Designing My Solar/Electrical System

[mattbus]

I'm not experienced with electrical systems at all... but that's what my skoolie build is all about, learning! I'm a bit of a tech geek and I don't plan on installing a propane system of any kind, so my solar setup is fairly beefy from what I've seen on other short bus skoolie's.

For now, this layout is just to make sure I'm not missing any components and that I'm understanding how everything works and goes together. Next step will be detailing the wiring. Any and all suggestions or comments are appreciated! I've been reading a ton, but a lot more to learn.

1) 6 x 100W Solar Panels - 600W Total
2) Small Breaker Box - 1 breaker between panels/controller, 1 breaker between controller/battery bank
3) Victron MPPT Charge Controller 100V / 50A
4) 4 x Trojan T105 AGM 6V 225ah (900ah total) (wired to 12v)
5) Victron BMV-702 Battery Monitor / Shunt
6) Victron Multiplus 12V/3000W Inverter / Charger
7) Victron Color Control Monitor
7) 110V AC Breaker Box
110V AC Outlets for Appliances
9) 12V Fuse Block for 12V Appliances
10) 50A Power Inlet for Shore Power

Accidentally labeled 7) twice, but you get the idea...

I really love the Victron functionality and hardware from everything I've read so far. The ability to combine solar/battery/shore power is awesome. And the control monitor is really slick looking.

 

[Deezl Smoke]

Racking for the panels and cabling for the 12v system should also be included in your list as I think they are of high enough expense not to be considered misc. hardware. IMO.

Depending upon where in the world you will be running this system, if you plan to use the microwave and other 1k watt draw items very much, you best get a few more batteries.

Are you going with the 100 watt panels for space constraints, or durability issues, over the larger 200+ watt panels?

There will be various opinions on inverter sizing. If you do not wish to be very actively involved with operation when on solar, then one of the local to me retailers and installers suggests inverter sizing to be double your max watt draw estimation. I disagree with this, but I am not in the field nor any sort of even amateur much less expert. A brand and model that is considered to be good, has a static consumption of over 75 watts.
I personally would rather be involved in the operation and would have 2 inverters, so I can run a small one when lights and computer are all that is needed, and a larger one when higher draw is required. But then, I have no issues with changing my life schedule to make the most of the power available. Some people do not wish to do that.

 

[chrislind]

I noticed that you have your battery bank listed at 900Ah. From my understanding, when you are connecting two 6v batteries together, you will be running 12v at 225Ah per 2 batteries. So, you actually will only have 450AH in that configuration. If you are running at 6v, you'd have 900Ah. If you had four batteries that were 12 volt , you would have 900Ah at 12 volts. I am also new to this so please let me know if I am wrong.

 

[ermracing]

I noticed that you have your battery bank listed at 900Ah. From my understanding, when you are connecting two 6v batteries together, you will be running 12v at 225Ah per 2 batteries. So, you actually will only have 450AH in that configuration. If you are running at 6v, you'd have 900Ah. If you had four batteries that were 12 volt , you would have 900Ah at 12 volts. I am also new to this so please let me know if I am wrong.

That is my understanding as well. We are in a similar phase of our build so are trying to figure out which batteries to use. I'm a little confused about #2. Why have a breaker box there? Wouldn't a simple cut-off switch serve the same purpose?

Are you going to have a feed from your alternator to the Inverter/Charger as well?

 

[Drew Bru]

I'm a little confused about #2. Why have a breaker box there? Wouldn't a simple cut-off switch serve the same purpose?

Should be a breaker, not a cut off switch. Breakers protect from an overloaded circuit. And both the input and output from the charge controller should be fused. Here's a quick rundown. https://www.renogy.com/blog/how-to-fuse-your-solar-system/

 

[o1marc]

I noticed that you have your battery bank listed at 900Ah. From my understanding, when you are connecting two 6v batteries together, you will be running 12v at 225Ah per 2 batteries. So, you actually will only have 450AH in that configuration. If you are running at 6v, you'd have 900Ah. If you had four batteries that were 12 volt , you would have 900Ah at 12 volts. I am also new to this so please let me know if I am wrong.

Depends on if you run your batteries in series or parallel. In parallel if you have 2-6v-225ah batteries, they would be hooked neg/neg and pos/pos you would have 6v @ 450ah. If you ran them in series , neg/pos, you would have 12v @225ah. HTH

 

[ermracing]

Should be a breaker, not a cut off switch. Breakers protect from an overloaded circuit. And both the input and output from the charge controller should be fused. Here's a quick rundown. https://www.renogy.com/blog/how-to-fuse-your-solar-system/

I stand corrected. Ours does have a fuse there and we were planning on installing a switch as well so the breaker would serve both purposes. But it would have to be a 12v breaker, assuming that's what coming in from the panels, right?

 

[Drew Bru]

It should be a DC breaker, mine is 100A. I use it as a switch when I need to isolate the charge controller for whatever reason.

 

[roach711]

I noticed that you have your battery bank listed at 900Ah. From my understanding, when you are connecting two 6v batteries together, you will be running 12v at 225Ah per 2 batteries. So, you actually will only have 450AH in that configuration. If you are running at 6v, you'd have 900Ah. If you had four batteries that were 12 volt , you would have 900Ah at 12 volts. I am also new to this so please let me know if I am wrong.

This is correct. When cabling two batteries in parallel (neg to neg, pos to pos) the voltage stays the same and amperage doubles. When cabling in series (pos to neg) the voltage doubles and the amps stay the same. To cable your 4 6v batteries into a 12v bank you would cable 2 6v battery pairs in series to get 12 volts then cable the two pairs together in parallel to double the amps.

Also, keep in mind that for decent battery life you should only discharge your bank to 50%. That means that you should only draw 225 amps before recharging.

 

[Drew Bru]

This thread brings to mind the idea of balancing the battery bank. It's been posted elsewhere, but it bears repeating that there are many ways to configure a battery bank, with some edging out the others.
SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank