Hoping for some feedback on our 24V Setup/Wiring Diagram

[Tophies]

Hey Gang, long time lurker here.

Long story short our living situation is changing next year, so we are shifting into a moving truck full time, next year.

We are tight on funds and in the middle of nowhere at the moment, so have designed a system around the equipment and components we have scrounged together from our last build and staying in our comfort zone. Most of the parts are similar to Will's old 2000 Watt 24v system.

Attached is the wiring diagram. It is quite a big 24v system for us so we were hoping for any advice or feedback you may have. As well as just some more eyes on it to see if there are any improvements or glaring mistakes we may have missed.

Cheers heaps and let me know if you need more details.




More info:
Batteries: 2 x Renogy 24V 200Ah
Charge Controller: The old aluminium Epever 40A MPPT
Inverter: Giandel 24v 4000w
DC2DC: Enerdrive 24v 30A Battery Charger

We will closely monitor appliance usage on both the DC and AC sides.

 

[crossy]

What's the Voc of your panels and the maximum solar input voltage of your MPPT??

How cold does it get in your area?

 

[Tophies]

Hey Crossy, thanks for getting back to me.

The Voc on the panels is 42.54.
The MPPT can handle 138V or 1560 watts

It only gets down to under 10 degrees celsius (50 farenheit) for a month or so and never freezing.

 

[crossy]

OK, you should be ok on Voc that was my only real worry.

 

[Tophies]

Ah awesome, cheers for checking this out .

I probably should of posted in the Safety Check channel in hindsight haha

 

[chrisski]

You have 1500 watts of panels to a MPPT that will produce 900 watts to the battery. 40 amps our at 24 volts is about 900 watts.

You could be losing production.

This could produce 1800 watts to 4500 watts per day in my area. The inverter may use 500 Wh a day, so check the idle draw.

A 4000 watt inverter is a lot. With inverter losses you’re below, but close to the 200 amp fuse limit at full wattage and normal voltages, but at the SOC of the battery, will exceed 200 amps.

 

[crossy]

You are a bit over-panelled for a 40A controller, but it's not going to hurt anything and would spread your production to start early, finish late.

Maybe move one panel onto a second controller if budget permits.

@chrisski beat me to it.

 

[Tophies]

Hi @chrisski! Thanks for this.

So the size of the inverter is covering a few edge cases we had planned for during the day (cooking whilst working) and it was very cheap and available to us. I don't think we could use more than ~3500 watts at once but should we at the very least upgrade the breaker?

We didn't plan on leaving the inverter on at all times, is it bad to turn it off at night or when not in use as we did this a lot in our van haha

Ah yup awesome thanks @crossy.

So you both think the MPPT is the first thing we should upgrade when we have the funds?

 

[crossy]

So you both think the MPPT is the first thing we should upgrade when we have the funds?

Yup, either a bigger unit or another the same and move one panel to it Check the MPPT start-up voltage will run with just one panel.

 

[Tophies]

Ah nice.

We have the 30A DC2DC charger that is also an MPPT that can take up to 800 Watts 45VOC.
Would it be better to just move one of the panels over to that for now?

 

[DThames]

What is the 24v car battery for? Not sure you can charge 24v with 24v very effectively. I guess it depends on the charger.

 

[chrisski]

Hi @chrisski! Thanks for this.

So the size of the inverter is covering a few edge cases we had planned for during the day (cooking whilst working) and it was very cheap and available to us. I don't think we could use more than ~3500 watts at once but should we at the very least upgrade the breaker?

We didn't plan on leaving the inverter on at all times, is it bad to turn it off at night or when not in use as we did this a lot in our van haha

Ah yup awesome thanks @crossy.

So you both think the MPPT is the first thing we should upgrade when we have the funds?

The formula I got off here for amps wiring and fusing is

Inveter rated wattage / low voltage cutoff / efficiency of the inverter * 1.20 safety factor

4000 / 20 / .85 * 1.20

282 amps

If you change the voltage so it’s 24 volts, you see the amps drop. Same thing if you use a 28 volt charging voltage, so 282 amps is worst case.

A 250 to 300 amp over current protection and wiring to match would be good. I’m not sure 275 amp fuses are available and 300 amps starts to have thick wire.

Many people will fuse to the 24 volt inverter voltage and not low voltage cutoff.

 

[chrisski]

Also, with your switches, to remove power from the inverter, need to shut off the battery switch, panel switch, and car battery switch.

Nothing wrong with that. When I forget to shut off the charge controllers after shutting the battery off, my inverter stays on, but will fault out at any load. Also, if there’s no load, it’ll fault out at sunset and sunrise.

————

I also recommend you use a precharge resistor for the master battery. A 4000 watt inverter on a lithium battery will make a spark that will fling a small piece of molten metal.

 

[Tophies]

@DThames This is all going in our truck, which has a 24v alternator and battery bank.

@chrisski aaaahhh ok, Yeah I see thankyou for breaking this all down for me.

 

[Tophies]

@chrisski

Sorry I meant the inverter has a remote to turn it on and off when we go to bed and stuff.

Ah yup good call on the resistor, this battery system is much bigger then our little 12v one, I would of just gone for it.

 

[Tophies]

So based on everything we have chatted about does this look a bit better?

 

[chrisski]

Just check the specs on your 24 VDC charger MPPT that comes from the battery to be sure the panel meets the specs for that. Sometimes MPPT input voltages are quite low. Same thing with the 30 amps. Just see if it’s a 30 amp out based on combined solar battery input, or a max of 15 amp output battery or 15 amp output panels.

With my RV, I have 3 MPPTs. Two on the roof for two different arrays and one for a ground mount.

 

[Tophies]

Oh man sounds like your RV is fully sorted then ey

Awesome will double check everything. I think from my understanding we are good though.

The DC2DC charger prioritizes one or the other based on input voltage. It seems it should do close to the full 30a on solar. "Maximum achievable output on the DC2DC 24V when using 43Voc Solar Panels will be approximately 30amps."

The 40A Tracer has lots of example tables but mostly just states to keep it in the VOC.
Max. PV open circuit voltage: 1560W/24V
Max. PV Array Power: 138V

Thanks heaps @chrisski and @crossy

If this all looks good I am looking at installing this after new years. Exciting!!!

 

[DThames]

@DThames This is all going in our truck, which has a 24v alternator and battery bank.

@chrisski aaaahhh ok, Yeah I see thankyou for breaking this all down for me.

I am no expert on this but you don't want your car battery drained while engine is off and the charger will need to be able to take say, 25v in and output more than the input voltage. So look carefully. I have used some little chargers that you can program the min input (before they cut off) and will step up from input to output. Something like that would be functional, I think.

 

[Tophies]

@DThames Yeah I have heard some people have issues with them. This one is a pretty pricey unit.

We had it in our old van and I installed one in my father-in-laws and a friends cars with no issues. It has a volt sensing relay that doesn't draw till the alternator has been running for a few minutes. And yeah we can program the start and cutoff voltage on the car battery and over/under voltage etc on the house etc. Output can go as high as 29.2 volts.

They do seem sketchy on paper ey haha