Sunday, February 21, 2010

Battery Pad Results

Results: AMAZING!

After installing the pads I left them on all night, and the next morning the pack was at 76F and the drive was GREAT! I had a massive EV grin mixed with an EVil EV laugh as I zipped up the largest hill in my commute.

I did find something interesting this morning. I left my heater plugged in last night, and it got the pack up to 76F in 20 minutes (it was already 63F) and then shutoff for about 4 hours before it got cold enough to reactive. The problem was it didn't turn back on! The voltage regulator I used wasn't the one designed for cold temps, it has a range of 0c-75C, where I need the one that goes from -30C to 125C. I did find a few in my electronic component stash that I will install tomorrow.

Thursday, February 18, 2010

Heater Pad Installation

Today I spent the afternoon installing the Farnam Battery Heating Pads I purchased from KTA-EV. What took the longest was lugging the batteries out from the basement out to the EV, then hoisting them into the EV.

This is my temperature control circuit for the heater pads. This is essentially a massive on/off switch that uses a temperature sensor set to a value that trips when it is reached, then it shuts off the AC power to the heaters. I have it set to 75F and it will reactivate at 71F. I have also a fuse, master on/off switch for the AC and a solid state relay that does the heavy work.

And here are the pads themselves, installed in the trunk. They are 35 watts each, and I have one under each battery.
I did a test yesterday with the whole setup in the basement, and it got the pads up to 75F from 50F in about 3 hours. During this test I used a thermal probe between the battery and pad, now in the EV I am using the thermal sensor from my PakTrakr, which lays on top of battery 1. After I finished reinstalling everything, I turned on the battery warmers for 3.5 hours and the Paktrakr sensor recorded 58F from 49F. I insulated my batteries so there is little space for the heat from the pads to rise, except through the batteries themselves.

I have to neaten up the electrical cord for the pads, so I shut them off for the night, but tomorrow I will sort that out and take the EV out for another drive, then apply the pads. Right now it is 35F out and 58F in my batteries, so I am curious to see how my new insulation packing will work out and check out the temps in the morning.

Wednesday, February 17, 2010

Winter Proofing

When I ordered my battery heating pads I also ordered this:
And official "ELECTRIC" sign! My last sign was a computer printout half laminated with scotch tape that one of my dad's coworkers put on. It was one since August and finally fell off last week after removing snow from the car.

This past weekend I removed all my batteries to clean out the trunk and install my battery heating pads. What really happened was that I removed all my batteries, then spent the next two days equalizing my batteries, checking voltages and playing with a hydrometer. Then I finally got around to finishing the circuit that controls the temperature and spent the next few days dealing with snow.

Anyways, today I tested the heaters and circuit this afternoon in the basement with my batteries on it, and it did really well! After an hour it got the batteries up to 62F from 50F, and while that sounds low, it was also heating a concrete floor at the time.

Tomorrow I have a half day and the weather looks good, so I should be able to get the pads and batteries back into the EV after I finish vacuuming out the trunk. My next post will contain all the pictures and information on my battery heaters and what I did, etc.

I still haven't finished the cabin heater circuit, mainly because if I don't get heated batteries, I wouldn't have enough usable capacity to even run the heater.

Also, nearly every day this past semester the EV professor keeps asking when my EV in coming back, and I am hoping it will make it's 16.8 miles return next week, assuming I get the cabin heat completed and I so some range tests to make sure I can hit the 16.8 miles with heated batteries.