Overview

Model: Back-UPS ES 750

Battery Details

Lithium Iron Phosphate Battery Replacement

I ordered this LiFePO4 battery off amazon which is the exact same size as the original.

Cost: $63 CA plus Taxes.

NASTIMA 12V 8Ah Rechargeable Lithium Iron Phosphate Battery,Built-in BMS, 4000+ Cycles LiFePO4 Battery Pack

https://www.amazon.ca/dp/B0B5WBHDDN?smid=A32QMQUDJWY3FO&ref_=chk_typ_imgToDp&th=1

Tested this battery's capacity pulling 2A. Capacity came up as 8.8Ah.

Note: Battery voltage stays at 0v once discharged until voltage is applied. Does not bounce back on it's own.

I performed a capacity test on the old lead acid battery. The battery had a 3 Ah capacity when drained to 10.5v at 2A.

Testing the Battery Under Load

I ended up having some quick shutdowns after replacing the battery.  

On this UPS I have the following items connected:

Ok, so battery has a 10A max output, which is 1A at 120V.

Lets figure out what are real power usage is....

References