Does anyone make a Li-ion UPS?

I'm just wondering if anyone makes a computer UPS that runs on Lithium Ion batteries? I'm having a hard time finding that information.

I'm tempted to convert my UPS to LiFePO4 but it looks like it might be too much work.

I'm just tired of buying lead batteries every few years and I hope that Lithium batteries would last longer in a UPS.

 

Well just as an experiment I bought a LiFePO4 drop in replacement for a 7Ah lead battery.

Here is the link.
LiFePO4 26650 Battery: 12.8V 6.8AH (87 Wh, 25A rate) built in PCB , Replace SLA with 10 times longer life & 61.77% lighter weight

This battery has over voltage protection, under voltage protection, and over current protection. So I'm pretty much covered from damaging the battery.

I ran some tests on it and the UPS will charge it to about 75%. A 115 watt load will run for about 33 minutes. A 310 watt load will run for about 8 minutes but the terminals will get very hot. About 185F.

310 watts is more than I would normally put on it so it looks like this battery will work just fine. The only issue now is how long will it last in terms of years? Hopefully it will be a long time before I find out.

 

There is really not much to say about my upgrade to LiFePO4. I bought 4 more of the 6.8Ah batteries for my rack mount UPS and a 40Ah battery for my large UPS.

So far they are working fine. I wont know how well they will work until I get at least 4 years of use out of them. Thats about how long the lead batteries last before they bloat and outgas.

If my Hymotion battery in my Prius is any indication of how well these batteries in the UPS will do I think the batteries will out last the UPS.

The only thing I'm concerned about is the BMS board on these batteries. They use shunts to balance the batteries and Jack Rickard has convinced me that these BMS's are very bad. But since the UPS's are designed for lead that means the LiFePO4 batteries are being under charged. So I think I might be OK.

Since it will be about a year since I bought these when I get some time I will try to get some measurements of the cell voltages and capacity.

 

The lithium batteries still work in my UPS but I dont know if the capacity had dropped. Two other UPS's I had batteries in either killed some of the cells or the BMS killed the cells. From the looks of one dissected battery it was the fault of the BMS. The BMS also causes issues with my APC rack mount UPS's. When the voltage gets to less than 10v the BMS will cut the voltage to the terminals. Only a 12v source can reactivate the BMS. Since the UPS can operate just below 10v this means if I dont shut off the UPS before it drains the battery I have to open the UPS up and apply 12v the batteries to turn them on. The UPS will not turn on if it does not have a 12v from the battery and it wont "kick start" it either. Only option is to open it up and apply 12v to the battery.

So as far as longevity goes its looking good. As far as BMS goes dont bother. A good bottom balanced LiFePO4 battery pack without a BMS is just fine as long as the UPS does its own cutoff voltage of 10v which most if not all should do. And the UPS should not over charge lithium batteries either since SLA maximum charge voltage is less than a 4 cell LiFePO4 pack.

I plan on redoing my UPS's with no BMS sometime to see how well that will work but I have too many things to work on at the moment.

 

LiFePO4 batteries can be discharged to 0v just fine. They may loose some capacity but they wont catch fire. Reverse voltage can be an issue but thats where bottom balancing comes in and a controller that wont let a pack voltage drop below 2v per cell. Over voltage is what cause LiFePO4 cells to catch fire and its not so much a fire but more like a lot of heat and out gassing. Still can be a fire hazard though.

Active top balancing BMS's should be avoided.