EcoRenovator (
-   Lawn and Garden (
-   -   Reviving a free, dead 12V cordless Black & Decker mower (

MetroMPG 07-03-14 09:00 AM

"$70.19 - $94.49" Canadian prices

Black & Decker M3300 replacement 12V Battery

MetroMPG 05-26-15 04:02 PM

season 5!
Hard to believe this is the start of year #5.

I plugged the mower in several times over the winter to keep the batteries happy (or as happy as they can be at this advanced age) and sharpened the blade a couple of weeks ago.

And the freebie e-mower rides again! ... I mean "is pushed again!"

The batteries are now well past being able to do both the front & back yards on a single charge. Grass cutting is now a 2 day event with an overnight re-charge. Assuming they hold up for the rest of this summer, next year will need new batteries, a smaller lawn, faster pushing, a hybrid approach (a bit of manual reel mower usage mixed in), or some combination of the above.

Daox 05-27-15 10:20 AM

Not too bad getting a few years out of it!

MetroMPG 05-24-16 12:52 PM

year #6!
The salvage mower runs again!

Hard to believe it's on its 6th season.

But it's definitely not happy this year. So far I've only mowed 3 times, and I'm sagging the voltage well below safe levels to get the job done in 2 cuttings (front... overnight recharge .... rear).

I've always used the guideline of not dragging a 12v battery below 10.5v under load to avoid battricide. But I'm seeing ~9.x volts this year if I want to get the job done. I expect that'll kill the batteries before too long. We'll see!

However, since I got the mower, a new source of cheap, used 12v batteries has shown up in town in the form of an electric bicycle & scooter shop. I may go see what he has available. He even offers a 30 day exchange if the used one he sells doesn't work.

MetroMPG 06-04-16 10:53 AM

Yet another free e-mower
Good news: since the weather warmed up and the growth has slowed down, it looks like the old batteries may just deliver another season of service!


The Mower Fleet Expands Yet Again!

Also, a neighbour gave me his old 24v mower, which just quit working.

"It's probably just the battery," I said.

"I checked the voltage, and it seemed OK," he said, "and my wife wanted the lawn cut an hour ago, so I just went and bought a new mower".

25 minutes of tinkering confirmed its battery is toast. I haven't decided if I'll fix it or just give it away to someone else, along with the diagnosis.

wogga 05-04-17 12:27 PM

Update on my similar mower
Just to let anyone who cares know, I got just about 10 years from my similar B&D rechargeable 12v mower. In the end, the tenth year was a bit of a joke. My 6000 sq ft lot often needed two separate mows to get it all done.

In any case, 10 years for lead acid batteries isn't bad at all. I credit it to the constant trickle charge the battery got, the small size of the lot and a desulfator I bought on ebay and used over the years when the battery seemed tired.

I paid about $90 locally for a replacement battery. It was interesting to see yours said 28AH; mine was original, I think, and said 24 AH. It was replaced with same sized 26AH "Duracell".

In case I didn't say it before, the connector to charge the unit is the only tricky thing -- if you don't have an OEM B&D charger. Any old charger above 13V will work. I used, as mentioned earlier, 10W solar panels designed for a "12v" system, meaning they put out about 20 V open circuit. That's how I got the 10 years. I only used the OEM charger when I needed another mow within a few days ... and after the solar panel wiring got eaten away a year ago.


MetroMPG 05-25-17 09:30 AM

Year #7
Hi Carl - Thanks for the update on yours. I'm also surprised at how long the batteries are lasting.

I just started year #7 on my used batteries of unknown condition/age. Maybe the charger is particularly suited to not killing them?

Though the capacity is at minimum. I'm doing the small yard over the course of 2 days: front lawn, recharge, rear lawn, recharge. I will be pleasantly surprised if it will do even that for another year.


And update on the free 24v mower I mentioned a few posts back: I gave that one away. Too many projects!


wogga 05-25-17 10:11 AM

I'm partial to using a few batteries as possible, so mine is a 12v. I think continuous trickle charge mixed with never bringing the battery below 50% capacity, preferably not down below 70% helps a lead acid battery. My solar 'array' of 2 5 watt panels stopped working last year, due to wire damage, so I hope to get a 15 watt replacement up and running again soon to get the free charge and trickle again. It helps to lubricate the motor bearings, keep the wheels set very high and sharpen the blade frequently in addition to the obvious things like not mowing wet or waiting until the grass is very very high to mow.

MetroMPG 05-25-17 10:17 AM

Funny thing is: I do everything that you mention that shouldn't be done.

I know I'm hard on these batteries. I watch voltage as I mow, and I try to keep from drawing them below 10.5v under load (on battery expert advice to prevent potentially reversing a weak cell), but I sometimes even exceed that.

About the only "nice" thing I do is make sure the batteries never sit discharged for any period of time after mowing, which prevents sulfation if memory serves. They go on the charger as soon as I'm done cutting the grass.

MetroMPG 07-13-17 08:39 AM

She's dead, Jim
I went to use the mower this week and when I checked the voltage before starting (my usual habit), it read only 9.x.


I always recharge the mower right after using it, so my first thought was that I must have forgotten last time. So I plugged it in and left it over night.

Next day: voltage reading topped out at just 12.1. I confirmed the charger output voltage was OK.

So, the batteries are toast. (Well, just one of them is. But in parallel, it was dragging down the good one with it.)

A local e-bike store has used 12Ah batteries for $20 apiece that will work, but considering I have a spare corded electric mower, that's the route I'm going to take from here on.

All good things must come to an end! R.I.P., Black & Decker M3300!

All times are GMT -5. The time now is 05:55 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Ad Management by RedTyger