As far as batteries, I've had a 40V Greenworks saw for several years. I did lose one battery, possibly due to letting it sit without use. But the other 40V batteries seem to work just fine, and are over 5 years old.
I did get the 60V and 82V saws recently. I'm not super excited about the "smart" battery technology. One can log into the batteries, but the program control is minimal. We'll see how they last.
As far as the mowers, the Greenworks Commercial mowers are mighty expensive. They would price themselves out of most homeowner use. But the Pro versions are within reason. It all depends on one's usage. Mowing a 5 acre field?
One advantage of the individual batteries is that if one battery goes, one can replace that battery instead of replacing the whole pack. Or if something new comes out, one can upgrade.
I have a 40V push mower that takes 2 batteries. It works OK, but I haven't used it a lot. An interesting thing about it is that it uses one battery at a time. So it is no different from running it on a single battery or two batteries. In fact, by using a single battery one can monitor the state of charge easier, and recharge before the battery reaches zero.
If I was purchasing a $5,000 to $25,000 mower, there would be several questions I'd ask the vendor. Is it using the batteries in series, parallel, or sequential. Half the pack? That would be critical to know if you plan on building a mixed battery pack, and might also help you predict battery heating, charging, and etc. Also, does the mower have an onboard charger, or do all the batteries have to be removed to charge?
Greenworks reported voltages are somewhat optimistic. One report I saw indicated that both 80V and 82V batteries were actually 72V. Perhaps I'll do some testing of my batteries. I don't know the actual voltage of their 60V batteries.
Ok, for smaller power tools, 18V and 20V batteries are supposed to be essentially the same (different brands). Likely that is multiplied, so a 36V and 40V would be the same, or 54V and 60V, or 72V and 80V.
Anyway, you lose a few volts here and there. I wasn't particularly impressed with the 8AH 60V Greenworks battery. I don't have an 8AH 80 or 82V, still hunting, but I wonder if the 8AH 60V is similar in performance to the 4AH 82V. So, buying a 60V mower might actually reduce your battery pack performance more than would be expected over 80/82V.
. So Id need 6 to mow my lawn… so $1800 in batteries. That’s the cost of a 27Hp commercial engine, that I could run for 20+ years honestly, at 50 hours per year.