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diy solar

Use of water distiller as battery capacity measure or inverter efficiency measure

outsider

Solar Enthusiast
Joined
Jun 25, 2024
Messages
510
Location
Colorado USA
I used distilled water for various things, and it occurred to me that the distiller could be used for measurement purposes. The distiller consumes about 850 W and distills a gallon of water in about 4 hours. So, first off, that's about 3.4 kWh. So, for example can an alleged 280 or 300 or 320 Ah (12 V) battery do the whole gallon? But, better, if it quits early, or still has charge and you can start a second gallon, you can make the measurement actually quantitative. To the extent that you always use the same temp water, and you fill the distiller the same amount every time, you can actually make measurements just by measuring the total amount of distilled water.

There is a minor catch in that a decent amount of energy is required just to bring the water to boiling, before the first drop of distilled water appears. Second, the inverter (and the distiller!) may have some inefficiency, so after the water is boiling, you don't get quite the ideally calculated amount of water, for each additional kWh consumed.

But, I've found that a 200 Ah battery can't distill a whole gallon, but both the Dumfume 280 ("300") and the Techcella 320 Ah batteries can. Actually, the Dumfume distills more water in the second gallon than the Techcella does (!)

By measuring the water using the same battery and inlet water temp, I get repeatable results within 1-2%, which is 1-2 ounces error in a gallon.

So for example I can see that my 100 Ah battery is quite anemic, and that the Ecoflow units also have significantly less than stated capacity. A given battery could be checked again from time to time to see how its capacity degraded. Etc.

All this - plus, I get distilled water!
 
Using the same battery with two different inverters, the more efficient inverter will distil more water. Using the same inverter with two different batteries, the battery with more capacity will distil more water.
 
Using the same battery with two different inverters, the more efficient inverter will distil more water. Using the same inverter with two different batteries, the battery with more capacity will distil more water.
I'd buy Victron Smart Shunt way before the end of the first gallon ...
 
When the battery dies, the inverter stops and then the Kill-a-Watt loses its display and data. I should hack one to run off a different power source, other than the one it is measuring. At least the Smart Shunt can broadcast its last message to something else.
 

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