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joeoffgrid avatar image

Blue Solar overheating -- load off despite no indication?

When the ambient temperature of my BlueSolars is like 38°C consumers connected to the load terminals are sometimes not working despite both LEDs are steady and the app reading "load on" and battery voltage at float.

Two different consumers (fan and compressor box) on two completely separated solar setups behaving like that.

If they overheat, why is there no indication at all?

MPPT - Solar Charge Controllermppt smart solar
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4 Answers
joeoffgrid avatar image
joeoffgrid answered ·

Nobody with an idea?

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @JoeOffgrid

What is the exact load on the output? We need to know the following:

what loads specs and also can you measure the load output voltage terminals on the product itself when the issue happens (and on input terminals to compare please)


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Hi @Daniël Boekel (Victron Energy Staff) ,

I trust the readings of the controller: Somewhere around 13V. On battery and load terminal. Loads are a small compressor cooling box (5A max) and a fan respectively (2A on separate Blue Solar).

Does the Blue Solar have an over temperature protection at all?

Any way the controller is indicating it's derating or is it left up to the user to guess?



ddickov avatar image
ddickov answered ·

Hi there I know from previous posts regarding temp I think I maybe right in saying 40c is max for charge controllers they have been reported as functioning irrational at certain temps, I would try and cool the unit more down to 30c if possible and see if that fixes your error, if possible power it down and allow to cool properly then boot back up, also just to double check the cooling fins at the rear are clean as to dissipate maximum heat. Hope it helps a bit thanks David

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Hi. Thanks for your reply.

Unfortunately no chance to cool the unit down inside of the van. It's so hot when it is sitting in the sun. Actually, I have a fan on the load terminal that is supposed to force cold outside air in.

No problem Joe I would say it’s definitely temp related perhaps relocating the mppt might be worth considering as that temp will shorten its life also so the cost to relocate it will pay you back time over if it’s not possible I would urgently get another high powered fan to blow from the bottom up the cooling fins to make the heat rise quicker and thus cooling it faster, I would expect premature failure of the unit operating at that temp thanks david

I have the small versions of the chargers. They don't even have cooling fins. I mounted them on the inside to a metal wall that isn't heated by sunshine.

It's a 4x4 metal cargo van. Really no other place to mount the chargers than inside. :(

I didn't know they were that frail.
I mean that is normal automotive conditions...


Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @JoeOffgrid

What model do you have exactly? If you have the smallest model, a cooler is probably too big of a load. a compressor has a very high starting current.

Also: there is no derating on the load output. And if the charger is measuring the load voltage and indicating that the load is on (as he said), his load should be indeed on. If not, I would double check the wiring again

If there is voltage on the load terminals, and his load does not turn on, you should check the system.

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Yes, in the meantime I checked both my systems and my conclusion is that it is several issues coming together.

It is a considerable voltage drop over the cable and probably on both my systems the batteries are getting old.

On the controller side the remaining issue is that it takes a while (time!) for the controller to
start charging the battery despite considerable drop in battery voltage.

There is plenty of solar power available to feed the consumers irrespective of the battery, but the voltage drop on the battery is so deep after -- say -- 30s of compressor running that the battery protection on the cooling box is triggered.

How to make the controller start using the available solar power sooner (timewise)?

I see the voltage drop in the reading in the app, nevertheless 75/10 remains in float for too long.