OK, Wai, here's a full-time electrical engineer at your sevice.

In you earlier post, you mentioned you require a power source that can deliver 18 amperes at 12 volts (dc) for minimum 6 hours.

To me, that means that:

1. The device you are powering consumes 18 * 12 = 216 watts.

2. The batter capacity you require is 18 * 6 = 108 AH (or 108000 mAH)

Hypothetically, if you wish to construct such a battery pack using AA NiMH cells with 1800mAH capacity at 1.2V, you will need to:

1. connect 10 batteries in

**series** to give you 12V, this will give you 1800mAH at 12V. The voltage adds when you connect in series, but the capacity remains the same.

2. connect a total of 108000/1800 = 60 sets of the 12V assembly described above in

**parallel** to give you the total capacity of 108000 mAH. The capacity adds when you connect in parallel, but the voltage remains the same.

So the total number of AA batteries required is 600.

Even if you go to 9000 mAH 1.2V D size batteries, you will still need to connect 10 in seriese to get 12V, and then 108/9 = 12 "tubes" of the 10-in-series connection in parallel to get the 108 AH capacity. That means a total of 120 batteries.

The only suggestion I can give you is to look at car batteries.

May I know what devices you are trying to power? I am curious about the 18 ampere requirement. Driving that kind of current will heat up the cable to very high temperature due to cable resistance. You will need cables that look like jump-start cables for cars.

- Roy

ps. sorry for going OT, Darren. could not resist an electrical discussion.