# Re: [EVDL] warm batteries ==> warm charger and cord ends

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Re: [EVDL] warm batteries ==> warm charger and cord ends

Chuck,
Just to give you an idea of the difference 8 degrees in battery temp can
make, our ET's would go from 16 seconds to 15 seconds from 92 degrees to 100
degrees. The nominal voltage was the same but the resistance in the
batteries dropped enough to let the electrons flow smoothly. I'll be
interested in hearing your results. -Tom

Chuck Hursch <[email protected]> wrote:

> Ah yes, but my charger is constant current at that 1st bulk charge
> stage. So a hot set of batteries are probably not going to get much
> more current, if any, than a cool set of batteries. I don't think
> enough extra current to explain the extra heating of the AC-side
> connectors. 0.5A out of 13A is about 3%. Well, on the DC side, 3% of
> 9A is about 0.3A. If I get another hot set of batteries, I'll try
> clamping on with the ol' ammeter and see what the DC reading is. Could
> be I'll discern greater current, if the charger is letting a little more
> slip by. Guess I'd also have to watch DC voltage, to see what the total
> KW is delivered by the charger. Ok, well I have my marching papers -
> we'll see what happens...
>
> Thos True wrote:
> > Not only do the batteries discharge harder at 100 degrees, but they also
> > absorb (Charge) more easily, so the "suck" the amps in as fast as the
> system
> > will allow, and yes, that would tend to heat up the cords and connectors
> as
> > well. -Tom
> >
> > On Thu, Aug 26, 2010 at 3:04 PM, Chuck Hursch <[email protected]> wrote:
> >
> >> Yes, I think the internal resistance is less for warmer batteries, so
> >> you'll put less of that charge current up as heat. I'm happy there
> >>
> >> However, I still wonder about the warmer cord ends / connectors /
> >> charger. Seems less internal resistance in the batteries should make an
> >> easier life for those parts. Hasn't anyone else noticed the seeming
> >>
> >> Thos True wrote:
> >>> Chuck,
> >>> I suspect that you are seeing what we saw back when we were racing
> using
> >>> We strived to get the batteries up to 100 degrees as that is the
> optimal
> >>> temp for charging/discharging. In other words, that was where we saw
> our
> >>> best ET's and had the fastest charge results.
> >>> In other words, it takes less effort to put the charge back in 100
> degree
> >>> environments.
> >>> -Tom
> >>> On Wed, Aug 25, 2010 at 1:04 PM, Chuck Hursch <[email protected]>
> wrote:
> >>>
> >>>> Been in the midst of a mini heat wave here in the Bay Area. Was in
> the
> >>>> mid-80s here at the apt for the hot point yesterday, 90s at work (San
> >>>> Rafael), and got up to 104 (I heard) in Novato (further north and
> >>>> further from the Bay or Pacific). I expected my pack to be warm, and
> >>>> charger and cord ends / connectors to be warmer also.
> >>>>
> >>>> Pack was sitting at about 94degF (the warmer batteries were probably
> >>>> closer to 100) shortly before I plugged it in for the night. Usual
> 12.6
> >>>> mile roundtrip to the evening job. Get the bluetooth connection set
> up
> >>>> for monitoring the charge voltages from the apt. upstairs. Went back
> >>>> down after half an hour or so to check on things before turning in for
> >>>> the night.
> >>>>
> >>>> Yep, charger (Zivan K2) warmer than usual. AC connections quite warm,
> >>>> warmer than usual. KillaWatt meter reads low 13A range instead of mid
> >>>> to upper 12s early in the charge cycle (putting about 9A DC into the
> 96V
> >>>> floodie pack), power factor read from the KillaWatt in the high 0.60s
> >>>> instead of the usual 0.70-0.75. Odd: wattage seemed a bit low:
> ~1050W
> >>>> instead of the usual 1060-1100W; AC line voltage under load was its
> >>>> usual 115-115.5V, give or take. Everything warmer up to and including
> >>>> the plug in the outlet in the ceiling over the carport. I bet the
> >>>> wiring all the way up to the circuit panel in the apt. was a bit
> warmer
> >>>> too. Could be an unknown greater crest factor, or temperature
> sensitive
> >>>> KillaWatt meter, but things ARE warmer.
> >>>>
> >>>> This always seems to be the case when things are warm. More so than
> >>>> just it being 10 or 20 deg warmer outside. Many years ago someone
> told
> >>>> me that the pack is stiffer (lower internal resistance) when warm, and
> >>>> I've been comfy with that for quite some time. I also heard many
> years
> >>>> ago that a good way to burn up a charger was to put it across an
> Optima
> >>>> (which are very stiff). I assumed in that case the charger was not
> well
> >>>> current limited, so the current would go quite high as the Optimas
> >>>> lapped it up. But my Zivan is more or less constant current in the
> bulk
> >>>> charge mode, so it's DC current will stay within its usual range. I
> >>>> would think a stiff pack in that case would be easier on a charger and
> >>>> keep the cords cooler, since the packs voltage would stay lower for a
> >>>> given DC current, thereby not making the charger work as hard to push
> >>>> the current in. I know that as the pack voltage goes up, the AC side
> >>>> current goes up as the DC current droops a bit (down towards 8.5A at
> end
> >>>> of constant current bulk charge stage). But cooler charger and cords
> >>>> are not what I feel on warm nights. What's the juice?
> >>>>
> >>>> Oh yes, the warmer it is, the lower the charges' total kwh as reported
> >>>> from the KillaWatt, which makes sense. Was 4.97kwh for the charge,
> >>>> which ran midnight to 6AM (timer shutoff). Pack is cooler, the kwh
> will
> >>>> be 5.10 to 5.25. Lower internal resistance of the warmer pack implies
> >>>> less energy wasted as heat. Also have to factor in the Zivan's
> >>>> temperature correction for the 2nd stage constant voltage, and how
> that
> >>>> might be affecting current and total kwhs.
> >>>>
> >>>> Muttering in my thoughts, hopefully not too dumb,
> >>>> Chuck
> >>>>
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> >>>
> >>>
> >>
> >> _______________________________________________
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> >
> >
> >
>
>
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--
Remember, it is not that the glass is half empty, in reality, the glass is
merely twice the size that it needs to be! -TNT'82
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