Trying to figure out best option for 18'x8' box truck build

[MrPsychedelic]

So I am building out an 18' box truck into an rv. The roof is 18' x 8', I want to have as much solar as possible up there, with room for a max air fan. I am going to build a battery from 304ah grade a eve cells, 16 in series for around 15kw. I am thinking of doing (2) sets and wiring those in parallel for around 30kw at 48V, but I haven't decided if I want to spend all that money yet or not. The inverter I think I will be going with is the MPP Solar LV6548 Hybrid.

I have looked at a few panels, a 70V panel so I could wire all in parallel, and the rest would be around 32-36V panels and need to be 2s2p. I am trying to configure the best placement off the sizes, while getting the most power, but its proving kinda difficult as its obviously not going to be a perfect fit.

I was also going to order from San Tan solar, but you need to order a minimum of 10 and no way I'd be able to use that many, I'm in Maryland so if anyone knows a place within reasonable distance I could pick them up so they don't get damaged in shipping.

My question is basically if you know a place in a reasonable range that I could pick the panels up from, and what size panels I should be going with. I'm really struggling figuring that out and want to get the panels up ASAP before summer really gets here and its blazing hot everyday.

Thanks everyone!

 

[Dinobot248]

For limited space applications (e.g. RV), the main driver is size of solar panel (including VOC and ISC or max volts and amps) and mounting kit.

You likely want to pick panels that …

0. Figure how much electricity you use and how many days you want to survive with worst case of no sun or ability to collect Solar. For example, if you use 5kwh as normal operation and 3kwh as critical. Then consider battery of 30kwh really becomes 20kwh after estimated 20% efficiency loss (6kwh) and 4 kWh as reserve power to ensure food cycle life. Note trying to keep simple round numbers here. Don’t want to always drain battery to zero percent. Net net, effective battery is 20kwh so you have 3 - 4 days of backup on normal usage and about 5 - 7 days if you really conserve.

Forgot to mention idle loads. A typical AIO inverter will consume say 50 - 100w so for 24hr x 80w = 2kwh. In a case of no sun or parking in shade, that can really eat up how many backup days you have, hence I listed a range above.

1. Can collect the most sun. For example, you may be able to fit 2 panels the within 8ft width of truck or 3 panels within that same width depending on orientation.

2. Fits your Solar charge controller (SCC) whether it be built in to an all in one (AIO) or standalone SCC. This less important than #1 above but still needs consideration. If VOC is 40v and you AIO max box is 250v, then you can get max series string of 5 or 200V with a cushion for low temp voltage increase. Now if VOC is 32v, then max panels would be 7 but depending on panel orientation, realist max panel is 6.


I rely on eBay and Amazon for solar panels since it’s more convenient for me. Depending on inventory and location, buying local maybe better.

Don’t forget box truck roofs can be this very thin plastic to minimize weight which means adding solar is more difficult.

And last, I recommend the Victron ecosystem of products since they just work, provide good software, and low idle consumption (15w compared to 50-100w), and Power Assist. Yea it cost more but long term, you will save and recoup it back through efficiency and reliability (lack of worrying).

Please ignore spelling errors. Responding on a phone sucks.

 

[Rocketman]

Look at your local sources and call around. Sometimes installers have orphaned panels they will sell for a good price. Look for something for pickup.

Pick several different sized panels and see how they fit. On RV’s size (watts on the roof) is king. Sometimes you can get more panels by going smaller - even if it costs more.

On my MotorHome- I had to use 200w panels- too many Air conditioners, vents, skylights, etc. cost more - but that’s life.

Also if you can figure out a tilt - tilting adds lots of power if you can park in the proper orientation.

Good Luck

 

[MrPsychedelic]

For limited space applications (e.g. RV), the main driver is size of solar panel (including VOC and ISC or max volts and amps) and mounting kit.

You likely want to pick panels that …

0. Figure how much electricity you use and how many days you want to survive with worst case of no sun or ability to collect Solar. For example, if you use 5kwh as normal operation and 3kwh as critical. Then consider battery of 30kwh really becomes 20kwh after estimated 20% efficiency loss (6kwh) and 4 kWh as reserve power to ensure food cycle life. Note trying to keep simple round numbers here. Don’t want to always drain battery to zero percent. Net net, effective battery is 20kwh so you have 3 - 4 days of backup on normal usage and about 5 - 7 days if you really conserve.

Forgot to mention idle loads. A typical AIO inverter will consume say 50 - 100w so for 24hr x 80w = 2kwh. In a case of no sun or parking in shade, that can really eat up how many backup days you have, hence I listed a range above.

1. Can collect the most sun. For example, you may be able to fit 2 panels the within 8ft width of truck or 3 panels within that same width depending on orientation.

2. Fits your Solar charge controller (SCC) whether it be built in to an all in one (AIO) or standalone SCC. This less important than #1 above but still needs consideration. If VOC is 40v and you AIO max box is 250v, then you can get max series string of 5 or 200V with a cushion for low temp voltage increase. Now if VOC is 32v, then max panels would be 7 but depending on panel orientation, realist max panel is 6.


I rely on eBay and Amazon for solar panels since it’s more convenient for me. Depending on inventory and location, buying local maybe better.

Don’t forget box truck roofs can be this very thin plastic to minimize weight which means adding solar is more difficult.

And last, I recommend the Victron ecosystem of products since they just work, provide good software, and low idle consumption (15w compared to 50-100w), and Power Assist. Yea it cost more but long term, you will save and recoup it back through efficiency and reliability (lack of worrying).

Please ignore spelling errors. Responding on a phone sucks.

0. I'm working on finishing my design to know the total amount of power I'm going to be using daily. Thank you for telling me how little power the Victron system uses when idle. I used Victron in the grooming van, but didn't install solar on that so I thought it would be nice for an all in one. I'll have to weigh the options because 350W/day compared to 1600W/day is a huge difference. I'll have to run them 24/7 since I got a 120V fridge/freezer. I was tired of the 12V chest ones.

2. Would it be best to run all the panels in series? I was planning on running in parallel if I got the 70V panel, or if the 35V I was going to run series to 70V and parallel for the rest, depending how many fit. Most likely would have been 2s2p, since I would need an even number.

I keep looking at Fb marketplace and they don't have any deals. They're all asking more then online prices since you avoid the shipping costs.

For the box truck roof, I'm going to reinforce it with 2x3s at every rib which is about every 14-16", Tied into the wall framing I'll build secured with hurricane straps. So it should make the roof pretty secure and stable after that, thats the plan atleast.

Feel free to correct any thinking I may have wrong lol

 

[MrPsychedelic]

Look at your local sources and call around. Sometimes installers have orphaned panels they will sell for a good price. Look for something for pickup.

Pick several different sized panels and see how they fit. On RV’s size (watts on the roof) is king. Sometimes you can get more panels by going smaller - even if it costs more.

On my MotorHome- I had to use 200w panels- too many Air conditioners, vents, skylights, etc. cost more - but that’s life.

Also if you can figure out a tilt - tilting adds lots of power if you can park in the proper orientation.

Good Luck

Did you wire yours in series or parallel on the roof? I assume since it's an RV its a 12V system and not a 24 or 48 system?

I am definitely trying to figure out a way to get them to tilt without having to physically climb up everyday lol, were you able to come up with a system?

 

[Rocketman]

12v battery- I have a few arrays on the roof - put on one needed more - had room - added another array.

My big array - four 200w panels in a 2s2p arraignment- going into a Victron mppt 100/50.

Second array - two 210w panels in series (2s) going into a Victron mppt 100/30.

Third array- three 100w panels in series 3s going into a Victron mppt 100/20.

I want at least double the battery voltage going into the mppt - so 2s or 3s - then with four panels I went with 2s2p.

2s2p and 3s2p are what I would use with 4 or 6 panels on an RV - (Just my opinion).

Good Luck