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 batteries to use it?
Because I have a 20000mah inui battery that is rated for 12v at 1.5A is this a good practice to buy several of these (since they are about 20 bucks) disassemble them and use them as ups batteries?
No, your UPS is tailored to the characteristics of the lead-acid charge/discharge cycle. Some LiFePO4 battery assemblies are built with charging electronics that simulate lead-acid for a drop-in replacement, but those are never cheaper than traditional lead-acid batteries.
This is correct.
Additionally, you would not want to substitute a larger or smaller capacity battery as the charging cycle of the UPS is built for a specific capacity.
A larger battery generally works fine with an older, dumb UPS. You will just have to connect an external charger if the battery gets deeply discharged. Adding a cooling fan to the UPS would be a good idea since it will be running for a longer time though.
I’ll admit, it could, but the battery conditioning might still struggle.