Another first timer system check-in before the build

[North01]

I'm looking to build upon Will's 5000w SunGoldPower handtruck system, also taking into account boflyer's recent modifications for full 5000w output. Thanks to 420hmsPA for his input on that thread - just looking to get as much input on this before I finally pull the trigger in the next week or so.


Quick background - I'll be building a small shed to house the Sungold and batteries - then running heavy duty extension cord to a trailer and yurt. No AC, wood heat, propane fridge in trailer. Main draws would be a well pump (looking at RPS, Vevor, etc), 120V washer/dryer, WiFi, laptop, lights etc. Should all be well within the Sungold's capacity - but we're in PNW and will be supplementing with generator in the winters as needed.

My biggest questions at this point are on wiring sizing, and if I need any added layer of protection (breaker/fuses) in the battery connection, as I'll be running 4 x 12v lead acids in series for the initial build - I know LiFePo4 batteries have built in BMS and breakers. The wiring specifications section of the SunGold manual (pasted below) says a 2P 200A breaker for the battery side, would this be fitting? -

I also have some DC breaker sizing and model questions - any pertinent difference between these two DiHool breakers for the PV panel disconnect switch? -
If 25A is recommended in the manual I should opt for 30A, even if my calculations regarding the ISC of the in series panel string only came out to 16.146 (10.35 ISC x 1.56 = 16.146), correct?




Rough diagram of the build - not sure if this adds any pertinent context for you all, but it was helpful for me to visualize.

Hoping for some confirmation on these wiring sizes, all should be pretty minimal length runs -
12 AWG from panels to DC breaker
4 AWG from DC breaker to inverter
2 AWG from Inverter to battery bank (likely with extra breaker added in this stretch) - on the other thread 420hmsPA mentioned he thought this should be upsized - any thoughts on how much?



Wiring section from the Sungold manual -



Thank you all for reading and any input you may have!

 

[robbob2112]

Wires, fuses, and breakers should be sized to handle 125% or expected current.

Lead acid batteries have a much higher internal resistance than LFP batteries which means they deliver a lot lower current when shorted so the AIC of the breakers and fuses can be lower.

That said, if you plan to upgrade to LFP batteries you should get the black version of that MCCB large breaker that has a 1000v rating and a 50ka AIC rating.

When you do upgrade to LFP batteries buy the correct battery at 48v verse putting 12v batteries in series... LFP batteries in series dont behave like lead acid... and if you try to string them together you have to use an external balancer and still take them apart once in a while to full charge all of them.... save the headache...buy the battery voltage you need.


Now back to sizing.... you have 5000W / 51.2v = 97amps * 1.25 = 125amps.... this is the wire size and breaker size from the battery to inverter....if the inverter install manual calls for higher go with that....

For 125amps the wire needs to be 1/0.... technically 2awg will do it, but for surges and the like 1/0 would be a better choice.

You need to use a constant wire size between the batteries and to the inverter... you won't change from 2awg to 4awg or any of that...

So you string the batteries in series with 1/0... then use 1/0 to the MCCB... from there to a shunt on the negative side and on to a bus bar... on the positive it goes from MCCB to the positive bus bar.

Every positive wire needs protection of some form or another.... in this case fuse or breaker on each....

The wire from the bus bar to the inverter needs to have a fuse inline.... if you think LFP batteries re in your near future put a class T fuse there.