DC Power Supply to MPPT SCC Input

[rack04]

I was watching Will's 1st milk crate video and noticed that he connected a DC power supply (AC 110v-20v to DC 0-48v) to the MPPT solar input to boost the charging amps. Is this safe to do?

 

[Brewman]

Inquiring minds want to know...

 

[Brewman]

I'm thinking if you use reverse diodes, it should be safe. If you read all the comments from the video you will see where they bring them up.

 

[Brewman]

After thinking more about it I would never do both at the same time. I would isolate each input and switch between them if needed.

 

[rack04]

After thinking more about it I would never do both at the same time. I would isolate each input and switch between them if needed.

Agreed but my question is more general. Even when switched is it safe for a MPPT SCC to have a DC power supply @ 48v 10a for AC charging?

 

[Brewman]

I would set the power supply to a level below your panels max rating.

 

[OffGridGuy]

I was also surprised to see Will hooking up a PS to MPPT solar inputs.

About 10 years ago, I contacted engineers at both Midnite and Morningstar about that.

Midnite said NO WAY. Morningstar said they would call me back. Which they did....

Their official response was the only MPPT controller they have, that will support that function, was their SS-MPPT-15L.

Since then I have used a couple of those units. Mainly to charge my 12 volt backup battery bank from my main 24 volt battery bank.

I have a contactor, in series between the 24 volt bank and 12 volt bank, that is activated when the 24 volt banks goes into float mode.

You can find these units on ebay and I've bought a few, as backups.

BTW.... Morningstar has a 5 year warranty on their products. After 5 years you have to toss it. They do not fix out of warranty units, even if you promise them a wheel barrow of bux......

 

[Brewman]

I got my PS and did some testing tonight. Using anderson connectors I can now connect the PV or PS to the SCC. This way I can never have the PV and PS connected at the same time. I set the PS to 30VDC and connected it to the SCC and got 14.6V 20A going to the battery.

 

[Bud Martin]

I got my PS and did some testing tonight. Using anderson connectors I can now connect the PV or PS to the SCC. This way I can never have the PV and PS connected at the same time. I set the PS to 30VDC and connected it to the SCC and got 14.6V 20A going to the battery. View attachment 39304View attachment 39305View attachment 39306View attachment 39307

So the readout makes sense, output of 14,5V @ 20A of charging current to the batteries corresponding to 30V input and current draw of 10A from the power supply connected to the SCC PV input, it works as expected as long as you are not exceeding the power supply rating limits..
BTW, what is the power supply rating?
Also if you watch HOBOTECH videos, he uses the power supply to check the max PV input rating and to simulate PV output.

 

[Brewman]

 

[Bud Martin]

View attachment 39325

So if you want to charge at higher than 20A you will need to get higher rating power supply, I myself limit the current draw from power supply to about 80% of the max current rating of the power supply for safe operation.

 

[notarichman]

i found a power supply that uses 220vac input, 0 to 331vdc at 10 to 15 amps output. but no info. on how to adjust the output.
i have a victron 450v 100a mppt and would like to set the output to max. voltage and 10 amps = 3320w input. set the mppt for
10amps input. put a breaker and fuse between the ps and mppt. then when the batteries are down, no sunshine, no genset i could
still charge the batteries. i looked for days on the internet for a charger that i could afford with no luck for 48volts.