Still Bill

iTrader: (16)

A few hours ago, I charged (@ 5.5 volts with a .04 cutoff) a 6 month old GP3300 matched 1.17+ V battery pack on my GFX and it topped out at about 1600 mahr. The cells on both ends were pretty hot; so, I took temps of each cell in the pack within 20-30 seconds after the charging ended.

The temps were as follows: 180 - 150 - 120 - 120 - 150 - 185 (temps rounded to nearest 5 degrees)

Don't think I've ever had such variances between cells after charging a pack. I would call it warm in the center going towards hot on each end

Anyone have an idea what is wrong?

fatdoggy

Check each cell with a volt meter to make sure you don't have any dead cells.

Johnny J

That sounds pretty bad. Try putting it on a tray and deep discharge the individual cells.

R/C Anonymous

iTrader: (1)

get an equalizing tray ....problem solved

sturla

How long should they rest on the tray for maximum result?

AdR|aN

IMHO, cycle them a few times then get a reading again.
It might be caused by maybe 1 or 2 bad cells.
NiMH cells arent suppose to sit in a tray for too long or it will kill them.

Still Bill

iTrader: (16)

Hi fatdoggy,

All are 1.24-1.25 V after discharge. Should I give it another charge and measure them that way?

I do tray my batteries weekly. Have an Octane 2. Typically use them twice on race day because they charge better the second time around.

Thanks.

fatdoggy

If they are all reading 1.24-1.25v then you don't have a dead cell. I'm not sure, weird. Not too much solder on the solder joints?

raving-monkey

if you deep discharge your cells (to below say 5.4v for the whole pack) they will never recover.

do not discharge at below 0.9v per cell (5.4v per pack)

this is why its better to get an equalising tray that cuts off at 0.9v.

or if you know your circuits make your own with some 0.9 zenna diodes and a couple of resisitors/capacitors...what ever they are

fatdoggy

The integy chargers discharge to .8v per cell (4.8v) and I've never had any problems.

raving-monkey

well my dad works with this guy and specialises in cells/power etc and wegot him to design us a circuit for an equalsiing tray, and we were gonna get it to cut off at 0.7...but he said that was to low and it will discharge the cells too low. and he said the lowest to go is 0.9v per cell.

once he has finsihed the circuit i will post it if you want.

Still Bill

iTrader: (16)

Hi again fatdoggy,

Have a 60W iron and it does a nice job for me. Pretty confident that soldering is not the issue.

So, I charged it again tonight. Not much of a rest. Only went to 2650 mahr; but, it didn't have any high temp issues.

Funny that the temps were basically opposite from the previous. Being 110 - 120 - 130 - 130 - 120 - 115 across the pack. So, for this case, they were warmer in the middle than on the ends.

Then, I charged up its "sister" battery (bought at same time) and it went to virtually the same mahr and temp figures.

Pretty much going to be using these two packs for practice at this point in time. Got new packs on the way.

Going to chalk this whole thing up to a fluke occurence.

Thanks again.

Still Bill

iTrader: (16)

In concept, I agree. However, there have been multiple times that I have discharged beyond .9v with excellent mahr readings on the following recharge. It's a mixed bag.

raving-monkey

yes but maybe that is why your have 2 dodgey packs.

you discharged them lower than 0.9v per cell (not much lower) and they will not recover all the way, but say if you discharged them at 0.7 and down they would never recover.

BigDogRacing

iTrader: (12)

Raving Monkey- please stop telling people how to manage their batteries when you don't know what you are talking about. .9volts is the cutoff for high amperage discharge (10-30 amps). It's perfectly fine for him to discharge his cells in a discharge tray until the lights go out. If they have never been dead shorted I wouldn't leave them in the tray for very long. If you onlt race in stock class you can dead short your new packs after the first cycle. Make sure to deep discharge them in a tray that takes them to 0 volts before you short them.

I'm sorry to be harsh Monkey, but you obviously don't have a clue on what we are doing to the newer GPs. You might try listening more and typing less before you become all knowing....