Well, it is electric....

[reagle]

Hey Andy, how is your mower behaving ?
Getting ready to finally convert my Yardworks to Headways here- I let it keep its SLAs for a year to see how they perform.
They didn't It was OK-ish when grass barely grew, but once rains started, things would get bogged down in the new growth quickly. Thinking of either 8S1P or 8S2P configuration, with a yet to be designed BMS and a stock Headway 5A charger. Any pointers/suggestions based on your experience so far?

 

[AndyH]

Hey Andy, how is your mower behaving ?
Getting ready to finally convert my Yardworks to Headways here- I let it keep its SLAs for a year to see how they perform.
They didn't It was OK-ish when grass barely grew, but once rains started, things would get bogged down in the new growth quickly. Thinking of either 8S1P or 8S2P configuration, with a yet to be designed BMS and a stock Headway 5A charger. Any pointers/suggestions based on your experience so far?

Hi Reagle! The mower did a great job this summer. The blades spin faster longer than when powered by the lead pack. The stock mower had a 40A auto-reset circuit breaker that never tripped - even when the overweight beast came to a stop in tall grass. The 'new' mower is lighter and faster and will chew up tall grass until the breaker trips (stress-tested by cramming the mower thru 8 inch grass until something stopped). I still have to raise the mower for a first pass to handle taller grass, but it cuts much better with the lithium pack. The two 4110 MOSFETS in the active LVC are holding up well.

Later in life the 20Ah SLA pack wouldn't cut the .14 acre lot with one charge. The 10Ah LiFePO4 pack hasn't yet hit LVC in use.

I got rid of the switch and the stock 24V 2A lead acid charger this summer. I'm finally using the LiFePO4 charger's XLR connector to enable the BMS. The mowing and charge process are fully wife tested and approved.

I think you'll like the difference once you install the lithium!

Andy

 

[reagle]

That's very encouraging. So you did not need to do anything to actively limit current to the motor? I was afraid with lower battery impedances, the inrush would be causing problems. I guess I better get off my #%# and start working on mine
Thanks!

Hi Reagle! The mower did a great job this summer. The blades spin faster longer than when powered by the lead pack. The stock mower had a 40A auto-reset circuit breaker that never tripped - even when the overweight beast came to a stop in tall grass. The 'new' mower is lighter and faster and will chew up tall grass until the breaker trips (stress-tested by cramming the mower thru 8 inch grass until something stopped). I still have to raise the mower for a first pass to handle taller grass, but it cuts much better with the lithium pack. The two 4110 MOSFETS in the active LVC are holding up well.

Later in life the 20Ah SLA pack wouldn't cut the .14 acre lot with one charge. The 10Ah LiFePO4 pack hasn't yet hit LVC in use.

I got rid of the switch and the stock 24V 2A lead acid charger this summer. I'm finally using the LiFePO4 charger's XLR connector to enable the BMS. The mowing and charge process are fully wife tested and approved.

I think you'll like the difference once you install the lithium!

Andy

 

[AndyH]

That's very encouraging. So you did not need to do anything to actively limit current to the motor? I was afraid with lower battery impedances, the inrush would be causing problems. I guess I better get off my #%# and start working on mine
Thanks!

I wasn't able to measure the initial current from the lead pack because it finally died. The initial surge with the lithium pack was about 192A. I forget what the unloaded (no grass) current was, but it doesn't bother the 40A auto-reset breaker on the mower, or the pair of 4110 MOSFETs on the disconnect board.

Get with it - it'll be spring soon - you won't be able to keep hiding behind lake-effect snow much longer!

 

[BMI]

It just so seems that electric mower lithium battery upgrades seem to be very popular at the moment. I am no exception since the lump of lead which currently powers my Black and Decker Stealth electric mower is severely dying so it is time for a lithium transplant to give the old girl new life!

My plan is to fit a similar pack to what Andy has done and use 8 cells. Unlike Andy's mower the Stealth mower is powered by a 12V motor instead of a 24V motor. The original battery which comes fitted to this mower is a 12V 40Ah SLA pack. For the last 12-18 months I fitted a pack made of 5 pieces of new 12V 7Ah SLA batteries connected in parallel. These were left over unused from a UPS installation.

I have already given the motor a complete service/overhaul since I have had it in pieces and cleaned it out thoroughly. The commutator was skimmed and new front and rear bearings fitted so it is almost as good as a new motor now.

My plan is to use 8 of our LiFeTech X1E 10Ah Energy cells connected in 4S 2P so I have a capacity of 12V 20Ah. I am still undecided as whether this will be enough capacity and if I should connect an additional 4 cells to make a 30Ah pack.
Initially I will monitor the state of charge/discharge via a Turnigy copy of the Watts Up meter (which I have already) so as to not excessively over discharge the battery. In about a month our factory will have a new BMS + auto cut off board so I plan to use this when it becomes available to protect the cells from over discharge.

Anyway I will post more photos as the project progresses.

 

[reagle]

How true- it's all nice and snow covered now, with nothing to mow at the moment

I wasn't able to measure the initial current from the lead pack because it finally died. The initial surge with the lithium pack was about 192A. I forget what the unloaded (no grass) current was, but it doesn't bother the 40A auto-reset breaker on the mower, or the pair of 4110 MOSFETs on the disconnect board.

Get with it - it'll be spring soon - you won't be able to keep hiding behind lake-effect snow much longer!

 

[grindz145]

My plow-tractor's little briggs and stratton has been giving me all kinds of trouble (it is 40+ years old). I found a 5HP Brushed DC motor which should work nicely, and a bunch of cheap lead will do wonders for keeping the wheels from slipping in the snow 8) . Thanks for the idea

 

[reagle]

Well, it's been a while, but my SLAs finally died and I was forced to get cranking. So far running with a well balanced and charged on the bench 8S Headway pack, it's like night and day I went from 2x12V 17AH SLAs (24 LBs of lead) to a single pack of Headways, that's 6.5Lbs.
The weight reduction plus the fact that things no longer bug down made all the difference. I can now briskly walk across the lawn, barely pushing the thing and cut my lawn in no time. My 0.25 acres took about 4.6AH to cut, so a 10AH pack seems well sized at least for now.
Watching the current, I see about 14-15A idle/low grass, 20A when cutting tall.
Now, on to a simple BMS to do OVC/UV/Balancing

 

[MN Driver]

I've read through this thread and did a forum search and found other threads using Lithium in these 24v mowers. I found a Black and Decker 24v on Craigslist that says it's ten years old with a bad battery that I'm offering US$40 for. The post is about a month old, if I get a reply, I'll take it home as long as the bearings don't sounds like they've been ground up. This one is green in color instead of orange but looks all the same. I've got a stash of 100amp rated(30 continuous) 6.5Ah D NiMh cells that I can recycle into it, I've got a quarter acre lot and the cells are a little worn but I can get 18 together(in 6 cell packs) that match 6Ah well enough for the job. I could do 24 cells but a fully charged NiMh 24 cell pack would hang at 33.6volts without load and with an unloaded blade, it isn't going to have enough sag to where I think it won't overspeed the blade, unless the motors are wound slow enough to begin with but I don't think I'll be willing to take the risk walking behind it. If I didn't have these to recycle, I'd go with some 6S 5Ah LiPo or 8S LiFePO4. NiMh will be a little shy of 12 pounds, double it if I want 12Ah but if I did that, I'd probably just do the backyard and swap the pack to do the front yard if it came to needing the range. If I don't feel like pushing around the weight, I could put the NiMhs in a backpack and wire the backpack to the mower. 12 pounds is nothing on the back compared to trying to push it around and up the slanty parts of the yard.