New build plans - travel trailer

[OnTheFlyPDX]

As parts start to arrive, I’m getting pretty close to starting my first solar/lifepo4 build. I’m hoping to get some feedback from you all on my plan and wiring diagram. I have been learning about PV and battery systems on the fly here, so I appreciate any/all feedback. Our travel trailer is a 2010 ORV Creekside 18ck. It’s stock with two lead acid batteries on the tongue and no solar.

Installing MPP LV-2424 hybrid with 24v 200 Ah lifepo4 battery. I’ll use a 24vdc to 12vdc buck converter to tie into the trailer’s DC panel. I will also be removing the trailer’s factory battery charger, as the new lithium batteries will be charged through the LV 2424 with PV or shore power when plugged in.

I’m still shopping for PV, but plan on installing 4x 350-400w used residential panels. There’s quite a bit of variability in voltage and amperage specs on those panels, so I’m still up in the air on whether I’ll run a 2s2p or 4p configuration. The LV 2424 all-in-one I’m using has a PV voltage range of 30-115 VDC (80 A max as well). I have taken into consideration that higher voltage = less voltage drop, but I think I’ll be fine using 8AWG for a 4p setup and it would be more efficient (less affected by shade) than a 2s2p setup. Practically all 350-400w panels have a Vmp over the solar charger’s minimum of 30 V (usually 40-65 Vmp), but is there a reason I should I be aiming to get a higher voltage value out of the PV array with a 2s2p setup?

thanks in advance!!

 

[John Frum]

Your 175 amp breaker should be as close as possible to the battery positive terminal.
That minimizes the chance of an un-protected short upstream of the breaker.
You should probably connect all the main components to busbars.

I like this one for the positive side because it integrates fuses.

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This one is good for the negative side.

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You also need a fuse on the 12 volt side of the buck converter.

Its good to include the wire guages, fuse sizes and terminal sizes for each circuit.

 

[OnTheFlyPDX]

Your 175 amp breaker should be as close as possible to the battery positive terminal.

I’ll make sure to do that.

You should probably connect all the main components to busbars.

Already ordered some. Should have included/noted that in the diagram.

You also need a fuse on the 12 volt side of the buck converter.

Its good to include the wire guages, fuse sizes and terminal sizes for each circuit.

Will do on putting a fuse on the 12v side. I need to update and make the diagram more clear on wire sizes. Going to use either 8 or 10 AWG for all the PV wiring depending on the final max amps I end up with based on array setup. Going with 8 AWG triplex for AC side of things just to be on the safe side.

The inverter will be 2-3’ from battery so 2/0 should be more than enough for that.

I need to go look at the amp values on the trailer’s dc fuse panel before finalizing the amp size I purchase for the dc-to-dc buck converter (trailer is in storage). Right now I’m assuming a 50 amp buck converter will suffice, meaning: (1) 12 AWG wiring for 24v side, and (2) 8 AWG wiring and 75 amp fuse for 12v side. Distance between batt and d/c fuse panel is less than 10’. Does those gauges and fuse size sound right?

Thanks so much for your feedback and great advice!

 

[John Frum]

I need to go look at the amp values on the trailer’s dc fuse panel before finalizing the amp size I purchase for the dc-to-dc buck converter (trailer is in storage). Right now I’m assuming a 50 amp buck converter will suffice, meaning: (1) 12 AWG wiring for 24v side, and (2) 8 AWG wiring and 75 amp fuse for 12v side. Distance between batt and d/c fuse panel is less than 10’. Does those gauges and fuse size sound right?

Thanks so much for your feedback and great advice!

The converter will have a continuous amp rating on it.
That would be a good rating for the buck converter.

As for your question in the original post... Its generally preferable to have your panels configured for the highest voltage your solar charge controller can support.
Generally... but not always.
You may want parallel strings to mitigate shading issues.

 

[HRTKD]

Check the dimensions of your roof. I had planned to put up four 200 watt panels, but the layout of the objects on the roof squashed that plan. I ended up putting on two 320 watt panels and those took up the entire width of the roof, with a vent between them. My trailer is ~102" wide.

8 awg PV wire is overkill for your scenario. 10 awg (as you have in your diagram) is fine. 2s2p may be less expensive to wire than 4p since you don't need fuses between the two strings, but do need fuses between four strings.