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Question about 70C ambient operation for Smartsolar 250|100

Hi,

I've been testing a Smartsolar Victron 250|100 under my worst case high-temp conditions, and I wanted to get more detailed information about the max operating temperature that the Victron can handle.

The manual states that 60C is the max operating temp (I assume ambient) with full rated output at 40C (again ambient?).

My worst case test setup
- 115VDC, 25A solar input (Voc could go as high as 200VDC)

- 90A charging output (limited to 90A from user settings)

- 70C ambient directly surrounding the Victron

- 2 awg stranded cable with ferrules fully inserted into all four terminals

- All four terminals torqued to 5NM

- Test runs indefinitely (until batteries are charged or Victron overheats)


K-type Thermocouple Measurements

- 70C ambient surrounding victron (2in above Victron)

- 80C case temp (middle top surface of Victron)

- 90C terminal temp (thermocouple touching the "battery -" phillips screw during 100A output)


The 90A current limit seems to allow this setup to run indefinitely whereas 100A output only lasted about 1 hour before a terminal overheating error code appeared (occurs at 90-91C terminal temp)

I had a few questions about my setup
- Will 70C ambient degrade the Victron and lead to premature failures since it is technically out of spec?
- Can I rely on the the Victron terminal overheating error code or should I throttle the Victron before the terminals reach 90C?

- How does the Victron measure the terminal temperature? I didn't see any temp sensors close to the terminals when I disassembled a unit.
- What internal temperature (that is reported over serial) corresponds to terminals overheating? I'd like to use the Victron reported internal temperature to know when to start manually throttling the chargers output current.


Thanks in advance, any help is much appreciated.

MPPT - Solar Charge Controllervictron productsTemperature Sensorerror codes
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3 Answers
TC777 avatar image

@kai, thanks for the information, very helpful. My worst case setup would see 70C for an hour or two each day, but then quickly drop off to 40-50C ambient.

@Johannes Boonstra (Victron Energy Staff), thanks for the insight, good to know. Is there a temperature at which the Victron cannot properly report its own data? I ask this because we noticed our Victron sending false temp readings in 60-70C ambient.

It sounds like it's worth throttling the Victron from my side if a specific ambient threshold is reached.

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kai avatar image

Lifetime of certain electronic components, such as capacitors is highly dependent on ambient temp, and its a continuous curve. There's no sharp threshold where if you stay under you're "ok" indefinitely and if you go over you're instantly toast. Higher temperature, shorter lifetime. Just because its not giving you an overtemperature error doesn't mean it has the same lifetime as operating at 20C ambient.

The arrhenius equation predicts for every 10C increase expected lifetime halves. Its not universal to all components but gives you a reasonable stab in the dark. So a +50C (over the reference lifetime at say 20C) increase means lifetime at 70C is 3% that of the 20C lifetime. Lots and lots of caveats and assumptions went with that calc.

If you're wanting to maintain system operation at elevated temperatures like you're proposing you better have replacement on hand and ability to replenish spares. Either that or think more about thermal management.



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Johannes Boonstra (Victron Energy Staff) avatar image

Yes, Electronics will have a shorter lifespan when used in higher ambient temperature. 70C is certainly (too) extreme and should be avoided. Also output power will be constantly derated. The terminal sensing is for an extra protection against bad wiring/installation. Normally this should not be these temperatures by far of course.

Make sure there is enough cool air so that the charge controller will operate well within its specifications. Pushing to the limits is mostly a recepy for disaster, so avoid that!

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