diy solar

diy solar

am i crazy to buy a 15KW generator as solar back up

as those Magnums dont do "grid" pass through all your input AC power is just converter to DC charger power. Specs say 60A @48v or ~3000w. 15% conversion loss = ~3300w *2 = 6600w. With some head room 8kw looks to be your usable generator size.

If I read the spec sheet on the batts right. ~1200AH capacity (50% capacity = dead) so you need to make ~600AH. Lets say your inverter draw is ~50% at any given time so net charging amps = 60amps into 600AH means you have to run the generator for ~10 hrs to charge.

Napkin math says throwing more generator at this wont speed up the time as your limited by the size of the chargers you have. Which for the record assuming you have 2, is going to be under charging per the 155a recommended charging spec for those Rolls
can i wire it direct to my busbar and let the inverters do their job? HELP?
As I understand it - No you can not as your inverters do not frequency match, So you can NOT tie the output of the generator to the output of the inverter.

Basicaly the input from the generator ONLY goes to the inverters (not your normal house loads) The inverters convert the 120v AC and output DC. (either for batts or the DC inverter side)

As a side note I think this is why you frequently find AC transfer switch as part of this kind of setup, So you isolate the house loads from the inverter side and power everything off the generator when its running. This frees up an extra 60 amps of charging for batts cutting your charge time in half. However this also requires an automatic transfer switch.
 
If your talking dark months, unless you have sustained loads, get a smaller one that will produce 100% of your daily consumption averaged over 20 hrs. You will basically run this generator all winter, just stopping for oil changes. your existing system will deal with the big hits (heaters, motors, etc) and basically the generator is the trickle charger
 
My 8HDKAK Onan Cummins (8kw) along with my SI6048 Sunny Island can put 300Ah back into my battery in just a hair over 3hrs, and a touch over 1.5G diesel fuel. Once my charge rate drops for a full charge and goes into float we switch over to the 3.2HDZAA and it can run for 7 hours topping off the battery on about 1.5G diesel. In the darkest times of winter we run the generator 2-3 hours a day - in the summer we run it maybe 2-3 hours a week.
 
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