HOW TO: Remote mount the controller of a suitcase solar panel (not inside the trailer)

[John E Davies]

EDIT 05/10/21: related thread:   ...  https://olivertraveltrailers.com/forums/topic/3247-how-to-external-solar-dc-power-cable-using-factory-furrion-port/

Some background.... most panels will come with “industry standard” MC4 connectors, which can be used with up to 10 AWG wire and are waterproof.

But if you have one disconnected and drop it in the dirt it will fill with crud, so you would need to spray that out with contact cleaner or alcohol. Anderson Powerpoles are used extensively in ham radio and other applications, they are not at all waterproof, but they are self cleaning by design, the spring loaded contacts "wipe" each other when you plug them in. They are more compact and they are color coded. The connectors are goof proof, they cannot be plugged in backwards. For this application the 30 amp bonded pair connectors are appropriate for the wire size. You must use their ratcheting crimper or a version of it. I replaced every existing MC4 connector with the Powerpoles.

 

My 100 watt Renogy solar suitcase came with the PWM controller mounted on a hinged flap, this is perfectly fine if the panel is to be used say 10 feet away, but you cannot place it much further because resistance losses along the wires will reduce the charging voltage at the batteries. The controller reduces the 18 to 20 volt panel voltage to say 14.5 volts, and it is less at the trailer. Ideally the controller should be located RIGHT at the batteries, and the panel itself can be far away. The (almost) full panel voltage is delivered to the controller, and at that point the controller reduces that value to charge your system. How far away you can place it depends on the wire gauge, the bigger the wire, the less voltage drop along the run (you must calculate the two wires as a pair, the "in and back" distance).

I happened to have some of these neat MTM in-safe storage boxes, the small size fits beautifully. The price is for three, they also have a 12" long version if you want a little more internal volume).

I mounted the controller using long 1/8" pop rivets with washers. I drilled a couple of 3/8" holes at each end so the cables could be fed through and the lid closed. It is not at all waterproof, but it is splash proof. The controller itself is advertised as "rainproof". (Older versions were NOT.) I color coded the connectors with self adhesive heat shrink tubing so that when swapping them it would be clear which was which.

I modified my existing Furrion solar port harness (used with my ARB fridge in the truck) by splicing in a short pigtail. The wire is 12 AWG solar cable, for exterior use. It is very tough but not very flexible. In this pic, the solar panel is 20 feet away, and the controller box is tucked up on top of the front tire, for rain protection and so it won't get stepped on. The BAT lead is fully extended (not coiled inside).

The charging section for my ARB fridge is coiled up when not needed (or it could be used as an extra 5 foot extension, if the fridge is not being used):

Or the box can be placed on the ground:

Or connected directly to a battery using the supplied alligator clips. You can add an additional 20 feet of cable, 40 feet total, it doesn't affect the charging amps.:

I added strain relief ties to reduce stresses on the screw connections.

Everything, including the extension cables, fits in the folded unit. I will hopefully get to test this in a few days, I will be camping in a shady site, if the sun shines I can try it out.

John Davies
Spokane WA

 

[John E Davies]

I am camped at Kettle Falls (Lake Roosevelt COE) campground and the solar exposure is not great in the afternoon due to trees, so I set up the Renogy panel in a bright spot using 40 feet of cable. No worries, I am seeing a steady 6.5 to 6.8 amps, and the big rooftop ones are only putting out half that, and it is highly variable. Yay, I am pleased. Highly recommended mod!

John Davies

Spokane WA

[MAX Burner]

@John E DaviesAwesome setup, JD!  Sweet!  

[CnC]

John...  no heat issues with the controller mounted in the small enclosure?

Charlie.

[Geronimo John]

On 4/28/2021 at 12:01 PM, John E Davies said:

Renogy panel in a bright spot using 40 feet of cable. No worries, I am seeing a steady 6.5 to 6.8 amps,

JD:  Those look like hte100 watt solar suit cases. Assuming your batteries are at say 70% SOC = 13.2 volts X 6.7 amps = 88 Watts input to the controller.  That's really good!

Question:  Curious why you did not mount the charge controller inside your trailer?  Maybe with your Battleborns?  Then use a solar port through the battery box door?

GJ

[John E Davies]

2 hours ago, Geronimo John said:

JD:  Those look like hte100 watt solar suit cases. Assuming your batteries are at say 70% SOC = 13.2 volts X 6.7 amps = 88 Watts input to the controller.  That's really good!

Question:  Curious why you did not mount the charge controller inside your trailer?  Maybe with your Battleborns?  Then use a solar port through the battery box door?

It is a PORTABLE panel, I did not want to restrict its use to just the trailer. For example I could power my truck battery or help some other person in need. With an automatic transmission, you can’t bump start the truck with a failed battery, I am pretty paranoid about shutting it off in the back of nowhere and then finding that it won’t turn over. I do carry a portable jump start box (Viking from Harbor Freight - most excellent). The solar gives me the opportunity to keep the truck battery topped up when, for example, I am operating my portable PCP (airgun) air compressor off its terminal.

Portable means portable. I do some strange things sometimes, contrary to mainstream ideas, but usually there is some sort of valid reasoning behind it.

John Davies

Spokane WA

[Geronimo John]

6 hours ago, John E Davies said:

but usually there is some sort of valid reasoning behind it.

JD:  Yep for sure on that one.  Thanks for filling in the rationale.  

All: 

I'll likely mount our solar suitcase charge controller out of the weather in the Ollie battery compartment.  My Keep it Simple is to just roll out the panels and plug them into a solar port on the door of the compartment..... IF it does not put out significant heat when charging at capacity.

Anybody have the larger 200 watt Renogy solar suit case  with the 20 amp charge controller think it puts out more heat than should go into the OE2 batter compartment?

Thanks

GJ

 

[Jim and Frances]

I noticed use of a 20A charge controller - is that too large an output if one is using the external Zamp connector? 

The owners manual seems to say the external Zamp connector has an inline 10A fuse (F52).   I understand the SAE connector is rated to a max of 20A (per a Zamp comment on Amazon). I am guessing  internal wiring in trailer (10G?) drives 10A fuse limit?  Just guessing and trying to size a controller for use with panels that I have for a solar generator - looks like I will not be able to use all 3 panels.

Am I missing something here?

 

[John E Davies]

Jim, the external contacts are the limiting factor for amperage, 10AWG wire is up to 40 amp. You should upgrade the connectors to Anderson Power Poles, they are rated at 45 amps  and they make a round weather tight panel mount that will work. SAE connectors suck big time, pardon my grammer….

https://powerwerx.com/anderson-power-powerpole-sb-connectors

The controller must be rated at well over the maximum possible amps coming from the panels.

 

 

John Davies

Spokane WA

[Jim and Frances]

John,
Thanks for your comment.   I agree, without replacing the external Zamp connector and fuse inside the trailer, one seems to be limited to approx 10 amp/140 watts max given the internal fuse limits (connector limit <=20A, inline fuse 10A, 10 AWG wiring should be good for 30 amp given the short runs inside the trailer). 

😁Hoover factor is high with MC4 and SAE/Zamp style connectors compared to Powerwerx/Anderson style connectors you suggest.

For larger panels/arrays it seems that in addition to replacing the Zamp connector, the internal 10A fuse would also need to be changed up to 400-500 watts - or - simply go straight to the battery as you outlined in your article. 

Victron has a cool spreadsheet to help size their MPPT controllers given your own panel specs (spreadsheet attached). I use Southwire's wire sizing tool here.

Thanks again!

VE-MPPT-Calc-4_0.xlsm