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LakeLeaf
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Battery temperature display

Thu Jun 24, 2010 2:11 pm

It looks like quite a bit of display real estate is devoted to monitoring the battery temperature.

For the folks who have been driving EV's - does the battery temperature really change so much as to need to devote that much prime display space to monitoring it? Even if you know what the temperature of the batteries is - can you alter your driving to positively effect the temperature?

Do you think this is a good use of display space, or are the other parameters that you would rather have the ability to monitor on an instantaneous basis? It might be nice to see a rotating display (a la the Prius) where you can display battery temperature (if that is really needed), regeneration specs, instantaneous energy usage (watts per mile or some other meaningful metric to help you determine how much energy you are pulling at that instance in time), energy usage over time, etc. etc.

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garygid
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Re: Battery temperature display

Thu Jun 24, 2010 4:11 pm

The battery temperature might be of interest when in hot or cold weather, and the driver will need to plan ahead for shorter trips due to decreased battery performance.

However the car should be smart enough to warn about (and deal with) any temperature issues that would degrade the battery's useful lifetime.
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evnow
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Re: Battery temperature display

Thu Jun 24, 2010 4:20 pm

LakeLeaf wrote:It looks like quite a bit of display real estate is devoted to monitoring the battery temperature.


I'm sure they are still showing their development /test screens. Though Nissan should be showing production intent screens as well at this point to get good feedback.
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Nubo
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Re: Battery temperature display

Tue Jun 29, 2010 2:00 pm

I can't saw how it plays out in an EV, but I've had battery-powered devices that put a heavy load on battery packs, and they can get HOT! At a max power delivery of 90KW, the pack will be pushing a whole lot of amps. Find yourself climbing a long steep hill and battery temp could become important. I'm sure the car will keep you out of trouble with alerts, and reduced power if need be. But it's good to have a readout to help keep you out of that zone to begin with. I'd consider it to be the equivalent of a coolant temperature gauge in a gasoline car. Rarely an issue but still an important gauge to have.
I noticed you're still working with polymers.

AndyH
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Re: Battery temperature display

Tue Jun 29, 2010 3:32 pm

Nubo wrote:I can't saw how it plays out in an EV, but I've had battery-powered devices that put a heavy load on battery packs, and they can get HOT! At a max power delivery of 90KW, the pack will be pushing a whole lot of amps. Find yourself climbing a long steep hill and battery temp could become important. I'm sure the car will keep you out of trouble with alerts, and reduced power if need be. But it's good to have a readout to help keep you out of that zone to begin with. I'd consider it to be the equivalent of a coolant temperature gauge in a gasoline car. Rarely an issue but still an important gauge to have.


Battery loads for EV VS. cell phone is apples and oranges.

Phones and other small consumer products are small and demand a small battery volume - high energy density. Most use lithium cobalt or lithium polymer cells and work them hard. They're only expecting the battery to live 1-2 years and almost guarantee this by using an inexpensive charger that often overcharges the cells.

EVs have much more room for the battery and there's an expectation and battery life target of 5-10 years. This forces lower stress on the pack, smarter charging, and better battery/cell management.

My best guess for the Leaf pack is here: http://www.mynissanleaf.com/viewtopic.php?p=9074#p9074 Chances are very good that the pack can easily handle 600A+ loads but will only be required to provide ~250A max. It's a pretty easy life for a battery.

Andy

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Nubo
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Re: Battery temperature display

Thu Jul 01, 2010 9:16 pm

AndyH wrote:
Nubo wrote:I can't saw how it plays out in an EV, but I've had battery-powered devices that put a heavy load on battery packs, and they can get HOT! At a max power delivery of 90KW, the pack will be pushing a whole lot of amps. Find yourself climbing a long steep hill and battery temp could become important. I'm sure the car will keep you out of trouble with alerts, and reduced power if need be. But it's good to have a readout to help keep you out of that zone to begin with. I'd consider it to be the equivalent of a coolant temperature gauge in a gasoline car. Rarely an issue but still an important gauge to have.


Battery loads for EV VS. cell phone is apples and oranges.

Phones and other small consumer products are small and demand a small battery volume - high energy density. Most use lithium cobalt or lithium polymer cells and work them hard. They're only expecting the battery to live 1-2 years and almost guarantee this by using an inexpensive charger that often overcharges the cells.

EVs have much more room for the battery and there's an expectation and battery life target of 5-10 years. This forces lower stress on the pack, smarter charging, and better battery/cell management.

My best guess for the Leaf pack is here: http://www.mynissanleaf.com/viewtopic.php?p=9074#p9074 Chances are very good that the pack can easily handle 600A+ loads but will only be required to provide ~250A max. It's a pretty easy life for a battery.

Andy


That's encouraging. I'll be taking her to the top of Mt. Diablo (~3800 foot climb) to test the limits, and to enjoy a nice long regen on the way back down. :)
I noticed you're still working with polymers.

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garygid
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Re: Battery temperature display

Fri Jul 02, 2010 7:38 am

Unless Nissan decides to provide a variable Regen, it is quite possible that even the ECO ("B") drive setting will not provide enough braking coming down Mt. Diablo (lived in Danville).

Prepare for a hot-brake test, and please let us know how it goes.
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MikeBoxwell
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Re: Battery temperature display

Sun Jul 04, 2010 12:36 pm

Battery temperature makes a huge amount of difference in an electric car. If the batteries are too hot or too cold, performance suffers, range suffers and the battery is more likely to fail prematurely.

In an electric car, a huge amount of effort is devoted to maintaining the battery temperatures at an optimum figure so that this is not a problem. However, not every manufacturer gets it right - I've driven a prototype electric car a few months ago with a summer range of 85 miles which drops to nearer 35 in really cold winter conditions. Since then, this particular car has had a battery pack redesign in order to incorporate battery heating to resolve this particular problem, so it should not be an issue when it is launched at the end of this year.

So it is unlikely that you'll have these sorts of problems with a Nissan LEAF, because all these sorts of issues should have been ironed out by now. However, if you are ever in a situation where you're driving an electric car and the battery temperature warning light comes on, here is what to do:

If battery temperatures are too hot:
Switch off anything that you don't need - including air conditioning and radio, and switch to eco mode whilst you find somewhere to pull over safely.
Pull over as soon as possible and let the batteries rest and cool down. Allow at least twenty minutes and preferably longer.
When you start driving again, drive slowly and gently, using eco mode only and using as few other facilities in the car in order to protect the batteries.
When you get to the end of your journey, let the batteries cool down for several hours before plugging the car in to recharge again.
Call your dealer - you could be looking at a faulty battery cell.

If battery temperatures are too cold:
Drive slowly and gently, using eco mode only and using as few other facilities in the car in order to protect the batteries.
As you continue your drive, the battery temperatures should increase again. Once the battery warning light goes off, you can drive normally, which will increase battery temperatures even more.
When you get to the end of your journey, plug the car in to recharge immediately.

To be honest, most people never have temperature problems with their electric car batteries. But if you end up being one of the unlucky ones who do, now you know what you can do.

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