I'm on my second battery mower. The first was a Black and Decker. Sometime during its life they had a recall and basically replaced the motor and battery (entire deck). So I got a brand new mower about 5 years into it. I'm not sure what happened to it, but a chunk of deck bigger than my fist broke out under the motor exposing the motor to the grass. I immediately drove to HD and got the EGO self propelled mower. I already had three EGO tools, so all the batteries and chargers are interchangeable. I have three batteries for the four tools (mower, string trimmer, leaf blower, and chain saw) and use the mower charger for all of them. With three batteries there are always batteries in reserve. My lawn is 3,000 square feet of dense St Augustine. With some hills I use the self propulsion all the time. Still at the end, about 45 minutes, the battery light is green. Recharge to full takes about 40 minutes, but again, if I needed to go a few more minutes, the smaller batteries from the smaller tools fit into the mower and will drive it.

I no longer have gasoline or oil in the garage. It's great for the home owner.

Check the YouTube reviews for battery powered mowers.

How big is your yard? That is the key to answering your question.

I have a 3/4 acre yard (about 30000 sqft) with about 20000 in yard. It takes me a little over an 90 minutes to mow the property with my lawn tractor with a 38" mowing deck.

Obviously what will work fine on 3000 sqft may work fine, but not on the one that is 7 times larger.

Mine is 1/2 acre. Flat.

I had an electric-powered robot mower for fifteen years that I loved until a certain somebody who was trying to help me reseat the carapace broke the front wheel.

I love you, dear, but you are not mechanically inclined.

In my case, the batteries could be replaced by simply lifting and shifting them out when they discharged, to be replaced by a freshly-charged one. Restart the mower and off it went.

I loved that thing. Like, seriously loved it.

I'd have it fixed professionally, but it's really rather too old to bother. The motors have worn, the gears are worn, and the programming is far out of date. There are much better models around today, with lithium instead of lead batteries that I had to replace and recycle every 3 years (cheap, though).

At about 10,000 square feet of grass, it was entirely capable of doing the entire thing with no issues, perfectly, every time, twice a week, without invading the gardens or damaging trees, eating toddlers, or otherwise destroying shrubs or conquering the planet.

I'll buy another at some point here. That isn't even in question, I just have to sit down, do the research, decide what I want, and then get around to doing all the freaking work to reset the property wires and whatnot to deal with it.

A concern I have is about the battery degredegation over time. Batteries are expensive.

The Harbor Freight Atlas mower looks good and gets great reviews. It's 80v Li-ion and is available in push and self propelled. It has a governor that conserves power when the mowing load is light and kicks up the power under a heavy load.

" A concern I have is about the battery degredegation over time. Batteries are expensive. "

Tru dat. My batts were $100 per and had to be replaced every 3 years to the tune of $300. For a robot, that really wasn't that much as all other maintenance was in my range and it otherwise only cost me in terms of electricity. By which I mean $10 per year.

Newer lithium batteries are more expensive, but also more stable. They look to run about $150 per battery (for the Snapper model I chose randomly where the batt is 5 Ah and does about 5,000 square feet), so $300 if you have the two-batt model.

At worst, you should get 350 charging cycles if you drain it to the dregs and recharge it, let it sit on the charger, and drain it to the dregs again. Then let it sit over the winter in the garage.

On average, if you have a wee bit of charge remaining most of the time, treat it OK, and store it reasonably well over winter, they expect 500 cycles.

Treat it well--partially drain the batteries only (so get a mower that has more power than you really need), take it off the charger and let the battery sit disconnected until needed, store in reasonable temperatures until used, and store properly over the winter--and you can get 1,000 charges or more.

I'd count on 500 charges for most of us. Even I expect the battery to serve me, not the other way around.

Source: I'm kind of a battery hound. Lithium-manganese batteries are a hobby of mine and please ask about output power curves and how to save your batteries and make them last longer. Some of these batteries are Li-Mn with major safety circuitry, others are lithium-Fe due to the inherent safety of it (and with additional circuitry because humans are idiots).

Thanks, Morph.

What battery would you recommend in a self - propelled mower for 1/2 acre?

I see 40-80 volts, a variety of amps. And wide range of prices!

Any, really. By which I mean a lithium; lead batteries, these days, are not worth it.

Personally, I would recommend oversizing your battery a bit, at least. You have half an acre, which is quite large at 21,000 square feet. That's pretty demanding and may not be terribly realistic in terms of what I'm seeing, but don't consider myself an expert on mowers by any stretch of the imagination).

I like to play with small electronics and circuit design* to eke out the last tiny micro-erg of power that can be made to produce a useful or interesting photon or motor-motion somewhere along the line.

So my recommendation, if you do it, would be to get a mower that can do 25,000 square feet. The battery would have charge remaining (and be quite large and, one presumes, expensive) at the end of the run, which means you wouldn't have to replace it as often--because it wouldn't be drained at the end of the run so it wouldn't be running very hard. Plus, it has excess capacity, so even as it loses capacity with usage and age, you have some margin to give up before needing to replace it.

Or a mower with a battery you can change out, and have two of them, each capable of mowing at least 12,000 square feet each. Or four batteries, each capable of mowing 6,000 square feet...

The reasoning is how lithium batteries--and other batteries, but we're worried about lithium here--work, and how capacity drops over time. Which is by wear and age. The more wear and the more age, the more capacity drops. Age you can't change, but you can reduce wear by using a higher capacity battery so your "wear" each time is lower because you aren't using the full charge.

Here's the short course. You can look up a whole heck of a lot more online.

Lithium batteries, all of them, have "safe" voltages. Lithium-iron batteries are exceptionally forgiving (read: do not get explodey when you violate these, but do die faster). Lithium-manganese die a lot faster, and can get Extremely Annoyed. Lithium-ion are not typically used in these kinds of applications due to their inherent instability.

Going dead is an absolute killer for lithium batteries (although Li-Fe are much more forgiving of this) to the point that some will self-destruct in a matter of days. Hence the circuitry on board, which won't let you do this and generally stops the battery usage at 5-15% charge and shuts things off. Very smart circuits change that as the battery ages, downward, to compensate for lost capacity. The battery dies faster, true, but...

The more often you "full stroke" the battery instead of using a half charge or three-quarters charge instead, the lifespan also shortens (again, you approached the edge of the safe voltage). One might, for instance, get 500 full charges off a really good battery. One might get 2000 half charges. Or 100,000 one-tenth charges. Those numbers are actually relatively reasonable for a decent Li-Mn battery.

Even so, age also takes its toll. Five to seven years is the outside point for any lithium.

When stored, they're best stored at 50% charge (their lowest stress point). So for winter, store at this state, or as close as you can get it. Anything from 40%-80% is fine, really. Very close to full or very close to empty isn't good. And most batteries have internal circuitry that will slowly drain them down over time, so you do want some charge in there so they don't go dead. Check your manual for storage recommendations as well--sometimes, for winter, circuitry can be disconnected. Some can be winter-stored in the garage while others recommend the cellar. Lithium batts aren't cold-sensitive...but the circuitry can be!

They hate extreme heat. But so does every other battery. And gas engines aren't exactly fans of heat either...

* Yeah, if you've been keeping score, just throw this one on the pile. It's a long story.

As I chew on it a bit more, pricing differences are going to be by brand, voltage, and amp-hour.

Personally, unless it's vouched-for, I'd stick with name brand.

Volts times amps equals watts, which is a nice way of equalizing battery power and comparing them from the same footing.

A 40V battery with 2A is 80 watts of total power.

If, for instance, you're seeing an 80V battery at 5A, it's 400 watts of power. Or, quite a lot more than many people might think at first blush, just from a glance at the specs and an idle comparison!

That second battery has five times the power of the first, so it's reasonable that it would be five times as expensive...even if the amps are only 2.5 times as great.