View Full Version : Battery life/ run time question

08-28-2011, 06:51 PM
I have (2) 12V - 18Ah batteries in series.

The way i understand it is if I had a 1amp load the one battery should last 18 hours.

Does that apply even if the batteries are in series for 24v? I know the voltage doubles but what happens to the Amp hour rating?



Mike Green
08-28-2011, 07:01 PM
The Ampere-hours refers to the amount of current only. If your device draws 1A, an 18Ah battery will supply 1A for 18 hours. The voltage doesn't matter. If you're using a switching regulator, it's a little different. If you have two 12V (13.8V actually) 18Ah batteries in series and this feeds a switching regulator and the output of the switching regulator feeds a 1A load, the input to the switching regulator will draw a bit more than 1/2A, not 1A and the batteries in series should last for a bit less than 36 hours.