Energy needed for the cold weather package to heat batteries

[LindsayNB]

What magnitude of energy is the cold weather package likely to use to warm the batteries? Will the batteries stay warm by themselves once they are warmed and you are driving? If not, what sort of draw is likely?

 

[AndyH]

Dunno yet what Nissan did. It should use MUCH less energy than the cabin heater, though, as the pack heater is more like putting a light bulb in a doghouse to keep it from freezing, not like running a blowdryer full-bore 24/7.

The easiest and most efficient way I know to heat a sealed battery box is to use 'heating pads' like these: http://store.kta-ev.com/farnambatteryheaterpad.aspx These use 35W.

The battery box should be insulated as part of the package. Pre-heating the pack (or better yet - keeping the battery warm thru the night) won't use much energy. One wouldn't need to keep the heater running while driving.

With a system like this, the only time one would need to drive with a cold battery is if they parked overnight in the open and didn't or couldn't plug-in.

I do have cold-country battery heater and engine heater experience (Nrn. Michigan - Lake Superior shore) and do have real-world on-road lithium experience, but do not yet have EV battery warmer experience...

 

[TomT]

Do we even know for a fact that Nissan heats the batteries? I've not seen anything definitive on this to date.

What magnitude of energy is the cold weather package likely to use to warm the batteries? Will the batteries stay warm by themselves once they are warmed and you are driving? If not, what sort of draw is likely?

 

[mynameisjim]

Do we even know for a fact that Nissan heats the batteries? I've not seen anything definitive on this to date.

What magnitude of energy is the cold weather package likely to use to warm the batteries? Will the batteries stay warm by themselves once they are warmed and you are driving? If not, what sort of draw is likely?

Someone quoted the Canadian leaf package, that included battery heaters. I believe the Japanese one did too but I'm not certain.

 

[rnkepler]

Do we even know for a fact that Nissan heats the batteries? I've not seen anything definitive on this to date.

Yes, the cold weather package includes a battery heater which comes standard on all Canadian models: Canadian Leaf Pricing

80 kW (107 horsepower) AC synchronous electric motor;
...
Battery heater system
Front and rear heated seats and heated steering wheel;

The battery box should be insulated as part of the package.

So if they do insulate the battery box what effect does that have in the summer? We have below freezing temps here often enough in the winter, but in the summer we have more 90+ degree days. Does the Leaf not generate enough heat in the battery pack for an insulated battery pack to be an issue with heat dissipation in the summer? Any idea on what's worse for the battery, cold or heat?

 

[kmp647]

On these low internal resistance cells not much heat is generated during discharge

cold weather temps are more of an issue so holding some warmth in the pack during the summer is not as detrimental as a dead cold pack in winter

its the lesser of evils

I know I have said this a million times but please Nissan make the cold package available soon

seems like all us tier 2 and 3 people will get 2012's anyway

Interesting that the canadian model is listed as selling this fall as a 2011 ?????
and comes standard with cold pack

BTW Nissan in Northern Virginia on April 1st its 29 degrees and sleeting
our winters are october thru april as far as I am concerned

 

[nater]

But what happens in 110 degree heat over a black parking lot while on the charger? This is my reality here in Colorado.

Nate

 

[davewill]

But what happens in 110 degree heat over a black parking lot while on the charger? This is my reality here in Colorado.

Insulation keeps heat out as well as it keeps it in.

 

[nater]

Right, but eventually, after the car has sat in the sun in 110 degree heat, while charging, the batteries will see 110 degrees.

Will this damage the batteries?

Nate

 

[AndyH]

No nate. These cells run cool - they're very efficient and don't make significant heat even during quick charging.

DoE/NREL cell studies show temperature rises of 2°C at the end of a complete hybrid cycle discharge for Compact Power LiMn cells - tech peers to our cells. This cycle has much higher currents in and out of the battery than we'll see in EV service.

We don't get into cell damaging temperatures until we get into the 60-65°C range (140-149°F).

Fully insulated battery boxes (1-1.5 inch foam inside a 1/2 inch or 3/4 inch plywood box) fitted with heaters and filled with very inefficient lead-acid batteries do not overheat in summer - there's not a chance our cells will overheat.

 

[nater]

I understand they don't make much heat; I'm worried about them being exposed to high ambient heat. It seems that 110 degrees several days a year would shorten the battery life, would it not? Damage from heat is more of a gradient, isn't it? Isn't 70 degrees still better for the battery?

Nate

 

[AndyH]

110 degrees several days a year? If there's any loss it wouldn't even be noticeable in the noise of time-based and per-mile pack degradation.

 

[nater]

I'm talking about potential damage to the pack, not temporary loss of range. Yes, the heat did cause my rav4 to have reduced range, but it was nothing compared to a cold snowy day. I think the worst range hit ever was on a -15 degree day in the middle of a blizzard with studded snow tires. The car performed like a champ, but the range dropped almost to half, even with pre-conditioning from the grid on both ends of the commute. To be fair, the twin furnaces in my home ran continuously and never got the house above 55 degrees. It was extremely cold that day.

Honestly, as long as you have enough charge to get home it doesn't matter.

Nate

 

[AndyH]

I'm talking about potential damage to the pack,

So am I!

If we put the battery in a 110°F oven 24/7 for 8 years, we'll be able to log the temperature-related and time-related degradation.

But out here in the real world things are not like an oven and the real temperature numbers are 'wiggley'.

IF there's any long-term degradation from a couple of days over 110°F, one won't be able to isolate it from the normal time-based, cycle-based, and jack-rabbit start/L3/DC quick charge impacts.

Put another way: Even if we move to an area that's 70°F 24/7/365, and even if we only use the middle 50% of charge, and only use the first 1/4 of available throttle pedal movement and never drive up a hill, the battery will still lose capacity over time. Nissan's taken care of the main reasons for pack damage/degradation. It appears to me that anything under our control is way down into 'diminishing returns' territory.

 

[nater]

Good thoughts, Andy.

Nate

 

[AndyH]

Good thoughts, Andy.

Nate

I hope so too - it's not getting any cooler in South Texas these days - and my garage is routinely at or over 100°F through most of the summer. When my car arrives it'll probably spend more time in the 'cooler' outside.