flippineck
- Sep 8, 2013
- 358
- Joined
- Sep 8, 2013
- Messages
- 358
Source #1 is a solar power setup as follows:
3 x 80 watt solar panels "nominal 12V" in parallel
One allegedly MPPT but probably PWM, 10A solar charge controller
2 x 12V 110Ah lead acid deep cycle batteries in parallel
one 1000W cont / 2000W peak pure sinewave inverter (which can realistically handle 600W)
The controller has a pair of input terminals for the panels, a pair for the battery, and a pair marked 'load'.
The 'load' terminals supply 12VDC and are switched off automatically when the battery voltage falls below a programmed level. When battery voltage rises above a seperate programmed level, the 'load' terminals begin to supply 12VDC again.
The controller will only accept certain programmed values such that, the 'load off' voltage is always a bit below the 'load on' voltage.
Source #2 is, a standard UK 13amp domestic mains ring outlet.
You can feed a 12V load directly off the controller 'load' terminals. The controller is only rated at 10A though. I never get much above 9 or so amps from the panels, but I often want to take much more than 10A to feed the inverter. So, I have the system rigged up such that the controller only controls the battery charging; the load terminals are left unconnected and I draw power directly from the battery for the inverter.
The controller seems happy with this and charges ok.
What I was thinking about doing was to use the 'load' terminals on the controller, to power a ganged 3 way, 2 pole relay coil.
Connect the 3 commons to the final outlet socket, one for L, one for N, one for CPC.
Then wire each fixed contact of the relay with one pole going to the inverter (source #1) and the other to a 13Amp plug to go in source #2
That way, when the controller thinks there is enough battery power to run the inverter, it will switch the inverter through to the final outlet. but when the controller decides the battery is too flat, it will changeover the relay and disconnect the inverter before connecting the grid mains through to the final outlet.
Problems I've thought of are..
(1) There'll be a 'brown-out' on the final output when the relay switches. I'm powering kitchen appliances like a steamer, can opener, waffle toaster etc though rather than sensitive electronic devices so hopefully that won't matter? They don't seem to mind when I replug them manually.
(2) What should I do with the CPCs / grounds / earths?
One idea would be to use a relay with three ways, so I'd switch live, neutral and CPC fully and completely.
This would mean that momentarily the load would be left without the CPC connected. Only for a brief time whilst the contacts flick over, and during that time, the live conductors would also be disconnected. My worry here would be behaviour under fault conditions?
Also 2-way relays are common and cheap whereas ones with 3 seperate gangs are less so, so I thought it might actually be better to just connect all the CPC's together permanently and only switch the lives and neutrals.
But would this be OK? I'm guessing (dirty word) the inverter's output's earth / ground / CPC pin wouldn't mind being tied down to the grid's CPC but I vaguely recall something about computer power supplies not being straightforward in the earthing department, wondered if power inverters tended to be similar in that regard? Should I keep the grid's earth and the inverter's output socket earth away from each other?
I was wondering.. if I used a standard relay, it would take 75mA to keep energised all the time the battery was deemed to be OK. Could I convert the load output from the controller to a pulse output with a suitably sized capacitor / resistor, and then use some kind of latching relay rather than one which requires to be permanently energised? Like some kind of flip/flop latch on / latch off type.. I dunno if these are commonly available. but, 75mA at 12V is something of the order of one watt, that should only cause a negligible battery drain shouldn't it.. is it worth bothering making it operate off a momentary pulse?
Thanks for reading to the end of the ramble, thoughts appreciated
3 x 80 watt solar panels "nominal 12V" in parallel
One allegedly MPPT but probably PWM, 10A solar charge controller
2 x 12V 110Ah lead acid deep cycle batteries in parallel
one 1000W cont / 2000W peak pure sinewave inverter (which can realistically handle 600W)
The controller has a pair of input terminals for the panels, a pair for the battery, and a pair marked 'load'.
The 'load' terminals supply 12VDC and are switched off automatically when the battery voltage falls below a programmed level. When battery voltage rises above a seperate programmed level, the 'load' terminals begin to supply 12VDC again.
The controller will only accept certain programmed values such that, the 'load off' voltage is always a bit below the 'load on' voltage.
Source #2 is, a standard UK 13amp domestic mains ring outlet.
You can feed a 12V load directly off the controller 'load' terminals. The controller is only rated at 10A though. I never get much above 9 or so amps from the panels, but I often want to take much more than 10A to feed the inverter. So, I have the system rigged up such that the controller only controls the battery charging; the load terminals are left unconnected and I draw power directly from the battery for the inverter.
The controller seems happy with this and charges ok.
What I was thinking about doing was to use the 'load' terminals on the controller, to power a ganged 3 way, 2 pole relay coil.
Connect the 3 commons to the final outlet socket, one for L, one for N, one for CPC.
Then wire each fixed contact of the relay with one pole going to the inverter (source #1) and the other to a 13Amp plug to go in source #2
That way, when the controller thinks there is enough battery power to run the inverter, it will switch the inverter through to the final outlet. but when the controller decides the battery is too flat, it will changeover the relay and disconnect the inverter before connecting the grid mains through to the final outlet.
Problems I've thought of are..
(1) There'll be a 'brown-out' on the final output when the relay switches. I'm powering kitchen appliances like a steamer, can opener, waffle toaster etc though rather than sensitive electronic devices so hopefully that won't matter? They don't seem to mind when I replug them manually.
(2) What should I do with the CPCs / grounds / earths?
One idea would be to use a relay with three ways, so I'd switch live, neutral and CPC fully and completely.
This would mean that momentarily the load would be left without the CPC connected. Only for a brief time whilst the contacts flick over, and during that time, the live conductors would also be disconnected. My worry here would be behaviour under fault conditions?
Also 2-way relays are common and cheap whereas ones with 3 seperate gangs are less so, so I thought it might actually be better to just connect all the CPC's together permanently and only switch the lives and neutrals.
But would this be OK? I'm guessing (dirty word) the inverter's output's earth / ground / CPC pin wouldn't mind being tied down to the grid's CPC but I vaguely recall something about computer power supplies not being straightforward in the earthing department, wondered if power inverters tended to be similar in that regard? Should I keep the grid's earth and the inverter's output socket earth away from each other?
I was wondering.. if I used a standard relay, it would take 75mA to keep energised all the time the battery was deemed to be OK. Could I convert the load output from the controller to a pulse output with a suitably sized capacitor / resistor, and then use some kind of latching relay rather than one which requires to be permanently energised? Like some kind of flip/flop latch on / latch off type.. I dunno if these are commonly available. but, 75mA at 12V is something of the order of one watt, that should only cause a negligible battery drain shouldn't it.. is it worth bothering making it operate off a momentary pulse?
Thanks for reading to the end of the ramble, thoughts appreciated