Tuesday, September 1, 2009

Little Tricks

Today was the first, real, Official full time EV use to work and back. I was welcomed on this September first with 48 F weather! It was in the 90s last week, and all of a sudden it was cold and brisk. On the way in, I did notice the cold had an effect on the batteries, and I messed with the charger yesterday didn't help.

First, the charger. I was reading that I should set the float on my charger to 14.4 volts, so I did. Well, some batteries didn't get fully charged because of that, so it went right back to 14.8 volts this morning when I got it.

Now the temp. According to this: http://www.windsun.com/Batteries/Battery_FAQ.htm#Temperature%20Effects%20on%20Batteries the batteries were down to about 87% capacity due to the weather, and that was dead on. I usually have 40-50% left, but I was closer to 25% left and did my best to slow down. I did a few trial last winter and found that betteries were much warmer when left charging over night and range was quite decent compared to cold batteries, so tomorrow I will get to see if it still true since I will have the EV charger most of the night.

It's time to start thinking about installing the ceramic heater and get down to insulating the batteries, for real this time. I am looking into sheet metal or some type of cheap plastic to house the foam insulation.


Gregess said...

Do you actually monitor the battery temperature? Or are you assuming that the batteries cooled down to match the air temp? There's a lot of mass in those batteries - it should take a long time to cool down.

David Harrington said...

Yes I do have two temperature sensors, one monitoring the air temp in the trunk and one monitoring the batteries. The air temp was 48F and the battery was 52F the first morning without being on the charger, and the next morning the air temp was 48F again, but this time the batteries were about 67F.

I believe if I can insulate them, I get keep them at 75F when charging.