Cargo Trailer Conversion with 1200Watt/ 24Volt 300 AH system

[dsilver]

3 Years ago I converted a cargo trailer to a travel trailer. We have loved it and used it so much, I have decided to build a new one that has more space and has a more useful solar system.

My first trailer only has a 100 watt panel and a Renogy PWM Wanderer charge controller. Solar is used solely to keep my battery topped off between travel days, run the fantastic fan, lights, and charge our 12v electronics. The Battery goes to a PD4045 AC/DC Disribution panel that supplies all the branches with power throughout the trailer.

On the new trailer we want to have a full system that will allow us to easily boondock with solar or hook up to 30 Amp shore power in state parks. We want to be able to plug in to Shore power and not have to worry about transferring power manually from solar to shore power.

I started researching...several months ago. I found Will's Mobile Solar Power website and then this forum. I have learned so much, but feel I have a ways to go.

Here is what i am thinking: (I need advice and guidance! Please chime in)

1200W Array (3 200 watt panels in series then paralleled to another set of 3 200 watt panels in series)
Victron 100/50 Solar Charge controller temp sensor to charge controller (Battery temp for SCC) or is the one in the Battery sensor enough?
24V 300 AH LiFoPO4 DIY battery (Two of these) in series to an 8s 100Watt BMS.
Victron BMV 712 With Temp Sensor
24-12 volt converter
Victron Multiplus 24/3000W Inverter
Shore power will come into the Multiplus then out to the AC side of an AC/DC Power Dynamics Distribution panel.
Battery will go to the 24-12 Volt converter then to the DC side of the AC/DC Power Dynamics Distribution panel.
From the AC/DC distribution panel I will have all my branches from there to all my AC and DC loads.
From the negative lead off the battery, I will have a negative Busbar with the Victron BMV Shunt, solar charge controller, inverter then grounded to the chasis.
From the positive lead off the battery, I will have on a busbar, the fused charge controller then a battery cutoff, to the inverter, then to the DC side of the Distribution panel withe the 24-12v converter in between.

It is very much like this (Blue Print from Explorist.Life), but I need to put in the 24-12 volt converter somewhere, then I also need to make sure I have the right size fuses and gauge wires.

Things that I still am working out:

• What parts am I missing?
• Should I go with the Victron Multiplus? I go back and forth on using the Victron multiplus or just getting the items separately (transfer switch, converter, inverter, charger) Would it be cheaper? I am also a little worried on the complexity of getting all the items separately versus buying the multiplus.
• Where do I put the 24-12Volt converter? I believe between the Positive lead busbar and the DC side of the distribution panel.
• What size fuses and wires do I need through the system? Can I just use connectors and y connectors in the solar panel arrays with the series then parallel setup? How many feet can I go for the 10 AWG PV wire from the array to the charge controller, then from the controller to the battery. Controller will be within 2 feet of the batteries. Panels will be about 10-15 feet from the charge controller.)

 

[Carly]

I'm working on a 1300W (4 x 325W in series-parallel) 24V 280AH 8S LFP system for my cargo trailer. That is about 69V @ 19A from the panels. I had ordered a Cotek SC-2000 24V inverter/charger, but am in the process of returning it for the Victron MultiPlus 24/2000/50. Doing that for the 5 year Victron warranty, and because I already have the Victron 100/50 SCC and 712 with temp sensor (Smart Battery Sense is not needed for installations which already have a BMV-712 with a temperature sensor accessory - this is from the Victron Smart Sense Manual).

I did look, but don't know that you can put together a better inverter/charger/ATS system than the MultiPlus regardless of price (?). I certainly could not!

I'm fusing the panel array with a 30 AMP/150V DIN rail breaker in a Midnite Solar Baby Box (with appropriate strain relief connectors). The array output goes thru that and to the 100/50 SCC, the output of which goes through a 63 AMP/150V DIN rail breaker (and acts as a disconnect for the SCC). I have a 150 AMP MRCB DC breaker with switch for the inverter, and a 250A battery terminal fuse. These are all below and were specifically chosen by the solar designer/dealer for the components I chose (and before I switched to the MultiPlus):

• https://www.solar-electric.com/mrcb-150-amp-dc-circuit-breaker.html
• https://www.solar-electric.com/mnepv.html (DIN rail breakers)
• https://www.solar-electric.com/misobigbabox.html
• https://www.amazon.com/gp/product/B0019ZBTV4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 (battery terminal mount fuse)

I have this 24V to 12V 40 amp converter:

• https://www.amazon.com/gp/product/B07B4HLLWJ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I think that is the one Will recommends in his video below (I time-stamped the part where he points out that it is fused):

Instead of using the battery protect to connect the converter (which is not recommended due to fire hazard), I am using a bus bar.

Also, instead of the distribution panel you have chosen, I'm using a simple two-circuit AC breaker box with a 15 and 20A breakers:

• https://www.amazon.com/gp/product/B000E2AHOI/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
• https://www.amazon.com/gp/product/B009OYAFAI/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

And the Blue Sea 12V fuse block:

• https://www.amazon.com/gp/product/B001P6FTHC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I am new at all this, and know just enough to be dangerous at this point. But hope some of it is helpful.

 

[Carly]

Victron recommends a 200A fuse at the battery, btw.

https://www.victronenergy.com/upload/documents/Manual-MultiPlus-Compact-2000-120V-EN.pdf

 

[dsilver]

I'm working on a 1300W (4 x 325W in series-parallel) 24V 280AH 8S LFP system for my cargo trailer. That is about 69V @ 19A from the panels. I had ordered a Cotek SC-2000 24V inverter/charger, but am in the process of returning it for the Victron MultiPlus 24/2000/50. Doing that for the 5 year Victron warranty, and because I already have the Victron 100/50 SCC and 712 with temp sensor (Smart Battery Sense is not needed for installations which already have a BMV-712 with a temperature sensor accessory - this is from the Victron Smart Sense Manual).

I did look, but don't know that you can put together a better inverter/charger/ATS system than the MultiPlus regardless of price (?). I certainly could not!

I'm fusing the panel array with a 30 AMP/150V DIN rail breaker in a Midnite Solar Baby Box (with appropriate strain relief connectors). The array output goes thru that and to the 100/50 SCC, the output of which goes through a 63 AMP/150V DIN rail breaker (and acts as a disconnect for the SCC). I have a 150 AMP MRCB DC breaker with switch for the inverter, and a 250A battery terminal fuse. These are all below and were specifically chosen by the solar designer/dealer for the components I chose (and before I switched to the MultiPlus):

• https://www.solar-electric.com/mrcb-150-amp-dc-circuit-breaker.html
• https://www.solar-electric.com/mnepv.html (DIN rail breakers)
• https://www.solar-electric.com/misobigbabox.html
• https://www.amazon.com/gp/product/B0019ZBTV4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 (battery terminal mount fuse)

I have this 24V to 12V 40 amp converter:

• https://www.amazon.com/gp/product/B07B4HLLWJ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I think that is the one Will recommends in his video below (I time-stamped the part where he points out that it is fused):

Instead of using the battery protect to connect the converter (which is not recommended due to fire hazard), I am using a bus bar.

Also, instead of the distribution panel you have chosen, I'm using a simple two-circuit AC breaker box with a 15 and 20A breakers:

• https://www.amazon.com/gp/product/B000E2AHOI/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
• https://www.amazon.com/gp/product/B009OYAFAI/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

And the Blue Sea 12V fuse block:

• https://www.amazon.com/gp/product/B001P6FTHC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I am new at all this, and know just enough to be dangerous at this point. But hope some of it is helpful.

Thank you so much, this gets me more details and the combiner box that I should use. I had heard in the video from Will too about not using a Battery protect. I plan to use a bus bar for that as well. The 200A fuse at the battery is good info too. Are you ordering parts then installing yourself?

 

[Carly]

Yes, I have most of the parts, just waiting on the batteries. Holding off on ordering the MultiPlus till they arrive from Shenzen. And I just noticed the manual I posted was for the 2000/50, so the fuse for your 3000/70 might be different. If you order most of the components from a good dealer, they will review your plan and make sure you have the appropriate cables, fuses, breakers, etc. I purchased most of my major components from Northern AZ Wind & Sun and they were super helpful (and patient with questions).

I notice a lot of cargo trailers have the solar panels mounted too close to the roof. Heat reduces output, and my panels called for around 2.5" of clearance from the roof. I spent a lot of time trying to come up with a way to mount my four panels (~65 x 39", I think they are). Ordered Iron Ridge rails with UFO mounting clamps and L-brackets to connect to the roof. You can order shorter rails (7 foot) to avoid freight charges, and connect them with an internal strut or brace made for them. The Iron Ridge site has a planning page which is a bit confusing at first (it's not for trailer roofs). But I found it helpful. Here's a video that shows the rail system. It's the best one I found to illustrate how it all goes together. I think Will mentions that smaller panels are safer, so hope mine don't blow off! But their page gives all kind of data for wind, etc, and I think they will hang on!

 

[dsilver]

Thanks for the tip on the dealer to properly select fuses and wires. The rails look good too. I am thinking of something similar, but not sure how I will fasten them to the roof. I was thinking of L brackets so I screw into the side of the trailer rather than the top with cross rails to mount the panels on.