (voltage drops very slowly), so I increased to 0.50A then to 1.0A discharge rate). After discharging for a short while, I stopped to check the unloaded voltage 4.31v, 108mAh has been discharged from the INR18650-30Q (from 4.48v --> 4.31v).

(after discharging 108mAh, it now reads 4.31v on the MS8229 -- as the MS8229 over-reads around 0.02v, true voltage might still be 4.29v)

I connected again to the EBD-USB+ meter and continued discharging at 1.0A current load, after 262mAh capacity was discharged, took out the battery which now read a safer voltage of 4.08v.

Question is: has my INR18650-30Q been severely damaged with the severe overcharge? This is one of my few INR18650-30Qs (several batteries I ordered from AliExpress were cancelled due to shipping, so I have a really hard time getting batteries...).

Also, is it "safe" to still use this INR18650-30Q? Or should I let it rest awhile and then due some Charge-Discharge cycles at a low current to "recondition" (if this applies) the battery?

2

Prob a little more risk but most likely still works but with limited capacity

3

My question is; why did it over charge?

4

Overcharge drastically reduces lifetime if it stays at that level

If the cell did not get very hot at the point where it cant handly any more voltage I would recycle it otherwise it should be fine

5

That’s what I’d like to know, unfortunately, getting 18650s shipped to my country is extremely difficult and I only have a few ones that I don’t want to test much further unless I get a fresh supply of 18650s.

The INR18650-30Q I tested is from Banggood (bought the BLF A6 with INR18650-30Q), since it was my first “genuine” Samsung 18650, it has gone thru quite a number of cycles (my guess would be perhaps 15 or 20) — I got the battery last year Sept 2017.

When I placed it in the C4-12 charger, the battery was still nearly full, 4.10v or so (can’t remember exactly, but the “capacity charged reading” on the C4-12 is 187mAh.)
I can’t remember exactly if I manually changed the current in the C4-12 (probably didn’t), in my previous tests I just used the automatic current set by the charger.
I think I’ve already charged 8 or so batteries ever since I got the C4-12 a couple of days ago, so far hadn’t seen any problems with charging until today.

6

D_T_A, you have two threads concerning this issue.

7

My charger started acting up after about eight charge cycles on slot-3
I have two brand new C4-12’s I have not even plugged in yet.

8

This thread is about the battery — if it’s still OK to use or how to recondition it (incidental cause of overcharging is the charger).

The other thread is about the charger — that it may be dangerous to use (at least the Slot #3).

(was thinking it warrants a different thread)

When I removed the battery from the charger, it was not hot at all (the C4-12 reads “31 deg C” which is within room temperature; compare to the 29 deg C MS8229 ambient temperature reading)

9

Hello d_t_a

we are very sorry for this issue， now, our engineers are busy to finding out where is problem.

Please can you help us try more batteries in bay 3 and other bays, and sent us photos, video is better.

We will sent you a new C4-12 no matter what problem is.

Thanks

Leo

10

This is a little off topic, but in the Philippines can you purchase replacement laptop batteries?, powerbank? Or power tool batteries. Well if you can you have plenty of access to 18650s tear into these packs and their loaded with them. I pull and test them out the recycle bins all the time. Sort the good ones recycle the bad ones again. But I have purchased new laptop batteries off eBay for like 10-20usd usually depends on how many cells are inside 6-12

11

just run it down a bit and it should be ok.
and do any further tests with old laptop pulls outdoors.
i suspect its a bad solder joint or wrong value resistor on the sense divider on that channel.
look for unflowed solder paste(cold spot) or a tombstone (uneven heating during reflow)

12

To address to op’s concern, this specific cell has been tested at the factory to be safe after being charged as high as 20 volts, see page 7:

http://www.datasheetspdf.com/mobile-pdf/951041/Samsung/INR18650-30Q.html