Wiring Diagram draft for 24v off grid LiFePO4 system - please help break it!

[sunharvestman]

Hey all. Dan from NZ here. With gratitude to Will Prowse's resources, I am about to buy a bunch of components to set up my very own off grid 24v solar system and as a rank beginner would love to find out what I've stuffed up or missed on this wiring diagram before finding out after I get all the stuff. Any comments much appreciated, particularly gaping flaws, missing fuses, or places I'm about to waste money.

 

[TimOhopeNZ]

Hi Dan, I’m new to the forum and also in NZ. I’m currently going through post relating to NZ suppliers and equipment or importing threads for LiFePo4 batteries.
Being no expert I can’t find fault with your design. I’m on a simple journey with our motorhome that has installed solar, but on FLA batteries that are on the way out and an non-sine wave 1kW inverter. I’m planning to upgrade when the electrical WoF is due in April 22, but looking to get equipment now and start experimenting.
Where are you ordering your equipment from (I see the batteries from Sunnytech)?
im based in the eastern bay in Ohope, but currently living on the road on the central plateau.
cheers

 

[Eric Fowler]

HI Dan - I like your diagram. i used it in understanding my own 24v system. I moved it from the shed to my RV and in doing so I added a 24 to 12v converted as you have here. The only difference is I have a 24V 1200w converter and I don't have either of the circuit breakers that you have. I had two big questions in doing this: 1. was what do I do about the 12v charger that used to charge the 12v batteries when the RV was connected to shore power and 2. what do I do when I tow this and the 14v input comes in from the truck to try to charge the battery. So for number 1 - I just disconnected the 12 volt charger (unplugged it from the 110 outlet it was plugged into (duh)) and now I am looking for a 110ac to 24v charger to replace it with but for now - good to go on that one. For number 2 I installed a cut off switch on the 12v output wire coming out of the 24v to 12v converter. so when I need to tow the RV I just turn of the switch which disconnects the the 24v system from the RV all together. So good to go there. The only other question i have is how to connect my 1200w inverter to the RV 110v system because I don't know what will happen if I have the 1200w converter connected to the system and I plug in to shore power and receive 110v from there. When I know how that works I will connect it up that way. If you or anyone else knows that let me know. In the mean time I will just continue to enjoy all of the power from the sun.

 

[sunharvestman]

Hi Dan, I’m new to the forum and also in NZ. I’m currently going through post relating to NZ suppliers and equipment or importing threads for LiFePo4 batteries.
Being no expert I can’t find fault with your design. I’m on a simple journey with our motorhome that has installed solar, but on FLA batteries that are on the way out and an non-sine wave 1kW inverter. I’m planning to upgrade when the electrical WoF is due in April 22, but looking to get equipment now and start experimenting.
Where are you ordering your equipment from (I see the batteries from Sunnytech)?
im based in the eastern bay in Ohope, but currently living on the road on the central plateau.
cheers

Hey Tim! Since this diagram I decided to go with a Victron easy-solar all-in-one unit. Are you the same Tim that Dave Dobbin mentioned about a bulk LiFePO4 order by the way?

 

[sunharvestman]

HI Dan - I like your diagram. i used it in understanding my own 24v system. I moved it from the shed to my RV and in doing so I added a 24 to 12v converted as you have here. The only difference is I have a 24V 1200w converter and I don't have either of the circuit breakers that you have. I had two big questions in doing this: 1. was what do I do about the 12v charger that used to charge the 12v batteries when the RV was connected to shore power and 2. what do I do when I tow this and the 14v input comes in from the truck to try to charge the battery. So for number 1 - I just disconnected the 12 volt charger (unplugged it from the 110 outlet it was plugged into (duh)) and now I am looking for a 110ac to 24v charger to replace it with but for now - good to go on that one. For number 2 I installed a cut off switch on the 12v output wire coming out of the 24v to 12v converter. so when I need to tow the RV I just turn of the switch which disconnects the the 24v system from the RV all together. So good to go there. The only other question i have is how to connect my 1200w inverter to the RV 110v system because I don't know what will happen if I have the 1200w converter connected to the system and I plug in to shore power and receive 110v from there. When I know how that works I will connect it up that way. If you or anyone else knows that let me know. In the mean time I will just continue to enjoy all of the power from the sun.

Hey Eric and not sure about your questions sorry! Also further to by diagram above I'd add a circuit breaker near the batter positive outlet and one with the panels also.

 

[TimOhopeNZ]

Hey Tim! Since this diagram I decided to go with a Victron easy-solar all-in-one unit. Are you the same Tim that Dave Dobbin mentioned about a bulk LiFePO4 order by the way?

Hi Dan, yes I am the same person DD has mentioned.

 

[APhoton]

is 4awg wire large enough for 24v/3000w inverter??

 

[rmaddy]

is 4awg wire large enough for 24v/3000w inverter??

No. At least 1AWG should be used. 3000W / 24V / 0.85 = 150A. 1AWG is good for 150A. This should be used with a 175A fuse.

The original diagram is dangerous. There is no fuse on the battery nor protecting the wire to the inverter. Note that the OP stated in post #4 that things changed a lot. This reply applies to the original diagram. I have no idea if any of this applies to their current setup.

The 4AWG wire will get really hot (maybe too hot) if a full 3000W is put on the inverter. And there will be a lot of voltage drop.

The 60A breaker between the charge controller and bus bar is probably too small. The SCC can put out 60A so a 60A breaker will trip needlessly. I would use a 75A breaker and at least 6AWG wire (4AWG is fine for the SCC).

There should be a disconnect breaker between the solar panels and SCC. This will allow the panels to be disconnected from the SCC if needed.

 

[nogridhome]

If Watts = Volts x Amps (and they do).
3000= 27 x X so 3000/27=111 so your 24V wiring will need to carry 111 amps at 3000 watts. Your 60 amp breaker won't work out.
You likely will spike your power when pumps or motors start as well.
I would use a 150Amp fuse, 150A wire, 150A breaker.
I prefer the type T marine fuses for robust reliability. #2 welding cable would be my choice as it is rated for high capacity and is pliable making it easiest to work with.
#2 welding cable - ebay
Fuse

Please do not connect the batteries like that.
Connect them in series - like this:

24vdc + red wire-----POS Battery NEG------POS Battery NEG-----black wire 24vdc -

Probably going to want disconnects or breakers on the 230 in and 230 outs.

Likely collect 4kwh - hope that is about what you expected.

Battery monitor will likely be built into the inverter.

It takes power to run the inverter. My big inverter uses 250W (6kwh), my smaller inverter uses 100w (2.4kwh) / day. This is being consumed when the inverter is powered on, there are also efficiency losses in the charging, discharging and inverting processes.

Friend I have compiled much of my experience into this video, you might find some value in it. GOOD LUCK, ALL THE BEST!!!
Solar Power for the Full Size Home

 

[rmaddy]

Please do not connect the batteries like that.

I had the impression that the OP had 2 24V batteries so wiring them in parallel was fine. Your comment assumes they have 2 12V batteries that would need to be wired in series.

Note that the OP hasn't been on this site since August 2021 so that will likely not get clarified.

 

[nogridhome]

I had the impression that the OP had 2 24V batteries so wiring them in parallel was fine. Your comment assumes they have 2 12V batteries that would need to be wired in series.

Note that the OP hasn't been on this site since August 2021 so that will likely not get clarified.

you are exactly right! I should pay closer attention to the note stating that. ;-)

 

[APhoton]

I'm building a 24v system with 3000w inverter. I'm going with 1/0 wire battery to inverter and back. Look at https://diysolarforum.com/threads/24v-diagram-review-for-travel-trailer-please.27855/

24V diagram review for travel trailer please​