Wish you had affordable lithium batteries for UPS?
Apr 7, 2024 2:44:54 GMT -6
feralferret likes this
Post by papaof2 on Apr 7, 2024 2:44:54 GMT -6
If you can do some DIY, you can build your own. I've pointed out some known brand (LiitoKala) cells on aliexpress.com and banggood.com so you can shop there. If the US warehouse of either has the item, you'll get it within a week. In the past month, both vendors have offered LiFePO4 cells from 6 to 20AH. If you consider how much space 25 18650 cells take, fitting 4 or 8 26650 LiFePO4 cells (or some larger cells) into this would be easy. Be nice to have the fitted cell holders and the pre-cut multi-cell nickel strips if you're using lithium-ion cells but I've found that Kapton tape holds the 26650 LiFePO4 cells together just fine - and the perfectionists will find 26650 cell holders available.
www.aliexpress.us/item/3256806140393706.html
EMPTY case for typical 12V 7AH size AGM battery is about $3.60 (varies by color) plus shipping**.
Same case with the battery separators, nickel strips and 3S 25 amp BMS for li-ion cells is $6.60 - NO CELLS (plus shipping**).
If you have a source of good 18650 lithium ion cells, and a cell welder ($13 and up) you can make your own replacement battery for many UPS units. Just remember that a 25 amp BMS assumes that 7 cells in parallel can deliver 25 amps. Even some of the "near junk" bargain 18650 cells deliver 1.6AH. 7 of those in parallel would deliver 11.2 AH so you'll have better than the 7AH the AGM battery in that size can handle - whether all those cells you have can also deliver 3+ amps continuously is something to test. 3S gives you 3 * 4.2 = 12.6 volts fully charged, 3 * 3.7 = 11.1 volts for much of the discharge cycle and 3 * 3.2 = 9.6 volts at low voltage shutdown. Will your UPS be happy with those voltages? I can make that determination - but I have an adjustable power supply that can deliver 0-16 volts at 20 amps. 20 amps at 9 volts is 180 watts so within the range of a lot of UPS loads.
I have some 40 volt Ryobi batteries that have 20 18650 cells in them so that might be a future option using those with the parts in the $6.60 kits. But I prefer LiFePO4 cells for their "less likely to self immolate" characteristics.
**Under $10, shipping is $1.99. Over $10, shipping is free. Battery cases are available in black, green, yellow and blue.
For now, I'll be building some LiFePO4-based replacement batteries for some UPS units because I have the LiFePO4 cells. Even if the UPS runs the battery pack to shutdown, the LiFePO4 cells are good for 1000+ cycles. With the shutdown voltage on the last LiFePO4 BMS I used being 9.2 volts or so, the 9.7 volts Low Voltage Shutdown of many of the UPS units won't ever bring the LiFePO4 battery down to its BMS shutoff.
I have 3 cases on order (black, green, yellow) so I can build three different pack types and be able to tell them apart without picking up the pack so I can read its AH and Max Amps ratings - with LiFePO4, that might be different Max Amps on charge and discharge.
www.aliexpress.us/item/3256806140393706.html
EMPTY case for typical 12V 7AH size AGM battery is about $3.60 (varies by color) plus shipping**.
Same case with the battery separators, nickel strips and 3S 25 amp BMS for li-ion cells is $6.60 - NO CELLS (plus shipping**).
If you have a source of good 18650 lithium ion cells, and a cell welder ($13 and up) you can make your own replacement battery for many UPS units. Just remember that a 25 amp BMS assumes that 7 cells in parallel can deliver 25 amps. Even some of the "near junk" bargain 18650 cells deliver 1.6AH. 7 of those in parallel would deliver 11.2 AH so you'll have better than the 7AH the AGM battery in that size can handle - whether all those cells you have can also deliver 3+ amps continuously is something to test. 3S gives you 3 * 4.2 = 12.6 volts fully charged, 3 * 3.7 = 11.1 volts for much of the discharge cycle and 3 * 3.2 = 9.6 volts at low voltage shutdown. Will your UPS be happy with those voltages? I can make that determination - but I have an adjustable power supply that can deliver 0-16 volts at 20 amps. 20 amps at 9 volts is 180 watts so within the range of a lot of UPS loads.
I have some 40 volt Ryobi batteries that have 20 18650 cells in them so that might be a future option using those with the parts in the $6.60 kits. But I prefer LiFePO4 cells for their "less likely to self immolate" characteristics.
**Under $10, shipping is $1.99. Over $10, shipping is free. Battery cases are available in black, green, yellow and blue.
For now, I'll be building some LiFePO4-based replacement batteries for some UPS units because I have the LiFePO4 cells. Even if the UPS runs the battery pack to shutdown, the LiFePO4 cells are good for 1000+ cycles. With the shutdown voltage on the last LiFePO4 BMS I used being 9.2 volts or so, the 9.7 volts Low Voltage Shutdown of many of the UPS units won't ever bring the LiFePO4 battery down to its BMS shutoff.
I have 3 cases on order (black, green, yellow) so I can build three different pack types and be able to tell them apart without picking up the pack so I can read its AH and Max Amps ratings - with LiFePO4, that might be different Max Amps on charge and discharge.