[S10-EV] Battery Warmer
Niel Nielsen
When I first got the truck and charging indoors was ok, it only spent about 9 hours outdoors per day, and the rest in my attached garage which used to stay at about 55 degrees. Between the heat from charging and the heat from the garage, the battery temperatures stayed in the '60s. But having to move the truck outside for charging, and my wife also keeping her car in the garage (which adds another 3500 pounds of cold metal inside every day), the garage isn't as warm now, and the truck batteries get down in the '40s, and they don't perform well at this temperature.
Of course, had GM intended for this truck to be used in Chicago, they would have insulated the battery box, which would have solved most of the problem. So this is not a fault of EV's, it the fault of someone taking a California EV out of California.
One solution would of course be to heat the entire garage up to 60 or 70 degrees, but this is an expensive approach. So I bought a "foot warmer mat", which is a 30" x 16" x 1/4" thick rubber mat with a 130 watt heater distributed over the area. I put this on a couple sheets of foam insulation, and that on top of a kids-sized air mattress that I could inflate to come in contact with the battery box.
The heat transfer worked pretty well. After a couple of hours of operation, the average temperature in the battery box rose several degrees, and doing this every night would solve the problem for a small amount of money....
BUT
After the two hours of warming the bottom of the battery box, one sensor (#2) went from 45 degrees to 65 degrees, while the rest went to about 47 degrees. I know that there's no way that one battery gained this much heat in this time, so I suspect that there is one sensor that is laying on the bottom of the box and is sensing the temperature of the bottom of the box and not the air temperature inside the box.
If I let this go overnight, the sensor #2 will probably read in the 80's and the other sensors in the 60s. The result is that the battery cooling will get triggered when I charge in the morning, until the battery box blower circulates the air and equalizes out the sensor readings. I certainly don't want to be running the battery chilling system in the winter!
Obviously, I could rig up something to run the battery box blower to circulate air during this warming, but that would be a big project. Does anyone who's had a battery box apart know if sensor #2 is supposed to be picking up the temperature of the bottom of the box, or has one of my sensors fallen from its correct position and laying on the bottom?
This is a '98 native NiMH truck.
Thanks,
Niel
Stephen Weitz
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Steve Hawkins
Neil,
I only get the digest, so if this has been answered already, my apologies.
I believe the sensors are in the same locations in the ‘97s and ‘98s. Attached is a .pdf showing the locations of the sensors from my ‘98. For the PbA 1260Us they are all attached to the end of the battery under the HV connector, none are on or close to the floor of the battery box; however, because of the method used in attaching them to the battery, I can easily see how one could drop off and fall to the floor. As for the NiMHs I believe (though I haven’t physically seen this) that the sensors are secured under a strap on the side of the batteries, but I can’t speak to how secure that method is (although it looks good in the EV1 manuals I have, assuming they used the same sensor in the s10es). The only “box attached” sensor is the air flow temp sensor at the front of the box at the air intake location. One caveat, my experience only represents what I found when I opened my box, Don and others see a lot more variations then I do.
I also live in the cold (rocky mountains) and appreciate hearing about the options you are exploring so thank you for sharing the data.
Steve
