I think this is one for Rick or Ian,

I have some GP4300 Cells (not the really odd ones Rick, these are new odd ones), that I charged today for the first time @ 3Amps on the novak charger. They are 2 sets of 4 cells for the Mardave.

They both seemed to take a good charge, i.e. were charging for 80 of 90 mins or so. I did not let them peak as I just wanted some charge in them before I charge them and use them in the car on Sunday.

However, I noticed that both packs sounded like they were 'clicking' very faintly just before I took them off charge and for a minute or so once they were off the charge. They would click every 30 seconds to a minute.

The cells were slightly warm when they came off charge. None of the cells were hot, or even warmer than the other cells in the pack.

Any ideas, or advise? If I am likely to blow the kitchen up I'll need to warn the wife.

When charging, the cells vent through holes on the positive side between the can and terminal. This is normal but can be a little disconcerting when charging cells for the first time. The important thing is they don't get hot. Warm is good, if you can measure the voltage, when they peek you will see the voltage drop, if the drop is very slow or the voltage stays static and one or more of the cells are hot then you have a problem. You can bring them back by putting them on a balance charger or by buying a cell doctor. They are cheap, they take the cells down to 0.5 volts individually which helps when you charge as all the cells are starting form the same voltage but if one or more cells are kaput this won't help.

Ian, Rick, have I missed anything.

YES i think discharging below 0.9 volts is a bad idea, and will lead to internal short circuts, causing more self discharge, more internal shorts, and so on.

i guess some venting on a first charge is nothing major to worry about, but keep a good eye on the temp of the cells for the first few charges, to be safe i'd charge them somewere safe if your worried.
Also keep an eye on the voltage during the weeks between racing make sure that each cell holds atleast 0.9v.

Hmmm, I'm not disagreeing with you Rick but I have just watched the latest episode of RCTV live and they say 0.5 volts for NIMH which is what the cell doctor does automatically.

Like said, sounds like venting, probably nothing to worry about. Always best to stay near by when they're charging and keep checking the temps, if they're warm rather than hot they're probably fine. A good sign if they're all an even temp. I wouldn't look at discharging at all unless they show signs of being unbalanced i.e. different temps.

Many thanks to all three of you for the advice.

just had a look what the cell doctor does, it's just a discharge tray that goes down to 0.5v it's about 4 years old though. Also it has a led for each cell which switches off at 0.7V but then carries on discharging down to 0.5V so there's no real way to know if the cells are equal without leaving them on for ages after the last led goes out. If you wanted a discharge tray the novak smart tray is the one to go for. either way i don't discharge my cells lower than 0.9, and since i've got the spintec i don't bother at all!

That all sounds very sensible advice. If had the money I would do what Rick has done and buy a mega charger which sorts it all out for you. Failing that, a good backup would be the Novak smart tray, this is the one I would go for as well. I wouldn't leave it to chance if you think your cells are at all on the iffy side. If you get the cells charging at different temps you should consider doing something. I'm sure Rick will run them through his charger for you to see how good they actually are.

Thanks Glenn. I'll keep an eye on them this weekend when I charge them.

What sort of level should the threshold be set at, I always have set this quite low, so my cells never really get hot when charging/peaking. Not like back in the old days when I had a charger that cut off once the cells reached a certain temperature Nice and hot) and that was it.

I read a good thread about a guy charging his 4200s. Basically he was charging them at 6amps and then was re-peaking, charging at 7amps. The pack exploded and he now pits on his own.

I'm not sure on the threshold, the manufacturer or matcher sometimes has recommended values. But low is probably safer, if you're not false peaking and not bothered about squeezing performance out of them I'd leave it at that, so long as they are at least warm when they peak.

I would do that. To be honest, getting any extra performance will make little or no difference when driving anyway.

if threshold is the same as delta peak voltage, 5millivolts per cell is about as high as you should go, if there good matched cells 3mv per cell

i'm just charging a couple of sets of gp4300's for Dean and there making the clicking noise it's scary did pauls stop after the first charge or 2?

I charged them twice and then you did the business on your charger and I have not noticed it since. None of the cells got hot though.
It is a bit scary I admit!

My GP4300 do get discharged to 0.9 volts per cell though after every meeting just to be on the safe side! I don't think the mardave is too heavy on the cells though, they don't seem to get very warm at all after a race!