Schematic safty check.

[nycsteve]

Hi all. First post. Looking for advice and appraisal . There should be a picture of a solar plan for a small travel trailer included. I'm starting with a 100watt starter kit from Renogy purchased last Black Friday. Kit I included a Rover-20 charge control , 8 foot tray cable 10awg , 20 foot MC4 10awg cable , blue tooth module , 2 fuses in picture , 100w panel.
I purchased a second panel a 100watt Rich Solar. The numbers are not exactly the same as the Renogy but very close. Also purchased a Renogy 100ah minicore lithium battery.
The trailer is a small simple fiberglass Scamp. The solar will be stand alone , not integrated into the existing trailer wiring. The primary purpose of the solar is to power a 12v Dometic fridge which uses 1.29 ah/hrs. So 31 ah per 24hour day? The fridge will hook up to fuse block.
Also did not mention , I have a lithium battery charger I will use if needed when on 110v shore power.
I read that wiring g the panels in parallel is better when 2 panels are not exactly the same.
Where should the fuses go? Are the ones pictured ok?
Any more fuses needed and where?
Is an on off swith a good idea to disconnect panels from system?
Is 10awg wire sufficient to run from controller to the fuse block. It's about a 14 foot run.
Any comments, additions , general advice would be greatly appreciated.
Thanks in advance.

 

[robbob2112]

• Put a MRBF fuse block and fuse on the positive post of the battery --
• No fuse is needed on the solar panels unless you intend to parallel more than 2 strings together. But the input voltage on the MPPT is 94v max - so instead of putting the panels in parallel put them in series -- you won't need the Y connectors at all or the fuse.
• Don't run the fridge off the MPPT - connect the fuse block for your 12v stuff directly to the battery -- through the MRBF

Free program at https://www.drawio.com/ -- makes it easy to make and change drawings.

List the wire gauge when you revise your drawing so we can check that as well.

Personally I dislike the ANL style fuse for pretty much everything but at only 20amps it should work fine.

 

[nycsteve]

• Put a MRBF fuse block and fuse on the positive post of the battery --
• No fuse is needed on the solar panels unless you intend to parallel more than 2 strings together. But the input voltage on the MPPT is 94v max - so instead of putting the panels in parallel put them in series -- you won't need the Y connectors at all or the fuse.
• Don't run the fridge off the MPPT - connect the fuse block for your 12v stuff directly to the battery -- through the MRBF

Free program at https://www.drawio.com/ -- makes it easy to make and change drawings.

List the wire gauge when you revise your drawing so we can check that as well.

Personally I dislike the ANL style fuse for pretty much everything but at only 20amps it should work fine.

 

[MisterSandals]

• Don't run the fridge off the MPPT - connect the fuse block for your 12v stuff directly to the battery -- through the MRBF

+1

I'd put a cutoff switch to the solar panels too. Simple switch on positive is what i do. Surprisingly useful.

 

[Backyard]

Since your panels are not identical, you'll limit the higher panels output to the lower panel. I'd try it both ways, series and parallel to see what produces more output for your charger.

 

[nycsteve]

Thanks for the reply robbob. Sorry the attached pictures and text are 2 separate posts. I'm totally new to setting up solar so please dont take the following questions as disagreements with your answers , but as an effort to learn by me. I read and watched videos before sketching the possible setup , and for panels in series vs parallel , there were 2 things that made me think parallel was a good idea. First , it was suggested that if the 2 panels werent the same exact specs , parallel would help , second if one panel becomes shaded there wouldnt be as much of a loss with parallel. Definitly a possibility of one being shaded while the other not due to position. Also while both panels are 100w they are different manufacturers. The posted pictures show the specs for the controller and 2 panels. Is the imput voltage , Voc ? If so , is it just adding the 2 panels Voc ( 24.3 and 22.1 ) where input voltage is determined? Would that mean its safe , in parallel for my controller?
When connecting fridge to battery , is it acceptable to run a wire from the protected side of the battery fuse to a fused block and from that to the fridge? Theres a need for a couple of other 12v connections near the fridge . One wire running from fridge area to battery is easier.
As soon as I have clarification on those points I will draw up another schematic with revisions and wire gauge and wire run length.
Again , thanks.

 

[MisterSandals]

Since your panels are not identical, you'll limit the higher panels output to the lower panel. I'd try it both ways, series and parallel to see what produces more output for your charger.

Yah, and maybe more importantly, if you get situations where you get partial shading, parallel definitely better.

 

[nycsteve]

Also , thanks to Mistersandels and backyard , I was writing the text part that was to accompany the pictures when you guys posted.

 

[MisterSandals]

If so , is it just adding the 2 panels Voc ( 24.3 and 22.1 ) where input voltage is determined? Would that mean its safe , in parallel for my controller?

Its all totally safe.

The math, more than you cared to know...
Connecting in series, adds the volts and uses the lower of the amps:
(20.4Vmp + 18.1Vmp) x 4.91Vmp =189W

Connecting in parallel adds the amps and uses lower of the volts:
(4.91A + 5.52A) x 18.1V = 188.7W

So no theoretical difference!

 

[nycsteve]

Yah, and maybe more importantly, if you get situations where you get partial shading, parallel definitely better.

Are the numbers of the panels ok with my controller , as in safe?
I wanted to have an on / off swith to isolate panels if need be. Just didn't include in drawing. Location would be between panels and controller? The switch itself , can I use a regular single pole 110V switch to interrupt the panel positive? Or is there a better switch choice?
Also , what is the advantage of connecting the fused block directly to battery vs the draw receptacle on the controller? If going to battery directly , the fused block positive goes to protected side of positive terminal fuse , the negative directly to negative battery post?

 

[MisterSandals]

Are the numbers of the panels ok with my controller , as in safe?

Couldn't be safer.

Location would be between panels and controller?

Wherever you will be when messing it it. Near controller is nice spot.

can I use a regular single pole 110V switch to interrupt the panel positive?

NEEDS to be a DC switch!

And its 120V since like 1950... (people freak out when they measure 120V expecting 110V so best to make this known).

 

[MisterSandals]

Also , what is the advantage of connecting the fused block directly to battery vs the draw receptacle on the controller?

Batteries are made for this. SCCs are not and why stress your electronics unnecessarily? Probably low amp limit in SCC output anyway.

 

[nycsteve]

Its all totally safe.

The math, more than you cared to know...
Connecting in series, adds the volts and uses the lower of the amps:
(20.4Vmp + 18.1Vmp) x 4.91Vmp =189W

Connecting in parallel adds the amps and uses lower of the volts:
(4.91A + 5.52A) x 18.1V = 188.7W

So no theoretical difference!

Math is good.

 

[MisterSandals]

Math is good.

 

[nycsteve]

Thanks for all the help! I'll revise the schematic and post, I definitly have better direction.

 

[nycsteve]

View attachment 290130

So I redid the schematic using the suggestions from you kind folks. I will post the pictures of the new schematic and a breaker/switch , and a fused block. Im having trouble posting text and pictures in the same post. Im open to suggestions if there are better choices.
10AWG from panels to controller.
8AWG from battery to controller.
Length of run on schematic.
Also unsure of AWG from battery to fused block to power 12V device(s) . The length will be about 16 foot.
Again , many thanks for the help past and future.

 

[nycsteve]

 

[MisterSandals]

20A charging from SCC to battery needs 12AWG, not 8AWG

Your fridge at 1.29A (at12V?) is only 16W which is wildly low.
Get your DC loads figured out and size wire and fuse for that.

 

[nycsteve]

20A charging from SCC to battery needs 12AWG, not 8AWG

Your fridge at 1.29A (at12V?) is only 16W which is wildly low.
Get your DC loads figured out and size wire and fuse for that.

Its not a full size fridge. From the specs , my model is on the far right , bottom line. The 2 I think count , Energy consumption KWh/24h 0.3729. And Energy consumption Ah/h 1.29 . The only other thing of any consequence that might be used at the same time as fridge is a TV. The only number I found for that was 36W. If the TV complicates things or is to much , I just wont use it.
I forgot to mention I found a MRBF terminal block fuse for battery positive that I think is applicable.
I will attempt to attach specs and fuse images to the post.
I would appreciate direction on fuse and wire sizes.

 

[nycsteve]

The easy part for me is putting it together. But determining the correct size choices is not something I can do.

 

[nycsteve]

First , thank you for info kindly provided so far. I found a calculator for determining wire size online , from the Explorist life utube channel. You put in length of run x2 , and amps required by the device. Im just double checking the logic here before committing. Im including a picture of the refrigerator tag. Amps required , 10? There will be a + and - run from the battery to a fused block which will feed the fridge , sometimes a TV and charging phone. To calculate I added all 3 devices amps in case all were on simultaneously. Calculator says 8AWG.
Double checking 2 other components before i order them.
The DC circuit breaker/ isolator 20A version (picture above) as an off switch between panels and cotroller
The 12v fused block (pictured above) run off the battery (16') to power fridge etc
Are these acceptable and safe choices?
Once the final components are ordered I can get on with the fun part!

 

[MisterSandals]

Amps required , 10?

At 12V. So it should be wired/fused for draw of 120W is how i read it.

Guessing 30% duty cycle: .3 x 120W x 24h = 864Wh per day. Maybe more like 100W while running believable too.

 

[Backyard]

At 12V. So it should be wired/fused for draw of 120W is how i read it.

Guessing 30% duty cycle: .3 x 120W x 24h = 864Wh per day. Maybe more like 100W while running believable too.

Wires are sized based on the current, insulation, allowable temperature rise and acceptable voltage drop. Not wattage

 

[nycsteve]

Is there enough info to determine the wire size? I know I'm asking to be spoon feed , but I'm pretty clueless here.

 

[Backyard]

Is there enough info to determine the wire size? I know I'm asking to be spoon feed , but I'm pretty clueless here.

From what I can see. You should be fine with 12 AWG across the board. But 10 AWG would provide a larger margin of overhead. You only have something like 13-14 amps being used if all devices are on at the same time. 12 AWG THHN is good for 20 amps. 10 AWG THHN is good for 30 amps

Adjust your MRBF to the amp rating of your wire. 20A for 12 AWG and 30A for 10 AWG

Then the individual fuses in the fuse block can be sizes for each appliance. The fridge can be a 15A, TV at 5A and phone charger 1A. If the phone charger or any other appliance is being plugged into a 12V socket then you can fuse the socket at the socket rating plus 20% overhead or the next sized fuse above that if no fuse size matches

I'd use 10 AWG myself