On 13.02.19 01:05, Greg Bentzinger via Emc-users wrote: > A trend I have been noticing in the DIY solar crowd is to salvage the > batteries from wrecked Tesla or Mercedes Hybrids. The Batteries are > series wired for output in the 400VDC range but can be rewired in > parallel for a 50-60VDC output. Just need to be sure the charge > controller has a custom or Li-po setting.
I'm not sure there are any wrecked Tesla or Mercedes Hybrids in Australia yet. I could lose a hand in the scrum for the battery or motor. What also scares me about Li-po is what happened to early Dreamliners, smartphones, and a few other gadgets which went up in smoke. LiFePO4 batteries aren't cheap, but they don't appear to catch fire, and are said to be more robust than Li-po. The redflow ZnBr flow battery is a techno-nerd's dream, but it's too expensive for me. NiFe batteries are said to be robust and long lasting, but fussy to care for. > I hope to rig up a 6Kw bank here at the ranch so it can handle the > Inrush starting demands of my deep well pump. Yup, even the latest hybrid inverter will output around 60% more taking power from the PV array than it will from the batteries. (Saves melting 'em, I'll admit.) Here the standard offering for domestic use is a 10 kWh bank, with double that advised for off-grid. (Two 10 kWh banks would be good for 6 kW drain, but it'd take an above-average inverter to do it.) > If I can off load the spare refrigerator, freezer chest and well pump > that will be about half my domestic electric cost. With luck I can > eventually get the whole house on solar + wind power. There's an article out in webland on converting a freezer to a fridge, to take advantage of the better insulation and that the cold air doesn't all tumble out when the door opens. We've been off-grid for 53 years, first candles and kero lamps, finally a generator, but still a gas fridge. That's not much chop on a 45°C day. I'm putting in 24v LED lighting, and a little 24v fridge/freezer for its much lower power consumption - important after the sun goes down. I was going to put a heat pump (for hot water) in the roofspace to cool that instead of installing aircon, but a belated calculation shows I'd need to blow through 800 m³/h of air for 4.3 hours to raise 50 litres of water by 20°C if the air is cooled by 20°C. That'd do me for summer, else the water heating is by in-flue heat exchanger on the wood heater. What I'd _really_ like to do now is find a smallish water-source heatpump (they all seem to be very big units for slab heating from a lake or groundwater). A modest unit could slowly cool a one or two tonne indoor insulated water tank while heating water in the HWS. Storing tens of kWh of "cool" in this cheap way would be great for cooling after the sun goes down. (Might have to import one, if I can find it. Hmmm, I have a fat 230:110v transformer in the garage, just in case.) > The shop will always have to be on the grid, the big CNC's have 26Kw > or higher startup loads. If the house is off grid then my electric > bill will be a 100% business expense. (/Greg) That's serious power. My machines are only 1.5 kW each, and the battery would only be needed for a cloud coming over, during the day. There are a _lot_ of 100% clear days 8 or 9 months of the year out there. One thing I've cottoned onto just in time is the fallacy of "Point your array toward the equator for maximum output." That'll drop your off-grid aircon out (or flog the battery) in the late afternoon when it's still hot, but the sun's both dipped and swung a surprising amount away from the equator as it's going down. I'll now be splitting my array - half facing due north (southern hemisphere), and half west-facing to keep an aircon plugging away on a 45°C afternoon. The hybrid inverter serves as both PV inverter and battery inverter/charger, previously separate in AC-coupled systems, saving quite a bit of cost. I like that a lot, and will be watching the new offerings until I have to screw one to the wall. We're limited in the array oversizing allowed if we're on-grid, but off-grid it's a case of anything the inverter is rated for. As a 6 kW array will only deliver 3 kW on a good winter's day, according to the boffins, I figure on passing a few extra panels up to the installers. In summer the excess will at least shade the roof. (And pay dividends on an overcast day.) Hope there's enough useful stuff there to make the OT worth it. Erik _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
