Battery Math

[Scott Martinez]

I'm struggling with understanding the capacity of my battery bank. I have 8 Trojan T105 6v wired series/parallel to 24 volts. They are rated at 225 amp hours at 6 volts. So double that in my system to 450 amp hours. To get watt hours, I take 450x24=10800 right? Divide that by 50% to get useable'ish 5K bank, or 5000 watts usable reserve from lead acid batteries in a ideal situation. In theory, I can run a 100 watt load for about 50 hours? Is this correct? I know my inverter uses some of this as well, and say the fridge will draw a bit more when the compressor starts, but just want to make sure my theory is close. Thanks for your help.

 

[svetz]

Your basic math is good, but with lead acid chemistry their is also Peukert's law (power goes down the faster you pull current) and temperature effects, from the battery spec:

 

[Scott Martinez]

Thanks Svetz, I just wanted to make sure I had the basic theory down. Thanks for the information.