# John Deere Lawn Mower



## Sunking (Aug 10, 2009)

KillahBee said:


> My second question is, is there any downside to using 6 volt batteries instead of 12v batteries in my pack? 6 volts AH ratings seem to be a lot higher for a better cost and would provide me with a pack with higher AH for the same cost as the 12v system. Was planning to get one of those chargers that has 4 leads on it for each 12v battery (or 2 6v batteries)


None of the above. because you will not be using lead acid batteries. Your pack operating voltage is going to be 48 volts minimum, and you would not use lead acid batteries, or at least you should not be using lead acid batteries. To be usable in the extremely limited space you have to work with should be using lithium 3.2 volt batteries. You would need 16 of them for 48 volts of as high of a AH capacity you can squeeze in the space. 

Example a 48 volt 100 AH lead acid battery would occupy roughly 60 to 65 Liters of space weighing in around 275 to 300 pounds. An equivalent Lithium Ion (LiFeP04) 48 volt 60 AH battery would occupy 25 Liters of space (less than half of lead acid) and weigh roughly 125 pound. (less than 1/2 that of lead acid). 

As for motors you will be using a 48 volt golf cart motor made for torque in the 3600 RPM range with a 500 amp controller. You would need an adapter plate or pin made.


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## KillahBee (May 30, 2016)

This was the setup I was planning on:
http://www.diyelectriccar.com/forums/showthread.php/sale-sep-ex-system-172954.html

I have been looking at the lithium option and to me the cost is to high which is why I was thinking the lead acid route. I was hoping for something 48v 150ah


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## Sunking (Aug 10, 2009)

Motor is fine, it is a high torque low RPM Golf Cart Motor as I suggested. But there is no way you are going to get 8-6 volt 150 AH or 6-8 volt 150 AH batteries on that tractor. You are talking about a battery requiring 100 liters weighing some 400 pounds. 

A good set of Trojan Ranger a 8 volt 160 AH battery will last you 2 to 3 years if you limit discharge to 50% DOD. You would need 6 of them and unit cost is $170 to $200 each or $1000 to $1200 total. 

Or you can buy say 16 CALBs 60 AH (roughly the same usable capacity) for $80 per unit ($1300) and will last 5 to 6 years. When you look at long term cost LFP is about half the cost. Not only less expensive long term, but will actually fit and work. Now you are down to 70 pounds, and 30 liters of space.

Do some math, look at the 6 and 8 volt Pb batteries weight and size. Tell us just how you plan to install them. Look at a golf cart battery tray dimensions. You are trying to put 10 pounds of chit in a 2 pound box.


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## KillahBee (May 30, 2016)

Ah ok, I got you. So because I can use the full capacity of a lifepo4 and it will still last longer, I can buy smaller capacity battery and don't need to spend that much. Ok thanks for the help on this!

I guess now I will just need to figure out how to get the shaft to work with the pully

And thank you for your help!


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## Sunking (Aug 10, 2009)

KillahBee said:


> Ah ok, I got you. So because I can use the full capacity of a lifepo4 and it will still last longer, I can buy smaller capacity battery and don't need to spend that much.


That is only half the story. Mr Peukert wants his cut of the action. 

Perkert Law States:* The greater the discharge rate, the lower the delivered capacity.*

Lead acid batteries are significantly effected by Peukert Law. Those Trojan Ranger batteries are rated at the 20 hour Discharge Rate, or 8 amps. So here is the deal, you will be discharging more like 1C around 100 amps and peak 500 amps. That means your 160 AH battery becomes 100 AH or less.

Lithium batteries are rated at 1C and very little Peukert effect. So in the real world th e60 AH lithium has more capacity than the 160 AH Pb at high discharge rates.


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## KillahBee (May 30, 2016)

Wonderful info Sunking, appreciate you taking the time to educate me on this!


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## dcb (Dec 5, 2009)

have you looked at 7/8 bore pullies? Not sure what the exact requirements are, but if vbelt then trivial costs.

http://www.surpluscenter.com/Pulleys/Finished-Bore-Pulleys/


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## KillahBee (May 30, 2016)

I did unfortunately it looks like this and I can only seem to find these ones in the 1" variety.


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## dcb (Dec 5, 2009)

might be able to use two motors or something too, one for the deck and one for drive (or 3, two for the deck, etc). My elec-trak uses 3: two smaller ones 1 for each blade direct drive, and 1 larger one for drive through a belt clutch and a gearbox/diff. But they are shunt/permanent magnet motors, and just run at a continuous speed unloaded.

you can see it is built like a giant battery box though. But the front is empty since adding leaf batteries, and w/15 batteries it is overkill, I charge like once a season...


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## KillahBee (May 30, 2016)

Yeah I was thinking about something like that, a motor for each blade. 
My plan is actually to see how this goes and than decide if I want to add motors for the blades. Right now the tractor is mostly just used for cutting grass but if I start using it more for hauling and such than that would probably be the route I take.


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## dcb (Dec 5, 2009)

I doubt this is "reccomended", but you can try an experiment w/this.

http://www.ebay.com/itm/7-8-to-1-in...k-Shaft-Sleeve-adapter-Predator-/380843550721


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## KillahBee (May 30, 2016)

Yeah unfortunately that's what I am aiming towards right now, it will just need some modification to work for me.


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## samwichse (Jan 28, 2012)

6 Nissan Leaf cans is a nice 48v 60ah battery... $600-700 if you shop around.


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## KillahBee (May 30, 2016)

That would be perfect, thanks Sam. I will start shopping around and see what I can find.


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## dcb (Dec 5, 2009)

also, I think you will want to keep the drive and deck motor(s) separate since you are getting a decent sepex motor w/reversing controller I think.

http://www.diyelectriccar.com/forums/showthread.php/sale-sep-ex-system-172954.html

but you will have some homework to sort out the controller config. Welcome to the world of proprietary controllers 

http://www.fsip.biz/Documents/Sevcon PowerpaK (SEM & MicropaK) Manual – with Calibrator Section.pdf

(or you can just make a "dumb" pwm bucking feed for the field and call it good).


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## KillahBee (May 30, 2016)

So for that it will be forward, only because the tractor has hydrostatic so it can do the forward and reverse.

How do I go about the dumb thing, considering I really just want the motor on at a constant speed or if I can just do a basic speed control I would be happy with that, I was hoping I could use the throttle that's on the tractor and rig it up so I can use it to control the speed of the motor.


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## dcb (Dec 5, 2009)

KillahBee said:


> How do I go about the dumb thing.


Honestly I'm a bit out of my experience here, I don't really know how the armature will like being at continuous 48v at full field (motor will be slower so less internal fan-age, and extra current in the motor field), but conceptually you *should* be able to take something like this and control the field strength manually (throttle?) and let the armature do what it is gonna do.

http://www.ebay.com/itm/2000W-10V-5...138456?hash=item2c7804c0d8:g:q4kAAOSwe7BW0Rj3

if it is in neutral and the field is too weak then it can overspeed too. Nor would I let the rpm get too low under load for any duration.

If you have a way of monitoring temps/current then that would be helpful, if not actually required.


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## KillahBee (May 30, 2016)

Ah ok, well I will keep that as an option in my back pocket. 
I have the controller so might as well see what I can do with that before trying something else.
Thanks for all the tips and help


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## dcb (Dec 5, 2009)

conceptually the field only control is a bit like like hydrostatic, turn up the field for high torque, low rpm. turn it down for low torque high rpm. and try not to melt anything or blow anything up


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