Post by papaof2 on Dec 4, 2023 17:00:14 GMT -6
I rarely recommend parts from AliExpress but I know that LiitoKala has historically made good batteries.
With many small UPS units using a 7AH, 8AH or 9AH AGM battery, you could build a replacement LiFePO4 battery pack that's comparable in available energy because of the long, flat discharge curve of LiFePO4 versus AGM.
An example is the 3.8AH battery pack I built with surplus cells from batteryhookup.com. That was to replace a 4.3AH AGM battery pack in a small UPS. With the same load, the LiFePO4 pack lasted within 5 minutes of the UPS manufacturer's spec for the runtime of a new 4.3AH AGM battery: 8 hours, 27 minutes on LiFePO4 pack versus rated 8 hours, 30 minutes on a new AGM.
LiFePO4 cells here: www.aliexpress.us/item/2251832800264287.html
That's their US warehouse and the shipping is free (if sometimes slow).
Cell specs: 6.5AH, 35 amps continuous discharge (maximum current is 55 amps but that has a short time limit). A "12 volt" LiFePO4 battery would be at about 13 volts so 13 * 35 = 455 watts into the UPS' inverter and at 80% efficient that's 455 * 0.8 = 364 watts output; at 85% efficient that's 455 * 0.85 = 387 watts output. Likely to work in any UPS rated at less than 500 watts if you don't fully load it.
You would need to add a 4s 40amp BMS and some Kapton tape for insulation or you could 3D print a case for the battery. Kapton tape works and is much quicker ;-)
The cells are $5.07 in single quantity, $14.74 for 4 cells - that's one 12 volt pack at $14.74, $42.90 for 12 cells - that's $10.73 each for three 12 volt packs. You can find 4s 40 amp LiFePO4 BMS units on Amazon for under $5 each. Do some soldering and add that Kapton wrap and you could have a near lifetime UPS battery for under $20.
You could also use a bigger BMS and use these packs to replace similar sized packs in old jumpstart units or the starting battery for a small gas engine (generator, maybe?).
In 20 reviews, there are 17 five-star and 3 four-star so the cells appear to live up to their advertising.
With many small UPS units using a 7AH, 8AH or 9AH AGM battery, you could build a replacement LiFePO4 battery pack that's comparable in available energy because of the long, flat discharge curve of LiFePO4 versus AGM.
An example is the 3.8AH battery pack I built with surplus cells from batteryhookup.com. That was to replace a 4.3AH AGM battery pack in a small UPS. With the same load, the LiFePO4 pack lasted within 5 minutes of the UPS manufacturer's spec for the runtime of a new 4.3AH AGM battery: 8 hours, 27 minutes on LiFePO4 pack versus rated 8 hours, 30 minutes on a new AGM.
LiFePO4 cells here: www.aliexpress.us/item/2251832800264287.html
That's their US warehouse and the shipping is free (if sometimes slow).
Cell specs: 6.5AH, 35 amps continuous discharge (maximum current is 55 amps but that has a short time limit). A "12 volt" LiFePO4 battery would be at about 13 volts so 13 * 35 = 455 watts into the UPS' inverter and at 80% efficient that's 455 * 0.8 = 364 watts output; at 85% efficient that's 455 * 0.85 = 387 watts output. Likely to work in any UPS rated at less than 500 watts if you don't fully load it.
You would need to add a 4s 40amp BMS and some Kapton tape for insulation or you could 3D print a case for the battery. Kapton tape works and is much quicker ;-)
The cells are $5.07 in single quantity, $14.74 for 4 cells - that's one 12 volt pack at $14.74, $42.90 for 12 cells - that's $10.73 each for three 12 volt packs. You can find 4s 40 amp LiFePO4 BMS units on Amazon for under $5 each. Do some soldering and add that Kapton wrap and you could have a near lifetime UPS battery for under $20.
You could also use a bigger BMS and use these packs to replace similar sized packs in old jumpstart units or the starting battery for a small gas engine (generator, maybe?).
In 20 reviews, there are 17 five-star and 3 four-star so the cells appear to live up to their advertising.