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Sla or li ion

g2c

Member
Hello, i made a 12v ups with a 9AH sla and motopower maintainer for a project consuming ~1A. Now i need another for a ~2.5A project (2 arduinos, router modem..) and was thinkig of a 30AH li ion which can be found for <$30 on AliExpress.

Is it a good idea?

Can someone recommend a maintainer for such a battery?
 

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rjenkinsgb

Well-Known Member
Most Helpful Member
I'd consider those batteries a scam.

The dimensions given for that battery (110 x 70 x 20mm) are just big enough for six, 18650 cells. It's totally impossible to get 30AH in that.
It's likely an accidentally-on-purpose extra zero in the print, which I've seen many times on ebay aliexpress etc. batteries and cells. Or, some sellers add the capacity of the series cells, another scam.

Plus from the way the shrink sleeve shows the ends of the cells etc., there does not appear to be any protection / balance board included, which makes it an accident waiting to happen!


Build your own, it's safer and will have genuine capacity.

To duplicate that you need several three-cell chains in parallel, plus a decent three cell balance and protection board.

I posted a similar setup for another user, showing both a six cell (3S2P) pack with protection board, and the charge / bypass circuit to make it work as a "UPS" type system.



You could also get some big RC flight batteries - they are reasonably cheap, eg. three cell 6AH

Add a balance / protection board as above. You could parallel them for higher capacity, either directly once you have charged them to exactly the same voltage, or add a balance board to each to make two-terminal packs like mine, then parallel them.
 

g2c

Member
Thank you very much.
Indeed it looked too good to be true. I made same measurements: with 3 music streams and an long wifi ftp to from pc to phone the router barely exceeds 600mA. the arduino with enet shield 185mA@5V=> ~86mA @12V assuming 90% efficiency so one router+ 2 arduinos (2nd w/o enet) would have nom consumption < 760mA. I still need to measure the phone to enet box but I dont have a 5.5X2.5 male. Yet I think Ill stick to the SLA and get a 20AH one locally for ~190ILS =~$55. The plus would be same technology in the barn and at home.
 

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