24V / 1000W DC Power supply for lawn mower needed?

[CableTangle]

Hi guys,

The batteries in my electric lawn mover died after ~8 years, which is to be expected. Unfortunately i cannot get a new one from the manufacturer. I opened the plastic case which holds the battery cells, and Jaycar sells them as spares (2x 12V cells), however they would cost more than a new lawn mower and would also only last ~4-6 years or so before the remaining capacity becomes unusable.
Idealy i want a more permanent solution and build a maintenance-free lawn mover that my children can inherit!

I was thinking of using a PC power supply that can support a beefy gaming graphic card and is rated for ~1200W, however they only supply 12V, while the motor expects 24V DC. I found a few 240AC to 24DC coverters online, but they are bulky, expensive and look like Lab equipment that probably wont last long outside.

What would be the worst that could happen when i run the Motor on 12V? What other options do i have?
I only opened the battery cover; i dont want to rebuild the whole lawn mover since i neither have the right tools or parts for that.

[Phil1977]

The most reasonable solution seems to be for me to purchase two 12V-LFP-batteries with integrated BMS. They (theoretically) last longer than the usual NMC-cells and are not as spicy to handle. Probably they don't work together with the original charger, so you would have to charge them up externally.

Using a power supply is more difficult. It starts with finding a weatherproof 1000W-supply and then you practically do not now if it cooperates with the motor controllers of the lawn mower.

[CableTangle]

I don't really expect the motor to have any sort of controller. The lawn mower dosn't have any fancy features or low battery warning and wasn't that expensive. It dosnt turn itself off when the battery power is low; the motor just keeps going until it is to weak to cut the grass. My guess is that it is just battery (with some charging controller), switch and motor.

[Stray Electron]

  1000 W sounds like a LOT of power for a lawn mower!  What kind of cells were used in the original batteries? Yeah, replacement batteries for just about an kind of rechargeable electronic device that uses a proprietary batteries are EXPENSIVE. And here is Life Lesson #1; NEVER buy anything that uses proprietary electric batteries! 

    But you can probably break open the battery pack and replace the individual batteries. There are lot of companies out there such as Batteries+ that will do that for you, for a fee.  But they're all going to use cheap crappy batteries so you need to buy good batteries and do it yourself or plan on going through the same process every few years. 

   If you are considering dragging around a 1000w power supply and an AC power cord with your mower, you'd be miles ahead to just go buy an AC powered mower such as the one made by Black and Decker.  I have one and it works fine but it only has a 18" wide cut, (probably the same or even a bit larger than what the battery powered mowers have).

   I have about 1/3 acre semi-suburban lawn (no tall weeds or heavy thick grass) and the B&D mower cuts it just fine. Several of neighbors have much smaller yards and use battery powered mowers and it takes them considerably longer to mow since their mowers only cut 14 to 16 inches at a time AND their batteries always die before they can finish mowing their lawns.

   I just took a quick peek and the Black and Decker mower is listed at $219 at one site that I looked at and they have an America Lawn Mower Company electric mower with a 14" cut for $165.

   I still have several very good gasoline powered mowers such as the ones that use the Honda engines and that have 22 inch cut, but I now use the B&D mower most of the time.  It's dammed nice to just be able to go out and plug in the power cord and then start mowing with absolutely no muss and no fuss.  I have electric outlets in the front and the rear of my house and I keep a 100 foot extension cord on a hose reel next to each outlet so I can literally pull out the cord, plug in the mower, then put the cord into an outlet and then start mowing.

[themadhippy]

get a goat or sheep,no batterys to go flat,no trailing power cords.keeps the grass fertilized and in a few years time they can be used  as dinner.

[eTobey]

Get one of these motorless lawnmowers. They are cheap, never run out of battery, and you dont need a gym then! 

[Seekonk]

Got any power tools?   Amazon sells adaptors for these packs to use with those miniature cars kids drive around on. Its good to settle on one battery pack type for everything.  I get battery packs at town recycling.  Amazing how many are still good. Town hates them as thy only recycle lead.  They have signs up not to drop them off yet people still do.

[bombcat]

Don't keep goats, they will eat grass roots and your lawn may have open space.

[Haenk]

Don't keep goats, they will eat grass roots and your lawn may have open space.

Yes, and they will bite into everything that is edible or not.

After all, keeping sheep and goats requires a lot of thinking and investment into fences. (As with Clarkson's Farm - "Sheep will try to kill themselves").
A simple spindle mower will do fine for a normal garden.

[eTobey]

A simple spindle mower will do fine for a normal garden.

I remember, i had quite a bit of fun with it, when i was a kid ;-)

[CableTangle]

Get one of these motorless lawnmowers. They are cheap, never run out of battery, and you dont need a gym then! 

No thanks, i don't eat lawnmowers, and they might wander into the traffic ...

[macboy]

I used to have a 24V lawn mower which used SLA lead batteries. Inside the removable battery case were two standard 12 V 20 Ah SLA batteries. I replaced them with new deep cycle ones when they failed. This cost less than half the price of an OEM replacement battery, which itself was about half the cost of the mower originally. Standard size SLA/AGM batteries can be purchased quite easily. I think I bought mine on amzn! Just 3 or 4 years later, the batteries failed again. I then replaced the mower with one which runs from two 18V Lithium battery packs which are compatible with my power tools (drill, etc.), but higher capacity. This mower is more powerful and runs longer than the lead powered one could ever do. When I mulch and bag my maple tree leaves in the fall, this mower sucks them up, finely chops them, and pushes them deep into the bag. The old mower just choked; the very idea of mulching leaves was laughable. When I did my kitchen reno, I appreciated having a couple of high capacity packs for my tools. This mower and its lithium packs have been going strong for about 7 years with no sign of fading. My mower came with a trimmer ('weed whacker') which uses the same battery pack. It, too, is more powerful than the NiCd powered one I replaced, and the batteries are so much easier to maintain (true maintenance free unlike either Ni or Pb ones).

A more "permanent" and maintenance-free solution might be an AC powered electric mower. The most maintenance you might need is to patch up the extension cord after you run over it!

I would not recommend trying to do an AC-DC conversion for your existing mower. The startup current usually peaks quite high, so you would need a very oversized supply. It might be worth looking into LiFePO4 based batteries to replace the Pb ones. As long as they can handle the peak and sustained currents, it should work well. You should be able to find them in the same form factor as the original batteries inside the battery case. Consider how you need to charge these, as the mower OEM charger is not likely suitable.

Last note: with battery powered mowers, it is critically important to keep the blades sharp. Dull blades really cause drag on the motor, which drains the batteries much faster. If the blades can cleanly- and easily slice the grass, the mower will not only do a better job, but it will run much longer. I learned this the hard way. At one point I was convinced I needed to replace the batteries because I couldn't finish my yard, but after sharpening the blade, I easily >doubled the run time.

[TimFox]

Get one of these motorless lawnmowers. They are cheap, never run out of battery, and you dont need a gym then! 

Forty years ago, when I was younger and we moved into our first house with lawns, I thought I could rely on a mechanical reel lawnmower from Sears.
I quickly found that it would not cut grass if it was already too high (maybe 5 inches? I don't remember the exact value) due to its construction.
Since I do not worship at the shrine of the immaculate lawn, but tried to keep the grass within reason, I had to get a corded electric mower that could actually deal with grass.
Much later, I got a battery-operated mower to avoid the nuisance of long cords.

[CableTangle]

I used to have a 24V lawn mower which used SLA lead batteries. Inside the removable battery case were two standard 12 V 20 Ah SLA batteries. I replaced them with new deep cycle ones when they failed. This cost less than half the price of an OEM replacement battery, which itself was about half the cost of the mower originally. Standard size SLA/AGM batteries can be purchased quite easily.

The store nearby where i buy the parts is not that cheap. I already opened the battery pack and it did have 2 12V batteries inside, but replacing them would have cost me as much as the lawn mower did cost.
I wouldnt really trust Amazon with parts, since everyone can open a store there and dropship cheap crap or fakes from china...

[Zucca]

I bet $50 your mower does not need 1KW unless it a riding on type....

Good thing they do not sell those lead heavy, poor energy density and short life 24V battery crap.

Take the 18V or 80V LiIon battery from your other power tool and built an adapter for your mower.
Normally a 24VDC output DC/DC Golf cart step down converter is cheap and reliable.

Also you will be pleased to see how faster your battery will charge up...

If you need the original battery to make the mower happy (battery handshake before starting up), here some inspiration for you.