Hi There: What a neat site and your projects are after my own heart!

Anyway, I have this mower (or a similar one) and I absolutely love it. Mine was 'dead' because the orange safety 'key' was missing. It's been running 4 years on the same as-found battery. I power it entirely off 5W or 10W solar panels that amazingly are 'plug and play' once you get the right connector. I've detailed it on this wikisorta page:

solarpowermower.wikia.com

sorry for having to cheat the 'no url's thing for new posters. Boohoo!
and for making me wait 30 secs to repost!

Hi Wogga - welcome to the site.

I'm planning to solar charge the mower next year too.

And thanks for reminding me: I need to look after the battery this winter so it doesn't self-discharge and die.

End of season update, 1 year later:

Another year of happy electric mowing. (Well, I'm not exactly happy to be mowing, but you get the idea.)

The mower had less work to do this year than last, since I installed a driveway and did some landscaping that exposed a good amount of granite bedrock in the front yard. Which means: yay, less grass to cut! Also, we had a severe drought which caused the grass to go dormant for much of the summer.

The old battery pack is holding up: it's still enough to do my small-ish property on one charge if I hustle (~15-20 mins), or over 2 charges (over 2 days) if I take my sweet time (usually how I did it).

3rd season for the free, previously dead, 12v lawnmower has begun!

I've only used it 3 times so far this year, but I think one of the pair of batteries might be acting up. I've been seeing some wonky voltage readings when charging & running. Have to investigate further...

Looking for an update. How have things been going with the mower? Did you get the voltage issue sorted out?

It's been working just fine!

Fortunately, the wonky voltage issue turned out to be an instrumentation issue: intermittent flaky connection to the permanently attached voltmeter/display.

The mower has seen regular weekly service this year, unlike last summer when we had a serious drought that gave me a month or two break from mowing!

And I haven't done any more landscaping this year, but the plan for next year is to replace more lawn to give me & the mower even more time off. The less lawn, the better!

back in action... season #4
 

Just thought I'd post that the freebie mower has gone back into service ... beginning of its 4th season.

The batteries are getting tired for sure. I've only used it 3 times, and haven't been able to do both the front & back yards on a single charge. Though it's possible they may "wake up" a bit with a few cycles after sitting all winter with just an occasional top-up charge.

Doesn't bother me too much, really - I let it charge up and come back to it later.

I haven't shrunk the lawn area any further which would accommodate the declining battery capacity, though that's an ongoing goal (for other reasons). I'll probably do more of that later this summer.

Funny story:

A neighbour emailed me recently saying he was searching for battery replacement options for his Black & Decker mower and found this thread.

He ended up going with a new, OEM style replacement instead of messing around like I did.

How much did that set him back?