DIY Electric Car Forums banner

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

614 Views 0 Replies 1 Participant Last post by  EVDL List
Re: [EVDL] warm batteries ==> warm charger and cord ends

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
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.
>>>> | OTHER HELP:
>>>> | OPTIONS:
>> _______________________________________________
>> | REPLYING: address your message to [email protected] only.
>> | Multiple-address or CCed messages may be rejected.

| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
1 - 1 of 1 Posts
1 - 1 of 1 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.