Problem charging GP3300's, help please

[SS Pede]

I have a couple matched 6 cell GP3300 stick packs that I charge with an MRC 969 charger. I usually only run my Stampede once a week or so, so the packs don't get a lot of use. Lately when I charge them, they haven't charged up all the way. For example, they might only charge for 20 minutes, peak at about 8.20 volts, and receive only 1800 mAh.

I figured that, since it's a very capable charger, the batteries were probably just false peaking/not charging correctly because they didn't get cycled much. I've read that NiMH batteries sometimes need a few cycles to "wake up" if they're not used much. So yesterday I cycled one of the packs 2 times. I charged at 4 amps, 30mV peak (for the entire pack), and discharged with my Reactor 20. Yesterday the pack got a little better charge into it the second time around, but still only charged for about 25 minutes, with 1760 mAh put into it. It was barely warm when it finished charging. Normally I'd hit the "start" button again to charge it the rest of the way, but I just discharged it from that point.

Today I charged the same pack again, intending to use it in my truck. I charged at 4.5 amps, 30mV peak setting, basically similar settings to what I've always used. The pack charged up fully today, but here is the problem: I think the cells vented somehow. When I checked on the pack after it finished, there was some condensation of some sort on the inside of the shrink wrap. I would describe the pack as being "very warm," hot even, but I could've held it in my hand all day without burning myself. It peaked at around 8.4 or 8.5 volts (not sure on this because I unplugged the pack immediately), and received 3406 mAh. In the past the pack has accepted up to 3930 mAh, and while this may be too high, it was not even quite as warm as it was today.

So why did this happen? Has the pack somehow been toasted? In the past it has gotten pretty warm when I've had to hit the charge button twice to get it to peak properly, but it has never been quite this hot and I've never noticed any moisture on the inside of the shrink wrap. I've never used higher than a 30mV peak setting or 4.5A charge rate. 3406 is higher than average (because on average it only takes in 1500 or maybe 1800 mAh before stopping, then I have to start it again and the mAh count starts over), but not as high as I've seen it. I discharge my GP3300's to 5.4 volts or a little below that after each run.

Why would the pack go from apparent under-charging to apparent overcharging from one cycle to the next, on practically identical settings?

Any help would be appreciated.

[HauntedMyst]

Have you tried charging at a higher amp rate with a lower mV peak detect? I charge at 5 amps with 8mV cut off and consistently get in the 3100 to 3300 range.

[AlexV2024]

so your packs are still taking 1500-1800mah? or did they go back up to 3300-3400? not too clear. any way if you stored them w/o a charge you probably damaged them. i did the same thing to 3 of my packs now they take about 2700-2900mah. you have to store them with at least 300-400mah in them per week. also try a higher MV, try 35-40 mv. my packs that only take 2700-2900 now like much higher mv, in the 54mv range, before they liked 30-36mv like my other packs. try putting a house fan on the charger and batts and see how they react. but keep in mind GP's run best hot off the charger.

i dont think your cells vented just got a few drops of water in their shrink wrap, unless your describing it wrong (or im interperting it wrong)

~Alex

[asw7576]

Is this problem happen to all packs or just one pack ??

All packs = your charger need repair

1 battery pack = replace the bad cell(s)

Charging over 3300mAH before and less than 2000mAH now means something it's not right.

[SS Pede]

so your packs are still taking 1500-1800mah? or did they go back up to 3300-3400? not too clear.
Sorry. Basically, most of the time they only take 1500-1800mAh before the charger shuts off, making it necessary for me to hit the charge button again to put more of a full charge in them. I cycled one of the packs a couple times to try to "wake up" the cells (since they usually don't get used more than once a week). Then I charged the same pack up again, hoping to see a better charge as a result of the recent cycling. It did in fact take a fuller charge, and charged up to 3406mAh without having to hit the start button again. Problem is, by the time the pack was done charging it was very warm (seemed too warm to me) and there was a little bit of condensation on the inside of the shrink wrap. Otherwise, the shrink wrap was not deformed or anything. I have not yet discharged the pack to try charging it again.

if you stored them w/o a charge you probably damaged them.
I was under the impression that GP3300's can safely be stored discharged, more or less how you would treat Nicad's. I know it is generally best not to let them hit dead zero voltage, and my packs never have. They're just stored with 5.4 volts or less in them. I did not think I had damaged them by doing this.

Have you tried charging at a higher amp rate with a lower mV peak detect? I charge at 5 amps with 8mV cut off and consistently get in the 3100 to 3300 range.
My charger, the MRC 969, cannot charge any higher than 4.5 amps. I've used the 30mV (for entire pack) peak setting because I didn't want the pack to false peak, which is what it seems like they've been doing. I can try a lower peak setting I suppose, as long as the packs will still charge fully.

[Cain]

I don't store my GP3300s ( newer style ) with a charge on them other than 5.4V on some of my packs. after going through several sets of cells using the partial charge method I went to the discharge method and I have not had any problems. I can regularly get 3900mah+ on my packs easily.

I personally think your charger is false peaking too early. If your packs aren't warm and you are peaking out at 8.2 volts something doesn't sound right. I usually peak out about 9.15 - 9.3 . When my cells have sat, I do have to hit them to start up again a few times, so its no big deal.

I currently maintain my packs in two ways.

1. equalize the cells before charging on an integy octane 2
2. after charge and discharge to 5.4V I put them to storage

or

1. equalize as stated above
2. after charge and discharge I bring them down to 0V on my octane 2 and dead short them till I need them. I leave this short on for at max 1 week till I cycle them again

I have also done bringing them down to 0V then letting them sit for max 1 week with no problems.

I would say for you, bringing them down to 5.4V before storing for max 1 week or so should be ok.

Main thing is also equalizing the voltages in the cells before charging them up. you may have a cell that is peaking out before the others causing the pack to false peak.

a good source for battery maintenance techniques is SMC.

Remember these are the methods I use and work for me, others may do things different that work for them.

[SS Pede]

Thanks Cain, hopefully the issue is just that the batteries tend to sit for a while between charges. I wouldn't think a $100 charger like the 969 would have many false peaking problems, except as a result of infrequently used cells. I will cycle my packs more often to keep them charging reliably. As they are stick packs, I can't equalize the cells individually, but I'll continue to leave them at 5.4 volts unless I'm storing them for a longer period of time.

Cain, how warm are your GP3300's after they receive 3900+ mAh? Why do you think my pack was so hot when it charged up to 3406?

Thanks for all the responses guys. :)

[nick51]

i have the yokomo bcs and my gp3300's never get up past 3000mah, could it be because they already have some charge in them, i run the batteries and then charge them again. I charge at like 4.5A and 20-50mv

[highroller]

Something I've found out and that eliminated most if not all false peaking with NiMh (nothing worked with Panasonics) but they are store with only .90 volts per cell (Sanyo 3000, 3300HV and GP3300) up to a month without using. Just before charging I place side x side pack in a equaling tray or use a single 1157 bulb on stick packs leaving on until bulb begins to dim or voltage reaches .15 volts. It seems the lower and closer you can get the voltage the better the cells charge with less chance of encountering false peaks. I used to discharge the packs (race packs) give them time to cool or store them then would charge them back up - the Sanyos began false peaking -the GP cells did not reach as high in MAH capacity (some reached 4000mah) but only reached 3585 to low 3700. Removing any voltage by whatever means before charging - getting all cells as close and a low as possible increased the MAH capacity back to 3800- 4000 for a few cells.
There is no need to cycle the packs if only used for recreational use and I have had some race packs that were stored for up to 6months of inactivity - it was more for racing that packs were cycled just to ensure they would be up to good performance on race day or by using the pack for practice - discharging then cool and using again in one of the race heats - most packs should be back up to normal.

You problem may be from several causes 1. you may have had a cell go back but unlikely from each pack you own 2. try to ensure the cells get discharged as low as possible (attach a single bulb and remove just as it dims) or install a pack equalizier made for stick packs (it can be expensive maintaining equipment but also increase the life and longevity), For charging I use 5 to 6amps for stock and mod racing, 7amp for stock & 19turn 4cell oval, .03mv for 4cell, .05 - .07mv for 6cell depending on the outside temperature. I'm wondering if charger could possibly be operating differently than what you are setting the defaults to -settings could actually wander after you set them. I had problems with panasonics, sanyo cells false peaking but not any of the GP3300 packs (matched race cells and some stick packs) charge fine and once I began discharging packs before charging the MAH peak rating have gone back up.

If NiMh cells leak there is a banana or odd rubber smell, the other could be just moisture if cells discharged or reached a high temperature and the place they were stored it reached a point it was very humid. Try to store packs in a place where temperature stays below 65-50 degrees and about no higher than 70 humidity and above all don't subject them to temperature below freezing.

[SS Pede]

Thanks a lot highroller.

The pack that had moisture in it did not really smell funny or get deformed, I was only worried because it was very warm. It has been humid around here lately, so the moisture was probably just water.

I don't know how I could tell if the charger's settings are "wandering" after I set them.

I didn't know there was such a thing as an equalizer for stick packs. I have Orions stick pack discharger, a Reactor 20, and my MRC 969 has a discharge function. I could discharge the packs further with the charger before trying to charge them up again. Is that .15 volts per cell or for the whole pack? And if I discharge like that before charging, how long should I wait for the pack to cool down before I charge it back up? Say I discharge it at the 969's maximum 3 amps. thanks.

[SS Pede]

A little update: I charged the other GP3300 pack today and it took 3 times hitting the charge button before the pack was reasonably full. By that time I figure it had about 3400 or 3500 mAh in it. I charged this pack on the 969's other channel, just to rule out a problem with channel B, and it did the same thing. Didn't charge all the way until I restarted the charge a couple times. So both GP3300 packs are acting just the same way.

I don't know why a nice charger like the 969 could be false peaking so much (I guess that's the only way to describe it). Any ideas? I can try discharging them more before charging, like highroller said. I could also try setting the peak threshold to more than 30mV for the entire pack, but then I'd be afraid of overcharging the cells.

[highroller]

For stick packs use one single 1157 bulb, discharge first with a higher load (string of 10 bulbs) then attach the single bulb and leave on until it begins to dim then remove. Allow pack to cool to room temperature before charging - if cells are too warm they may not charge properly and if cells are at different voltage levels this can lead to alot of the false peaking.

It's fine to let the pack sit for up to a month without use, just use some method to get cell voltage remove (store at 5.40 volts) do not charge and store as recommended. Cycling is only done for racing and in the long run shortens the life of the cells for bashing just charge it up and use it - if use again that day - after discharging and cooling should be a little more stable and consistant. The reason we cycle packs is just to ensure cells are up to race conditions, they may act irratic (seem soft or have no punch) all this is doing is increasing performance for race conditions but shortening the number of useable cycles by not using - cycling is a subsitute for racing.