I actually ended up with two batteries for my Ryobi stuff. I had bought the trimmer and blower a couple of years earlier. When I was looking to buy a new mower, the battery used for the trimmer and battery quit. So I just decided to buy the mower with the new battery and use the battery for all three items.
Stupid me, but a month or so later I saw a Home Depot ad that said Ryobi has a 3 year warranty on the batteries. I called Ryobi and they confirmed it. I had no receipt but they just asked me for the serial numbers of the trimmer, blower, charger and battery that I had originally purchased. He confirmed that these units were part of the same bundled package that I had purchased. The guy had me run a test on the battery and charger while on the phone and he confirmed the problem was the battery. He said yes, it is still under warranty. About a week later I had a new battery. Not a penny out of pocket. They just told me to recycle the old one or take it back to Home Depot for recycling.
In any case, I have the new battery that came with the mower and another new one that Ryobi shipped to me still in the box. One 5 aH battery is enough for me to mow the yard and then use the trimmer and blower.
Overall, extremely happy with the product and service.
Note: Maybe I need to buy a house with a larger yard so I can use both batteries the same day .... lol.
Rub a Dub