Battery added to grid tie inverter, no feed in tarif, need to regulate power output

(cristipurdel) #1

First post so hope is the correct forum.
I have 2x80W solar panels in parallel, a grid tie inverter and have a constant typical load of around 70W.
The grid-tie inverter is a Letrika SMI260, MPPT 21 V-55 V, which produces max 1kWh daily, with a peak of 210W.
What I want is add a battery, but also regulate the power coming out.
If I produce 210W, 70W should go to the grid, the rest should fill the battery.
If I produce 50W, 20W should come from the battery.
If there is no more sun, battery should be drained until desired %.

Is there any way to do this without messing with the panel braker, and with fewer components as possible?

I saw some victron solar MPPT chargers but not sure if they can do this sort of thing.


(Lee) #2

Hi Cristi,

No, sadly, there’s nothing that you can buy cheaply that will do what you want, unless you design and build it yourself.
You’re also going to struggle with 2 x 80W panels. There are losses (usually as heat) in all conversions like this, maybe 10% extra needed to charge the battery and more for the inverter. And you get hit double for the inverter running from the battery.
Also the panels only output 80W at their peak with bright direct sunlight, the rest of the time it will be less (or much less). Also, while the inverter can output 210W, you’ll need to feed it at least 230W to get 210W out of it. Your 160W of panels won’t do that.
What batteries are you planning on using?


(cristipurdel) #3

I saw some victron solar chare controller + battery with bluetooth support, but I could do a small setup also with 18650.
What would be the out of box solution, also having an interface via android?