12v system install on a '90 Alpenlite 25+2 5th wheel

[SmithsJunk]

My list of main components...

4x 100w Newpowa monocrystalline PV
17.2v 5.82a ea

60a Top One Power MPPT charge controller without a dedicated ground terminal

2x Mighty Max 12v 100ah AGM batteries

2x Bayite 100v meter w/100a shunt

I was planning on installing this system to run the 12v components of my 5th wheel but now that I've read the 12v safety sticky I'm wondering if these solar components should be used, or can be safely. I've read so much conflicting information over the last 2 years I've become lost in the storm of it. I bought these components with the intention of eventually using them to run grow lights but wanted to temporarily use them to run the trailer till I could afford a smaller, more suitable, setup. I have no intention of using this system to power an inverter at this time, only the 12v appliances and lights. We have frequent power outages so I had hoped it would be enough to run my 12v forced air heater and AC/propane fridge when it's switched over to propane during an extended outage.

If these components are unsafe for my intended RV install how should I adjust to make it work, ie; Is a single 12v 100ah battery okay, or is it imperative that I switch to a bank of 6v? How many of the 100w panels should I use? Do I need to buy a completely different charge controller? (*note* The trailer has a 40a 12v panel, is currently utilizing 2x 12v FLA in parallel, and the harness is set up for them)

I'm not going to ask the slew of questions I first intended until this is settled. One more thing, I don't have a lot of money and it took me some time to put this system together, so please refrain from suggesting things like lithium batteries or overly expensive components because I won't be able to act on your advice. If I do need to change components, AGM batteries are my preference for their low maintenance needs.

Thank you for taking the time to help me out and I'm more than happy to provide more info if needed.

[Sunking]

Not sure what you are afraid of? 12 volt systems only become dangerous when the loads become more than 80 amps which you are not coming close too. With 400 watts of panels at most will only generate 30 amps of charge current out of the controller. That is a little more than required for the 2 batteries, but being AGM should be OK. If all you intend to run is one battery, only use 2 panels and trash the other two.

Now if you want to build something more functional and matched up to work with 400 watts of solar panels you only need 40 amp controller (60 will work), but you would be much better off using a pair of 6-volt FLA batteries sized to 250 to 300 AH. Additionally throw the 100 volt meter and shunt in the trash as it does not tell you anything or add any useful purpose creating another failure point you can afford not to have.

Is your truck 12 or 24 volts? If 12 you have no need for the solar, just get an inexpensive electronic battery isolator and as much battery as you can find room for. The engine alternator can generate more energy in one hour than the panels can generate in a day or two.

[Mike90250]

I'd skip the meter and learn to understand the battery voltage, and how it compares to the amount of Absorb time the next day.

When you replace the batteries, use 6v 200Ah golf cart batteries. Batteries in series charge and discharge more equally then batteries in parallel.

Price out how many 100w 12V panels you need, compared to ~250W grid tie panels and a decent MPPT controller

[SmithsJunk]

Not sure what you are afraid of? 12 volt systems only become dangerous when the loads become more than 80 amps which you are not coming close too. With 400 watts of panels at most will only generate 30 amps of charge current out of the controller. That is a little more than required for the 2 batteries, but being AGM should be OK. If all you intend to run is one battery, only use 2 panels and trash the other two.

Now if you want to build something more functional and matched up to work with 400 watts of solar panels you only need 40 amp controller (60 will work), but you would be much better off using a pair of 6-volt FLA batteries sized to 250 to 300 AH. Additionally throw the 100 volt meter and shunt in the trash as it does not tell you anything or add any useful purpose creating another failure point you can afford not to have.

Is your truck 12 or 24 volts? If 12 you have no need for the solar, just get an inexpensive electronic battery isolator and as much battery as you can find room for. The engine alternator can generate more energy in one hour than the panels can generate in a day or two.

LOL, I was fine with my components until I read your sticky about sizing and safety. Thank you for calming me back down, l'll continue as I first planned (maybe w/o the meter).

I live in my trailer in a fixed location so vehicle charging is not an option but I will install that isolator in my truck(12v) just in case I do need to run connected.

Now that that's sorted, on to fusing and grounding. My panels are not rooftop yet. I am waiting till spring and better weather. For now they're installed on a stand I made from a couple heavy pallets and this set may continue in that location for when I repurpose them for their original intended use. I have a 20ft 10awg cable from the panels to the charge controller (30a fuse) and for the next few weeks I plan to run them 2x2 series-parallel. Like I said, I'm poor, so I could only afford 2x 10a mc4 diode fuses this month and I need to get these connected ASAP. That puts the panel output at 34.2v 11.64a. As soon as I can drum up another $20 I'll order two more 10a fuses and run all four panels in parallel 17.2v 23.28a. I don't know anything about pv fuses. Are the cheap diode fuses safe? If not, I'll replace them with the standard pv fuses that fit the mc4 holders.

Some questions on grounding...

I want to ground my panel frames to a true earth ground. Is there going to be any possible conflict between that and the powered portion of the system using a chassis ground? I do plan on buying a Midnite or Delta surge arrestor for the panels when they go rooftop.

My charge controller has no dedicated ground terminal so it would have to be grounded from a negative termination point. The trailer's harness has a central ground that connects to the negative battery terminal (8 gauge, I believe). Do I need to add another ground from there to the chassis for the charge controller? Adding another seems unnecessarily redundant to me considering it is good enough for the trailer's inverter/charger, which will be disconnected.

I'm buying lay in lugs w/WEEB washers next month to bond the panel frames. For the time being I'm planning on strapping them together with some 10gauge wire with crimped lugs and doing a couple foot run to the rebar from a single frame. I will sand the contact points. Is this an acceptable intermediate solution?

When I do connect the ground wire to the grounding lugs does it have to be solid bare copper or can I use that same 10gauge stranded with the insulation still on? Stripped?

Two of you are saying to ditch the meter because it's unnecessary but how do I learn my systems charge vs discharge rates without at least observing it for a while? I can do the calculations using the component specs but those aren't the actual numbers.

I have 275a battery isolator switches to disconnect the incoming and outgoing cables to the charge controller. I also have a 100a brass disconnect I can add on the battery bank to the RV fuse panel. I don't think the battery bank switch is absolutely necessary since the trailer already has a kill switch on the fuse panel but I like the idea of being able to completely isolate the bank when doing work on the system. This is probably overkill. I decided on these safety measures when designing the system for 800w at 24v-48v to run grow lights on my 1500w pure sine inverter.

I'm doing my best to ask the right questions and really appreciate you guys taking the time to answer my post.

[SmithsJunk]

Forgot to mention...

I have 5' of 6awg wire (+a few inches for the isolator switch, +pos side) from the charge controller to battery bank (or shunt on the -neg side) w/60a ANL fuse. 2awg 12" jumpers between batts and to the shunt if used. I wasn't planning on fusing the battery bank to the RV fuse panel since there's already 40a self resetting breakers in line and I dont know if that would cause a conflict or even be neccessary. If I use the pre-existing harness I figure everything is properly fused already as long as I program the mppt to a 40a charge rate. I can't think of anything else at the moment.

[Sunking]

LOL, I was fine with my components until I read your sticky about sizing and safety. Thank you for calming me back down, l'll continue as I first planned (maybe w/o the meter)

You are welcome. The issue on safety is when folks go hanging a 1000 watt or more Inverter off a 12 volt battery. Uo are not doing something stupid like that.

Now that that's sorted, on to fusing and grounding. My panels are not rooftop yet. I am waiting till spring and better weather. For now they're installed on a stand I made from a couple heavy pallets and this set may continue in that location for when I repurpose them for their original intended use. I have a 20ft 10awg cable from the panels to the charge controller (30a fuse) and for the next few weeks I plan to run them 2x2 series-parallel. Like I said, I'm poor, so I could only afford 2x 10a mc4 diode fuses this month and I need to get these connected ASAP. That puts the panel output at 34.2v 11.64a. As soon as I can drum up another $20 I'll order two more 10a fuses and run all four panels in parallel 17.2v 23.28a. I don't know anything about pv fuses. Are the cheap diode fuses safe? If not, I'll replace them with the standard pv fuses that fit the mc4 holders.

You are not going to like what I say. You wasted your money, no fuses required between Panels and Controller with two parallel strings. Only time fuses are required is if you have 3 or more strings using a combiner and feeder cable. Don't buy anything else as you are just throwing away money. You can use them if you want, but not required. Solar panels are current sources, not voltage sources. They cannot generated enough current to overheat the wiring like say a battery can.

Some questions on grounding...

I want to ground my panel frames to a true earth ground. Is there going to be any possible conflict between that and the powered portion of the system using a chassis ground? I do plan on buying a Midnite or Delta surge arrestor for the panels when they go rooftop.

Again you will not like this. You are throwing your money away on something that is not required or have any function. Complete waste of time and money. Earth ground is only required on buildings when the panels are elevated up on the roof exposed to high voltage electrical lines and lightning. You can do that if you want, but buys you nothing and has no function. Here is a basic wiring diagram of what is needed.

[SmithsJunk]

You are welcome. The issue on safety is when folks go hanging a 1000 watt or more Inverter off a 12 volt battery. Uo are not doing something stupid like that.





You are not going to like what I say. You wasted your money, no fuses required between Panels and Controller with two parallel strings. Only time fuses are required is if you have 3 or more strings using a combiner and feeder cable. Don't buy anything else as you are just throwing away money. You can use them if you want, but not required. Solar panels are current sources, not voltage sources. They cannot generated enough current to overheat the wiring like say a battery can.



Again you will not like this. You are throwing your money away on something that is not required or have any function. Complete waste of time and money. Earth ground is only required on buildings when the panels are elevated up on the roof exposed to high voltage electrical lines and lightning. You can do that if you want, but buys you nothing and has no function. Here is a basic wiring diagram of what is needed.

Hey man, I've got no issue at all with what you're saying. If I knew what I was doing I wouldn't be asking. Happily, nothing is wasted as I'm eventually going to swap systems out to a more appropriately sized one for the RV then beef this one up to run a set of 400w-600w lights on the 1500w inverter. When I bought the parts I was going to run it all on one (after upgrades) but decided it was safer, easier, and cheaper to split it into two systems.

I know of solar systems burning from bad installations so I'm being extremely cautious. This is my home. If it burns, I'm homeless.

You've satisfactorily answered all the questions questions I had. I really appreciate it. I'm happy that I was overdoing the safety. My concern was that I wasn't being safe enough.