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Minas Papageorgiou avatar image
Minas Papageorgiou asked

Cable to BlueSolar overheated

Lately I noticed a burning smell so today I checked with the infrared thermometer the battery cables on the chargers and the + was much hotter than the negative that was just 25c. So once the sun was down I turned off and removed the cable. It looks like burned. Checked all bolts. The negative on the bush bar took a bit of tightening (1/4 of turn max). Any idea what might caused it?

These are 50mm2 H01N2-D cables (recommended is h07v-k 35mm ) on a Bluesolar Mppt 70A and an oversized array of 2.7kw, so it runs for maybe 2hrs at maximum output 2KW 70A.I have an external fan hitting the device with a timer since installation,given it does does have any fan of its own. Since the cables were too thick to fit the terminal, I chopped off enough strands to fit. I have not used a terminal because it looks like the terminal of the BlueSolar is some kind of clamp pressuring like square? the cable so if I put a cylindrical terminal there will be less contact??

System is operating since July 1st 2022, this happened327375539-898844148099820-7497052449033999797-n.jpg last week.

MPPT Controllersbattery connection
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Alexandra avatar image
Alexandra answered ·

@Minas Papageorgiou

It was not tight enough. So basically a high resistance connection which causes heat. Especially when moving the amps it was in charging.

The manual states a torque. Use that information. It is also really important to also check periodically because of thermal cycling. Part of electrical maintenance.

A rising clamp system does not need a boot lace ferrule. So on that point you are fine. Just make sure the terminals are tightened correctly.

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Minas Papageorgiou avatar image Minas Papageorgiou commented ·
Any idea why it was oxidized in just 6 months?

Do you think that I used a 50mm2 and stripped off threads until it fitted the 35mm2 clamp on the BlueSolar while on the other side I used a 50mm2 screw terminal could increased the problem?


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