Re: R 3rd party lithium battery replacements safe & OK 2 use?

On Thu, 4/3/2025 3:50 PM, Ant wrote:

> 
> Thanks Paul. I was debating to get new APC Replacement Battery Cartridge 
> (APCRBC124) battery replacements for my old 865 watts APC Back-UPSes: XS 
> 1500 (model: BX1500G) and APC Back-UPS XS 1500 (model BX1500G). One of 
> them show a blinking battery icon due to its old age. :(
> 

The substitution of LiFePO4 for lead acid is a tempting one,
but I've seen nothing substantial regarding "what could happen".
Someone suggested "4S4P could work as an automotive battery replacement"
some time ago, but I've never seen an authoritative analysis of
the risk level associated with the idea.

And if a battery with enough amperes to do the job for that size
of UPS costs $1000, the idea is a non-starter. Lead acid has
pretty good current flow capability, for a cheap battery type.
Power-type LiCo could also work (they have twice the amperes of
kilowatt-hour LiCo cells), but then the risk of fire goes up.
LiCo will not accept any abuse. LiFePO4 will accept abuse.

On a car battery, the terminal voltage drops from 12.6V (charged
and settled) to 9.5V, when the load is 150 amps. That's to give
you some idea what the impedance of the battery is. The drop
across the battery (~3 volts) and 150 amps, means the battery
develops 450 watts of heat inside it during that 5-10 second discharge.

The Lithium can have a different impedance characteristic,
but it could also be more sensitive to heat than the
lumpy lead acid solution.

If this idea was a big win, they would have done it already
and these would be fitted to product at the store. I expect
it is the cost which is unattractive. Once the battery manufacturing
capability exceeds the market size, the price will drop
closer to reality.

   Paul