Corded Mower Conversion to Lipo

[edcastrovalley]

Well I finally did it! I converted my 18" Black and Decker corded mower to battery power and it works great! I basically gathered all my spare lipo batteries; 4s, 5s, and 6s which are all 5 amphour packs. Put them all in series with an Anderson connector wire harness for a 29s, 5ah pack. After charging they came to 120vdc which is about what I get at the outlet except it's AC. The mower seems quieter, smoother and probably cooler. The run time was phenominal . About 40 minutes with room to spare.

The area I mowed was a quarter acre of dry grass which was more dirt than grass. An easy job for the mower. Total run time so far was about a half an hour. Afterwards I measured the pack voltage for 115 vdc (started at 120vdc) so I took the mower to my old house and mowed the backyard there too since it's a small yard (about 15 x 30 feet). After mowing there the pack voltage was 113vdc which leaves quite a bit of juice left which I'll need for sure in the springtime. It felt so good to mow this yard without a cord! I usually use a 100 foot, 12 gauge cord which is heavy. For the far corner of the yard I also add another 15 foot, 16 gauge cord to that. It was making me want to get the old gasser mower out which I can't stand. Btw: I haven't bought gas in a gas can in a long time. Last time i bought gas for mowing, I paid about 2 or 3 dollars for a couple of gallons in the 1990's. A couple of months ago I filled up a 5 gallon can for nearly $20 and I was kind of in shock.

Now I want to buy a CA for the mower. I'll have to see if a CA can even handle 120 vdc. Also I'm concerned about the original handle switch after reading the thread about the chain saw conversion here under general discussion. Maybe I can have the handle switch power a contactor.

Also, there are a few places I would like to slow down the mower a little where there's more dirt and leaves than the tall dry grass. I end up making a big dust cloud with leaves going all over the place but, if i "pump" the handle and slow down the blade a little, I get good results. Maybe like a big rheostat or something? I don't want to loose too much efficiency otherwise forget it.

The other thing I have to figure out is bulk charging. Maybe i can string together some server power supplies?

 

[Ykick]

Pondering this on my very similar mower I was going to bypass the rectifier however judging by your pics it would seem you left it in circuit?

I measured 144VDC after the rectifier on the motor inputs but I'm sure it's a very dirty/rippled DC. Stands to reason you're noticing a quieter/smoother motor operation...

I wonder if there's any 120VDC brushed controllers out there for reasonable price? That would provide option to speed control rigged with a throttle? Or, depending on your demands it might cut fine running a little lower voltage?

Oh, here's dangerous thought - perhaps use the exisiting rectifier to assemble a super simple charger direct from wall outlet?

 

[edcastrovalley]

Rectifier? Now I'm begining to understand how these universal motors work. Thanks. You have some good ideas here I'm going to look into.

Pondering this on my very similar mower I was going to bypass the rectifier however judging by your pics it would seem you left it in circuit?

I measured 144VDC after the rectifier on the motor inputs but I'm sure it's a very dirty/rippled DC. Stands to reason you're noticing a quieter/smoother motor operation...

I wonder if there's any 120VDC brushed controllers out there for reasonable price? That would provide option to speed control rigged with a throttle? Or, depending on your demands it might cut fine running a little lower voltage?

Oh, here's dangerous thought - perhaps use the exisiting rectifier to assemble a super simple charger direct from wall outlet?

 

[Ykick]

My exact model is MM875 and there's large amount of room under the housing. That's also where you can access the motor terminals and rectifier which is what I did to get an idea of the voltage this thing was running.

Safety 1st - remove the blade if you're going to mess around. Unlike gasoline mowers it doesn't need the blade to run. Another bitch is that 100-120VDC is very NASTY stuff. Puddles, wet grass? Ideally, 24-48VDC motors would be better suited and much more manageable but getting into money.

Like you I've gotta fairly large amount of RC Lipo that's still useable but just not for commuting. Postage stamp yard only needs 5-10 min actual mowing time. Judging from your run time I would be good for the summer on one charge.

Thanks for sharing this!

 

[dnmun]

i think that B&D mower has a manual contactor for a switch. the lever on the handle pulls the switch arm down to close it as i remember and there is a key in the base of the lever for safety in the form of an axle with a fob on the end to hold it to stick into the case, and that is required to make the switch work.

 

[edcastrovalley]

I was looking up our two mowers, (MM575) and (MM875) and even though your's has a 19" blade compared to my 18", they both still have a 12 amp motor. So, maybe they have the same motor? Lipo may work just as well. Before connecting my mower to 120vdc I connected it to my bicycle battery pack of 60vdc and it seem to work fine although a little slower. Might be good test with a smaller pack first?

I'm going to look under the housing tonight and check out the electrical inside the mower.

And yeah, I have to be careful with the voltage. You can't be too careful with this stuff. A purpose built battery mower would be the way to go.

My exact model is MM875 and there's large amount of room under the housing. That's also where you can access the motor terminals and rectifier which is what I did to get an idea of the voltage this thing was running.

Safety 1st - remove the blade if you're going to mess around. Unlike gasoline mowers it doesn't need the blade to run. Another bitch is that 100-120VDC is very NASTY stuff. Puddles, wet grass? Ideally, 24-48VDC motors would be better suited and much more manageable but getting into money.

Like you I've gotta fairly large amount of RC Lipo that's still useable but just not for commuting. Postage stamp yard only needs 5-10 min actual mowing time. Judging from your run time I would be good for the summer on one charge.

Thanks for sharing this!

 

[edcastrovalley]

I'll look tonight to see if my mower has this. This might be a good thing. Thanks. 8)

i think that B&D mower has a manual contactor for a switch. the lever on the handle pulls the switch arm down to close it as i remember and there is a key in the base of the lever for safety in the form of an axle with a fob on the end to hold it to stick into the case, and that is required to make the switch work.

 

[edcastrovalley]

Well I opened the top last night. It was hard because all I wanted to do was go out and mow. I never expected an ev grin with a walk behind mower.

On the top you can see the motor brushes on the right and left. Also there's a rectifier with the little plugs on it. It has 4 terminals on it and there's 4 wires coming from the handle switch. I'm guessing the 4 wires are a neutral, hot (for motor run), electric brake, and maybe a ground? It looks like there's a chip there. Probably the rectifier. Not sure the electric brake is controlled by the chip at all. Looks like a simple design. Not really anything else in there.




I was looking at the morning paper and happened upon a Lowes ad for their "Kolbalt" battery push mower. It has a dual lithium battery arrangement of two 40 volt, 2 ahr packs. Doing a little math and I come up with a 160 watthour battery which compared to my 600watthour pack (120vdc times 5ahr) made me laugh. No wonder I was mowing all over the place.

 

[dnmun]

i was thinking this was the battery mower, which is why i was thinking you would find the manual contactor.

this one is AC so it has the regular toggle switch.

the four legged rectifier diode bridge is how the AC is converted to DC.

the DC is what drives the motor so you can identify the positive side of the rectifier bridge and know where the positive lead of the battery goes.

 

[Ykick]

Looks like the same motor and rectifier board but MM875 has tons more room under the cover than MM575. I haven't qualified the OEM switch used yet but we may be looking into it if/when high voltage DC messes it up?

Unfortunately I'm not home for a few weeks so I can't grab any pics but I'll be checking in as you iron this out. My yard is so small it's the damn AC cord which takes more time to dress and fuss with than the actual mow.

Cheap 120V 1000W brushed controller would be extremely cool....

 

[gogo]

I've had two corded B&D. The lever that actuates the switch wore down on one. I parked the other on top of dirt for the winter and ants made a nest inside the motor which then allowed the moisture present to get behind the magnets and pop them off when it froze. Another had a brush lead constrained due to poor assembly.

Here's a good site for particulars:
http://nickviera.com/electrical/lawn_mower/bandd/

 

[edcastrovalley]

Yeah, no contactor. Damn. It does look easy to bypass the rectifier. Thanks.

i was thinking this was the battery mower, which is why i was thinking you would find the manual contactor.

this one is AC so it has the regular toggle switch.

the four legged rectifier diode bridge is how the AC is converted to DC.

the DC is what drives the motor so you can identify the positive side of the rectifier bridge and know where the positive lead of the battery goes.

 

[edcastrovalley]

You can probably keep your batteries inside the cover. I started checking out brushed controllers. There are a couple 120v versions around but pricey so far...

Looks like the same motor and rectifier board but MM875 has tons more room under the cover than MM575. I haven't qualified the OEM switch used yet but we may be looking into it if/when high voltage DC messes it up?

Unfortunately I'm not home for a few weeks so I can't grab any pics but I'll be checking in as you iron this out. My yard is so small it's the damn AC cord which takes more time to dress and fuss with than the actual mow.

Cheap 120V 1000W brushed controller would be extremely cool....

 

[edcastrovalley]

I guess it's good to keep the mower in the garage.

I like the link you posted here. Thanks

I've had two corded B&D. The lever that actuates the switch wore down on one. I parked the other on top of dirt for the winter and ants made a nest inside the motor which then allowed the moisture present to get behind the magnets and pop them off when it froze. Another had a brush lead constrained due to poor assembly.

Here's a good site for particulars:
http://nickviera.com/electrical/lawn_mower/bandd/

 

[nechaus]

I wish we had 120 volts not 240

 

[Ypedal]

Well done !!..

I love my Lipo Leaf Blower

http://ypedal.com/Leaf/blower.html

The switches keep failing.. currently running directly to andersons and no more problems.

 

[veloman]

Usually you can find battery mowers with dead sla on Craigslist for free or very little money. I use a 48v craftsman with 14s 5ah lipo. Cuts great and is very lightweight. Love cutting grass now. Sold the gas mower for $80 and never buy gas again. True savings

 

[edcastrovalley]

Why thanks Ypedal! Your leaf blower video was exactly what convinced me to try this. I saw the video a couple of years ago but when I moved to the new house with a larger yard (smaller house but larger yard) I was left with few options but to try this. I mowed twice with the cords then couldn't get myself to mow anymore and the grass grew 2 feet high. Running around with the lipo on the mower probably took half the time to do.

That's interesting about the andersons. They're pretty much indestructable. Luckly with this mower there's enough room under there for a contactor.

Well done !!..

I love my Lipo Leaf Blower

http://ypedal.com/Leaf/blower.html

The switches keep failing.. currently running directly to andersons and no more problems.

 

[edcastrovalley]

I've thought of buying a used battery mower but finding one with dead batteries is not bad a idea! I think I'll keep an eye out for one.

Usually you can find battery mowers with dead sla on Craigslist for free or very little money. I use a 48v craftsman with 14s 5ah lipo. Cuts great and is very lightweight. Love cutting grass now. Sold the gas mower for $80 and never buy gas again. True savings

 

[Samd]

Great thread. I'm with Nechaus, a bit of a shame about the 240V AC in australia. I wonder if they use a different winding in the motors here or step the voltage down.

A cycle analyst on a mower. I reckon that'd have to be a first....

 

[ohzee]

Been trying to find a cordless mower on CL. Figure if I keep it up I will get one.

120volts tho sounds like to much trouble for me much rather just do 24/48 , but I understand if it's what you have.

 

[RLT]

About 7 years ago I (with the advice of Fechter and a couple other E-S guys) converted a cheap controller to 130+ volts.

Some discussion of it on previous pages, but the real 'meat' of it begins 3/4 of the way down the page HERE::
http://endless-sphere.com/forums/viewtopic.php?f=2&t=278&start=200

TNC Scooters still sells the controller I used, for about $40
http://tncscooters.com/index.php?route=product/category&path=41_75
An even the cheaper 24 or 36 V Yi Yun type controllers should be convertable with the same components and methods I used.

 

[edcastrovalley]

Great thread. I'm with Nechaus, a bit of a shame about the 240V AC in australia. I wonder if they use a different winding in the motors here or step the voltage down.

A cycle analyst on a mower. I reckon that'd have to be a first....

Yeah, 240 vdc would make for an interesting mower for sure. Might be a little dangerous.

I was checking into the CA and they do work up to 150 vdc. I was thinking of mounting the speed sensor magnet on one of the wheels to keep track of mowing mileage. I guess I can input a wheel diameter of 4" into a CA?

 

[edcastrovalley]

About 7 years ago I (with the advice of Fechter and a couple other E-S guys) converted a cheap controller to 130+ volts.

Some discussion of it on previous pages, but the real 'meat' of it begins 3/4 of the way down the page HERE::
http://endless-sphere.com/forums/viewtopic.php?f=2&t=278&start=200

TNC Scooters still sells the controller I used, for about $40
http://tncscooters.com/index.php?route=product/category&path=41_75
An even the cheaper 24 or 36 V Yi Yun type controllers should be convertable with the same components and methods I used.

This would be fun to try. Then I would get a throttle lever from a gas mower to control the speed. 8)

 

[silviasol]

Well done !!..

I love my Lipo Leaf Blower

http://ypedal.com/Leaf/blower.html

The switches keep failing.. currently running directly to andersons and no more problems.

Think of installing a relay switch?