To echo Lee's experience. Back in the olden days (early 1980s), I put
1" and 1.5" slabs of extruded polystyrene board around the lead-acid
battery packs and on top. 60-watt battery warmers underneath. Remote
sensing thermometers in the packs with read-outs on the dash. The foam
board also reduced ram air cooling of the front battery pack.
With daily driving (charging and discharging) about 30-40 miles (45-60
km) per day, that was plenty to keep the pack at room temperature all
winter - without using the battery warmers. Typical outdoor
temperatures are below freezing for about 5 months of the year here, and
going as low as -thirties (F or C - they cross at -40). Note: LCD
thermometer read-outs don't like really cold temperatures, but this is
easily resolved by warming them.
Used the battery warmers when the car(s) would be parked for over a week
in frigid temperatures.
In warmer weather, simply remove the top insulation panels to avoid
over-heating the batteries. I also installed small 12-volt blowers run
from the accessory battery controlled by a conventional house thermostat
to ventilate when pack temperatures went above 80F (about 25C).
Unplugged those when the top insulation panels were in place. Parts
were readily available and inexpensive (household or automotive hardware).
Today, given the bottom mounting of packs in OEM vehicles and tighter
spaces, I would likely be looking at much thinner insulation forms
(aerogel?) with good R-values. A removable front wall and back wall of
insulation might be sufficient for seasonal adjustments (controlling ram
air cooling ventilation). I would still put remote sensing thermometers
on the pack so I could monitor pack temperature daily, and especially if
I included additional battery warmers.
With current lithium battery technologies, it appears staying close to
room temperature would still be a good target.
--
Darryl McMahon
Freelance Project Manager (sustainable systems)
On 9/11/2019 2:39 AM, [email protected] wrote:
Message: 2
Date: Tue, 10 Sep 2019 16:19:14 -0500
From: Lee Hart<[email protected]>
To: Peri Hartman<[email protected]>, Electric Vehicle Discussion List
<[email protected]>
Subject: Re: [EVDL] li ion battery in cold weather
Message-ID:<[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Peri Hartman via EV wrote:
I'm really surprised the "balance" is so poor... My guess is that there's
virtually no insulation and the manufacturers are skimping because it won't
matter so much to the current buyers.
I think that is exactly it. Also, the big automakers have so little
experience with EVs that they don't realize they need battery
insulation. And, they don't tend to listen to advice from outside the
company.
I've learned myself that even 1" of styrafoam insulation is enough to
keep a half ton of batteries at 70 deg.F with just 100-200w of heat. A
30 KHW battery pack could supply 100w for almost 2 weeks! And if you
leave the card plugged in, that 100w can come from the AC line; not the
pack itself.
-- There is a computer disease that anybody who works with computers
knows about. It's very serious, and interferes completely with your
work. The trouble with computers is that you 'play' with them! (Richard
Feynman) -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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