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

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
> >> contradiction?
> >>
> >> Thos True wrote:
> >>> Chuck,
> >>> I suspect that you are seeing what we saw back when we were racing
> using
> >>> lead acid batteries.
> >>> 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
> >>>>
> >>>> _______________________________________________
> >>>> | REPLYING: address your message to [email protected] only.
> >>>> | Multiple-address or CCed messages may be rejected.
> >>>> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> >>>> | OTHER HELP: http://evdl.org/help/
> >>>> | OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
> >>>>
> >>>
> >>>
> >>
> >> _______________________________________________
> >> | REPLYING: address your message to [email protected] only.
> >> | Multiple-address or CCed messages may be rejected.
> >> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> >> | OTHER HELP: http://evdl.org/help/
> >> | OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
> >>
> >
> >
> >
>
>
> _______________________________________________
> | REPLYING: address your message to [email protected] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
>



--
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20100827/73cd1849/attachment.html
_______________________________________________
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev

Click to expand...