Off grid, I boiled water using an old automotive battery. The voltage dropped from 12.5V to 10.8V during 2 minute boil. Single cup should be sufficient for a warm beverage or cooking a cup of rice or beans in an emergency. Now to test battery life over multiple cycles.
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Total cost was $100. $85 for the DC/AC Inverter. $4 for a battery box https://www.amazon.com/gp/product/B00EOX2QJC … and another $5 for some quick access battery terminals https://www.amazon.com/gp/product/B0060YHLJS …. Not a bad investment since I live in a major Earthquake zone of the Pacific North West. Good insurance.
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2 cups was it. Battery undervoltaged after that and the inverter shut off automatically. A bit disappointed as I expect it will take a full day to recharge via solar. Might try bridging with a newer car battery. This one was removed from service and is 10 years old already.
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If a car battery is rated 50Ah, I would have hoped to have gotten 20-30 minutes of 1kW of coffee making out of it discharging at 2C - 100 Amps. Looks like I got about 5 minutes instead. I hate it went the numbers don't work out.
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Annoyed with last night's results. Battery fully charged again at 12.6V. Running a battery test this morning using my BML space heater, a 100W incandescent bulb as a test load. Drops voltage to 12.2V (vs 10.8V on 1kW Keurig). Will see how long inverter stays running at 0.2C load.pic.twitter.com/Kdee4aAHbQ
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Well this explains everything. T=-1m : 12.6V : No Load T=0m : 12.2V : 100W Load T=25m : 11.5V : 100W Load T=30m : 10.5V : Shutoff. My old 50Ah battery only gave me 5Ah. Maybe I should recycle it after all.
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FWIW, just checked my records and this battery was purchased new in 2012, so only 6 years old. That said, I replaced it in 2017 as the vehicle lights were left on twice, draining the battery to the point of needing a jump start. I wish cars used Lithium-Ion batteries.
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In closing, battery was a disappointment, but 1kW KRIËGER Inverter was not. It joyfully boiled water while displaying V and W and auto shut off. For my Oh-Shit kit, will add a second set of battery quick connect clamps and 4 AWG cables so I can bridge two batteries in emergency.pic.twitter.com/lIFfFsK5q7
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This really surprised me : In modern cars alternators produce 70-180 Amps ( 1kW and 2.5kW). Seems like boiling water solution is to idle a vehicle for a few minutes with the inverter hooked up. Not renewable, but would easily last for weeks on full tank.https://www.quora.com/How-many-watts-can-a-car-alternator-make …
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Replying to @bml_khubbard
Or you could just heat directly with combustion under a percolator. :-)
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If you want to make it renewable, replace with a parabolic mirror.
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Replying to @RichFelker
This is very cool: https://www.amazon.com/Solar-Kettle-Thermal-Survival-Temperature/dp/B009YFSKKY … If I was living off the grid, I'd look into something like this. Seattle can be so fickle sunlight wise though. What I like about my 100W solar panel + Battery solution is I can integrate cloudy days over time. Mirros can't do that.
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