Charger and battery heat question

[Coelacanth]

Not long ago, I received a hardly-used Onyx 230 charger in a trade, and have noticed something that seems odd to me. Maybe it's normal...

I have a specific battery pack - a 4200 mAh 7.2V battery with SMC matched cells. When I program the Onyx 230 to charge the battery to completion in 60 minutes, the battery gets noticeaby hotter on one side of the pack than the other. But here's the kicker: When I put the same battery on an older, simpler Onyx 200, it warms up more uniformly; the whole pack gets warm, not just one side significantly warmer than the other.

Furthermore, the last time I configured the 230 charger/battery to charge to 4200 mAh, using the 3 mV peak detection voltage, and 60 minutes charge time (and set it to AUTO-TRK to automatically trickle charge when peak is detected), before the 60 minutes expired, the Onyx 230 gave a TIMEOUT error. According to the manual, this means the charge time expired before enough charge was applied to reach 4200 mAh/7.2-plus volts.

Is this a sign of an issue with the Onyx 230 charger, or is it normal?

[Charlie don't surf]

What kind of run times are you actually getting out of the 4200 and are they 4200 worlds cells, or sHV's? And how often are you cycling them? All might sound kind of dumb, but there were some "good" runs of the cell-and some really fast and really short lived cells from Inellect
Sounds like you have one or more dead soilders in the pack, and that chargers profile or charge "pulse" is causing the cell to heat due to internal short or unusually high IR- I was running with SMC during the 4200 and 4600 periods and there were some killer packs, and some that commited hari-kari after 2 runs

[Coelacanth]

Sadly, I haven't been able to properly test the run-time of this particular battery. It was sold to me used, has SMC matched cells, and was a "home-build special". I had to shrink-wrap it myself, and re-soldered the tabs on the ends as they were getting in the way when trying to insert the battery in the Galaxy. There's snow everywhere here so I don't have any place to do a full run.

The thing I found odd was that the same battery seemed to get a nice, uniform charge (all the cells equally warm) when I charged it with the Onyx 200, but one side got hotter than the other with the 230. Judging by how I received the battery, I wouldn't rule out 'dead soldiers' either.

[Charlie don't surf]

At the time, and for racing they were superb- but we used to get them "bakery fresh" from SMC via Canada and they would hit the zapper then the 35 or 40a matchers and we did this before every National or large event, if they were older than 1 week off the matcher, forget it- C main was your best hope- and if you were smart as a team guy, you sold them right after the event-because they were junk 6 cycles after that. NiMh was a huge PITA-, Nicads were great

[jwscab]

yeah, it's probably a bad cell. if you can start with a very cold pack, and place it on the charger, the telltale cell will get warmest the fastest. You are probably feeling heat dissipating into adjacent cells and having a hard time telling which one is at fault. If you have a handheld laser thermometer, you can use that to pinpoint the bad cell pretty quickly.

alternatively, you can current load down the cells heavily and either measure the voltage at load, or take a temp measurement, the bad cell will be the hottest or have the lowest voltage across the cell.

[Coelacanth]

This info is actually a bit comforting...I'd rather have the battery be the problem than the charger.

[jwscab]

short story that helps relate to what you are probably seeing:

I have a dewalt cordless drill, 12v Nicad packs. the packs were junk after the first year, so I picked up some new cells. they are a really weird size. 4/5 sub C cells. so a sub C is smaller than a C and then this cell is 4/5ths of that. anyway, I digress.

the worked ok for a while, but the cells weren't the greatest, and tended to crap out under heavy loading, ie, drilling a decent sized hole. the last pack I rebuilt go so hot after drilling some holes I got worried the cells were going to burst, so I quickly dismantled it to make sure the whole deal didn't go up in flames. some of the cells were slightly warm. the bad cells were so smoking hot that they split the heat shrink on them, and were still hot like an hour later.

[Coelacanth]

Thank you, that does appear to be the case. I wish I had a place to do some runs, I have 2 good batteries and 1 known good charger to make comparisons with. In the past, I've usually associated cells getting hotter than other cells as a "bad cell" issue. I've dealt with that even in my years working on cars; a car battery with one or two cells burned completely dry while the others are still full is a good comparison.

[Coelacanth]

I thought I'd update this topic. It turns out that the problem may well have been the battery having some bad cells. My buddy had a pair of 3000 mAh batteries that seemed to not take any charge on his own charger, they weren't even getting warm when he tried charging them with his 1.5-year-old charger. I told him it appeared his charger wasn't working. I put the batteries on my Onyx 230 and they charged right up to almost 3000 mAh, got uniformly warm--but not hot. After the 1-hour fast-charge, the Onyx 230 automatically switched to trickle charge. So, my charger appears to be fine. Yay!

Thanks again for helping with the troubleshooting!