Use of a bench DC Power Supply as PV input to a Smart Solar Charge Controller

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Pat Davitt asked May 1, '19

Use of a bench DC Power Supply as PV input to a Smart Solar Charge Controller

I have an external system that ties into my Victron system via a Modbus TCP connection to my CCGX. My need is to refine some tuning parameters in the external system. To do this I need to control the PV voltage and amperage inputs to my Smart Solar 150/45 controller wired to a 48V battery bank. I will do this by removing the PV Panel connections and using the Power Supply instead.

Testing output from the Bench Power Supply will range from 60-75V and 0-33A, not to exceed 1200W total output power.

Are there any risks to the charge controller during this test scenario?

Just want to make sure I don't fry something.

Thanks,
Pat

MPPT Controllers charge controller compatibility

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nigelfxs answered · May 02, 2019 at 08:05 AM

I remember seeing an issue with Smartsolar MPPT units running older firmware.

These units could lose their voltage setting and reset back to "12V" when disconnected. Reconnecting the solar input of the MPPT to a 48V bench PSU could destroy them. This was because the PSU can deliver a high peak current for a short duration (unlike a solar panel).

EDIT: See release notes for MPPT Firmware version 1.37

Known issues:

- When connecting a power supply on the PV inputs, for example on a test bench, in combination with a battery (24V..48V) on the BATTERY input, a reset to default settings immediately triggers an error 38 (overvoltage). This enables the PV input short protection; and because there is a power supply connected; instead of a real PV array, the MPPT charger is damaged. Introduced in v1.26 and solved in v1.39.

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Pat Davitt commented · May 02, 2019 at 12:53 PM

Thanks for the information. I'm running 1.39 on the CC so I should be ok.

Also, I plan to set the constant voltage output of the power supply to at least Vbatt + 5V. Which in my case is about 60V. That way the charge controller should turn on normally. With this power supply if I set the Voltage to 65V then I can adjust the max amperage output from 0-18A and still remain in constant voltage mode.

Pat

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Answer 1 · 2019-05-01T20:07:23Z

wkirby answered · May 01, 2019 at 08:07 PM

I don't see any problem with that. I use a bench power supply when conducting my own tests.
As usual, the MPPT will only take as much power as it can, but in your case it will most likely outperform the power supply and hunt around for a MPP when the power supply starts to struggle.
What sort of topology is the bench power supply? Is it switching or linear? I've used linear ones, not sure how a switching one would behave.

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Pat Davitt commented · May 01, 2019 at 08:19 PM

It's a Kepco KLP75-33-1200. It is a switching PS. Datasheet is attached:

Pat

Kepco KLP Series.pdf

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kepco-klp-series.pdf (255.9 KiB)

Pat Davitt commented · May 04, 2019 at 11:27 PM

The KLP was due for a calibration, so I sent it to be re-calibrated. It will take about two weeks.

Will do a "smoke test" with the charge controller when it gets back, and post the results.

Thanks,

Pat

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Pat Davitt commented · May 30, 2019 at 02:14 PM

Finally got the power supply back from calibration. Set it at 70V and 15A output (1050W). The 150/45 MPPT (48V Battery System), maintained a steady output with the voltage to the battery slowly rising during the one hour initial test.

So far so good, will keep testing.

Pat

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wkirby ♦♦ Pat Davitt commented · May 30, 2019 at 04:22 PM

Did you notice any effect on the KLP when the MPPT did a MPP sweep?

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Pat Davitt wkirby ♦♦ commented · May 30, 2019 at 04:36 PM

Not really, but I have not put a scope on the KLP output yet. The only thing I noticed was that the KLP was continuously switching between Constant Voltage and Constant Amperage modes to keep the set voltage and amperage output constant.

I guess that's to be expected since the MPPT has the capacity to consume a lot more amperage than what the power supply was set to.

Pat

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