I just look it up on the specification sheet...
This is for the TROJAN T1275 - says this battery will produce 12VDC@25AMPS for 280 minutes or 4.6 hours... At the end of 4.6HOURS this battery will be reading 10.5VDC if you put a 25AMP load on it. This tells me I will only be able to use this battery for 2.3 HOURS of 25AMP DC drain if I want to recharge again at the 50% charge state.
These are the rules I follow at any rate for estimating battery capacity and it seems to pan out pretty good... I will re-charge when my battery voltage drops to appx 12.0VDC according to this chart
Roy Ken
