I have 40V electric lawn mower. It takes nearly the full charge on two batteries to cut my average suburban-sized lawn. Sometimes I can't even complete it on that depending how tall the grass is. Add in edge trimming and blowing away the clippings and then multiply that by a number of lawns or larger properties and I think you would need dozens of batteries.
BTW "more convenient and cheaper" are strong arguments when you're in a competitive business. Lawn services are usually just a guy with a truck hustling for customers. The more lawns you can cut the more money you make. Anything that causes downtime such as running out of charged batteries is going to be a large negative.
I have a 56V electric lawn mower. It takes nearly the full charge of one battery to mow my slightly larger suburban lawn. Trimming and blowing and what not gets handled by my second smaller battery. My largest battery isn't even the largest they make for this model line. I've been on the same two batteries for five years now. I use E-Go.
I'd say your system is just undersized for your needs. Judging by having two batteries, it sounds like your system is one of those based around hand power tools batteries and then attempted to scale those up to lawn mowers. I've mostly heard bad things about this path. There's a lot of other experiences out there.
We have a large lawn, and a pile of broken eGO products. They wear out fast and cannot be repaired.
We started replacing them witg Milwaukee lawn tools. We frequently hit overheat cutoffs, but haven’t broken any yet. We do have a pile of dead small eGO and Milwaukee batteries though. These days, we only buy the biggest capacity we can. Those tend not to die as fast.
Electric is clearly the future for this stuff, despite our problems. The remaining gas powered stuff is all > 10HP.
Honda has a new electric mower coming out that can do like 12-15 acres on a charge.
We're talking a commercial mower though. I haven't seen prices yet, but I'd guess you're in the $15k range.
I have a 40V (well, 2x 20V) mower, and use two pairs of batteries to mow the lawn. But that's fine; between the lawn mower, the leaf blower, the weed whacker, and the snow blower, I've got plenty of spares.
Insane that there's a market for a dude with a lawn mower these days when you can get a good enough robot mower for $1000 ...
Good enough for what? I'd love to have a lawn mower which can dump grass clippings in my compost pile (mulching them and leaving them behind is better for the lawn, I know, but my wife is allergic to grass so this would basically mean she never gets to use the lawn). Also, we have two apple trees which spend a few months dropping apples on the lawn, so I'd like to have a robot lawn mower which can pick up the apples and toss them in the compost pile too. Oh, and there's a gate separating the front yard from the back yard, so it would be great if it can open and close the gate.
Robot lawn mowers are getting better, but I have yet to see one which can handle every situation that humans routinely handle.