its %$*&ing cold up here... (EV winterizing tips needed)

[Oval_Overload]

...And I might just kill someone. More on that later.

EV enthusiasts, share with us your winterization strategies. The ideal temperature for lead acid batteries is 78ºF, and for those of use in a northern clime, winter means we have to get a-thinkin', how do we keep our traction packs happy in sub-zero weather.

The most successful strategy I've seen implemented so far was on the notoriously range deficient Zap Xebra. In stock form, the batteries hang out below for all the voyeurs to see. The solution was to give it a pair of underwear!

The batteries were removed (oh my aching back) and Pink Panther foam was placed underneath. An electric heater was taped to the foam and laminated. Thin, flexible closed cell foam was taped to the sides of the battery box. This is the foam that is used to insulate between a wall and sub-floor in new construction. This solution was enough to keep the batteries warm for several hours while parked but it still wasn't quite enough, so a 150 watt heat blanket was run along one side of the box and fiberglass insulation was stuffed in plastic 'construction waste' bags and stuffed in every crevasse. A wrapped bat of fiberglass was placed along the top of the batteries and topped with Pink Panther foam. The battery box was buttoned up and I parked the car outside. The next morning, it had a full charge at 70º F. The interior of the car was at 32º F and the outdoor temperature was 18ºF if I remember correctly, which leads me to my current conundrum...

I borrowed the black Wheego Whip from work to go look at an apartment two days ago. The car had been sitting out in the cold for days, so I plugged it in. The internal resistance warms the batteries while they charge. The pack temp climbed about 5º above ambient after a couple hours on the charger. I know that doesn't sound like much, but this car has not been winterized. It has a sealed, but uninsulated battery box. I left work with an 80% charge and an 18ºF pack. 4 miles of driving netted me 10ºF and the return trip bumped the pack to 38ºF, pretty good for an uninsulated car, I'd say. I drove a total of 8.5 miles with probably another mile left in the pack.

Yesterday, I went to this psedo party at the local Perkins (yeah, I know, Perkins >.< ). Partly because I wanted to learn how this car worked in cold weather, but mostly because I am sick of driving my parent's Suburban, I drove the Wheego. I left with a 75% SOC and a 28ºF traction pack. I arrived 5.5 miles latter with the pack at about 43ºF and a 20% SOC. What the hell happened??

I parked at the British Petroleum station that shares a parking lot with Perkins and gave the clerk some loose change to let me plug into the socket for the air compressor. After a short while, a troupe of electronics geeks and I checked on the car. Standing in the cold, we drew our calculations on the frost of the back window, trying to figure out how many KwH I needed to get the car back to the shop. One of the geeks was futzing with the CD player and made an off hand comment about the defroster... It was on. It had been on the whole drive over. The fan was on its lowest setting so I never heard it, but the temperature knob was cranked to turkey-roasting mode!

This is where Jimbo goes bizzerk. GOD&*%$ITMOTHER!@#$INGSONOFA&%@#$

Whoever used the car last left the heat cranked up. I burned through 635 wh/m! in a 2400 Lb AC drive car!

3.5 KwH later, I drove back to the shop using about 20% of the charge. The SOC meter barely moved. The pack temp was 58º F

[watt-a-mezz]

I can imagine how cold it gets there. I listened to Garrison Keilor tell about
it. Definately needs good heat. We had 0 to 5- here last week. My daughter
asked me if batteries will freeze and bust. I dont know, do they? Interesting
lingo, takes me back to my Navy days. Watt.

[Frank Lee]

Yes they can freeze and bust.

[SentraSE-R]

Yes, but you'd have to have -75ºF temperatures to do that to a battery that's 100% charged, and -35ºF to freeze a lead-acid battery that's 75% charged. Source

[Frank Lee]

We get -35 and WORSE on a regular basis here in gawd's country.

[SentraSE-R]

I saw -35ºF in Colorado, but not in my 6 years in Alaska. I had to put a Coleman lantern under my truck's crankcase for 45 minutes to thin the oil out enough to crank the engine over. The crankshaft felt like it was imbedded in concrete at first. After 45 minutes of heat, it merely felt like it was imbedded in molasses.

My friends living in colder parts of Alaska would take their batteries indoors with them at night.

[Frank Lee]

When car batteries freeze the case bulges out. It remains bulged out after thawing.

[dremd]

-35ºF Good Lord! I'd just die.
I doubt I could keep my house above freezing in those conditions.
My TDI JUST barley starts on B-100 at +32ºF I don't think I'd have a change even even with Petro Diesel at -35ºF.

Back on topic:
How many watts is the heater?
I keep thinking that a heat pump would be a good heater in an EV.
Glad you made it home.

[NiHaoMike]

For Lithium batteries, colder is generally better. Thus the suggestion to refrigerate unused Lithium batteries.
http://www.thunder-sky.com/pdf/TS-LFP40.pdf
Thundersky specifies a minimum *operating* temperature of -45C or -49F. (It does not specify the minimum storage temperature, so just assume it's the same as the minimum operating temperature.) So it looks like Lithium is the way to go for cold climates.

It should be very easy to make a battery heater from old electric blankets. Just take out the resistance wire (which I think would be insulated in plastic so sweat cannot cause current leakage) and string it between the batteries.

[Oval_Overload]

The 'electric blanket' method was used on the Xebras. Insulation is far more important than heat, but heat helps.

Charging at the shop drew 3.04 kwH. 3.04/5.5=553 Wh/m

This is not totally accurate because the charing cycles took place at vastly different temperatures, also note that this was all night driving so the running lights were all lit.

Nobody else has any winter EV stories or tips to share?