Mains backup to 12v solar power

[Tangoman]

Hi Guy's,

I currently have a single solar panel on my shed connected to a 12v leisure battery through a 12v charge controller, this powers 12v lighting, a Google Home Mini, a WiFi mesh node and a WiFi CCTV camera and these items run under 12v (with adapters where needed) I also have an inverter connected to the battery, should I want 240v to power a mains appliance.

However I've recently found the leisure battery dropping to below 12v of a night time, the lightning is only used when necessary and not all the time.

So now to my question:
I'd like to run mains to the shed, but rather than waste the solar setup, I'd like it to compliment it, switching to mains when it needs to, I've seen an ats that appears to suit my needs, but it seems to only output 240 using an inverter to take the 12v from the solar power, I'd only need mains to recharge the battery and maybe power the occasional mains appliance and don't want to rewire the other devices.

Your thoughts please?

 

[mikefitz]

A few questions.
How are you going to run the cable to the shed , what cable, how is protected mechanically and how is it connected to the household supply ?
Have we met on another forum?

 

[Rednecktek]

Cheapest way?
Mains -> Power Strip -> Battery Charger (any decent car charger from the auto store will do fine, the more amps the better of course) -> battery
+
Battery -> Fuse -> 12v Pure Sine inverter -> 240v devices

Simplest way?
Mains -> PowMr 1000w All-In-One (or comparable unit)-> Power Strip -> 240v devices

The MPP unit will take in the solar panel input (which you probably need more of depending on how big your panel is), charge the batteries, and output mains power. If the battery gets low and there isn't enough solar, it'll take in the mains power and use that to charge the batteries and provide AC output.

Since your other 12v stuff is already wired up to the battery, connecting another set of wires isn't going to be difficult at all as your existing stuff isn't tied into the AIO anyways.

 

[1234enough]

On a small PV set up I have running security system /wifi router, to overcome this very problem I used an old laptop adaptor and a buck converter that you can set the output voltage on.
Laptop adaptor stays plugged in and live at all times ( yes not fully efficient, but only uses a few ma with no load on it ) , then the buck converter is set to a voltage for keeping battery from dropping too low, once PV starts up in morning and produces more than the Load the buck converter stops supplying anything.
Been working well for over a couple of years.

 

[Tangoman]

A few questions.
How are you going to run the cable to the shed , what cable, how is protected mechanically and how is it connected to the household supply ?
Have we met on another forum?

4mm armoured cable run as a spur from an external house socket, I have a small consumer unit to fit in the shed, so it'll all be fused well enough!

I don't think we have met before, unless you're into Home Assistant and have seen me on the FB page

 

[Tangoman]

This is what I was considering using https://a.aliexpress.com/_mruZTHe
But is it overkill? All I really need is a means to switch on a mains powered battery charger when the battery gets below a given voltage

 

[Rednecktek]

You mentioned you'd need it to charge the batteries AND provide the occasional power for AC devices. For that you need an inverter AND a charger which mean either having 2 devices OR an AIO that does both and has the ATS built in already. If you just need to charge batteries, a bog standard car charger can be connected and left connected so it's helping your solar panel work all the time.

All and ATS does is change from one source to another and doesn't convert the 240v mains power down to 12v to the battery. If you just wired in the ATS then it would turn on the mains coming in once the battery went completely dead and feed the mains out to something else. What yo need is something that will convert the mains voltage from 240v to 12v when the solar can't keep up. The AIO, and units like it, can be programmed to supply power from the solar panels first, then kick in the batteries if the panels aren't enough, THEN kick on the mains if the battery is getting too low still. Once the sun comes out or the batteries get full, it turns off the charging to the batteries and waits for the sun to come out and start charging again. Rinse, repeat.

The ATS is just that, a switch. The only way to make that work would be to run mains to a battery charger, then have the battery charger as the #2 input to the batteries after the batteries themselves are too dead to keep the switch active, which is usually so low you've long since damaged your battery by draining it WELL below its 50% DOD threshold.

 

[Rednecktek]

This would be perfect if you can find the EU model listed.

 

[Leeds]

I also have an inverter connected to the battery, should I want 240v to power a mains appliance.

You say you're losing power overnight without the lights on.

Is there any chance that you've left the inverter hooked up to the battery around the clock and not simply when you need 220?

Inverters chew through energy when they are powered up, even when there is zero load.

If you have in fact left the inverter on then I'd suggest powering it down for a few days to see if your system works as designed. If so, all you need to do is turn the AC off when you don't need it instead of running the grid to the shed...