Chuck Hursch <[email protected]
>> 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:
>>> 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
>>> On Wed, Aug 25, 2010 at 1:04 PM, Chuck Hursch <[email protected]
>>>> 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,
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