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How is "cold battery" sensed? I want the charge.

602 Views 21 Replies 6 Participants Last post by  Markgm
I am a new owner of a used 2000 Legacy wagon. I have very interesting living conditions. Living in the car, I use my laptop all day. Sometimes, it's a little cold outside, too. So I break the rules and idle my car from time to time. I have a power bank/inverter that I charge, and the laptop via inverter uses 15-20 watts. Well, this car doesn't give out extra current for much.

When I start the car cold, it gives battery charge current, and I really enjoy using that. It reminds me of the charging of the old days, when the battery was always being charged. Well, I think I want to do this here. I want to charge the battery all of the time. I will use it.

Does my car have a battery temperature sensor, or is it another temp-related sensor somewhere else, that gives me this high cold-start charge? Secondly, I am wondering if there is a way to trick it into always being "cold", so to speak, so that the higher voltage/charge would always be on?

Cheers, Mark
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A year 2000 car has a basic alternator without sensors or any external control. The alternator is going to charge the car battery as much or as little as the battery needs at that time. You can't influence that, but if you could, you'd probably damage the battery. The reason you see it charging at a higher voltage when it's cold is because the battery gets discharged more. A cold battery loses some output, and a cold engine takes more power from the starter motor to turn.
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