EcoTech battery backup - testing the battery health?

[ps2cho]

I have an ecotech battery backup dated 2016. I pulled it from my old tank and my DVM still reads 12.98v on it. Is there a way to check the general health of the battery? Or should I assume since its still charged well, its going to perform reasonable well? I expect not to the same as new, but to some extent?

 

[Freenow54]

On auto batteries they check them under load voltage doesn't mean much as to load it can handle. Use it and see

 

[Malcontent]

Simulated power outage and measure runtime.