Was the module you were charging in a pack? i.e. was it compressed mechanically
by the end plates? There modules will explode if you charge them without
pressure being applied to the sides. I have also seen modules that are properly
mounted that have had an internal explosion in a dead cell. The cell it's self
was totally dry, all the water having been converted into hydrogen and oxygen.
My 4 Priuses are all the NHW10 original Japanese only models with "D"
cells. I have done a lot of work on these and have never seen a exploded cell,
all that happens to these is that the cells leak electrolyte if they get to hot.
-----Original Message-----
From: EV [mailto:[email protected]] On Behalf Of Robert Bruninga via EV
Sent: Thursday, 19 June 2014 3:01 a.m.
To: [email protected]
Cc: [email protected]
Subject: Re: [EVDL] [EVADC Listserve] Exploding cell
The prius has 28 modules, and each module (about the size of a paper back book,
only taller) has 6 cells. Each cell is about a 5 AH cell. So the module
voltage was about 7.5 volts.
Bob
*From:* [email protected] [mailto:[email protected]]
*Sent:* Wednesday, June 18, 2014 9:20 AM
*To:* [email protected]
*Cc:* [email protected]
*Subject:* Re: [EVADC Listserve] Exploding cell
Were you testing a pack of cells, if so, how many cells total in the pack and
what is pack voltage? Just curious Bob, I don't know much about NimH.
On Wed, Jun 18, 2014 at 8:54 AM, Robert Bruninga [email protected] [EVADC] <
[email protected]> wrote:
Kaboom goes the cell!
Was testing a battery module from my Prius on a battery analyzer. The test
plan begins with a several minute no-load, then a 1C load for up to 1 hour,
then a several minute no-load, then a charge at 1C until peak voltage is
detected.
After 3 minutes, a cell exploded that could be heard all over the building.
Best I can tell, there was a less than perfect connection to the battery
terminal. The initial 1C load only lasted 3 seconds (when it determined that
the low-voltage had been reached). So then, 10 minutes later it began a 1C
charge (on what was a full battery). And we all know that charging a full NimH
battery will explode.
Lesson learned. 1) Hang around and WAIT for the initial discharge and WATCH
that it is going correctly before leaving the test.
2) Always assume a battery may explode and do testing where it will do no
damage.
Programmers: When programming battery analyzers consider a bad connection on
the DIScharge cycle that might give an erroneous indication of a discharged
battery and fault the test. Do not then continue to the charge cycle.
Bob, WB4APR
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