Ep 4200 Has blown up in my face

[Northy]

I'm with Dan here.

G

[Richard Lowe]

It probably varies between suppliers, the cells I've had in the last few years have all been flat as a fart

[DCM]

does no harm though, to slap them on a tray to make sure does it, I did....

[Northy]

Originally Posted by Richard Lowe

It probably varies between suppliers, the cells I've had in the last few years have all been flat as a fart

But that's not gonna do them a lot of good is it? We're not supposed to store them flat........

G

[ashleyb4]

A EP 4200 went boom today at kiddy in there car. Found out he had been charging at 6 amps It sounded like a gun it wasnt that loud though

A

[Lee]

Cells come partly charged, if you get new cells and they are flat, send them back, they have been sat on the shelf too long.


I got an email from schumacher last summer about cells, saying that when we got them we had to build them and cycle tham asap so they dont go down.

[twisty]

All these dodgy cells should be recalled somehow.

[mark christopher]

Originally Posted by Richard Lowe

You don't discharge cells when new, they are already flat and equalised.

I don't know how it exploded without you putting any charge in it first, there shouldn't be any energy in the cell to explode

Originally Posted by Northy

I'm with Dan here.

G

me too

Originally Posted by DCM

does no harm though, to slap them on a tray to make sure does it, I did....

yup but the original post discharged em to 5.4 volt so he must have discharged as a pack not individually, there lies the problem, one flat cell would have all the power from other cells dragged though it, then it certainly would go bang

[mark christopher]

Originally Posted by gramey

I bought some of the EP 4200 mk II cells assembled for me by the seller and I was discharging and equalising them before charging them for the very first time. A cell in one of the packs exploded whilst I was discharging it, fortunately on a hard coffee table in my living room and the shrapnel was stopped by my armchair.
I returned the pack to the supplier and he replaced it no questions asked and I didn't have any trouble with any of them after that but it does make you think. I'm running nitro now but I never charged at more than 5 amps and like I said these hadn't even had one charge in them, I was discharging at 20 amps to 5.4 volts.

missed this from above post, you should put a 5 min charge in or equalize before trying to drag 20 amps out of cells with unknown voltage, sure i have read this in BRCA info some where

[Chrislong]

Originally Posted by mark christopher

missed this from above post, you should put a 5 min charge in or equalize before trying to drag 20 amps out of cells with unknown voltage, sure i have read this in BRCA info some where

Its more common sense, Id never discharge an unknown pack straight off. Put it straight on the equaliser and wait - nothing can go wrong then.

Infact, I can't remember when i last discharged a pack - if I did I would up the cutoff to 6.5v anyway. I tend to just equalise, and if it takes ages, so-be-it, but if a cell goes out straight off, charge for 2mins and equalise again.

[mobile chicane]

I have 4 packs of matched ib4200's one of which has a bad cell which I need to replace but I digress.

I discharge the packs on my charger at no more than 3 amps the equalize them to 0.9v on my novak smart tray I thought that dragging 20A from the packs would kipper them badly.

I only ever charge at 4A for the 4200's and 3.5A for the 3600's

I'll be going to lipo in a few months or sooner if I manage to blag some from flebay

[Southwell]

See me next meeting and ill give you a 4200 cell Giles.

[mobile chicane]

Originally Posted by Southwell

See me next meeting and ill give you a 4200 cell Giles.

cheers m8

[big air]

Originally Posted by mobile chicane

I have 4 packs of matched ib4200's one of which has a bad cell which I need to replace but I digress.

I discharge the packs on my charger at no more than 3 amps the equalize them to 0.9v on my novak smart tray I thought that dragging 20A from the packs would kipper them badly.

I only ever charge at 4A for the 4200's and 3.5A for the 3600's

I'll be going to lipo in a few months or sooner if I manage to blag some from flebay

I thought the discharge of a pack of cells whilst in a tc or buggy was some where near or over 30 amps, so i think 3 amps is no where near

[bigred5765]

but only in a surge not a constant 30 amps

[big air]

Originally Posted by bigred5765

but only in a surge not a constant 30 amps

still no where near 3 amps on average, in tc you are either on it or of it

[Lee]

A motor can draw 100A + from a standing start, so 30A is nowt.

I had 12t motors pulling 140A from a standing start on a dyno at times. I dont think its down to capacity, voltages, or even charge rates, its just a dodgy cell that has gone down that people try to charge and it obviously canti charged at 6+ amps upto 10 when racing on road and using IB 4200s.

Just equalise and keep an eye on your cells.

[gramey]

"Its more common sense, I'd never discharge an unknown pack straight off. Put it straight on the equaliser and wait - nothing can go wrong then."

I didn't consider these to be unknown packs as they were supplied by a very reputable company, Modeltech. This is born out by the fact that it was replaced without question. I certainly wouldn't expect Nimh cells to be supplied completely flat, who discharges these cells to 0v or stores them at 0v?

As stated in my previous post 'I didn't have any trouble with any of them after that'.

You only have to look at this thread to see how many differing views there are on how to maintain cells, which regime is right?

"there lies the problem, one flat cell would have all the power from other cells dragged though it, then it certainly would go bang"
This may have been the case or possibly a blocked vent, whatever it was once this cell was replaced the cells performed faultlessly.

To put this into context I had two faulty cells in 6 years of electric racing, one Team Orion matched GP3700 cell which was completely dead, and this one EP 4200 cell. On both occasions the packs were returned and the indivdual cells replaced and no further problems arose.

With the number of cells manufactured worldwide proportionately there are very few failures.

[mobile chicane]

Oh I know that the speedo draws high amps but I'm sure gentle discharge is better for cells than hard discharge.

[showtime]

i just did a google search on "discharge" & you don't want to know some of the horrors i've been exposed to