Relay automation of Grid and Generator - Sol Ark and AC Coupling

[byteharmony]

Does anyone have any thoughts about using the relay idea detailed below to automate the grid and generator input to my sol ark 15k grid input.




Pardon the word art, I'm traveling and don't have VISIO or something better.

The relay would before the 2 hot wires, 200 AMPS from the grid, 30 AMPS from the little generator.

Neutral and ground would all be connected all the time.

I've seen a few automatic transfer switches, $700 - $2000.
I've seen one relay that seems like it could do it $600
Is

Does someone have a recommended relay or auto transfer switch?

You may wonder why I want to do this with an Sol Ark 15K having a generator input. The answer is that I want to use the generator input for AC Coupled solar power. Sol Ark support seemed less than confidant when I asked them if I could AC Couple the power on the load side of the sol ark. - I'm going to start a thread on that if it doesn't exist.

With this system I'd never need to switch my input wiring and I could even rig up some automation for starting and stopping the generator.

 

[byteharmony]

Looks like this topic is getting attention already:

Sol-Ark 15K AC coupled setup to reduce grid supplied power

I'm about a day away from starting up a new 15K installation and am curious about what the right configuration should be to achieve my goals (see below). Any thoughts from experienced Sol-Ark users is greatly appreciated. GOALS PRIMARY: Use as little grid power as possible, and use solar when...

diysolarforum.com

 

[byteharmony]

Reading this form makes me think, perhaps instead of AC coupling, what if you used a DC Boost that was set for your max battery voltage and connected it directly to your battery system?

Would this assist in charging the batteries and then if the voltage goes higher than parameter ranges on the sol ark the sol ark would sell the excess power back?

 

[timselectric]

The only issue I see. Is if it switches to generator. The Sol-Ark wouldn't know to not export. And that would damage the generator.
I would just have the dry contacts start the generator. And use a Chargeverter to recharge the batteries.

 

[byteharmony]

After a little thinking the solution I think I like most is this:
Run 48V sol ark battery wires to the place where my lawn tractor charges.
In that place I have 4 occasionally partially shaded panels, I'd connect them to 4 independent cheap MPPT DC boost devices set just above the max voltage of the sol ark configured battery max voltage.

I think this would address every issue REALLY cheap:
- panel shading
- slowing / stopping power production when batteries are fully charged
- export of power to the grid when it is online

Another option for AC coupling I thought of was this one:

Sol-Ark 15K AC coupled setup to reduce grid supplied power

That would cycle battery and switch SolArk between 100% and off. Can you get it to operate smoothly with Rule-21 frequency-watts? The only time you need to throttle AC PV production is when the grid is down. For those times, if the batteries are at 80%, I'm ok with turning off AC PV for a while.

diysolarforum.com

Have the AC coupled inverter on the load side lose it's grid connection (the load output of the sol ark) when the battery voltage reaches a point where the sol ark can't dump the extra power into the battery.

Wonder if the sol ark is smart enough to take into account the grid outage and use any possible excess power on the load terminals on the battery charger?

 

[timselectric]

Have the AC coupled inverter on the load side lose it's grid connection (the load output of the sol ark) when the battery voltage reaches a point where the sol ark can't dump the extra power into the battery.

It's a possible option.
I believe that Sol-Ark recommend not allowing the battery to get above 90% (or something like that) in that configuration.

Wonder if the sol ark is smart enough to take excess AC power on load and push it into the battery charger instead of the export path?

Yes, from my understanding.

But the Chargeverter is a better choice, in my opinion. It removes the possibility of problems.

 

[byteharmony]

It's a possible option.
I believe that Sol-Ark recommend not allowing the battery to get above 90% (or something like that) in that configuration.

Yes, from my understanding.

But the Chargeverter is a better choice, in my opinion. It removes the possibility of problems.

That fits the plans perfectly! I plan on having the batteries sitting at 80% all the time. I can make the DC Boost programmed for 85%.

Hoping cutting the grass only brings the batteries down to 40%.

I can easily justify the additional wiring for the 48V. I can see people needing to use the AC coupling if the panels were far away and they didn't want to add additional copper.

 

[timselectric]

I plan on having the batteries sitting at 80% all the time.

I would recommend a full charge, at least every week or 10 days. So that the cells can get balanced.

 

[byteharmony]

I would recommend a full charge, at least every week or 10 days. So that the cells can get balanced.

What do you think of the JK-BMS?

I've been testing an 8 cell LIFEPO4 48 AH superbeast from batteryhookup.com with the 100 AMP discharge / 1 AMP active balance system.

So far I love it! I monitored it with Bluetooth, wish it had WIFI. System showed the full 1 AMP balance being applied to keep the system in good shape. Starts active balance at 0.01v difference .

Attached is a screenshot of the 8s battery.

It's the most cost effective powerful BMS I've seen for this type of task.

My next test is the 30 AMP 16s version. It's the start of the homemade powerwall . I know 30 amps isn't much, but its going to be paralleled with many of it's friends to extend run time.

 

[timselectric]

What do you think of the JK-BMS?

It's the only one I recommend.
It's also the only one I have used. lol
I do a lot of research before any purchase.
And, I couldn't find anything better for my needs.

Edit: I forgot to answer the question.
Very satisfied with them.

 

[byteharmony]

It's the only one I recommend.
It's also the only one I have used. lol
I do a lot of research before any purchase.
And, I couldn't find anything better for my needs.

Edit: I forgot to answer the question.
Very satisfied with them.

I've used Dally and ISDT devices - not really impressed.

I have been impressed with the JK-BMS.

One issue still has me confused. The JK-BMS does active balancing so why do you recommend the full charge every 10 days, why?

I could understand that if it was just passive balancing and needed to top off cells to get them all to the same peak voltage. If they are actively balanced within 0.01 volts by default what's the point of cycling the cells?

 

[timselectric]

One issue still has me confused. The JK-BMS does active balancing so why do you recommend the full charge every 10 days, why?

Cells drift over time. Theoretically, they shouldn't. But they do. So they need to be re balanced every so often. It's not much drift, but it adds up over time.

 

[byteharmony]

Cells drift over time. Theoretically, they shouldn't. But they do. So they need to be re balanced every so often. It's not much drift, but it adds up over time.

What is drift?

If it's different cell voltages from losses in the system doesn't active balancing correct the difference in voltage?

 

[timselectric]

What is drift?

If it's different cell voltages from losses in the system doesn't active balancing correct the difference in voltage?

Yes, and that's why you should charge to the top of the curve. Where the balancing happens.

 

[RCinFLA]

You cannot immediately jump between two asynchronous AC inputs to a hybrid inverter.

You have to let the inverter pass-through relay release first before applying a second AC input source.

Inverter locks its phase to attached AC input source and immediately jumping to another async input will possibly join two out of phase AC sources.