Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Combine Grid power & Solar power

Not open for further replies.


Member level 1
Sep 21, 2013
Reaction score
Trophy points
Activity points
Latelly I've been pondering on the best way to make myself a solar battery sort of setup.

What I have:
-> 1-4 250Watts Panels, 60 Cells
-> 2KW Li-Ion battery, to be set as 12-96V

Ideally I would like to have a setup similar to a transfer switch, where the power I was able to generate from the solar side would be 'added' to the grid (similar to an interactive UPS unit), probably on a 36V bus to directly charge the batteries from the solar (thus the batteries acting as the low impedance/MPPT) and use a full bridge mosfet + toroid to feed power into the mains. Finding UPS' with a efficient toroid transformer, seems like a no go, however, so standby losses always a challenge.

Another option is a dedicated circuit, fed from 12V, followed by an inverter. I have a 500W sine wave inverter on hand that could be used for this purpose, with a manual transfer switch and a dedicated buck converter acting as the MPPT to each of the solar panels.

I could also boost that to 300'ish volts and PWM my own sine wave as I do for the motor control units that power the fridge/etc.

I'm planning to build my own BMS based on a MCU signal, sitting on each battery. A digital (I2C) optoisolator would be used to communicate with the load side and enable a relay/fet, etc. I don't like the traditional BMS on/off aproach and would like to charge to more conservative voltages (3.0V discharge, 3.45V charge) on LiFePO4.

Injecting into the grid is not really an option, so for any grid tie instalation I would need to make sure I am not exporting. The simplest seems to be by tracking a half wave rectified supply and setting a boost converter feeding each half cycle, operating as a constant current source of varying voltage.

Any other ideas? Any projects?

2KW Li-Ion battery,
You mean 2KWh?

So I see you have several options. Usually one takes this as a good thing. What prevents you from implementing one of these solutions?


You mean 2KWh?

So I see you have several options. Usually one takes this as a good thing. What prevents you from implementing one of these solutions?

Nothing preventing me, but if I can avoid re-inventing the wheel that would be good. Would be good to hear about others that implemented such systems. That is, a custom made setup, not a comertial device.

Isn't this what most grid-tied systems do?

I have two PV arrays, one peaking at about 1.7KW output and the other at about 350W, both connected to grid tied inverters. I don't have batteries in the system but there is no reason they couldn't be added. Many models of inverters have chargers built in.


Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to