Hi

I have been trying to build a DIY dew heater for my DSLR camera with a 12v battery source. I have been using nichrome wire, and it was working great with only 4 AA batteries, but when I upped it to 8 AA batteries for more heat, the wire heated nicely but the battery pack started to overheat about 10 minutes in. Is there any way I can mitigate it overheating? I tried adding a resistor on the negative side, but it caused the strip not to heat up at all.

Thank you

 

You have a Catch-22. Enough current to give you the heat you want is also heating the batteries. If you reduce the current, the batteries won't get as hot but neither will the wire.

How were the 4 and the 8 cells arranged, all in serial?

Do you have an idea how much current was being drawn? I'm wondering if maybe one or a couple of your cells were heating while the others were fine. Were your cells all more-or-less the same and fresh when you tested them?

 

You have a Catch-22. Enough current to give you the heat you want is also heating the batteries. If you reduce the current, the batteries won't get as hot but neither will the wire.

How were the 4 and the 8 cells arranged, all in serial?

Do you have an idea how much current was being drawn? I'm wondering if maybe one or a couple of your cells were heating while the others were fine. Were your cells all more-or-less the same and fresh when you tested them?

All the batteries were arranged in serial inside the normal RadioShack plastic battery holders. Not too sure how much was being drained off. However, the batteries have all been drained off at the same time. When I was testing it earlier it was all the batteries heating, not just one.

Thank you

 

I might suggest NiMH batteries for their low internal resistance (compared to alkaline batteries).
Another method would be to use a small 12V lead-acid battery because it is large enough to dissipate the heat and because most of these self built heaters use more power than people expect. Running out of juice in 20 minutes? That would mean you need a bigger battery.

 

You also also realize that by doubling the batteries you have quadrupled the power to the heater?

You might try bumping it up a little less.

 

Thank you for all the replies. I think I may try to just add more cable to the circuit, it will be connected to another device that needs 12V so I can't be flexible on the voltage. Is there an equation I could follow to determine how much of the wire or resistance I need before the battery starts overheating?