Batteries in Parallel

[MCahoon]

I think you will want to go with a design that has more margin - I might suggest about twice the expected maximum current. Consider something like http://www.st.com/stonline/products/...stps120l15.pdf possibly? Has lower forward voltage drop at maximum current and somewhat lower thermal resistance.

A significant part of the current rating of the devices has to do with the amount of heat the package can transfer away, given that you have provided adequate heat sinking. I could suggest a number of tutorials for selection of the heat sink (e.g. http://www.wakefield.com/pdf/thermal_tutorial.pdf, among others. Just searched on the internet, I have no association with Wakefield).

The tutorials will help you define what kind of power you need to dissipate, how to calculate thermal resistance of the total path, and give you some information on properties of particular materials and thermal grease, and how the surface area per inch of heat sink affects how much you need, and whether you want to blow air over the fan, etc.

Have fun exploring there.

Hope this helps.

[RyanN]

I've had good luck with the marine battery selector switches. We have one on our 20' Boston Whaler that works good, and I decided to put on on our T-Shirt Shooting robot, and I can switch batteries without cutting the power at all. You have the choice of running 1, All, or 2, as well as an off position. Diodes are great and all, but for the current that you are running, I have trouble seeing diodes supplying that current without getting hot. The battery switch stays cool and transfers a lot of current (I think ours is rated at like 120AMPS continuous, 200 < 30 seconds, 300 < 10 seconds or something like that...