Charge batteries when on grid Solar is generating

ctdctd

I have a 2.5Kw Solar on-grid setup in the UK.

I also have a 24V 100Ah battery setup with an 250W AC charger which I use to power stuff at night.

At the moment, I charge the battery when the sun is out - this works well, but I tend to micromanage it and spend far too long looking at the net generation figure on the Smart Meter display!

So, what I want is a Gizmo that does something like:-

1) Is net generation > 300W?

2) If yes, switch on battery charger

3) If no, switch off battery charger

4) Wait 5 minutes or so, then go back to 1)

Nice and simple - programmable thresholds and time would be useful as would an additional switch to use with something else on really sunny days.

My searching shows Solar Diverters like iBoost designed to give variable loads to immersion heaters or EV chargers - I don't want this, just a simple switch.

Does such a thing exist?

thevilla

I have something similar using a raspberrypi which monitors the solaredge inverter using their API. When solar reaches a threshold it switched on a smart plug which switches on the dishwasher.  The dishwasher was previously stopped mid cycle and thinks there's been a powercut!

Mine doesn't account for whether the generation is surplus or not but I could modify it to use the Zappi API.

All this does need some programming knowledge but if you fancy trying there's loads of help online and raspberrypi are pretty inexpensive.

ctdctd

thevilla said:

I have something similar using a raspberrypi which monitors the solaredge inverter using their API. When solar reaches a threshold it switched on a smart plug which switches on the dishwasher.  The dishwasher was previously stopped mid cycle and thinks there's been a powercut!

Mine doesn't account for whether the generation is surplus or not but I could modify it to use the Zappi API.

All this does need some programming knowledge but if you fancy trying there's loads of help online and raspberrypi are pretty inexpensive.

Thanks.

I suspect I'll need a current clamp to read if generation is surplus. My Smart Meter display gives me the info but as far as I can see, there is no API to get the data out of it.

I was hoping there was a commercial product that did something suitable but I might need to dust off my programming and electrical skills!

QrizB

You could use an iBoost to drive a contactor but that seems excessive; the hardware would cost far more than the energy you'd save. (In fact that's a problem with iBoost-like dvices in general.)

You *could* make a device to detect the "constant red" LED you get on your electricity meter when you're exporting, and turn the charger on then. You wouldn't need to worry too much about sensing the export power; if you're exporting less than the charger draws, switching on the charger will stop the export and the red LED will go out.

It wouldn't be too hard to incorporate a delay before reconnecting to stop it cycling on and off repeatedly under low generation conditions.

thevilla

ctdctd said:

thevilla said:

I have something similar using a raspberrypi which monitors the solaredge inverter using their API. When solar reaches a threshold it switched on a smart plug which switches on the dishwasher.  The dishwasher was previously stopped mid cycle and thinks there's been a powercut!

Mine doesn't account for whether the generation is surplus or not but I could modify it to use the Zappi API.

All this does need some programming knowledge but if you fancy trying there's loads of help online and raspberrypi are pretty inexpensive.

Thanks.

I suspect I'll need a current clamp to read if generation is surplus. My Smart Meter display gives me the info but as far as I can see, there is no API to get the data out of it.

I was hoping there was a commercial product that did something suitable but I might need to dust off my programming and electrical skills!

Shouldn't be too difficult to get a RPI to read the voltage on the clamp and determine the power flow.  Sounds like it could be fun to do if you're that way inclined

EricMears

ctdctd said:

Thanks.

I suspect I'll need a current clamp to read if generation is surplus. My Smart Meter display gives me the info but as far as I can see, there is no API to get the data out of it.

I was hoping there was a commercial product that did something suitable but I might need to dust off my programming and electrical skills!

Have you looked at 'Glowmarkt ?
https://glowmarkt.com

Reed_Richards

ctdctd said:

So, what I want is a Gizmo that does something like:-

1) Is net generation > 300W?

2) If yes, switch on battery charger

3) If no, switch off battery charger

4) Wait 5 minutes or so, then go back to 1)

How will your gizmo know when the battery is fully charged?  Or doesn't it matter?  What happens if the charger is on, somebody (e.g.) switches on a kettle and net generation goes negative?

ctdctd

Reed_Richards said:

ctdctd said:

So, what I want is a Gizmo that does something like:-

1) Is net generation > 300W?

2) If yes, switch on battery charger

3) If no, switch off battery charger

4) Wait 5 minutes or so, then go back to 1)

How will your gizmo know when the battery is fully charged?  Or doesn't it matter?  What happens if the charger is on, somebody (e.g.) switches on a kettle and net generation goes negative?

Doesn't matter if batteries are fully charged as it's a smart charger. 
If net generation goes below the threshold in 1) or negative, the charger needs to switch off. 

ctdctd

EricMears said:

ctdctd said:

Thanks.

I suspect I'll need a current clamp to read if generation is surplus. My Smart Meter display gives me the info but as far as I can see, there is no API to get the data out of it.

I was hoping there was a commercial product that did something suitable but I might need to dust off my programming and electrical skills!

Have you looked at 'Glowmarkt ?
https://glowmarkt.com

Sort of - they don't have anything in stock that supports real time & V2 Smart Meters - but might have this month! 

Meatballs

https://openenergymonitor.org/ fed into home assistant automation 

ctdctd

Well, after a lot of internetting, I've decided the existing solutions are overkill and / or too expensive for what I need.

I've ordered a clip on current transformer, a Wemos D1 mini and a set of 433Mhz TX/RX boards to talk to wireless sockets.

Last programmed anything 20+ years ago - I may be some time - wish me luck!