Solar Design - How's it look?

[xbcsutter]

Originally Posted by Rocketman3

Here are some items to think about.

This is almost exactly like my setup I installed last year.

The Victron 100/50 charge controller will only handle 50 amps which is 700 watts. At times your solar charge will be clipped to the 700 watts. Just wanted to make sure you realized that. I figured that was an acceptable compromise for the cost. Thus adding an extra panel will only be of benefit cloudy days and evenings. ( in my opinion- not worth it unless you add another solar controller or upgrade to a 150/65).

I wired my panels in a 2s2p system - I think it was better because 2 panels were up front and 2 towards the rear.

In my setup ( which is not ideal), I have a long run (12 feet) from the solar controller to the batteries- thus I bumped up that wire to 4ga. I also put the breaker between the controller and batteries right next to the batteries. I didn’t want that wire to become a welding cable with 440 ah of batteries running it.

If you use a bmv712 the shunt can tell the the charge controller the battery voltage and temperature.

Good luck

Thanks Rocketman - I didn't realize the 100/50 would be the limiting factor. Definitely going to upgrade controller, prob stay with 4 panels to start. Think that gets me really close to what I need.

[xbcsutter]

Originally Posted by RVingNow

1. So the advantage of running in series is to reduce amperage and hence smaller wire gauge runs to the controller. So why is there a 60 amp breaker? Is your plan to run 8 ga wire? A 200w panel will generate maybe 12 amps (check your panel specs) so the wiring could be 12ga for the longer runs without significant voltage drops with a 20 amp breaker for safety.

2. As suggested above, you could have two strings of panels to deal with the partial shading issues. While that's the configuration on my boat (port string and starboard string) it may be less of an issue on an RV. (You don't hoist a sail do you?)

3. Review your wire gauges, and breakers and size appropriately for the amperage and run lengths. Bump up sizes now to plan for additional panels if that's your intent.

Good Luck

I wasn't sure of appropriate breaker for panel to controller. Running 48-60v 12amps. How does this product look: https://www.ecodirect.com/MidNite-So...ar-mnepv20.htm

[R Cabesa]

Originally Posted by xbcsutter

Thanks Rocketman - I didn't realize the 100/50 would be the limiting factor.

I'm going to suggest running 2- 100/30 controllers parallel with a pair of panels in series to each one.



Get the "Smart" versions and you can monitor each set of panels.



If you have A/C and vents on your roof, place and wire the panels so the pairs will be shaded at different times of day


I am running 3 controllers for my system and it works great

[Rocketman3]

The 100/50 is a “good” fit for 800 watts of panels. It is cost effective, and you have used all the capacity of the unit.

Sometimes, when your batteries have had a good use last night, and you are at higher altitudes, and it is a clear bright day, you may notice (if you are looking), that the controller only delivers 700 watts of power. (700watts/14 volts = 50 amps). Four 200 watt panels could deliver about 57 amps. Thus your controller clipped your panels.

I figured the benefit of those few amps was not worth the cost increase to go to a 150/65 controller. Mainly because with 50 amps going into the AGM batteries, really soon they will be in absorbing mode then they would be using less power. Plus usually on those days the sun will continue to shine.

Good luck with your project!

[xbcsutter]

Thanks again Rocketman! Upgrading to a 150/70 Smartsolar Controller is same cost as one more panel. If I go with a 100/50 controller, another panel is not an option. So - I'm putting the money up front into a better controller and gain the option of another panel or even two. My new "Opulent Beast" is power hungry and first thing in the morning push button coffee is pretty sweet... Splitting system in half with two controllers is a great suggestion, but I have one pair of solar-prep wires - gonna stick with those and series to a single controller. You all have been a big help. Will follow up with pics, etc.

[xbcsutter]

Thanks to some solid advice here, completed my system. Upped things to three 400 watt residential type panels and a Victron SmartSolar 150/85. Controller has a really nice Bluetooth interface. An battery monitor and LiFePO batts are in my future. Seems batt upgrade would be more effective due to no absorb mode on LiFePO? Also, screenshot from phone shows midday output of 915 watts. Wondering if that’s it or if it varies by battery SOC? Thanks again for earlier input!

[astrocamper]

For flat mounted panels getting about 75% of panel rating is pretty normal.

65 amps of battery charging will go a long way to power independence. Enjoy your new setup.

[creativepart]

Originally Posted by xbcsutter

screenshot from phone shows midday output of 915 watts. Wondering if that’s it or if it varies by battery SOC? Thanks again for earlier input!

You'll notice, when driving, running the genny or plugged in if the batteries are being charged by an outside source the Solar Charge Controller will back off charging from the panels. That's just normal.

[hclarkx]

Originally Posted by xbcsutter

. . . . . Seems batt upgrade would be more effective due to no absorb mode on LiFePO?

Indeed it will. But much more than just using all of the solar for charging instead of just to the end of bulk mode. LiFePo4 won't have the 10% plus losses during discharge and the 95% or less charge efficiency.

If your solar does the job now, you will likely have 50% more than you need once you go LiFePo4. Luxurious amounts of energy.

[xbcsutter]

Thanks xclark - that’s all great to hear! Have 8 flooded 6v batts now, not even a year old. Thinking I may get by with 4-6 LiFePO 100ah when I replace. Maybe price will work it’s way down too...

[hclarkx]

Originally Posted by xbcsutter

I wasn't sure of appropriate breaker for panel to controller. Running 48-60v 12amps. How does this product look: https://www.ecodirect.com/MidNite-So...ar-mnepv20.htm

Probably a bit late now, and you've probably figured it out, but that isn't the breaker you want. You want a free-standing surface mount. Something like this

https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

Here you can see a pair of these under each solar controller ..... makes it easy to switch the battery side on first then the solar side (after boot-up is complete) ..... or switch off solar first then battery when powering down for service.

[757driver]

Originally Posted by hclarkx

Probably a bit late now, and you've probably figured it out, but that isn't the breaker you want. You want a free-standing surface mount. Something like this

https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

Here you can see a pair of these under each solar controller ..... makes it easy to switch the battery side on first then the solar side (after boot-up is complete) ..... or switch off solar first then battery when powering down for service.

Attachment 296847

I don’t think the original poster would want a 12-24v breaker coming into his solar controller when his voltage is 100v plus.

[hclarkx]

Originally Posted by 757driver

I don’t think the original poster would want a 12-24v breaker coming into his solar controller when his voltage is 100v plus.

Strictly speaking, you are correct.

I'm open to suggested alternatives. What would you suggest?

[757driver]

Originally Posted by hclarkx

Strictly speaking, you are correct. And higher voltage units surely do exist, but the voltages quoted for these are for the operating voltage and don't tell what the maximum voltage interruption capability is. There is always a very large margin between operating voltage and interruption voltage capability.

DC is much more difficult to interrupt than AC (no current zeros). When DC current is broken by the opening of the contacts, the voltage transients can be huge at any voltage, dwarfing even the series panel voltages we use. And it doesn't take much breaker contact spacing to hold back 100 or 200 volts. These have plenty in my experience. I've been using them for six years.

I have had them fail but only mechanically. There is an over-center spring mechanism that fails. I've torn two failed ones apart. The contact spacing is good for hundreds of volts. I'm okay with 100V on them.

They are not UL approved and likely don't meet the SAE J1625 standard (50V and under IIRC). There is another SAE standard that applies, I forget the number. I didn't find an SAE standard that applies above 50V but it might exist. Access to the standards is only available to SAE members. There might be ANSI or IEEE standards that apply. Having a breaker/switch that's tested to a standard would be the only way to get what you are looking for.

For me the ones I linked to are throw-away if they fail. They could hammer the panels or solar controller if they fail to interrupt (think sustained DC arcing and large voltage transients applied to the panels or solar controller). But, that's pretty unlikely (the event and the damage)

These are a better device, but are still only rated at 48V DC. And pretty expensive.

https://shop.pkys.com/Blue-Sea-7135-...ps_p_2286.html

I'm open to suggested alternatives. What would you suggest?

I was in the same dilemma when I upgraded my panels. The voltage coming in from the solar panels was much higher than the 48v for the surface mount breaker that I had so I went with a suitably sized Midnite DC breaker rated for 150v DC and mounted it in a mini breaker box. Perhaps overkill but I wanted to err on the safe side. Never thought about the spacing of the contacts to help determine the voltage it can handle vs. what it is rated for. Learn new things all the time.

Yes, that breaker from Blue Sea is an expensive one to say the least!!”