200 watts of rich solar polycrystalline panels and 20a epever charge controller

[XERTYX]

So I pulled the trigger on a 2 pack of rich solar 100 watt polycrystalline panels and built a frame to attach it to the luggage rack on my 06 Dodge Caravan.

I'm no carpenter so I'm pretty proud of it.


Once I had the frame built it came time to do the wiring. I'm very publicly NOT a fan of MC4 connectors. So using a flat head jeweler's screwdriver jammed into all 4 corners I popped out the door on the junction box and unscrewed the waterproofing nuts and cut the wires off.

I couldn't figure out how I was gonna attach the 10 gauge wire to the terminals so I finally decided to bend the tabs up where the wimpy MC4 wiring was soldered onto and insert a ring terminal over the tab and bend it back down and liberally apply solder.


As you can see I decided to wire the panels in series. So far it seems to be doing the job. It ran my alpicool c20 fridge just on solar in the twilight of the days sun for over 2 hours yesterday. It was pulling nearly 60 watts and still had a surplus after 5pm when the sun was behind the trees. I didnt have any other loads I could connect to try it. I had my fridge and a USB fan running at full tilt and as I say if was still floating the battery until after 6pm.

I'll probably be updating this thread and I'll answer any questions that I can.

 

[XERTYX]

Just a quick update it's raining today. HARD. As my dad used to say it's raining like a cow pissing on a flat rock. I checked it at 10:30am in heavy rain and the sun isnt even up yet and its outputting 1.4 watts right now. Not groundbreaking obviously, but there is very little light available. Its actually as dark outside right now as it normally is at about 7am around here.

 

[XERTYX]

Jeez. So disorganized. I forgot the before picture of the junction box. Zoomed way in so you can see the thin barely better than speaker wire of the MC4 cabling. Reason number 4075 why I think MC4 connectors are stupid.

 

[RVTravel]

thanks for sharing your setup.

 

[PeterPiper]

So I pulled the trigger on a 2 pack of rich solar 100 watt polycrystalline panels and built a frame to attach it to the luggage rack on my 06 Dodge Caravan.

I'm no carpenter so I'm pretty proud of it.

Once I had the frame built it came time to do the wiring. I'm very publicly NOT a fan of MC4 connectors. So using a flat head jeweler's screwdriver jammed into all 4 corners I popped out the door on the junction box and unscrewed the waterproofing nuts and cut the wires off.

I couldn't figure out how I was gonna attach the 10 gauge wire to the terminals so I finally decided to bend the tabs up where the wimpy MC4 wiring was soldered onto and insert a ring terminal over the tab and bend it back down and liberally apply solder.


As you can see I decided to wire the panels in series. So far it seems to be doing the job. It ran my alpicool c20 fridge just on solar in the twilight of the days sun for over 2 hours yesterday. It was pulling nearly 60 watts and still had a surplus after 5pm when the sun was behind the trees. I didnt have any other loads I could connect to try it. I had my fridge and a USB fan running at full tilt and as I say if was still floating the battery until after 6pm.

I'll probably be updating this thread and I'll answer any questions that I can.

Thanks for sharing this.

Funny, I just added two 100watt solar panels to my 2006 Dodge Caravan.
But I went with Parallel Wiring in order to increase the Current to approx 10Amps.   Why did you want to increase the voltage?  Do you have a 24v controller?

I took a totally non destructive approach to this install.   Absolutely nothing was changed on the vehicle.
I fabricated 4 custom steel supports that clamped around the OEM luggage bars for mounting.   That also gave me a VERY low profile to the panels which are only 2 to 3 inches off the roof.  However....if I later decide to add even one more panel, I will have to convert to a rail system like you did.

 

[PeterPiper]

One word of caution.

The way you have your panels end to end.......be care of that front one.
At highway speeds the amount of lift that can get underneath could be almost as if a strong guy has grabbed the front corners pulling up as hard as he can.

Looking at a close up one more time, I don't see anything supporting (holding down) the front 2 feet or so of the panel in front.
I would be very careful with this type of setup unless there is more bracing that I can't see in the photo.

Mine are solidly secured down at at or near every corner of each panel.

 

[Scott3569]

I agree does not look like much is supporting the front of that panel.. It would be totally possible to construct a wind deflector that will also second as a support..

 

[XERTYX]

Yeah I'm going to have to add another support or 2. I originally was going to go with 3 cross bars but I ran into problem after problem just getting the damn thing mounted. Especially with almost no tools.

As far as why I went series instead of parallel was to have higher voltage than higher amperage. Way less voltage drop at the end of the beefy cables. Also i went with an MPPT controller and as i understand it they benefit from the tracking with a higher voltage input.

It's raining today and my panel voltage is hovering around 14 volts. If they were parallel they'd be at 7 volts. As the sun gets higher in the sky today I'm actually seeing useful charging, and its completely cloudy without a glint of sunlight. I checked a few minutes ago and it seems to already be into absorption charge cycle.

 

[PeterPiper]

I would encourage you to rethink your connection strategy.
The short distances you are dealing with are negligible if you use at least 12gauge wire.

Besides, in Series you are going to have as much as nearly 40volts....20v per panel.
Is your controller capable?  What charge controller are you using?
If you go with a 24v controller you will need at least 2 batteries in series or one 24v battery.
Then you need a 24volt inverter.   A bit much for a 200watt system no?

I have a 200watt setup on my 2006 and have had zero issues with voltage drop using 12gauge wire.
But I do get excellent current to the batteries.  Often a full 10 amps.
I "could" change to 10 gauge and possibly get 10.5amps but I'm happy at 10amps.
Currently I have 10 feet of 12gauge wire from the panels to the charge controller.  5 feet in a coil.  The wire does not get warm at all.

You want CURRENT for that small setup to charge those batteries....not higher voltage.

 

[XERTYX]

I'm running an epever AN series 20a MPPT charge controller. It supports up to 60v input. Yesterday with full sun I was seeing 39-41 volts. And I'm running 10 gauge cables. Seems to be very efficient. Today its overcast as all get out and still sprinkling a bit. You cant even see where the sun should be behind the clouds and I've been running a 12v compressor fridge since yesterday. It was still cycling pretty heavy after sundown until like 10pm because I had it set to 27° to chill everything down. It's been set at 34° ever since Its 3:20pm now and it's almost out of absorption charge cycle. I'll be surprised if it's not at float voltage in the next 30 minutes or so.

 

[highdesertranger]

There seems to be some confusion here,

Most so called 12v panels actually put out in the 21v range. Once you get much above that you go with a MPPT controller you don't have to go to a 24v system just because your panel output voltage is higher . It all depends on what you want the voltage of your system to be and then you choose the right controller for that voltage. The panel voltage has nothing to do with it once you go with higher voltage input to the controller.

In other words there is no such thing as a 24v panel or a 12v panel for that matter.

Highdesertranger

 

[XERTYX]

Right. MPPT controllers are more efficient than PWM, and many have a much higher PV max input voltage. PWMs if your panels were in series would need a 24v bank. MPPT controllers often support 100v or more input. Since mine is only a 20a charger it only supports 60v input. The 30a, 40a, and 60a model support 100v. I think the 80a and 100a model support 150v PV input.

Side note the sun is better aligned to where I'm parked now (based on yesterday cuz I still cant see it) and its outputting 24 watts RN. I should have at least another hour of "sun" again based on yesterday's solar position. About 1/8th rated max power on a day where I cant see anything but gray seems pretty good to me. I'm planning to build a tilt into the mount but that's in the next revamp.

 

[PeterPiper]

I'm running an epever AN series 20a MPPT charge controller. It supports up to 60v input. Yesterday with full sun I was seeing 39-41 volts. And I'm running 10 gauge cables. Seems to be very efficient. Today its overcast as all get out and still sprinkling a bit. You cant even see where the sun should be behind the clouds and I've been running a 12v compressor fridge since yesterday. It was still cycling pretty heavy after sundown until like 10pm because I had it set to 27° to chill everything down. It's been set at 34° ever since Its 3:20pm now and it's almost out of absorption charge cycle. I'll be surprised if it's not at float voltage in the next 30 minutes or so.

Great.
So how many AMPS are you seeing at the controller ?

Remember, it's not volts that charges your battery or powers things.......current does.  And you only need 14.2 volts.  That's it.
ONE 100watt panel can do that just fine.
(If you are using 12v batteries)   Perhaps you are not and so my mistake.

But if you are using 12v battery
With 2 100watt panels, your BEST BET is to connect them in parallel and increase the CURRENT.

But, to each his own.

 

[PeterPiper]

There seems to be some confusion here,

Most so called 12v panels actually put out in the 21v range.  Once you get much above that you go with a MPPT controller you don't have to go to a 24v system just because your panel output voltage is higher .  It all depends on what you want the voltage of your system to be and then you choose the right controller for that voltage.  The panel voltage has nothing to do with it once you go with higher voltage input to the controller.

In other words there is no such thing as a 24v panel or a 12v panel for that matter.

Highdesertranger

Right.
I have two 100 watt panels on my van connected in parallel and seeing 10amps often in full sun when my battery is low or loaded.

For a relatively low current, small application like this there's no huge advantage to 24volt system.  in fact, in a car like this, it is more of a disadvatage because you need a 24v to 12v converter for anything 12v.

I use a Xantrex 40C PWM controller in my Dodge Caravan with excellent results in terms of keeping the batteries charged.
With 2 panels it's optimized.

The OP thinks that having higher voltage is better.  For a home situation or an RV with larger banks of panels, longer cable runs yes,....for 2 100watt panels on a dodge caravan....no.   UNLESS, you have specific 24v requirements or already had that equipment and batteries.

 

[wayne49]

Renogy 100W panels come with 10ga cables.

No issues using a 20A MPPT with solar input of 40V @5A charging a 12V (nominal) battery bank. A Renogy 20A MPPT can take 236W solar as input. An Epever is probably about the same.

The current loss across a cable at 12V is significantly greater than the loss at 40V. One would need a really fat cable to overcome that at 12V.

If you have to make a decision over where to mount a controller/charger, mount it as close to the battery bank as you can, and run the longer cable to the serial connected panels.

On a 25 ft MHC with an under the hood house battery bank and existing solar panel wiring run down the fridge vent towards the rear, this issue can show up.

 

[PeterPiper]

We're talking about a cable run of less than 6 feet in the case of the OP.
All of this is irrelevant.

Remember he is never going to get 200 watts to the controller due to losses.   Maybe 130watts from the two combined.

in this case he can safely use as low as 12gauge with no issues at 10Amps
And with his panels in series he will only get about 5.5amps max.

He may as well use only one panel.   He will get the same end result in this case.....5amps to the controller

 

[highdesertranger]

Yeah I have a 60amp Morningstar MPPT the input voltage is 150v max but since my panels are right under 80v I ran them in parallel. The output is for a 12v system. The most I have seen with just the solar is 56amps @ 12.9v. Highdesertranger

 

[XERTYX]

Great.
So how many AMPS are you seeing at the controller ?

Remember, it's not volts that charges your battery or powers things.......current does.  And you only need 14.2 volts.  That's it.
ONE 100watt panel can do that just fine.
(If you are using 12v batteries)   Perhaps you are not and so my mistake.

But if you are using 12v battery
With 2 100watt panels, your BEST BET is to connect them in parallel and increase the CURRENT.

But, to each his own.

Yeah the amps at 40v are less than the amps of 2 20v panels in series..... BUT amps × volts = watts. It's the same thing. The advantage is that the higher voltage sees less drop especially as I have over gauged the cables. The MPPT controller handles the conversion. The amps to the battery times the battery voltage is equal to the voltage times the amps in from the PV. Or close to it.

Earlier I was seeing 34v 0.8a in 27.2 w
Output to the battery was 2.0a with a voltage of 13.1 26.2w. Also that was with a 45 watt load running at the time so it's hard to say exactly. I'll be able to have a better idea and more exact measurements next week when my ebox-wifi com port adapter comes in from amazon.

 

[PeterPiper]

lol.
You don't realize it but you just nailed my case.  

About 2amps is all you are ever going to get with your panels connected that way.  Makes no difference how much voltage you get up to the max for that setup.

Or, just as an "experiment", you could try connecting them in parallel and watch your charging rate soar.

Eventually you'll see it.

Peace.  I'm out

 

[XERTYX]

Ok bro. Agree to disagree. Even though yesterday in float mode it was outputting over 4 amps to the "battery" which was full with 2 loads running. I didnt have any other loads to hook up to it to push it to the limit.