Some simple electronics help.

[Glaucus]

It's been a fair few years since I've done any electronics. I was never brilliant. But I can't work this out.

If I have a device that is rated at 50A at 14.8V How many mAh would I need to run it for 30mins.

If I linked two in parallel, the voltage would stay the same but I would need double the mAh?


and if a battery is rated as a maximum discharge of 30A would that mean 10 batterys linked in series would be capable of 300A maximum discharge?

 

[Dr.EM]

Not certain on the first one, but 25Ah (25,000mAh) should do it? More accurately, it is dependant on what the minimum voltage the device could operate at along with the discharge curve of the battery in question. My advice would be to leave a decent safety margin (oversized battery).

Linking most types of battery in parrallel is unadvisable. The voltages are invariably slightly different and so they "fight" against each other trying to equalise the voltage. With nothing but thier internal resistance (low in lead acid types) to limit it, they will get hot! If you must do so, place a small value, high power resistor between thier positive connections. The voltage would stay the same but theoretically double the current capability and discharge time (assuming identical units).

Linking batteries in series will reduce the "discharge", or preferably termed maximum current capability. This is since additional internal resistances are added by series connection and so further losses are experienced in the cells. You increase the voltage by doing this (voltages add) but lower the current capability