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-   General Race Chat (http://www.oople.com/forums/forumdisplay.php?f=8)
-   -   Ep 4200 Has blown up in my face (http://www.oople.com/forums/showthread.php?t=8070)

Northy 10-02-2008 07:16 PM
I'm with Dan here.

G

Richard Lowe 10-02-2008 07:29 PM
It probably varies between suppliers, the cells I've had in the last few years have all been flat as a fart :)

DCM 10-02-2008 07:33 PM
does no harm though, to slap them on a tray to make sure does it, I did....

Northy 10-02-2008 07:40 PM
Quote:
Originally Posted by Richard Lowe (Post 92643)
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........ :eh?:

G

ashleyb4 10-02-2008 07:41 PM
A EP 4200 went boom today at kiddy in there car. Found out he had been charging at 6 amps :eh?::eh?::yawn: It sounded like a gun it wasnt that loud though

A

Lee 10-02-2008 07:46 PM
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 10-02-2008 08:37 PM
All these dodgy cells should be recalled somehow.

mark christopher 10-02-2008 08:45 PM
Quote:
Originally Posted by Richard Lowe (Post 92455)
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 :confused:
Quote:
Originally Posted by Northy (Post 92635)
I'm with Dan here.

G
me too
Quote:
Originally Posted by DCM (Post 92645)
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 10-02-2008 08:50 PM
Quote:
Originally Posted by gramey (Post 92440)
:)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.:eh?:
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 10-02-2008 09:06 PM
Quote:
Originally Posted by mark christopher (Post 92714)
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 10-02-2008 09:20 PM
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 :D

Southwell 10-02-2008 09:20 PM
See me next meeting and ill give you a 4200 cell Giles.

mobile chicane 10-02-2008 09:24 PM
Quote:
Originally Posted by Southwell (Post 92761)
See me next meeting and ill give you a 4200 cell Giles.
cheers m8 :thumbsup:

big air 10-02-2008 09:31 PM
Quote:
Originally Posted by mobile chicane (Post 92759)
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 :D
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 :eh?:

bigred5765 10-02-2008 09:43 PM
but only in a surge not a constant 30 amps

big air 10-02-2008 09:51 PM
Quote:
Originally Posted by bigred5765 (Post 92789)
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 10-02-2008 10:00 PM
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 10-02-2008 11:27 PM
"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 11-02-2008 08:02 PM
Oh I know that the speedo draws high amps but I'm sure gentle discharge is better for cells than hard discharge.

showtime 11-02-2008 08:31 PM
i just did a google search on "discharge" & you don't want to know some of the horrors i've been exposed to :wtf:

josh_smaxx 11-02-2008 08:35 PM
Quote:
Originally Posted by showtime (Post 93289)
i just did a google search on "discharge" & you don't want to know some of the horrors i've been exposed to :wtf:
http://www.discharge.co.uk/

Was this it? or was it one of the other links? :woot: :o

Southwell 11-02-2008 08:42 PM
Quote:
Originally Posted by showtime (Post 93289)
i just did a google search on "discharge" & you don't want to know some of the horrors i've been exposed to :wtf:
O dear god! why o why did i put that into the image search!!!!!!!! :lol:

showtime 11-02-2008 09:12 PM
oh yeah, i went for images too ;)

Welshy40 12-02-2008 05:35 PM
Quote:
Originally Posted by big air (Post 92344)
I just can't understand why it went up, like i said it was on top of a plastic box, I only moved my gear out there last week i used to pit in my living room and ive got a 12 week old baby :o what if it went up last night or if i wasn't there the whole house would of went up, Im ok apart from my ears are killing me it was like a Bomb going off, :o
You are one lucky bugger! But I must admit these new cells are not as user friendly like the SCRCs, heck you could twelve volt em before a race and they didnt mind. These nimh are too fragile and seem very dangerous


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