Post by papaof2 on Feb 20, 2023 13:21:48 GMT -6
16 LiFePO4 3.7AH, 3.2 V cells for $29.99 + tax + ship
That works out to $1.88 each (+ tax + ship) so less than $2.50 each for some nice NEW cells. This is the dealer from whom I got the 3.8AH cells that I'm currently using in several small UPS units.
I used 4 of the 3.8Ah version of these in a small UPS (rated 75 watts) to replace a 4.3AH, 12 volt, AGM battery and got a longer run time with the slightly smaller (AH rating) LiFePO4 pack, probably because of its long, flat discharge curve. 8 of these in 4s2p would be 7.4AH and an excellent replacement for the common 7AH AGM battery in many small UPS units. Maybe $4 - $5 for a 20 or 30 amp BMS and you have a 12 volt 7.4 AH LiFePO4 battery that will fit in the original battery space if you're at all neat in assembling the pack ;-)
Remember that LiFePO4 is good for 2000+ charge/discharge cycles to 80% discharge but the AGM batteries die at 200 or fewer of those cycles. The BMS will probably set to limit discharge to 10.0 volts but the UPS probably has a low voltage shutoff of 10.5 to 10.7 volts so the UPS will shut off before you reach that minimum voltage.
The continuous discharge current for a single string is 7.4 amps but a 2p pack would be 14.8 amps and your maximum input power would be 13 volts * 14.8 amps = 192 watts which would likely handle whatever load you have on a smaller UPS. I have a BN4001 which is rated 257 watts and I usually don't load a UPS more than 75% of its rated capacity so that would be a good match. For the UPS units that are loaded lightly to get an hour of power (home network, cordless phones) that's far more power than you need and a 4s1p pack at 3.7 AH might be adequate but the 4s2p pack would give a lot of backup time ;-)
batteryhookup.com/products/16x-3-2v-3700mah-11-84wh-26650-lifepo4-cells?mc_cid=0afebc56e4&mc_eid=7c6358641e
The 3.8 AH cells sold out quickly so I'd expect the same of these. The email was sent less than an hour ago so you have early notice ;-)
That works out to $1.88 each (+ tax + ship) so less than $2.50 each for some nice NEW cells. This is the dealer from whom I got the 3.8AH cells that I'm currently using in several small UPS units.
I used 4 of the 3.8Ah version of these in a small UPS (rated 75 watts) to replace a 4.3AH, 12 volt, AGM battery and got a longer run time with the slightly smaller (AH rating) LiFePO4 pack, probably because of its long, flat discharge curve. 8 of these in 4s2p would be 7.4AH and an excellent replacement for the common 7AH AGM battery in many small UPS units. Maybe $4 - $5 for a 20 or 30 amp BMS and you have a 12 volt 7.4 AH LiFePO4 battery that will fit in the original battery space if you're at all neat in assembling the pack ;-)
Remember that LiFePO4 is good for 2000+ charge/discharge cycles to 80% discharge but the AGM batteries die at 200 or fewer of those cycles. The BMS will probably set to limit discharge to 10.0 volts but the UPS probably has a low voltage shutoff of 10.5 to 10.7 volts so the UPS will shut off before you reach that minimum voltage.
The continuous discharge current for a single string is 7.4 amps but a 2p pack would be 14.8 amps and your maximum input power would be 13 volts * 14.8 amps = 192 watts which would likely handle whatever load you have on a smaller UPS. I have a BN4001 which is rated 257 watts and I usually don't load a UPS more than 75% of its rated capacity so that would be a good match. For the UPS units that are loaded lightly to get an hour of power (home network, cordless phones) that's far more power than you need and a 4s1p pack at 3.7 AH might be adequate but the 4s2p pack would give a lot of backup time ;-)
batteryhookup.com/products/16x-3-2v-3700mah-11-84wh-26650-lifepo4-cells?mc_cid=0afebc56e4&mc_eid=7c6358641e
The 3.8 AH cells sold out quickly so I'd expect the same of these. The email was sent less than an hour ago so you have early notice ;-)