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tkmbe avatar image
tkmbe asked

Can a SmartSolar MPPT load output be used to power an inverter?

Hello

I used a Smartsolar MPPT 100/15 with 24V Batteries and 24V equipment's about 4 month without any problem.

Now I tried to test an inverter (12V/1500W), of course I guess I cannot use 1500W with load output.

BTW: the 15A output is for 12V or 24V or both? In fact the limiting should be W not A...

So either 24*15=360W or 12*15=180W should be limiting. What is true?


So I connected 2*6V old batteries I had, mi inverter to load output and turned on inverter which turned on. After connecting a 15W bulb to inverter still ok. Put mi office stuff (mostly router, switches, AP etc. and there my MPPT shutdown the output. So I putt off load from inverter but output still down. Put off inverter output still down.

load configuration is always on.

Changing to always off and again to always on.did not work.

I had to cutoff power from pv and battery, and sometimes to take away 20A fuse so the output goes on again.

After that I was not able not even to turn on inverter without shutdown of load output...

What is this behavior? Is this if load it to high? I had about 140-240W

I guess output cannot be burned up with high load if it could, for what is the fuse?

So I tought it could be battery too, because battery minimum showed me 0V but I guess this was because I removed batteries today...

Nevertheles I put mi car battery to test... Same thing.

So I put the invertder directly to battery and then it worked...

Inverter tells me 180VA, mi office 140W with cos phi of 0.8 .so I guess this is ok.

Still in doubt what is the problem to use load output and how to reset if output down.

What about VA versus W on Smart Solar devices and about the 15A limit?

Any hints?


MPPT Controllersbatteryinverter current draw
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3 Answers
Justin Cook avatar image
Justin Cook answered ·

@tkmbe, the load output of an MPPT cannot be used to directly power an inverter; there are a myriad of reasons for why this is impossible, but the most compelling is simply that the inrush current of the inverter charging its capacitors upon startup is usually ~5-10x the maximum current of the inverter itself, which is obviously far higher than the MPPT can possibly handle. Inrush current only lasts for a few milliseconds, but it's more than enough to shut down the MPPT, as the MPPT will see that as a short circuit and will likely shut itself down.

Furthermore, the fuse in the MPPT is for its own self-protection in case of reverse polarity; any load you connect to the load output of the MPPT still needs to be fused for protection of that circuit.

Even furthermore, you cannot use a 12v inverter on a 24v system.

The acceptable way to do what you're trying to do is to connect the inverter directly to the battery as it is designed (meaning, connect you 12v inverter to a 12v battery), and use the load output of the MPPT to trigger the remote on/off of the inverter (if so equipped).

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tkmbe avatar image
tkmbe answered ·

Ok I didn't knwo that of the inverter (10x higher load on startup)

But of course this inverter handles 12v and 24V. The 24V stuff was to inform that loader worked nice.

I have written that I put 2x6V batteries to get 12V for the inverter....

But thanks for answer.

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marcin-tomasik avatar image
marcin-tomasik answered ·

Ok but what about if I connect 120W (MAX 7.5A) mikroinwerter and make something like this:

whatsapp-image-2024-03-01-at-204636.jpeg

The key is the DC/DC STEP DOWN converter with current limit set to 4.5A and voltage limit set to 24V.

Mikroinverter verion GMI120L 120W specyfication:

whatsapp-image-2024-03-01-at-205111.jpeg

Will it work with LOAD socket of Victron SmartSolar 100/20?


whatsapp-image-2024-03-01-at-204636.jpeg (205.8 KiB)
whatsapp-image-2024-03-01-at-205111.jpeg (373.1 KiB)
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Justin Cook avatar image Justin Cook ♦♦ commented ·
Doubtful, but you're always welcome to try (at your own risk of course).

But why so much effort to make it more complex than necessary? Just connect the inverter to the battery bank as designed.

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marcin-tomasik avatar image marcin-tomasik Justin Cook ♦♦ commented ·

It works. 20A at LOAD port is enought for starting 120W mikroinverter in this case. But as I said before I used DC/DC step down converter to decrease current to 5A and regulate voltage to 24V between Victron SmartSolar charger and mikroinverter. It looks like below. It is only test environment.

whatsapp-image-2024-03-10-at-192701.jpeg

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whatsapp-image-2024-03-10-at-192701.jpeg (595.4 KiB)

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