A123 lawn mower...

[zeropointbug]

Hey guys, I just wipped out my electric lawn mower(24volt) that was bought two years ago, the batteries(Pba) were such shit in it that it could only be used for about 1/2 of it's charge (cuz the voltage curve was poop). One full runtime was about 25 - 30 mins, and you have to walk slower to cut the grass compared to my other 5hp push mower which will cut through pretty anything up to 1 inch trees! lol

Anyways, I threw in an 8s1p A123 pack and viola, spins right up with more power than the big dual 12v/17Ah lead acids that were in there. I went to cut the grass, and I got exactly 4.5 minutes of runtime and then instant dead. Took the pack off, pretty warm (thats 15C discharge)... so i charged it back up again right away and went again. (I'll have to admit, it looked pretty darn funny cutting the grass with this tiny little battery sitting on the mower. lol)

I hooked up the Eagletree the second time around and the results are:

Voltage idle state: 28.2 volts
Voltage when plugged into mower: 23 volts
Amperage: ~30 amps
Watts: 650 watts

I am thinking about making an 8s6p battery for this thing. That should be good for 25 - 30 minutes of runtime. The power output should higher too as the voltage should be somewhere more like 1000 watts peak.

Anyways, I thought i would share with you guys, kinda silly to post it here, but oh well. If you have any better solutions, I'd love to hear them. The motor is kinda low on power, so if you knew where to get a '2hp' electric DC motor (24v) for less than $200, please let me know.

[snellemin]

Awesome man. Another good use for A123's.

[Metallover]

Pictures

[sikeston34m]

Hi ZPB,

I have lots of questions here.

I'm working on a RC Lawnmower.

How many inch cut is yours?

You said you were looking for another motor? Can you push that motor by bumping up the voltage some?

What's the general size and what size shaft? RPM range on 24 volts?

I know you don't wanna spin the blade too fast or it could have a come-a-part.

[Metallover]

I think the rpm is around 3000.

[zeropointbug]

Thanks guys...

Originally Posted by sikeston34m

Hi ZPB,

I have lots of questions here.

I'm working on a RC Lawnmower.

How many inch cut is yours?

You said you were looking for another motor? Can you push that motor by bumping up the voltage some?

What's the general size and what size shaft? RPM range on 24 volts?

I know you don't wanna spin the blade too fast or it could have a come-a-part.

The cut width IIRC is 18 inches? I could be wrong.

I was thinking the voltage boost from the 8s6p pack would just keep the voltage high enough that it would give it that extra power needed. Although, a 10s5p pack might work good too, because I just went and tried a 10s1p pack and i sounded like it had potential if it had enough capacity and voltage holding

I don't know on the shaft size or the RPM/v, couldn't tell you. I think the motor shaft must have some kind of adapter on it to make it the right size for standard mower blades.

[zeropointbug]

Here's the eagletree... notice the time Not too bad for 2300mah!, actually these cells are 3 years old now and are returning 2250mah, with a conservative guess of 200+ cycles.
Looks like it takes 120 amps at start up (can't see it in graph), or 2400 watts, and last a little less than 1 second.

[zeropointbug]

It doesn't seem to matter how much load you apply to a mower, most of the power is taken in spinning that blade that is pitched to suck the grass up. Cutting no grass takes about 550 - 575 watts, and cutting thick stuff with leaves in it takes 850 watts, so it's probably beneficial to move as fast as you can while still cutting the grass.

[Metallover]

It's not self propelled, is it?

[What's_nitro?]

It could be......

[zeropointbug]

Nope, 100% home grown walking.

[Metallover]

Hey, It builds character.

Looking at that lawn mower, is that the one with the lever that changes the cut height on all four wheels at once? I think I saw that on youtube...

[zeropointbug]

Yah! It's a breeze to use! Don't have to ream away at those stupid levers at each wheel, make sure you got them all the same height.

I'm thinkin there is alot left in this motor, like maybe it was a higher voltage motor that was under volted for this application... merely based on the fact that it's not even a degree warm when I take the pack off.

[zeropointbug]

I am going to use a large 6s lipo pack made from 3 Hyperion 6s-4350mah 25C packs. I picked them up at aircraft-world.com for only $90 each.

So this should give me roughly 25 minutes grass cutting mayhem, and then a recharge. This is factoring in with 80% DOD. So we'll see how it goes.

[zeropointbug]

Hey Linc, how would suppose I wire these packs up? Should I wire them up as one pack? Wire them up in parallel at the main leads, and wire the balance plugs together? (bad idea?)

thanks.