How thick of solar panel extension cables do I really need?

So I got tired of waiting for good sun and decided to do half of my "how much loss do you get in the real world with skinny little 14 and 12 ga MC4 solar panel extension cables.

I was going to do one high voltage (4) 120 watt series connected panel and one lower voltage with a single panel. A thought popped into my simple mind after work and it was: Just perform the low voltage test using the 24 volt output from your EF1500 connected to your Jackery E300. This will give you a steady voltage to work with and eliminate the solar panel variable. So below is what I saw:

Details:

(BASELINE) No ext cables= 26.57 volts / 2.93 amps / 77.5 watts

14 ga Acopower MC4 extension cables (crimped)

20’-14 ga ext. cables=26.19 volts / 2.91 amps / 76.1 watts

40’-14 ga ext. cables=25.82 volts / 2.91 amps / 75.3 watts

12 ga. handmade copper MC4 ext cables (crimped & soldered)

20’- 12 ga ext. cables=26.22 volts / 2.92 amps / 76.5 watts

40’- 12 ga ext. cables=26.00 volts / 2.92 amps / 75.9 watts

60’- 12 ga ext. cables=25.76 volts / 2.92 amps / 74.9 watts

Connect everything I had on hand together to get…40’ of 14 ga + 85 feet of 12 ga= 125 total extension MC4 cable length. Holy cow, can power even get transmitted through these thin wires at that length?..hmmmmm

24.94 volts / 2.92 amps / 72.7 watts…for a total of 4.8 watt loss from the baseline no extension readings.

Summary…even in this low voltage scenario, you would be losing approx 1.5% of the wattage by using thin 14 ga cable over a 40 foot extension run. That would extend your charging time approx. 4 minutes compared with no extensions of any kind added. I think that proper positioning of the panels is far more important to getting max power than worrying about wire losses from 14 ga. cable.

Even the worst case of 125 feet of extensions with all these cables, it resulted in a 6% loss which would add 17 minutes to the complete charge cycle. Would anyone in the real world even notice this difference when running an inflated 125 foot distance?

Final summary…it is my opinion that running anything over 12 ga pure copper extension cables except in the case of fixed installations you are wasting money and sacrificing ease of handling and portability which is why you bought a portable unit in the first place. You simply won’t miss the watts on these small units.

STAY TUNED FOR THE RESULTS OF MY HIGH VOLTAGE 4 SOLAR PANEL TEST CONNECTED TO MY AC200. I WILL WORK ON THAT TOMORROW CONDITIONS PERMITTING.

TEST PART TWO RESULTS:…
The what effect does wire size and solar panel extension cable length have on charging my AC200§???

(4) Acopower 120 watt Panels (I gave my Bluetti panels to my daughters) connected in series on a clear SW Florida afternoon at 3:34 p.m. Temperature was 66 degrees. Unit was my BLuetti AC200 and was at exactly 50% state of charge. Readings were taken directly from the AC200 panel. readings would move up and down and the readings are the high points of the cycle. I ran a real world charging test from no extension cables all the way up to l25 feet with both 14 and 12 ga cable thicknesses.

Conclusion for those of you that don’t care about the details:
You can run 14 ga or 12 gauge cables out to 60 feet without any worry about loss. the wattage was 362 with no extensions and 353 with 60 feet. Keep in mind the sun was a variable and those 9 watts between 0 cable and 60 feet are pretty close and you would not miss them.

DETAILED RESULTS
No Extension cables…77 volts / 4.9 amps / 362 watts
20’ of 14 ga, extension…77 volts / 4.9 amps / 361 watts
40’ of 14 ga. extension…77.2 volts / 4.9 amps / 359 watts
20’ of 12 ga. extension…77.3 volts / 4.9 amps / 360 watts
40’ of 12 ga. extension…77.2 volts / 4.8 amps / 355 watts
60’ of 12 ga. extension…77 volts / 4.9 amps / 353 watts
Now for the fun one…125’ consisting of 40’ of 14 ga. and 85 feet of 12 ga extension cables in 6 sections all connected together:
125 feet extension…75 volts / 4.9 amps / 346 watts *this is a worst case 15 watt loss or 4% loss with small gauge wire with multiple connection points over 125 feet.

AC200 cable conclusion…use any size cable you want (I personally recommend 14 or 12 ga) and don’t worry about lengths out to about 100 feet. Spend the time you would be worrying about what loss you are getting and put it towards placement and proper angle of your panels which will yield far better efficiency results than cable wire size.

I also ran three of the 120 watt panels connected in parallel to my Ecoflow River Max that was at 50% SOC in the same conditions as above to see what the effect of the lower voltage and higher aperage would have on the charging watt rate of the River 600 Max. Volt and amp reading taken from in line meter. Watts taken directly from River 600 panel. Results are below:

(3) 120 watt panels in parallel
No extensions…21.17 volts / 9.97 amps / 197 watts
40 ft 14 ga. ext…19.8 volts / 12.75 amps / 197 watts
125 ft of 14 and 12 ga ext…14.14 volts / 11.7 amps / 168 watts
(2) 120 watt panels in parallel
No extensions…20.15 volts / 8.84 amps / 154 watts
40 ft 14 ga. ext…20.21 volts / 8.8 amps / 143 watts
40 ft 12 ga. ext…20.21 volts / 8.8 amps / 147 watts

So…the lower voltage / higher amperage combo of the R600 series definitely sees a higher watt loss rate that the AC200 test above. I would expect the Bluetti AC50 to act in a similar fashion. And would recommend you use 12 ga. cables limited to 50 feet if you are running two or more 100 watt panels to charge your Ecoflow or AC50S.

3 Likes

Great recap. I am getting educated. Thank you James

@Scott-Benson thank you for this! I had no idea the loss would be that minimal in this application.

I will be doing a high voltage test tonight with my AC200 and four 120 watt solar panels and I think the losses will be even less with the higher voltage. The watts lost should go up but the overall percentage of loss should reduce.

I wish I could find a source for good high quality 12 ga. pure copper wire MC4 extensions cables ready made that were flexible and came in lengths of 10, 25, and 50 feet. I bought a few spools of 25’ silicone insulation / copper wire from amazon and made my own. So far they are my favorite. You have to carefully slit the two wires apart (separate the red and black wires with a razor or knife) to make sure the insulation separates evenly. I peel this back about 4 inches and shrink on a 1" piece of shrink tube to keep the red and black from peeling further. Crimp and solder (optional, but I love to solder) the MC 4 connections and they are ready to go.

These are the MC4 connectors I use. I crimp and solder them:

Cheap assortment of heat shrink tube sizes

2 Likes

@Scott-Benson yea this sounds like it’d probably be the best bet. I like that you’ll also know exactly what mc4 connectors are being used too. As I’m noticing that some of them are slightly different and one can run into issues with getting them disconnected, if they need to use one of the “connector-tools”.

I have had some success with “too tight” male MC4 connectors by using green scotch brite or fine sandpaper and smoothing the outer diameter of the male fitting. Also, you can wipe a small amount of silicone spray with a qtip for a little lube.

1 Like