Wife wants to use her 1500 watt convection oven.

wkyongae said:

Happy wife happy life right.
So I have 6 panels totaling 1800 watts and use 8 Trojan 305p lead batteries. 4000 watt Samlex inverter and Flexmax 80 charge controller. Only during the cold days of winter can we use the oven during the day for any length of time. Wifey wants to be able to power it for at least two hours. Soo. Choices do I expand by three panels adding 900 watts and another charge controller or expand the battery bank to lifpo and delete the lead acid. Which is cheaper and which works best with my 2000 watt generator on cloudy days?

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chrisski said:

The only gotcha I see is the batteries can't be charged by more than ~1440 watts, ~180 watts per battery. (10% Max charge rate, 30 amps at 6 volts per battery = 180 watts. So 8 batteries ~ 1440 watts. (Your actual max charge rate Both % wise and battery amp hour will change this slightly in your favor, but not much).

So the panels will provide less energy than the oven, so it will continue to draw the remainder from the battery. When the oven is shut off, for a period of time the panels will charge the batteries in excess of the max charge rate of ~1440 watts.

It's supposed to be "not bad to shortly" exceed the max charge rate. I don't know what short was.

I do know that one reason I swapped from lead acid to lithium is the situation I described above. My max charge rate was 13% which equted to 60 amps, but my panels would push 72 amps after the microwave shut off until the batteries were charged again.

I don't know how truly harmful t is to a battery to overcharge it. A microwave did not run long and the battery recovered quickly. A 1500 watt toaster oven would run longer. I decided the risk to my $1000 batteries was not worth it.

Honestly though, when I used the microwave, it was usually earlier in the day before the panels had enough to exceed the max, it was only a handful of times the panels could push that much power.

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wkyongae said:

Happy wife happy life right.
So I have 6 panels totaling 1800 watts and use 8 Trojan 305p lead batteries. 4000 watt Samlex inverter and Flexmax 80 charge controller. Only during the cold days of winter can we use the oven during the day for any length of time. Wifey wants to be able to power it for at least two hours. Soo. Choices do I expand by three panels adding 900 watts and another charge controller or expand the battery bank to lifpo and delete the lead acid. Which is cheaper and which works best with my 2000 watt generator on cloudy days?

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sparrowhawk said:

Find a new wife.

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seneysolar said:

Assuming 48v system?
Not 2 strings of 4 batteries for 24v?

Trojan recommended max rate is 13% of the C20, so thats 42.9 amps. Plus with useage from the inverter, loses, and non perfect conditions. I wouldnt worry about adding 900w to the current 1800w array. Not all of the power goes "into" the batteries.

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wkyongae said:

Two strings for 24v

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