Complete Newbie adding solar to an RV

[Robin Hillier]

I am forced to enter a life of fulltime RV boondocking by failing health and finances. That means everything will be DIY. I have a travel trailer which I will be covering the roof with solar panels and building LiFePO4 batteries. Due to charging the battery bank from the truck during driving and the fact that the loads in the trailer are all 12 volts DC or 120 volt AC my thought is to make the system simpler by building multiple 12 volt batteries. As the rig may be in partial shade at times, I want to make it easier to add external ground placed solar panels (suitcase solar) also. The plan is to have all the panels in parallel to avoid shading issues, all feeding a roof mounted weathertight junction box. That will feed the charge controller(s) down near the tongue through heavy copper cables. That is also where the batteries, DC to DC converter, and inverter will reside. I plan to build a wind turbine in the future, so a charge controller to do all, or separate charge controllers are options. I know I have just opened a lot of topics, so building the batteries is my first concern. I have pretty much settled on 4,12 volt batteries built using EVE LF280K cells which I am ready to order. The BMS topic is where I am now gathering info and opinions. The batteries will give me an 1120 amp hour bank. The 4 batteries will be individually fused and switched before feeding a bus bar where the DC to DC converter will connect. That will then feed the inverter. If anyone has any thoughts on any or all of these topics, I will be glad to hear them. Thank you for reading my long winded intro.

 

[sunshine_eggo]

12V is good for 2000W, 3000W marginal.

Select battery voltage based on peak demand. If you might use 3000-4000W, 24V makes a lot of sense.

Higher battery voltage also reduces MPPT current needs. 1200W of PV into 12V means you need 100A of MPPT - EXPENSIVE. 1200W of PV into 24V means you only need 50A - half the price.

Consult the links in item #1 in my signature. Given that finances are limited, the better your planning up front, the better your system design and budget.

 

[HRTKD]

On the topic of roof and ground panels, I use separate solar charge controllers. I could have paralleled them (the PV panels) but it was just easier to put in a second solar charge controller. I wanted a bit of safety. The ground solar charge controller can be totally isolated from the port on the side of the trailer using a dual pole breaker. Just in case someone tries to feed power through the port that the controller can't handle.

If you have sufficient solar on the roof, you're unlikely to need much of a charge from the truck. My 560 Ah LiFePO4 battery bank gets zero charge from my truck.

As you get further along, draw up a diagram. It's easier for us to review a diagram.

 

[Robin Hillier]

12V is good for 2000W, 3000W marginal.

Select battery voltage based on peak demand. If you might use 3000-4000W, 24V makes a lot of sense.

Higher battery voltage also reduces MPPT current needs. 1200W of PV into 12V means you need 100A of MPPT - EXPENSIVE. 1200W of PV into 24V means you only need 50A - half the price.

Consult the links in item #1 in my signature. Given that finances are limited, the better your planning up front, the better your system design and budget.

Thanks for your input. I'm at the design stage, so everything is up in the air. I will look at your links. thanks, Robin

 

[Robin Hillier]

On the topic of roof and ground panels, I use separate solar charge controllers. I could have paralleled them (the PV panels) but it was just easier to put in a second solar charge controller. I wanted a bit of safety. The ground solar charge controller can be totally isolated from the port on the side of the trailer using a dual pole breaker. Just in case someone tries to feed power through the port that the controller can't handle.

If you have sufficient solar on the roof, you're unlikely to need much of a charge from the truck. My 560 Ah LiFePO4 battery bank gets zero charge from my truck.

As you get further along, draw up a diagram. It's easier for us to review a diagram.

On the topic of roof and ground panels, I use separate solar charge controllers. I could have paralleled them (the PV panels) but it was just easier to put in a second solar charge controller. I wanted a bit of safety. The ground solar charge controller can be totally isolated from the port on the side of the trailer using a dual pole breaker. Just in case someone tries to feed power through the port that the controller can't handle.

If you have sufficient solar on the roof, you're unlikely to need much of a charge from the truck. My 560 Ah LiFePO4 battery bank gets zero charge from my truck.

As you get further along, draw up a diagram. It's easier for us to review a diagram.

Thank you Jim for your thoughts. It sounds like you may be in the sunny West, whereas most of my time may be in the east where sun is less consistent, so I want to be prepared to top up the batteries during travel. I will consider your idea of a separate solar controller for the ground panels. I will do as you suggest and post a diagram of my proposed layout and invite discussion as soon as I'm smart enough to know what I'm doing. thanks, Robin

Thanks for your input. I'm at the design stage, so everything is up in the air. I will look at your links. thanks, Robin

If I arrange the batteries in a parallel series configuration to get 24 volts for the sake of charge controller price, where do I get my 12 volts from? Tap off from 1 battery? That would only give me access to 1/4 of my 12 volt capacity. What am I missing?

 

[HRTKD]

If I arrange the batteries in a parallel series configuration to get 24 volts for the sake of charge controller price, where do I get my 12 volts from? Tap off from 1 battery? That would only give me access to 1/4 of my 12 volt capacity. What am I missing?

No, you don't want to do that. You would have to use a 24-12 converter. It's a common device in an RV that is running a system voltage higher than 12 volts.

 

[Robin Hillier]

No, you don't want to do that. You would have to use a 24-12 converter. It's a common device in an RV that is running a system voltage higher than 12 volts.

I seem to be making a mess of this thread. Is there a tutorial for this site?

 

[HRTKD]

I seem to be making a mess of this thread. Is there a tutorial for this site?

It's not a problem. I figured out what you did.

There are three ways to reply.
1. Hit the reply button on the lower right corner. It will quote the entire message and you write your response below the quote.
2. Highlight the text you want to reply to. It will show a reply button next to the highlighted text, which will be copied into your response.
3. Just type in the empty box at the end of the thread.

I looked for a tutorial and couldn't find one. That was a good question. As of 2021 the software that is used for the forum does not provide a tutorial.

 

[Robin Hillier]

It's not a problem. I figured out what you did.

There are three ways to reply.
1. Hit the reply button on the lower right corner. It will quote the entire message and you write your response below the quote.
2. Highlight the text you want to reply to. It will show a reply button next to the highlighted text, which will be copied into your response.
3. Just type in the empty box at the end of the thread.

Thank you, I guess I just need practice.