diy solar

diy solar

Smallish home backup system.

Bazzar

New Member
Joined
Oct 6, 2020
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23
Location
North Carolina
The plan/goal is to have enough Battery Backup to not have to fire up a generator for 12-24 hours. with intentions of adding some solar later to supplement the generator. I have a Honda 2000i generator (1600w con, 2000w surge) I can use for backup to charge batteries and or boost the Victron inverters output potentially.

Critical loads are a full size fridge, upright freezer, 9cuft chest freezer, aquarium filter/heater, up to 50w of led lights and 50w of phone chargers.
My calculations for loads are up to 1200w constant plus an additional 1400w surge on the fridge (largest surge) for a 2600w max surge.

So far I have a Victron Multiplus 12/3000/120 with the usb adapter and Bluetooth adapter. Rated at 2400w constant and 6000w surge.
Also have a Victron 500a Smart Shunt to monitor real watts in and out of the battery.
I have 8x Lishen cells on the way for 2x 12v packs using overkill solar 120a bms's on each with upgraded 8aug wires.
Battery bank will therefore be 12v 500+ah with 240a continues discharge rating and a surge up to 560a for 10 seconds.

Still need battery/inverter cables, I figure 1/0 for each battery up to 4/0 to the inverter with as short of runs as possible of each
Also need a 400a fuse per Victron spec.

I know there are other details that I'm not thinking of right now so please let me know if I'm missing anything major.
But as far as to the overall plan and parts list does this sound like I have things figured out right?
 
Last edited:
...so far I have a Victron Multiplus 12/3000/120...
"Have" as in already purchased, or have as in this is what I'm planning? If still planning I'd get a higher voltage inverter than 12V for a 3kW inverter. While a single 1/0 wire is probably good for your 1200 watts, it is undersized for the inverter at 400 amps... so you'll want to bump the fuse size down to the maximum number of amps the 1/0 wire can carry (you want the fuse to blow before the wires catch fire).

You might want to run your numbers in watt hours. For example if you're pulling 1200 watts 8 hours a day that's 1200x8=9600 watt hours.
500 Ah at 12V is 500 x 12 = 6000 watt hours. Even without taking the inverter standby load or inefficiencies (inverter & battery) into account in that example it wouldn't last a day.
 
Thanks for the reply.

Yes I have purchased the Inverter, I did debate 12v or 24v for a while but I decided to stick with 12v for this even though the wire and amps at 12v are so high/big, So a 12v system it is for me.

As for the numbers in watt hours yes if everything is running 100% of the time id only got 12ish hours of run time but the fridge/freezers wont be on full time and the aquarium heater cycles also so I'm hoping for a bit better then 12hours. The Goal is 12-24hours so I think I'm still good and I can always add more batteries later if I decide I need to.

As for the wire/fuse, I'm planning on 1/0 from each battery pack up to a main fuse on the +pos and the shunt on the -neg, then either a 4/0 or 2x 1/0(recommended) from the fuse/shunt to the inverter. What I'm thinking is the bms's should protect the 1/0 wires before the main fuse, and then the 400a fuse where they combine to go up to the inverter should protect the 4/0 or 2x 1/0 wire going to the inverter.
 
As for the numbers in watt hours yes if everything is running 100% of the time id only got 12ish hours of run time
Yeah my math was off there a bit. 1200w for 5 hours will be 6000w hours. I have a wireless thermometer probe in every freezer and the fridge so I do have the ability to manually cycle them to perhaps extend the run time some there. Let me go back and break it down into watt hours, I may have overlooked something there.
 
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