ukpreppergrrl wrote: ↑Wed Aug 03, 2022 8:06 pm
jennyjj01 wrote: ↑Fri Jun 10, 2022 11:12 am
It's also shown me how much the fridge freezers need to run on, including the big burst of current used to start up the freezers
E.g. Modern under counter freezer uses bugger all MOST of the time, but takes 650W for a few seconds to start up and then 130W to tick over. On the basis of measurements, I'll decide what ( cheapest) inverter to buy, and how many panels and batteries. I'm still on my mission to get the best, minimalist, cheapest solar setup
Just some more real world figures to add to your experiments and consider.
ukpreppergrrl, Thank you for a brilliant post!
You've explained very well what I have discovered as my setup has grown. My mind was blown by the current in the 12V side. And realising that I needed super fat quality cables.
I discovered the battery Sag that you mention. I also discovered that there is 'Cable sag': With my 1500W inverter off a new and fully charged 110AH 12V Leisure battery, I was having the inverter trip out. It was voltage dropped in the temp cables that I was using ( A pair of 5ft jump leads. Dropping about 1.3V in each lead, it made the inverter trip out at any load over about 150W !!! I initially though the inverter was faulty or the battery was to blame
Fixed that with Monster Fat 35mm^2 SHORT 600mm leads
You're dead right about the currents drawn. My leads are short as can be and rated about 250A. Custom made at about £8 per short cable.
My project got shelved a while for a covid break, but another 170W of panels goes up this week, bringing me to 270W. I plan to rig a time switch relay, because even from fully charged, my batteries will barely run one fridge freezer overnight, where obviously it gets no solar. Resilience will only be as good as KWHrs of battery capacity. To be totally off grid, I'd need enough to run my load through the night and enough panels to feed the load and charge the batteries during daylight.. That's quite a stretch, so for now I'll supplement energy in from the grid through a scheme which is still in the design stage.
I've actually got a few design ideas in progress of being built..... a Relay to switch my load to regular mains at any time that the battery gets depleted PLUS a regular battery charger on another relay to stop the battery ever getting depleted in the first place, except in grid down. I.e. on a time switch, or maybe triggered by a smart socket. Design decisions depend on whether I'm happy to bring energy in from the grid, and how much to anticipate being off grid. In an ideal world I'll be sucking every possible watt out of my panels and my batteries will stay mostly charged, so they don't wear out. Just used for smoothing until grid down.
I've acquired a second inverter... A 24V one of (I think) 2000W rated That's for another later stage to the project.
So far, lots of pre-owned low price parts. Lots of testing with multimeters and watt meters. Worth their weight in gold. Discovered things like 'energy wasted in the charge controller and energy needed just to have the inverter ticking over.
I've learned SO much by experimenting and interrogating my 'Electrics guy'. It's certainly possible to get A LOT of solar resilience for a tiny fraction of the price of an off the shelf power station. About £300 so far including panels and the spare second inverter.
Incidentally, though my primary load is a 240V fridge freezer, I recognise the terrible waste inverting battery back up to mains. I've already started to discover what can run of native 12V.... LED ceiling lights... Garage door opener,,, Security cameras... Home phones... Router,
I even discovered a 12V small TV in the loft. Evenyually I might buy some 12V appliances. I have a 12V immersion heater for now: ) So that's coffee sorted.