DC fan from car to run on battery power

[Frank Drake]

Hi everyone! I’m new to the world of electronics and am looking to do a few small projects to help me better understand the theories and concepts I am learning. The first thing I wanted to do was make a piece of DC equipment I would plug into my cars cigarette lighter use a battery bank instead. I believe I have an understanding of how it should work but before I start slicing up cables and putting things together I was wondering if someone could double-check my ideas to tell me if I am on the right path or not.

I have a small 12V DC Fan I purchased at walmart. The sticker on it says it uses 10 Watts and 0.8 amps. It also has a fuse in the DC plug. I want to run this from a rechargeable battery pack instead of plugging it into the car cigarette lighter. My idea is to use AA NiMH batteries. They are 1.2V, 2100 mAh and 2.52 Watts.

1. The fan is 12Volt. I can add as many AA NiMH batteries to the battery bank that I want as long as I don’t feed it more than 12V?

2. Volts and Amps that get sent from the battery bank into the fan can be controlled by putting the batteries in series or parallel?

3. If I can guarantee the fan never gets more than 12V there is no need for that fuse in the fans DC connector?

4. As far as how many hours the fan will last I can figure that out by taking the total Amps ( convert from mAh to Amps) from the battery bank and then divide that by the 0.8A the fan uses correct?

5. The Amps will be under 10 so 18gauge wire correct?

6. If I use for example 8 gauge wire rated for 40amps the system would still work?

 

[BobK]

1. Correct.
2. Correct. In series the voltage adds. 10 1.2V batteries in series will give you 12V.
3. Wrong. The fuse is there to protect against a short, not overvoltage.
4. Yes, but be aware, batteries in series, the maH ratings do not add. I.e. the 10 1.2V batteries in series have the same mAH rating as a single cell.
5. The amps are under 1. 22 gauge wire is fine.
6. Yes, but why would you want to?

Bob

 

[Frank Drake]

Bob,

Thank you very much for the quick reply!

For point 3 is there a specific formula to use to know what type of fuse to use?

For point 6 I would not want to use 8 gauge but because this is a side project I was just going to use whatever wire I have laying around rather than going out and buying the specific wire if I could avoid it. Just wanted to make sure there were no adverse affects if I use a thicker wire.

 

[BobK]

You would use the same kind of fuse that came with the fan.

Bob