Solar powered pond - part 7

I nearly "lost" the two leisure batteries due to too much drainage ... and I couldn't figure out how to prevent it.  I did have grand ideas about using an automated switch - I setup an ESP8266 relay switch that  I could invoke from code over the WiFi network.  Then from my dashboard monitoring RPi, I could detect in node-red when the voltage got to a certain level and then make a call out to the ESP8266 and get it to switch on the battery charger and when at certain level then turn it off...

Then I sat down & thought about the real problem... the inverter was draining the battery down a few 0.x volts over night.  As it's now the start of December, the amount of charge during the day is not to nothing useful...it might blip every so often and keep the battery topped up above 12.75volts... however, after 4pm, the drain is almost a triangular line downwards unto the 12v or even worse the 11.8v angle!

I then found THIS device.

For around £12... what was not to like?  item ordered.... patiently awaiting delivery...

Delivered! Then I noticed the screw connectors were a little on the small size...but it is only pulling a small amount of power through the cabling to power the inverter; I'm only using something like 0.22Amps to power the 30watts of pond pumps; so I should be okay with some make shift cables (for now).

As you can tell by the dashboard image above - I fitted the device around the 14:00 region - just as you see that triangular decline cycle starting to kick in.... and then, around the 16:00 mark is when the above device kicked in & did it's thing... as you can see, the battery is now being held at a stable 12.6-12.7v range - this is a little high, I can tweak that to drop down a bit to 12.3v but for testing this is just great.  It proves that it is doing the job - it also shows how much power the "idle" inverter is consuming even when it is "doing nothing"... interesting.  I've set it to switch back on when the battery has 13.1v; so in theory tomorrow morning when the solar panels kick-in and start charging the battery up, it will creep up to 13.1v then switch the inverter on, then get to 13.3v and the ATS will switch over from mains power to using the battery power...and drain it down to 12.5v... then switch off the inverter / switch over to the mains and then charge the battery back up again....rinse & repeat.

Maybe the more expensive "spare" inverters I have in the kitchen (2000w) will be more efficient?

Anyway, just a short update - hopefully if this works out okay, I can then add the two leisure batteries back together and get more capacity again - that is if one of them isn't bad/dead and brings the other one down?  we'll see.... I still have the 12v LiPo lithium battery sitting in the kitchen, I'm hesitant to put it into action until I've ironed out all these kinks.. then it can go into action... and I will then use it to power a lot more than 3 little pond pumps!