Show us what devices you have already, with descriptions, links, links to datasheets etc. I'm sure you have looked up some of the future devices, include those too.
Shelly pro 3em is a connected domotic current meter. It can tell how much current you drain from the grid or how much you produce in real time. But I could use buttons to set charging level for start (Arduino logic out of scope, the scope is how to limit the charging current from AC outlet to the battery).
And I ve no pointers at all.
I have an Arduino. I will purchase some BMS and LFP cells. I have an AC/DC converter for the main input.
I understand some kind of MOSFET is involved that can process a PWM signal from the Arduino.
But as stated before I'm a total nooby in electronic. So any direction I could point will not be relevant. (I'm ok with soldering and high current wiring because I've built some FPV drones but that's it... I can follow schematic but I don't understand why you have to put resistance or capacitor at some place).
You should start with the communication between Arduino - Shelly. I have no idea what protocols that Shelly talks, if it's secure you need something better than the standard 328 Arduino.
After you get the communication working, a PID loop is needed, to prevent the whole charge process from oscillating but stabilize instead.
This is if you wanna set things on fire. There's plenty of energy involved in this that you don't wanna fool around with, experiment. Go with ready made solutions.
Don't be surprised if you get all your work chopped off any grid connect and at least a fine or jail time from the local authority.
They do not take kindly to "wannabees" putting people's life in danger downstream so-to-speak.
Now you can argue until you are blue in the face but it will not change anything with unqualified, uncertified add-ons.
Power doesn't go to the grid when there is an acceptable local load.
This is how my hot water system works during my switched relay system 9:00am to 4:00pm and yes I am qualified to do so and yes it is certified by the local authouity.
I do not need help for the Arduino part, I've already done this kind of loop with current variation detection from Shelly or other (it's software it's easy and not risky lol)
In fact an intensity variable LFP power supply would be nice.
Want the same thing but 24v and with a serial/pwm head that the Arduino could drive instead of a knob. So replacing a knob from an existing device can be an option.
Ps: I say 24v but can be 28/29v it's the threshold to activate the 8s BMS. Could be 48v but the battery must be 16s or I need to add some DC/DC buck down before.
I wouldn't suggest you to build lithium-ion battery charger as a first or second electronics project. Way too dangerous.
Get that variable battery charger from your link.
Get 270deg SG92R servo to do the adjustment.
Esp32 board to communicate with Shelly REST api and drive the servo according to your solar excess.
I think I will definitely buy one of these power supply. I'll tear it down and see if I could replace the manual potentiometer with a digital one. I think it's safe enough.
Anyway, water heating is much more cost effective.
100l electric boiler + triac is costing $200 and can store up to 10kWh of energy.
10kWh lithium battery + charger is costing >$5000.
