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TimeHorse
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Re: Battery Design and Engineering Issues

Tue Jun 29, 2010 7:55 am

DaveinOlyWA wrote:all this makes me wonder?? when is heat an issue the most?

when charging or discharging?

i thought it was when discharging. when the car is moving, air will be moving as well. if the pack is passive heat control, that would mean, heat exchangers, cooling fins, etc. seems to me that ventilation would be ample at all but parking lot speeds.
My guess is it's just as you say when discharging and think the real problem is charging, but, of course, when charging the thermometer can detect overheating and slow down the flow of the charge so you don't end up with another, massive Dell Laptop!
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evnow
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Re: Battery Design and Engineering Issues

Tue Jun 29, 2010 8:08 am

TimeHorse wrote:Bugger, can't we just set up a sales location in Washington, D.C. so I can drive my LEAF by the Capitol building and remind Congress that we need more EV subsidies?
You may have missed it - but they have extended the EV project to LA & DC i.e. now they are in the early rollout areas. You can get your Leaf early next year ...
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garygid
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Re: Battery Design and Engineering Issues

Tue Jun 29, 2010 9:21 am

Quick Charging can self-regulate (slow down) as needed to avoid cell over-heating.

The 240v 3.3kW (15-amp) charging is but a "trickle", and even the "future" 30-amp (6.6 kW, 4-hour) is unlikely to have a heating problem, but they could also self-regulate. The 120v charging (12 or 15 amp) is even less of a problem.

Regen is probably limited below what it could really do, just to be conservative on regen control and battery life, but it is likely that it would also self-control if heat is a problem.

Driving at parking lot speeds does not cause much heating. Faster speeds only heat a little, but very fast speeds, heat a bit more. Even heavy acceleration, which will generate substantial heat due to the high discharge currents, is usually of limited, short duration, so (unless frequent) is rarely a big heat-quantity producer.

The BIG producer is going up hills. Then, the car should self protect, and warn you of the approaching situation via the left-hand-side Battery Temperature gauge.

Self-protection might force you to slow down, or even stop.
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TimeHorse
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Re: Battery Design and Engineering Issues

Tue Jun 29, 2010 9:26 am

evnow wrote:
TimeHorse wrote:Bugger, can't we just set up a sales location in Washington, D.C. so I can drive my LEAF by the Capitol building and remind Congress that we need more EV subsidies?
You may have missed it - but they have extended the EV project to LA & DC i.e. now they are in the early rollout areas. You can get your Leaf early next year ...
Wow, that's sweet, EVNow! That's why I follow you on Twitter! :)
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DaveinOlyWA
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Re: Battery Design and Engineering Issues

Tue Jun 29, 2010 9:51 am

missed my point. charging usually does not generate as much heat as discharging. u will most likely charge in garage, out of sun, etc. batteries will be relatively cool especially if doing timer charge for better TOU rates.

one question that i am not sure of; for quick charging must generate some sort of heating issue. since mostly likely batteries would have been recently discharged so would be warmer than normal. wondering if time to 80% might be significantly longer in summer than winter especially in AZ?
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 3500.3 mi, 96.95% SOH
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Gavin
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Re: Battery Design and Engineering Issues

Tue Jun 29, 2010 10:01 am

The key is to not live in Arizona :)

Gavin

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garygid
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Re: Battery Design and Engineering Issues

Tue Jun 29, 2010 12:11 pm

In CA, we don't have much real weather, humidity, or bugs. We tend to have mostly over-crowding, smog, "crazy", and lack of water.

If it seems good when you visit, it was probably a hollywood set backdrop hung up for tourists.

"You don't want to move to CA", says Obie-Wan. :)
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AndyH
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Re: Battery Design and Engineering Issues

Tue Jun 29, 2010 1:09 pm

DaveinOlyWA wrote:missed my point. charging usually does not generate as much heat as discharging. u will most likely charge in garage, out of sun, etc. batteries will be relatively cool especially if doing timer charge for better TOU rates.

one question that i am not sure of; for quick charging must generate some sort of heating issue. since mostly likely batteries would have been recently discharged so would be warmer than normal. wondering if time to 80% might be significantly longer in summer than winter especially in AZ?
Hi Dave,

I would expect the pack would be warmer during the later stages of a quick charge, but since the quick charge is only to 80%, we stay away from the last 20% when most of the charging heat is generated.

I'd expect the motor and controller to generate more heat than the battery at high speeds and/or hill climbing. (But with water cooling this will be a non-issue.)

I'm still working on my battery guessing, but it's looking more like the pack of 48 four-cell modules is two strings of 24 for about 345V nominal. If the Leaf cells are the 33Ah capacity listed on AESC's site, and if they're capable of a 10C discharge rate,** then each string should be good for 330A continuous and two parallel strings should be good for 660A. I'm thinking the pack is going to be absolutely loafing during all phases of operation - and I really don't expect heat during charge or discharge to be a problem (or a factor). I'd be surprised if the Leaf draws more than 250A max.

** A 10C discharge rate is pretty low to average for current cells. These old 20Ah LiMn cells from EiG are 5C continuous, 10C peak. Even if the Leaf pack was made from 5C capable cells, that's 330A continuous for two parallel strings, and 660A for <10 second pulses.

Andy

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Re: Battery Design and Engineering Issues

Tue Jun 29, 2010 1:42 pm

curious since L3 charging is DC and a direct connection to the high voltage bus, wondering if the heat build up would be relatively small. in my Zenn, the batteries dont really heat up at all charging or discharging but the charger gets very warm. so warm that i usually pop the hood when home. it has only passive cooling with radiator fins and whatnot but it puts out a pretty good amount of heat.

if the charging system was more efficient, maybe heat buildup is not as much of an issue as we are making it out to be
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LeafHopper
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Re: Battery Design and Engineering Issues

Thu Jul 22, 2010 2:47 pm

The Nissan Leaf Info Screen at: http://green.autoblog.com/photos/nissan ... l/#3195511
may give us a clue about the A/C energy use. First the climate control shows a Kw scale of 0 to 6. Second, the screen has the following message "Turn on Climate Control for -22 miles".

When I compare the 6 Kw A/C use to the -22 mile range penalty, it seems nearly consistent. Since I live in a hot climate, this is an important clue as to the mileage penalty, I can expect from using the A/C continuously. It will be approximately 25%.

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