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Old 09-02-2014, 04:07 PM   #95 (permalink)
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Originally Posted by samwichse View Post
If you run the fan on 12v while grid charging (which you absolutely should), air is drawn in from the passenger compartment behind the passenger seat and exhausted outside the car.

Based on the fan orientation I had assumed it was drawing air from outside because it seemed to be pulling air through the battery and the vents in the hatch area felt like they had air blowing out. After your post I did some reading and found that it does indeed bring air into the battery from the cabin, but that there are two ways air can exhaust. When driving, the cabin has positive pressure, and hot air goes out through a flap in the back. When parked, the hot air comes out through a vent on the right side of the trunk area.

Good to know that cracking the windows does serve a purpose, just not for the reasons I assumed. The cabin will heat up if you don't have positive pressure.


Yesterday afternoon I took it off the charger and went for a drive. The battery meter was still reading ~50%, just as when I had parked it, and didn't really change for about half an hour. I put on the A/C and found some hills with which to burn through the battery. The last 3 bars took close to 20 minutes to chew through, because regen became rather aggressive and without a calpod switch I was struggling to prevent it. I let the car sit for a few hours, then put it back on the charger for the night.

Starting voltage: 153.8v
Final voltage after ~12 hours: 169.2v

Plan to let the battery "soak" for a day or two with a full charge.

Prior to this I didn't have a strong understanding of what a "soak" was. It's talked about vaguely over at InsightCentral as something to do with a grid charger that can help restore/improve capacity though I'm still not clear if it's essential in the balancing process, but apparently voltage is not a good indicator of charge in NiMH batteries. Voltage will remain high for a day or two after a charge, but chemical processes will take place in the cells when resting and the voltage will settle back down. "Soaking" is thus charging them up and letting the voltage settle back down with a full charge.

I don't have any hard numbers about the battery's capacity before the grid charge, but can provide subjective information in a few days, and it's possible there may be some differences that show up in the fuel log. My wife has a pretty consistent commute that is responsible for most non-trip miles on the car.

Last edited by Ecky; 09-02-2014 at 04:19 PM..
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