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[–] 3 points 23 hours ago (3 children)

Oh, this makes more sense. I never thought about a powered UPS as being similar to a car battery with an alternator.

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  • [–] 8 points 21 hours ago (2 children)

    An alternator is actually just a small generator! It converts rotation (from the engine spinning a pulley) to ~13v to ~15v DC at up to some level of current spec (usually 50Amps or more). Some of that goes to the battery to charge it, and some goes to powering accessories in the car.

    A UPS simply has an AC to DC charging circuit to perform that function, converting mains electrical voltage (~120v AC in the USA, varies by country) to ~14v DC.

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  • [–] 2 points 13 hours ago* (last edited 11 hours ago)

    To add the little bit I know to the comments above.

    Car batteries are not the same as AGM (often sold as scooter or marine batteries) or newer LiFePO4 batteries.

    While I think AGM and car batteries both are lead acid, car batteries are designed to have one big discharge to start an engine and then recharge from an alternator. The other batteries are designed for a slower discharge over time.

    The batteries commonly used in battery backups were usually AGM type, and now the LiFePO4 (usually used for solar) are starting to be used for backups and are much safer (I think they don't off gas as much?). The original post was a picture of a solar battery, but an SLA (sealed lead acid, of which some are agm) one from harbor freight.

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