Additional batteries (timeline)?

[wpns]

I'm about to install a mostly-off-grid system of EG4 18Kpv inverters and PowerPro WallMount batteries, and have had some interest from neighbors. Of course, they don't know their load or consumption profiles other than monthly electric bills, so they are more interested in starting small.

I absolutely understand that there are no absolutes or guarantees, but what's the safe timeline for adding additional PowerPro Wallmount batteries to an existing system? The common wisdom is "don't mix new and old batteries", but what's the reasonable timeline? Obviously a few months is fine, but how many years would be considered "too late" to add more (identical) batteries, assuming EG4 was still making them?

Thanks!

 

[DIYrich]

No problem mixing old and new lifepo4 batteries in parallel.

 

[wpns]

No problem mixing old and new lifepo4 batteries in parallel.

Even 20 years later?

 

[Sennen]

Individual BMS are neat like that

 

[Vigo]

Even 20 years later?

So i THINK that in general the difference in internal resistance between new and old lifepo4 is still small enough to be outweighed by resistances in cabling/connections, so even though 2 batteries of different age might not cycle 'evenly' if they were hooked through absolutely identical connections, that probably wouldnt even be the main factor in which 'contributed' more or less, plus the cycle life is ostensibly long enough that 'who cares' if one battery is getting cycled slightly harder than another. In parallel they will generally all stay close enough that it 'doesnt matter'.