On 4/7/25 09:02, jordi.palet--- via NANOG wrote:
Agree, LFP is the way to go. I did that in many types of UPS, different models & capacity, such as EATON and APC, but many others as well.
There are many suppliers, even in Amazon, Alibaba, Aliexpress, etc. that already have LFP cells that internally have the BMS and work in a transparent way to replace lead-acid, using same connectors and dimensions (but much lower weight). They are more expensive (3-4 times the price of the lead-acid ones), but they will last for 15-20 year, and they can be discharged up to 90% instead of 50%. They often provide a bit “extra" real power/capacity as well.
If you are going to build your own Li-Ion battery, a BMS is a must. But if you buy a pre-built Li-Ion battery, it will always ship with a BMS. In fact, many of the 12V Li-Ion batteries may be purchased with a Bluetooth controller option, which gives you real-time data of the BMS's performance via a phone app. I wouldn't say Li-Ion batteries are 3 - 4 times the cost of LA. At least in our market, you're looking at 2X, for just a pre-built battery with a BMS. If you want a larger system (24V or 48V), then yes, the extra controls, protections, build structure, e.t.c. can contribute to a 4X price difference. The only issue with using 12V Li-Ion batteries in a UPS is that most UPS's are 24VDC systems. That means you'll need 2x 12V Li-Ion batteries... the problem being that you'd have to balance them, and external balancers don't fit well inside small UPS chassis. Mark.