Electric Tractor

[Cosmacelf]

Easy to do. Large format lithium batteries, induction motor and controller. Actually have the parts laying around. Would be a great project!

Yeah I was thinking large format batteries like from CALB (http://www.calbusainc.com/), AC induction motor, regen braking (might not even need regular brakes, except as a parking brake).

The large format batteries allow you to have a charger setup such that you charge each cell individually, allowing you to automatically balance your cells every time you charge.

You do have to look at operating and charging temperature ranges though.

 

[MikeBur]

Did you see this previously?

{threads merged, link removed}

also, I sometimes have to manually ballast my tractor at the front to counter-balance weight of attachments at rear. Maybe have the batteries on underslung, repositioned, tray? No like we'd have to deal with high speeds and much momentum? ;-)

 

[JRP3]

 

[Kandiru]

Tesla of riding mowers, c'mon. This one is available:

 

[JRP3]

The large format batteries allow you to have a charger setup such that you charge each cell individually, allowing you to automatically balance your cells every time you charge.

I must say I don't know anyone who does that. Some people use a BMS on each cell that will bleed charge of the highest cells and shut off the charger if any cell gets out of range, but they are connected to a single charger charging them all in series. I've been running a pack of CALB's for 5 years just using a Manzanita Micro PFC battery charger and no BMS. I bottom balanced them initially and stay away from fully charged or fully discharged. Although on 3 occasions I've run my pack below 2.0 V per cell average, (jump out of the car and start pushing), with no damage, because I'm bottom balanced no single cell was driven below zero.

 

[Cosmacelf]

I must say I don't know anyone who does that. Some people use a BMS on each cell that will bleed charge of the highest cells and shut off the charger if any cell gets out of range, but they are connected to a single charger charging them all in series. I've been running a pack of CALB's for 5 years just using a Manzanita Micro PFC battery charger and no BMS. I bottom balanced them initially and stay away from fully charged or fully discharged. Although on 3 occasions I've run my pack below 2.0 V per cell average, (jump out of the car and start pushing), with no damage, because I'm bottom balanced no single cell was driven below zero.

These guys do it the individual charger way: lithium Batteries Solutions for LEV's

I've converted three golf carts so far with their setup. Seems to work fine, and I like the fact that you don't need to balance the cells.

 

[JRP3]

Interesting. For a small number of cells like that I can see it wouldn't be too bad, but obviously they are using a slow charge rate at 10 amps. I don't really like that they are charging to 3.65V, these LiFePO4 cells are about 90-95% full at 3.5V, taking them to 3.65 and holding them there as current ramps down is unnecessary. I usually take mine to 3.45 and don't bother with a current taper, and that keeps me around 80-85% charged.

 

[Cosmacelf]

To keep cost down, they have a much smaller battery pack in terms of KwH than the equivalent lead acid its replaces. Of course, the lead acid KwH specs don't reflect reality (I think they are quoted as 1/20C discharge rates usually), but nonetheless, I think they figure they need the capacity.