Re: Any NiMH battery experts?
- From: miso@xxxxxxxxx
- Date: Thu, 10 Apr 2008 19:53:46 -0700 (PDT)
On Apr 9, 8:27 pm, Spehro Pefhany <speffS...@xxxxxxxxxxxxxxxxxxxxxxx>
wrote:
On Thu, 10 Apr 2008 13:55:39 +1200, the renowned Jim Granville
<no.s...@xxxxxxxxxxxxxxxxxxxxxx> wrote:
Spehro Pefhany wrote:
Any experience in properly charging large, densely packed packs of
15-35 cells in series (state-of-the art AA cells or similar)? How
about with a few packs like that in a confined space?
I'm seeing some 'interesting' effects such as temperature increase
continuing after charge current is removed, likely due to chemical
reactions.
..and just simple thermal inertia?. The heat will come from the core,
but the sense point will be further away, so you would expect the heat
to climb after current it removed, especially on shorter charge cycles.
-jg
It does not behave like that-- early in the charge cycle the
temperature rise stops immediately upon removal of the charge current,
so something else appears to be going on.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@xxxxxxxxxxxx Info for manufacturers:http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
The initial charging of NiMH is endothermic, so cell behavior in the
early stages is atypical. [That is probably not phrased very well, but
the idea is for NiMH, you don't use temperature measurement in any of
the charging algorithms in the early stages.] Eventually the reaction
is exothermic.
What kind of temperature changes are you seeing when you cut the
charging current? Is it s few degrees? If so, maybe you can examine
the temperature of the cells with one of those IR boxes. That is, I'm
assuming you have some sort of thermistor scheme.
I got a smart pack returned to me because the manufacturer couldn't
figure out why the pack wasn't charging like it used to. I spent some
quality time with it and everything seemed kosher. [Translation: no
problem and a waste of my time.] However, it turns out the assembly
house (off-shore of course) was putting extra kapton tape around the
pack, insulating the thermistor, causing a lag in the temperature
measurement.
.
- Follow-Ups:
- Re: Any NiMH battery experts?
- From: Spehro Pefhany
- Re: Any NiMH battery experts?
- Prev by Date: Re: OSC and unity gain buffer
- Next by Date: Re: EIA 19" rack dimensions
- Previous by thread: Re: Any NiMH battery experts?
- Next by thread: Re: Any NiMH battery experts?
- Index(es):
Relevant Pages
|
