Adding Solar to a Class A RV

[Capt Tango]

2003 Monaco Dynasty which is a 40 footer with a 3kw inverter. This is what I am interested in adding to my existing charging system. We boondocking is limited by our water supply to 3-4 days The lower right is the proposed solar panel, battery and controller addition.
The current system has a 3,000 watt Magnum Energy RV inverter and has a lithium compatible remote control. The current 12 volt wet cells are charged by the rigs 200 watt alternator, 20, 30 and 50 amp shore power and a 7.5 kw generator.

I plan on replacing the wet cells with a single LiFePO4 (maybe second when money is available).

The solar addition will include
1 ea. Vatrar 12V 460AH Low Temp Cutoff LiFePO4 RV Battery
3 ea. Solar panels 435W SunPower : SPR-E20-435-COM for a total of 1,305 watts wired in parallel.
1ea. Victron 150/100A charge controller

I feel comfortable with this component configuration but will listen to alternatives and suggestions. I'm new to this and would rather lean from others than make mistakes.

I do have a concern about the wire gauge of the panel wiring. I plan to connect them in parallel using 3 to 1 connectors on the roof and the rig is prewire with 8 ga for 20 foot.

Thanks in advance.

 

[Isaac-1]

You will need a second battery, the one you specified has a 250A BMS, which is not large enough to support a 3000 watt inverter at max amp draw. Rule of thumb you need AT LEAST 100A of BMS rating for every 1,000 watts of inverter capacity, and this is with no real safety margin. Therefore you would be better off getting a pair of circa 200AH batteries with 150A BMS wired in parallel than the single 460AH battery with a 250A BMS, better yet would be a pair of batteries with 200A BMS each.

 

[Capt Tango]

You will need a second battery, the one you specified has a 250A BMS, which is not large enough to support a 3000 watt inverter at max amp draw. Rule of thumb you need AT LEAST 100A of BMS rating for every 1,000 watts of inverter capacity, and this is with no real safety margin. Therefore you would be better off getting a pair of circa 200AH batteries with 150A BMS wired in parallel than the single 460AH battery with a 250A BMS, better yet would be a pair of batteries with 200A BMS each.

Thanks, good to know that information.

 

[chrisski]

The 3:1 combiner likely exceeds a 30 amp rating on MC4 cables.

I recommend a 24 VDC inverter with a 12 volt step down converter for all the 12 volt loads. 24 volts also allows the some fast charge appliances.

A 3000 watt inverter running at a low voltage cutoff of 10 volts would pull close to 350 amps with DC conversion
losses.

I do like the Victron 150/100. Allows certain figuring up to a 48 volt system. That controller could be maxed out with the panels you plan on adding.

 

[MisterSandals]

The 3:1 combiner likely exceeds a 30 amp rating on MC4 cables.

That was my first thought too, but...
Specifications:

• Rated Power: 435W
• Open circuit voltage (VOC): 85.6 V
• Max power voltage (VMP): 72.9 V
• Short circuit current (ISC): 6.43 A
• Max power current: 5.97 A

 

[chrisski]

That was my first thought too, but...
Specifications:

• Rated Power: 435W
• Open circuit voltage (VOC): 85.6 V
• Max power voltage (VMP): 72.9 V
• Short circuit current (ISC): 6.43 A
• Max power current: 5.97 A

Wow. Those are some higher voltage panels. Only one 3P for the 150/100, and a 100 volt MPPT would likely be pushed to hard by one of those panels on a cold day.

 

[Rocketman]

Welcome,

I have put a solar system on my 2000 Monaco Dynasty 36’.

I had a few thoughts as I was looking over your plans

1. Engine Boost: while you can hit the boost switch to add power to a depleted chassis battery- DO NOT hit the diesel engine starter while boost is on - that has a potential to fry the FET’s in the bms (they cannot handle the LRA (locked rotor amps) of the diesel starter.

2. Generator - which battery is your generator on? Chassis or house? - Monaco did it both ways. You may be able to start the generator if you can get higher amp outputs on the battery.

3. Do you have the older Duvac alternator system? This has a big 3 post battery isolator in the rear electrical bay.
The issue is you have to cut off the charging or your lithium battery will continue to charge at the 14.1 to 14.3v the entire time you are driving. That will be harmful to the lithium battery once it is full and you still have several more hours on the road. The lithium battery isolator manger I don’t know if it will prevent that.(I just completely separated my engine/house systems then added a Victron Dc-Dc 30a charger to slowly charge while driving).

4. Panels: Can you physically fit those panels on your roof? I could not. I had to use 200w panels (I have 1400w of solar up there for the house + 100w for engine). Your current panels can only go in parallel. With 3 in parallel you will need each panel fused- they make MC4 fuses. If you want to go to 4 panels in a 2s2p arraignment- you would need to move to a Victron mppt 250/100. With 3 panels mounted flat you will never max out the solar charge controller- if you add a 4th panel - you will be over paneled- but that is not bad because you Will get more power with the flat panels - you could still go 4p into the 150/100.

5. Inverter/charger - I replaced my with a Victron- when my inverter was failing shortly after I got my Dynasty, so I don’t know the Magnum brand… does your inverter/charger have a charger mode that will work good enough for the lithiums? Also does the battery monitor have settings that will work for lithiums?

6.Mppt location. Do you have a spot picked out for the mppt location? In my rig, I completely reused the old solar wires. Coming from the roof was #8awg wire into a cabinet that housed the SCC, then it had #8awg going to the battery box, then a #10awg fuse. I re-used those wires for a Mppt 100/30 - even then the wires from the mppt to the battery box is long and I have some voltage drop on that wire (I replaced the #10 fuse with a #8awg fuse). You will need to run some 100a wire from the mppt to the battery -( #2 I believe). Also, make sure the negative wire from the mppt attaches to your shunt (load/charger side) - otherwise your shunt will not register the power from the solar. And the positive has a fuse.

7.Generator - I believe your generator is only 120v - the QD7500 run the same phase on both lines - but that’s just a FYI. Can you reprogram the auto generator start to a slightly higher voltage? Lithium’s at 12.0v are basically dead.

8. One item I changed out was the salesman switch relays. I changed them from the continuous relay to a Victron Smart BP65. The old relays used a lot of power - the BP65’s - almost none. Plus I set them to turn off at 11.8v (and back on at 12.1v). That way if I leave something on and my battery is VERY low - the BP65’s shut down - before the bms shuts down. That gives my bms a while before it goes to sleep. Waking up a bms can sometimes be difficult and stressful- better solution- is preventing if from going to sleep - then solar can just recharge it - no issues.

Good Luck with your project- if you run into Monaco questions - feel free to PM me.

If I didn’t explain something clearly on the above novel- let me know and I will try again.?

 

[Capt Tango]

Great information, I have some of those bases covered but defiantly not all. I'll update on the installation and PM you when I have questions.
Thanks so much.

 

[RvNaut]

Here is a look at how I incorporated a new system into my RV. You might want to look at a 24 or 48 volt battery, for several reasons, including ditching the 4/0 cable.

 

[Diamonddave2]

I'm trying to do a similar installation on my 2004 Monaco Knight 34 PPD D.P. class A. I'm buying the 12V 300Ah V2 | Heated & Bluetooth & Victron Comms | LiFePO4 Battery from Epoch. I also bought their 12V 15 amp charger. I'm removing the four 6V L.A. batteries and attaching the epoch battery to a lynx distributor with 4/0 cables and a Victron Smart Shunt. I have a 300W portable solar array (36V) and 50' of 10 gauge cable to run to a 75/15 MPPT Victron controller that I'll connect to the Lynx distributor. I'm going to have a breaker disconnect on the input of the solar line. I also bought a B.I.M. to control the alternator charging and isolate the house from the chassis batteries. There is a disconnect there that I'll incorporate into the system. I'd like to keep the Xantrex 2000W inverter in place. I'd like to not replace that inverter right now to save money. Eventually, I might replace it with a Victron Multiplus II inverter and another 300 ah battery in parallel. Any advice for me?