Solar panel extension cable length and wire size losses part 2

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.

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 conclusionuse 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 amperage 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.


Some losses are at the mating surfaces of the MC4 connectors. Any circuit that has splices and /or connectors will suffer minor resistive losses as current goes up. This is why you should use the longest single piece of wire for any connection, AC or DC.

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That would certainly be optimum however with portable panels and changing sun locations / panel locations it has been my experience that ease of handling the cables and panels outweighs the small losses incurred by connection losses or large diameter cables. Paying attention to panel alignment for optimal effeciency will usally yield the most wattage per day over connection / cable losses.


Thank you for this post. I’ve been debating whether or not to add another 20’ extension to my existing 30’ extension cable but was concerned about the potential loss. Wires are 10 gauge, so I think I will go ahead.

When the weather improves I hope to do some measurements and will post here if I do.

(On the other hand, your post just cost me $50. :grin:)

The higher the voltage for the same amps, the less loss. And I didn’t cost you. You bought a ticket to convenient real world of remote solar extension so you can see for yourself the truth about losses or the meaningful lack of. Please do share your wisdom after you get to try it all out

Well, that could be another interesting test — 50 feet of extension using a 20 and a 30, and just using a 50. How much loss in the connectors?

Almost nothing. I have used five sets of connectors out to 125 feet with little loss. You will gain more wattage by focusing effort on panel alignment to the sun

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@Scott-Benson Thank you Scott, good sharing! Hope to see more like this.

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… You will gain more wattage by focusing effort on panel alignment to the sin

But … I live in the country and there’s very little available sin around here. Besides, that would be a bit awkward don’t you think? :wink:

You must live in a holy place with little “sin”! :wink:
Of course you are writing about the Sun, and you need plenty of Sun.

Not at all awkward. Live a clean life, help others and all will be fine. :wink: :wink:

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Great post. Thanks for the time and effort.

I had contacted Bluetti support and asked them about extension cables and they indicated that extensions were not recommended due to loss. They left it at that.

My follow on question is, is anyone here partial to a supplier (aside from Amazon) for these cables?

I’ve purchased cables (with mc4 connectors) from Santan Solar in AZ. They come in pairs and I found the price is as good or better than most. I’ve had no problems with the extension. They also sell bulk cable with no connector on the end as well as MC4 connectors if you want to make a custom length extension.

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Hello, ive been reading through the forums trying to figure out best gauge. My concerns are that my solar panel has 12 gauge, my extension cable 100ft is 10gauge but my bluetti AC500 has only 14gauge connector. Why is the conne tor that cones with my hluetti Mc4 o only 14 gauge if i need 10 gauge extension cable. Solar panels are 460w, 41volt, 13A and i want to run 3 in series.

I read that you should bury long wire runs over 100’ for lightning strike protection, plus it protects the wires over the long haul. I just used some pvp pipes I had laying around, buying them only a few inches or so in the dirt. Any wires exposed to the raging Nevada sun get covered in loam tubing.