Overview
Model: Back-UPS ES 750
Battery Details
Specification | Detail |
---|---|
Image | |
Part | AJC-D7S |
Voltage | 12v |
Capacity | 7Ah |
Type | Sealed Lead Acid (AGM) |
Terminals | F2 |
Length | 5.94 in / 150.9 mm |
Width | 2.56 in / 65 mm |
Height | 3.7 in / 94 mm |
Weight | 4.5 lbs |
Considerations
Lithium Ion
Using Lithium Ion batteries is an option but would require modifying the charge circuit in the UPS. A lead acid battery will charge using a voltage of 14.4v unlike a 3S battery which would charge at a voltage of 12.6v.
Example:
3S7P
14Ah
Questions:
- Could we use a BMS with a DC-DC drop down converter to modify the DC going to the BMS to 12.6v?
Lithium Iron Phosphate
Using Lithium Iron Phosphate (LiFePO4) may be a better idea since it is a drop in replacement for Lead Acid. Charge Voltage for a 4S pack would be 14.4v (3.6v/cell).
Spec | Value |
---|---|
Model | ANR 26650 M1B |
Chemistry | LiFePO4 |
Dimensions(DxH) | 26mm(1.0") x 65.15 mm(2.6") |
Max Current | 50A |
Nominal Voltage | 3.25V +/- 0.05V Nominal, 3.2V Average |
Nominal Capacity | 2500 mAh (at 0.2C rate, 3.65 +/-0.05V cut-off) |
Charging current |
|
Temperature Range |
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Image |
Our battery has the following dimensions:
Length | 5.94 in / 150.9 mm |
Width | 2.56 in / 65 mm |
Height | 3.7 in / 94 mm |
150/26 = 5.7
94/26 = 3.6
We could fit about 15 batteries in the space of our current lead acid battery.
Conclusion
Will leave it for now. If I had some good LiFePO4 cells kicking around I may see how many I could fit. The ones I have are old and have a max capacity of about 1500 mAh.
References
Reference | URL |
---|---|
DIY Replacement Battery 12V 18650 Li-ion For APC Back-UPS 650 | https://www.yousun.org/archives/101 |
Replace battery | https://www.youtube.com/watch?v=_dydlRHFjrc |
Details | https://www.yousun.org/archives/660 |