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Switching out UPS batteries (lemmy.ml)

submitted 3 weeks ago* (last edited 3 weeks ago) by foremanguy92_@lemmy.ml to c/askelectronics@discuss.tchncs.de

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I have an UPS with two 12v 7ah lead batteries. If I want to change the batteries I would typically go with lead batteries but here's my question, can I use some portable mobile power banks to use it?

Because I have a 20000mah "INUI" lithium power bank that is rated for 12v at 1.5A, is it a good practice to buy several of these (since they are about 20 bucks) disassemble them and use them as ups batteries?

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[–] ChaoticNeutralCzech@feddit.org 0 points 3 weeks ago* (last edited 3 weeks ago)

What's an "inui battery"? Do you mean the INIU B5 powerbank?

Powerbanks can be used directly as USB UPS devices if their output is enabled while charging but most devices you would power with them already have "UPS" functionality (built-in battery). By "disassembling them" you mean using their raw cells? That gets you 3.7 Wh per dollar but I recommend going for the similarly priced raw LiFePO4 cells unless you want to lug them around, getting you great longetivity and cycle life. You need a BMS anyway if you put them in series, I recommend a 4S or 8S config to avoid dealing with large currents and lossy step-up conversion. They can save you quite a bit of money if you charge them daily with solar power. Professional solutions are available, whether they are worth it depends on how much you trust your skills.

What UPS would you put the cells in, anyway? Don't use one with a lossy and costly mains inverter unless you're powering something that really needs mains. You can find many that have ATX outputs, or if you're adventurous some ATX supplies can be run from 12V DC (exact!) supplied into the 12V rail and 5V into the 5Vsb rail because they use an inverter and buck converters to create all the other voltages from 12V. These can be identified by counting the mains transformers and windings of the main transformer. Don't backfeed 12V while it's powered from mains. You can use the internals from a cheap car USB adapter (they work from 9 to 30 volts) for 5Vsb from your 4S-8S cell configuration, but the cell-voltage-to-12V supply will have to be a beast - still smaller than the mains inverter you'd need.