How long in hours or mins.. will this battery system last

[Buick39]

I'm thinking about building battery backup using 300 ah lifepo4 battery using 16 to build a 48v system. Want to get a mppt to charge and invert to prefer 220vac but to run a couple refrigerators and a window AC and a few lights in the house all 110vac devices. would like to know how long it will run pulling a 4kw v contuse load?
Thanks for any input.

 

[John Frum]

I will assume you mean 4000 watts ac continuous.

4000 ac watts / .85 conversion factor = 4705.882352941 dc watts

300 amp hours * 60 minutes * 3.2 nominal volts * 16 cells *.9 cell imbalance = 829440 watt minutes

829440 watt minutes / 4705.882352941watts = 176.256 minutes, give or take.

 

[Buick39]

I will assume you mean 4000 watts ac continuous.

4000 ac watts / .85 conversion factor = 4705.882352941 dc watts

300 amp hours * 60 minutes * 3.2 nominal volts * 16 cells *.9 cell imbalance = 829440 watt minutes

829440 watt minutes / 4705.882352941watts = 176.256 minutes, give or take.

Thanks so much for the break down looks like 3 hrs and yes was thinking 4000 watts. Don't seem worth the expense figuring rough fully $ 4000 and that isn't any solar. Thanks again

 

[MisterSandals]

but to run a couple refrigerators and a window AC and a few lights in the house

The refrigerators should average to about 100W and a window A/C likely less than 1000W. How did you get to 4000W?

 

[Buick39]

The refrigerators should average to about 100W and a window A/C likely less than 1000W. How did you get to 4000W?

I have 2 refrigerators and 1 freezer upright and 10,000 btu window ac and just some general lighting would be my main stuff but have golf cart charger and 40gal water heater. So it was kind of a rough number. I have a generator 12kw that's on propane and does around 9kw and will run the house even the central air but no heat but will run a couple space heater with no issue. I have wondered if I should consider my trojan 48v deep cycle battery's in my golf cart as a option but would have to have a mppt that will do that kind of of charger on those battery's and wouldn't run them down to low to prevent damage.

 

[DThames]

The inverter has settings that prevent batteries from being discharged too low. About your lead acid cart batteries, lead acid total life cycles is a lot lower than LiFePo4, so if you plan to use this daily, you would greatly shorten the number of years your cart batteries would be in good shape. But if your goal is to replace the cart batteries with LiFePo4 when the Trojans wear out, then maybe using them would fit that plan.

 

[Bluedog225]

Welcome to the forum.

There is a lot of load management you could do to make solar more feasible. Inverter technology on the air con would be a large savings. Mini splits can come in around 800w. And heating water with solar is a huge uphill lift. Rarely/never a good idea.