3 ms·

"What in the WORLD!? This is a tiny 12v house lead acid battery. It is not designed or intended to be used as a stationary power source to POWER A HOUSE!" It's

by rsync 6y ago

"What in the WORLD!? This is a tiny 12v house lead acid battery. It is not designed or intended to be used as a stationary power source to POWER A HOUSE!" It's a totally reasonable use-case and is done all the time for a variety of reasons. It works just fine using an inverter like this one: https://gpelectric.com/products/3000-watt-industrial-pure-sine-wave-inverter/ https://gpelectric.com/products/3000-watt-industrial-pure-si... ... and although we use a different emergency power solution now[1], we used an inverter like this with the plain old car battery in my Chevy Silverado for 5-6 years. The issue is not that a 12v lead-acid battery can't be used for this - it's a common use-case, actually - it's that the backing store for that 12v battery is usually an ICE with a full gas tank and not a big bank of lithium batteries. But I don't see why it wouldn't work just fine ... [1] The excellent DEWALT FLEXVOLT Power Station which is a charging station for four 9AH tool batteries but you can also plug into it and get power out. So you use the batteries you already have for tools, you get a nice quad charger, and you have hours of 15A power out.

random5634 6y ago
The power station uses four lithium ion batteries. That is different than a lead acid. The amp hours on these is at 20volts. So some quick math 9 Amp-hours at 20 volts is .18kWH x 4 batteries is .72 kwh. Not bad (though far below Tesla's battery which may be 100x that). A good car battery might be 40AH at 12 volts or .5kWH? But if discharge rate is high you get less capacity. Someone running a 2kW inverter, is going to discharge the battery in 15 minutes. Then you add Peukert constant [1] of 1.2 or so? Maybe half that? Then you realize you need to stay above 80% DoD? Even worse? So a 2kW continuous load is CRUSHING this battery. A light bulb is 100 watts. any type of motor / blower etc is going to be what would be considered a high draw. When a refrigerator starts you may also be load spiking. All this could damage the charging circuit to the battery which was almost certainly not designed for this load story (hopefully not) You may be discharging at a higher rate then the desired charge rate, so just keeping an AGM charged at high draws may wreck it. Plug in a 20W charger? No problem, the math says that should be pretty easy to handle. A 2,000 watt inverter? Short burst? No problem probably. Continuous - probably going to be a problem as the user found out. There's a reason everyone refuses to replace these batteries used this way. [1] https://en.wikipedia.org/w/index.php?title=Peukert%27s_law https://en.wikipedia.org/w/index.php?title=Peukert%27s_law Note - I absolutely think Tesla should support this use case, a 100kwh battery pack in your house for when the power goes out would be amazing. The the HV pack could absolutely support house loads for most everyone. You've paid 60K for the battery and vehicle, what a use case that would be! But they'd need to a different path probably through charging cable and the regulatory hassle could be annoying - pushing a lot of power back into household circuits - the liability etc risks go up (but could probably wire as if it were a generator with a transfer switch and islanding etc)

by rsync 6y ago

random5634 6y ago

The power station uses four lithium ion batteries. That is different than a lead acid. The amp hours on these is at 20volts. So some quick math 9 Amp-hours at 20 volts is .18kWH x 4 batteries is .72 kwh. Not bad (though far below Tesla's battery which may be 100x that). A good car battery might be 40AH at 12 volts or .5kWH? But if discharge rate is high you get less capacity. Someone running a 2kW inverter, is going to discharge the battery in 15 minutes. Then you add Peukert constant [1] of 1.2 or so? Maybe half that? Then you realize you need to stay above 80% DoD? Even worse? So a 2kW continuous load is CRUSHING this battery. A light bulb is 100 watts. any type of motor / blower etc is going to be what would be considered a high draw. When a refrigerator starts you may also be load spiking. All this could damage the charging circuit to the battery which was almost certainly not designed for this load story (hopefully not) You may be discharging at a higher rate then the desired charge rate, so just keeping an AGM charged at high draws may wreck it. Plug in a 20W charger? No problem, the math says that should be pretty easy to handle. A 2,000 watt inverter? Short burst? No problem probably. Continuous - probably going to be a problem as the user found out. There's a reason everyone refuses to replace these batteries used this way. [1] https://en.wikipedia.org/w/index.php?title=Peukert%27s_law https://en.wikipedia.org/w/index.php?title=Peukert%27s_law Note - I absolutely think Tesla should support this use case, a 100kwh battery pack in your house for when the power goes out would be amazing. The the HV pack could absolutely support house loads for most everyone. You've paid 60K for the battery and vehicle, what a use case that would be! But they'd need to a different path probably through charging cable and the regulatory hassle could be annoying - pushing a lot of power back into household circuits - the liability etc risks go up (but could probably wire as if it were a generator with a transfer switch and islanding etc)