Coverting a Cargo Trailer into a Camping trailer

[Urban Elite]

Hello Everybody, I am new to the forum and the life of solar power from Alberta, Canada. I have just in the last year or so really dove into the solar idea and wanting to expand and bring it into my life. It started with a camping trip running a small folding solar panel with a USB battery bank to charge phones, gps, cameras, lights ect.. Now I want a bigger project!

I have been using the search function on this forum and others, but I do want my own topic where I can get most of my own questions answered for my own system with the parts and supply's I am using. My idea for a camping trailer is a waste ATM because I will be using it for camping/hauling my dirt bike and quad in with the gf, but also use the trailer for moving stuff around or hauling things, this is why I chose the enclosed cargo trailer instead of a holiday trailer for now. The trailer is a 16x7 I closed trailer, I plan on ordering my cabinets just for the front wall of the trailer soon, I have my solar panels already to start the project, but still need a good MPPT charge controller and a inverter, thinking of doing a 6v deep cycle battery system for my power bank.

THE PLAN: I plan on running a mini fridge 24 hours a day for our food items, a few 12v led lights throughout the inside of the trailer and one or 2 on the outside. Some other little power draws like phone chargers and such, but nothing too great or an amount of time like the fridge will be.

Solar Panels: 320 Watt, 72 Cell Panels I have 2 of these

Positive power tolerance from 0-5 W
Nominal Max. Power (Pmax) 320 W
Opt. Operating Voltage (Vmp) 37.1 V
Opt. Operating Current (Imp) 8.63 A
Open Circuit Voltage (Voc) 45.08 V
Short Circuit Current (Isc) 9.10 A
Module Efficiency 16.5 %
Max. System Voltage 1000 V (IEC) or 1000 V (UL)
Max. Series Fuse Rating 15 A
Power Tolerance 0 - + 5 W

FRIDGE DATA:

I started my testing with the fridge warm with nothing in it to start up, I then loaded the fridge with all different drinks, packed it right full as it will be that way once we go camping. My test results were any different after resetting the test 5 hours later with a cool fridge and cold drinks. I was opening the door on the fridge every so often as well. Here are the numbers

In 7.5 hours I used 0.367 KWH, 122.2 Volts plugged in, 0.68 Amps, 58-46 watts ( When it kicks on, then lowers slowly to run around 46 watts on the lowest. The fridge isn't on often from what I hear either, It has 5 power settings and just through testing I've been running it on 4 to get stuff really cold to see how much it actually pulls. Lowest wattage recorded is 1.1 watts, the highest spike is 748.3 watts.

So from what I get from this so far is that the fridge will spike under 800 watts to kick on, but during operating it is under 60 watts, as low as 46 watts.

Just seeing what you guys think of the project, Ideas for MPPT charge controller and battery bank size of AH and such.

I have been looking at the traccer 40A MPPT charge controllers and more powerful Midnite The Kid MPPT.

Great to meet you guys and hear feedback thanks!

[Rob Beckers]

Hi Urban,

Welcome to the forums!
Looks like your fridge uses right around 1kWh per day. Now, an inverter will use about 0.5 - 0.75 kWh per day, if it has to be running continuously. If your fridge has a mechanical thermostat, so it's actually off and not drawing power when the compressor is not running, it will allow most inverters to "sleep" and only run when the fridge (or other loads) are actually running.

There are DC fridges too; I've been plugging a Canadian brand called Unique lately. They make a number of chest and upright fridges and freezers that run on 12/24V DC, so no inverter is needed.

On the solar side, with 640 Watt in peak power you can expect around 1.7 kWh per average day between spring and fall, half that in winter. This will of course depend on where you are, and those numbers are for this area (southern Ontario), they won't be all that different for southern Alberta though, winter could be darker since it's further north.

So, what you have now will be just enough to run your fridge and inverter. A couple of lights should be no problem either, since those are just 8 watt for LED bulbs these days (there are 12V LED bulbs as well by the way).

Given the 640W in solar, I'd go with a 40 Amp charge controller. The MidNite Kid is 30A, and a little small (on a really sunny and cool day those panels can produce about 50 Amp to a 12V battery). We've sold a great number EP Solar 40 Amp charge controllers, for the price they are hard to beat. They work well. If you want to see what's going on you would also need their MT-50 display (also useful to change the charge Voltages).

-RoB-

[Urban Elite]

Hi Urban,

Welcome to the forums!
Looks like your fridge uses right around 1kWh per day. Now, an inverter will use about 0.5 - 0.75 kWh per day, if it has to be running continuously. If your fridge has a mechanical thermostat, so it's actually off and not drawing power when the compressor is not running, it will allow most inverters to "sleep" and only run when the fridge (or other loads) are actually running.

There are DC fridges too; I've been plugging a Canadian brand called Unique lately. They make a number of chest and upright fridges and freezers that run on 12/24V DC, so no inverter is needed.

On the solar side, with 640 Watt in peak power you can expect around 1.7 kWh per average day between spring and fall, half that in winter. This will of course depend on where you are, and those numbers are for this area (southern Ontario), they won't be all that different for southern Alberta though, winter could be darker since it's further north.

So, what you have now will be just enough to run your fridge and inverter. A couple of lights should be no problem either, since those are just 8 watt for LED bulbs these days (there are 12V LED bulbs as well by the way).

Given the 640W in solar, I'd go with a 40 Amp charge controller. The MidNite Kid is 30A, and a little small (on a really sunny and cool day those panels can produce about 50 Amp to a 12V battery). We've sold a great number EP Solar 40 Amp charge controllers, for the price they are hard to beat. They work well. If you want to see what's going on you would also need their MT-50 display (also useful to change the charge Voltages).

-RoB-

Thanks for the reply.

I think it does, cause while I did my testing there is points when the fridge isn't on and the wattage and amps are 0.

I will just be using the trailer in the spring-fall for camping, so not too worried about the winter numbers as for now. If I can get around those numbers I would be happy, from looking at sun tables I should get 8 hours min up to as much as 10 hours on good days.

I think with 640 watts of panels on the roof, a good MPPT charge controller and some good batteries I'll be set to run that fridge 24 hours and a few other things no problem.

I saw that after that it was a 30A and I would need at least a 40A. On the specs what do you look at to find how much amp controller you'll need? Is it IMP or ISC?

I have been looking at these as well, Seen wicked reviews about them and would get the display like you said also to see more in-depth whats going on and can mount the charge controller out of sight and have this in a nice spot to look at. Is this what you are talking about?

https://www.amazon.ca/dp/B01L6L1O60/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=17W1KTKS60DD4&coliid=I3HUMOCX9S3CP3&th=1

With my panels, I will have to wire them in series correct? To keep the voltage at 12v for a 12v system? As well Any battery recommendations or way to figure out what I'll want to get? Using renergy solar calculator just putting in the value of 60 watts for 24 hours with 8 hours of sun, and 92% eff I should be recommended solar size of 195.65 watts and 240 amp hours battery.

[Rob Beckers]

I saw that after that it was a 30A and I would need at least a 40A. On the specs what do you look at to find how much amp controller you'll need? Is it IMP or ISC?


Neither...
The Amp rating of a charge controller is based on the battery side. So, a 40 Amp MPPT charge controller can produce 40A into the batteries (if there's enough solar).

At 12 Volt, 40 Amp makes for 12 x 40 = 480 Watt. That is how much the solar panels would need to produce to reach 40A into the batteries. In reality a 12V battery charges at about 15V, so the 40A controller will handle 600 Watt before it clips. Panels rarely produce rated output, another factor to keep in mind.

With MPPT controllers you can generally oversize the PV side. The charge controller keeps output current in check and will simply clip (stick at) its 40 Amp (for a 40A controller). Having more PV than the controller can put into the batteries can have advantages on the dark & cloudy days.


I have been looking at these as well, Seen wicked reviews about them and would get the display like you said also to see more in-depth whats going on and can mount the charge controller out of sight and have this in a nice spot to look at. Is this what you are talking about?


Actually, this is the EP Solar controller I had in mind (this is our business site):
https://www.solacity.com/product/ep-solar-tracer-4215bn/

The display for it is this one:
https://www.solacity.com/product/ep-solar-mt50/


With my panels, I will have to wire them in series correct?


MPPT controllers need a higher Voltage on their input than the battery Voltage. The EP Solar controller can handle up to 150V DC on its input. Having a very high input Voltage and low (12V) battery Voltage makes the controller work harder and be less efficient though. So, for a 12V battery you can either put panels in parallel (they work at about 37 Volt, plenty high for a 12V battery), or at most 2 panels in series (70-some Volt input to the controller).


As well Any battery recommendations or way to figure out what I'll want to get? Using renergy solar calculator just putting in the value of 60 watts for 24 hours with 8 hours of sun, and 92% eff I should be recommended solar size of 195.65 watts and 240 amp hours battery.

We don't have "8 hours of sun" anywhere in Canada... Most of the day the intensity of the sun is much less than "full". There is a measure called 'sun-hours' that converts daylight into full-blast-sunlight as used for rating panels; in summer most places get about 4 sun-hours. Cycling over batteries takes off of the efficiency too, and if an inverter is involved it takes another hit.

For our area 1000 Watt of solar PV produces around 2.66 kWh per average day from spring through fall. 60 Watt for 24 hours makes 1440 Watt-hours (=1.44 kWh). That requires 540 Watt in solar PV (mounted facing south, unshaded, at a decent tilt angle).

For this amount of solar and with this type of load I would stick with 4 'golf-cart' sized batteries, those are about 250 Ah in energy storage, 6 Volt, each. We've had good results with Trojan T-105RE batteries:

https://www.solacity.com/product/trojan-t-105re/

-RoB-

[Urban Elite]

Great reply, so if you may I have new info and numbers for you.

So like I said before I have already 2x 320 watt panels. So far my fridge is on with a kill-a-watt meter and its reading 1 day 17 hours with 2.018 kWh used.

I would like to stick to the 2 days without solar so when I go camping for the weekend if the weather isn't great, I can still camp all weekend without problem, but with 640 watts, I should be able to go 3rd or 4th day with good weather all weekend with keeping my batteries up to charge.

I would like to stay in that 40a mppt charge controller area, Which way is the best way to wire my panels?

I'm looking at the s290 batteries cause they are $219 a piece for me.