Doubled my Inverter Backup Power - Any Experience with Mixing 1 Year old Battery with New One?

[Dataman]

On my AIMS 1250 I put in another 100ah Battery for 200ah. Last power outage we squeaked by by going to Generator Battery (used to start it). We had 8 hours downtime. Each 100AH battery should get 6 hours.

The 1st Battery (Sep 2018 New) ran for 6 hours and Inverter started beeping. (Beeping - Low Battery Trip Point is selectable at 10.0/10.5VDC). This battery only had 2 Discharge Cycles. One Test and one 4 hour use. Rest of the time float charge or disconnected.

I know your not suppose to use New and Old Batteries together. Anyone have any experience with using just 1 year old battery with New One?

 

[Socratic Monologue]

We have a small solar PV (~440 AH battery) on a detached garage. I originally built it with 220 AH, then needed to expand, as you do. No data, but I expected the old batteries to drag down the new one to about their level, and I think that's about what happened.

Solar is different -- batteries get down to 70% or so regularly, but they also get EQ cycles monthly (or so) to try to balance things out.

Your batteries are AGM, mine are FLA, so there may be some differences I don't know about between my situation and yours. Floating an AGM for a year and four months might not take much out of it. I never saw 10.5v, though (that's low -- ouch!).