Charge Controller and Grid Together

[truepudding]

Hi everyone! I have a really simple system I'm building for fun, but I have a question. My system now is a 100watt 12v panel that goes to an MPPT charge controller, which charges a battery. I have been considering hooking up this panel to a grid-tie inverter instead.

I know this forum is geared more towards off-grid, but my question is: can I split the power off the solar panel to go to the charge controller and the grid tie inverter? The thinking is when the battery is full, all the energy will just go to the inverter.

Will this work or should I build an A/B switch? If the answer is A/B, is there a way to automate this?

Edit: the battery is used for a few small DC items on a fusebox

 

[rodrick]

Are you talking grid tied or grid assist, going grid tied with a 100 watt panel is just not feasible or worth it

 

[truepudding]

Grid tied I believe? That being the case, id still rather do it. It's an $85 part. I could add panels later.

VEVOR Grid Tie Solar Inverter, 1000W MPPT Power Inverter, 50/60 Hz Solar Grid Tie System, Grid Tie Inverter, DC10.8-30V Input to AC90-140V Output Wind Turbine Grid Tie Inverter for Solar Panel System https://a.co/d/iqx6nxl

 

[rodrick]

Grid tied I believe? That being the case, id still rather do it. It's an $85 part. I could add panels later.

VEVOR Grid Tie Solar Inverter, 1000W MPPT Power Inverter, 50/60 Hz Solar Grid Tie System, Grid Tie Inverter, DC10.8-30V Input to AC90-140V Output Wind Turbine Grid Tie Inverter for Solar Panel System https://a.co/d/iqx6nxl

If you are going grid tied you first have to get permits and approval from your power company all of your equipment will have to be UL listed and approved by inspecting authority it’s not just a $85 dollar part you might do it for $8500.00

 

[zanydroid]

Cheapest new grid tie string inverter is like $600. You can also use a $50 used Enphase microinverter, assuming your POCO/State allows pre 1741SA hardware on the grid.

Switching DC is not easy to do safely. Well, for 100W/30VDC, it's easier than folks that ask about >100VDC strings.

However to do it officially you need to pay interconnection fee, permits, ... The panel needs to be mounted in a code compliant way to get the permit, as does the wiring. And people reviewing it may not take you seriously for going through all that trouble to generate 100W.

Minimal effort to do it unofficially is to tie the microinverter into a backfeed breaker in a subpanel, and <100W is not going to be noticed by a typical US electric utility.

OTOH, I don't see why you would go grid tie instead of off-grid inverter. Zero chance of getting in trouble, comparable equipment cost.

 

[truepudding]

Thanks for the information, this is all a learning experience.

The grid-tie inverter I linked, simply plugs into an AC outlet. It works more like an enphase microinverter from what I can tell?

I definitely don't want to mess with a backfeed breaker, seeing as I found this:

"Backfeeding is the tying of a portable generator directly to your home's electrical panel instead of using a transfer switch. It is dangerous. It is often illegal. And it should never be attempted under any circumstance."

I plan on building a much bigger system in the future. It makes sense (for me) to start off with something small and easy. Eventually I will have higher capacity/voltage panels with enphase micro inverters.

 

[pollenface]

You need to have an agreement in place with your grid provider otherwise you are painting a target on your back. They are usually pretty fussy about it.

 

[truepudding]

Thanks, I need to look into that more.

Does anyone know the answer to my question regarding an A/B switch and hooking up a grid-tie inverter and a charge-controller to a battery on a splitter vs switch?

 

[timselectric]

Thanks, I need to look into that more.

Does anyone know the answer to my question regarding an A/B switch and hooking up a grid-tie inverter and a charge-controller to a battery on a splitter vs switch?

They won't operate correctly if connected at the same time. They will compete for control. And neither will perform well.
A switch would have to be rated for the use.

 

[truepudding]

Makes sense. Thanks!