[NANOG] Re: Small Capacity UPS

[Mark Tinka via NANOG <nanog () lists nanog org>]

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.
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