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Old 02-25-2020, 02:12 PM   #1
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Designing new solar system (includes diagram)

Hi all. We've been full timing for about 18 months and we've learned we could benefit from getting some solar for our rig. I consider myself handy and a diy'er but have had limited knowledge about electricity until I started investigating solar. Six months ago, I couldn't have told you that Amps*Volts=Watts. I've spent many hours reading and learning and looking at other people's setups. I plan to do this install myself. I already have the batteries installed and we live well on the 300 AH, but run the generator far too long when it is time to charge. I'm sure I've missed something or could be doing something better. I have attached a diagram of my proposed system (sorry for the handwriting). Any thoughts and comments would be greatly appreciated!
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Old 02-25-2020, 03:14 PM   #2
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A few items I noticed things you may want to think about, you have fuses marked - in just upstream and downstream of the mppt. Think about using circuit breakers instead. That way you can easily turn the on and off. Also (important) you need a fuse or circuit breaker near the batteries on the wire to your mppt. I actually have a breaker on both ends of that wire - because my wire is about 10 to 12 feet and somewhat exposed.

Also- how long of a wire run between mppt and battery? Do you have a battery monitor? If not consider the Victron BMV-712. If both the mppt and BMV are bluetooth - they can talk to each other and the BMV can pass battery voltage up the mppt so the mppt can compensate for line losses (if any)
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Old 02-25-2020, 03:40 PM   #3
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With lithium batteries I believe a DC to DC battery charger is required. Check with Battleborn cuz maybe there is something in the BMS on the batteries to preclude getting the charger.
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Old 02-25-2020, 03:41 PM   #4
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#10 is getting close to max if you have a long run, I would run the 3 panels in series, then no chance to max out your wire. If no increase you can always go back to parallel. The old wives tale about one shaded cell you lose everything is false. All modern panels have bypass diodes to prevent this.
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Old 02-25-2020, 04:17 PM   #5
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Don't worry about a 30 amp fuse between the controller and panels, it will never make more then 28 amps anyway. A switch for testing and working on it will be handy though.

You will want the fuse or circuit breaker between the controller and batteries very close to the batteries.
The batteries have the energy potential to burn up wiring, so the closer the better.
A second fuse or breaker, near the controller, is not needed. It will be rated higher then the controller output, so again it will not blow or trip.

12 gauge wire from the panels may give you some unacceptable voltage drops.
You can move up to 8 or 6 gauge or stay with 12 gauge and wire the 3 panels in series. Your controller will handle the 100 or so volts from the panel and you'll be down to 10 amps on that wire. Much less voltage drop.
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Old 02-25-2020, 05:29 PM   #6
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I use a breaker disconnect between the panels and the MPPT controller and a disconnect between the MPPT controller and the battery bus bars. You need to disconnect the solar power to the MPPT controller before disconnecting the link to the batteries.

I would use a combiner box on the roof for each of the 10 AWG panels back to the combiner box. I used 6 AWG between the combiner box and the MPPT controller.
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Old 02-25-2020, 06:01 PM   #7
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Check out Handy Bob's Solar.....not me!.......He's in Wyoming...
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Old 02-25-2020, 09:12 PM   #8
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Quote:
Originally Posted by Rocketman3 View Post
A few items I noticed things you may want to think about, you have fuses marked - in just upstream and downstream of the mppt. Think about using circuit breakers instead. That way you can easily turn the on and off. Also (important) you need a fuse or circuit breaker near the batteries on the wire to your mppt. I actually have a breaker on both ends of that wire - because my wire is about 10 to 12 feet and somewhat exposed.

Also- how long of a wire run between mppt and battery? Do you have a battery monitor? If not consider the Victron BMV-712. If both the mppt and BMV are bluetooth - they can talk to each other and the BMV can pass battery voltage up the mppt so the mppt can compensate for line losses (if any)
Good idea about the breakers in case I want to shut them off. I could put a fuse box in the bay right next to the batteries. I suppose I don't need one on the side from the panels to the mppt, as someone said since I'll never make more than the 28 amps. I do have the Victron Battery monitor already, as I purchased it with the batteries. I like being able to look at it on my phone. This is why I wanted the Victron Solar Controller - so I can see what it is doing on my phone . I had no idea that the BMV could talk to the solar controller and up the output if necessary - that is awesome!

Also, the wire run was placed by Tiffin when it was manufactured and I estimate it is 10-12 feet max.
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Old 02-25-2020, 09:16 PM   #9
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Originally Posted by astrocamper View Post
I use a breaker disconnect between the panels and the MPPT controller and a disconnect between the MPPT controller and the battery bus bars. You need to disconnect the solar power to the MPPT controller before disconnecting the link to the batteries.

I would use a combiner box on the roof for each of the 10 AWG panels back to the combiner box. I used 6 AWG between the combiner box and the MPPT controller.
Thanks I should have put the combiner box on there. The way I have it drawn out (in parallel), does it make a difference if I wired the panels as shown or just connected each one directly to the combiner box?
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Old 02-25-2020, 09:19 PM   #10
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Originally Posted by SteveJ. View Post
With lithium batteries I believe a DC to DC battery charger is required. Check with Battleborn cuz maybe there is something in the BMS on the batteries to preclude getting the charger.
Not sure what you are saying here. I haven't seen anything about a DC to DC battery charger. Can you (or anyone else) elaborate?
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Old 02-25-2020, 09:25 PM   #11
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I have the 712 and two victron bluetooth solar controllers and the Victron 3000 inverter. While I can read the information and adjust settings on my tablet, cannot see how any of them communicate with each other by bluetooth. Just bought the new 30 amp dc to dc charger so I can charge my lead acid start batteries and lithium house batteries at the same time. It also is bluetooth but only communicates with my tablet.
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Old 02-25-2020, 09:42 PM   #12
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Originally Posted by TiffinAlleg View Post
Not sure what you are saying here. I haven't seen anything about a DC to DC battery charger. Can you (or anyone else) elaborate?
I should have been a bit clearer. The DC to DC charger is to replace engine alternator charging as the engine charging system is not very friendly to lithium batteries at all. Also, you don't want to have too big of charger as it will over tax the alternator unless it is a commercial Leece-Neville or similar. I know Delco also makes a commercial/big truck type of alternator.

I would be cautious on anything over 40 amps. Make sure that your alternator can handle the extra current on a continual basis without over heating if you go bigger than 40 amps. Another thing some folks do is add another charging system to include an extra alternator but that is above my pay grade and can get complicated. More useful for very large battery banks needing a large charge. Think 800 and up for AHs.

Instead of a DC charger you could to charging manually, cutting off the alternator feed to the lithiums when they are charged. Very problematic, though along with not being an ideal charge rate anyhow.

This is mostly info that I have gleaned from the class b forum from a few folks over there that have installed similar. I do not have a lithium system. In particular, a gentleman going by rowie-bowie over there just recently did a change over to lithiums and has some pretty good info on gotchas and stuff.
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Old 02-25-2020, 10:05 PM   #13
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Just replace your current isolation solenoid with a Lithium BIM 225 isolation system.

No need for a battery to battery charger.Click image for larger version

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Old 02-25-2020, 10:11 PM   #14
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Quote:
Originally Posted by SteveJ. View Post
I should have been a bit clearer. The DC to DC charger is to replace engine alternator charging as the engine charging system is not very friendly to lithium batteries at all. Also, you don't want to have too big of charger as it will over tax the alternator unless it is a commercial Leece-Neville or similar. I know Delco also makes a commercial/big truck type of alternator.

I would be cautious on anything over 40 amps. Make sure that your alternator can handle the extra current on a continual basis without over heating if you go bigger than 40 amps. Another thing some folks do is add another charging system to include an extra alternator but that is above my pay grade and can get complicated. More useful for very large battery banks needing a large charge. Think 800 and up for AHs.

Instead of a DC charger you could to charging manually, cutting off the alternator feed to the lithiums when they are charged. Very problematic, though along with not being an ideal charge rate anyhow.

This is mostly info that I have gleaned from the class b forum from a few folks over there that have installed similar. I do not have a lithium system. In particular, a gentleman going by rowie-bowie over there just recently did a change over to lithiums and has some pretty good info on gotchas and stuff.
I have monitors on the dash for both house and chassis batteries and was doing what you said, just using the "combine" switch for 20 on and 10 off. A PIA. I went with the DC to DC charger, limits current to 30 amps, so no chance of maxing out your alternator.
This is the one I got, you can set up everything on your bluetooth phone. https://baymarinesupply.com/electric...c-charger.html
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