Oops. I forgot the editor automatically removes leading spaces, so my ASCII diagram looks even worse than I imagined.
Just picture a bird’s-eye view of a car battery with the “+” terminal positioned on the left and the “-” terminal on the right. “A” is the top-side of the battery (12:00); “B” is the right-side (3:00); “C” is the bottom-side (6:00); “D” is the left-side (9:00).
This is an interesting angle that would have never ocurred to me but I doubt this would have any effect. The liquid within the battery would prevent any significant temperature difference from forming unless you had some serious outside temperature conditions. But the thought is clever.
Sailor:
You may be correct that this is non-issue; I don’t know. Has anyone studied this and published results?
We should be able to do a rough calculation to find out the magnitude of current that would flow due to a temperature gradient. I suppose we would need to know the following:
As I say, i thought it was quite ingeneous to think of this angle because it would have never ocurred to me.
On the other hand I just cannot see it affecting the battery in real life conditions. I think it would be difficult to have a temperature gradient inside a battery cell of even a fraction of a degree. It is relatively well insulated and full of liquid that would soon cause convection.
that’s just my WAG. If you have anything more concrete I’d be interested. I have seen batteries installed in places with temperature differentials and never seen any measures taken to avoid them. That is why this angle would not have ocurred to me.
If your concrete was radioactive, the main effect would be to ionize the air. This would make it more conductive, and could allow the battery to discharge faster. But I doubt it would be much of an increase.
But keeping the battery cooler would make it discharge slower. I think this effect would be more significant.
So, as long as your garage floor isn’t really ‘hot’ in the radioactive sense, and is ‘cool’ in the temperature sense, I think there would be a net increase in charge life, compared to a warmer spot.
However, I doubt that putting a board under the battery would warm it. If the temp in your garage shifted a lot, the insulation value of the wood would keep the battery from cooling to a new, lower temp as quickly, but it wouldn’t change the situation in a room that kept more of a steady temp.