View Full Version : what is the battery life of a 12v 9 ah battery

11-01-2011, 07:18 PM
I have a 12V 9ah battery and i want to know how long it well last with something that has a power consumption of 20W

11-01-2011, 07:34 PM
12V*9ah = 108 watt hours, so 108/20w = 5.4 hours. You probably want to test it if its important though, since battery specs can be depend on certain conditions.

07-28-2012, 11:30 PM
I know this thread is old, but since I have been reading a lot about batteries recently I felt the need to comment in case anyone else reads this.

Battery Amp Hour ratings are based off a baseline discharge rate listed on the spec sheet. So for a given time of 20 hours, how much power does the battery supply before reaching some lower voltage limit. Discharge rate for 20 hours would be at 450mA, if your system draws 1.5A though the battery may only provide ~7Ah of power.

These figures are based on the PS-1290 12V 9Ah Lead acid battery. As with all things, read the spec sheet carefully!