Ideas for EV farm machinery

Electric cars, trucks, ATVs, NEVs - things bigger than a motorcycle.
wjr   10 W

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Ideas for EV farm machinery

Post by wjr » Nov 23 2019 7:24am

While I'm still busy to get my first EV project going (an Kawa enduro conversion),
I'm already thinking about electric farm machinery.

Has anybody similar thoughts?
I'd like to share and discuss.


I work on 100 ha (organic agriculture) and spend ~ 10 000 l diesel fuel each year.
This adds up to 30 .... 50 kWh electricity, which is only a quarter to third the photovoltaics on my roofs were able to supply.

So the winners questions: how to get the Sun from the roof to the soil?

my preferred solution would be to leave the Agritechnica style of construction pradigma, which boils to
"if it is not double the HP, double the weight and quadruple the price than last year's, then that's not innovation"

So my first idea were a 1-shear plough - since ploughing is the largest single amount of diesel fuel consumption.
(maybe equal to grain harvesting, but that's a much more complex thing)

Currently I run a 140 HP (= 105 kW) tractor with a 5 shear plough, so 20 kW per shear is a reasonable starting point.
Quality ploughing is slow, and my tractor runs half throttle most time, mabe with the exception of steep hills and some wet potholes.

But high peak power margin is cheap in EV, it's battery capacity that costs.
So 20 kW peak and 10 kW cont average I think is a good planning figure.

My current equipment weights ~ 6 ton the tractor, 2 ton the plough, gives 1600 kg per shear.
Thrust is proportional to weight, given similiar tyre technology, so that's a cornerstone as well.
So battery technology is not restricted by weight, even lead acid might be a consideration.

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Re: Ideas for EV farm machinery

Post by wjr » Nov 23 2019 7:36am

My next idea was to use LTO as the Chinese use in their buses, since they allow very fast charging (10C, maybe even 20C) and provide elctricity cables to the field edge aka headland.

This might be a viable solotion for grid power, but within the current framework of the German renewable energy scheme (EEG), this might heavily hurt economy, since the energy peaks of chrging might exceed the capacity of my photovoltaics.
I had to sell my own energy for cheap and buy grid energy some minutes later.

I could use a fixed battery storage to solve this (and others). But then I end up in shuffling energy from the fixed storage battery to the EV tractors battery - with losses and cost.

So the consequence were a system of mobile changeable batteries that are charged at home from the roof PV and physically moved to the field EV. With forklift and similiar gear, this is proven technology for decades.

However, considering economy of labour, a 1-share plough had to be self guided by GPS or sth.
So not to spoil this, the battery exchange hat to run automagically as well, I'd prefer.

OK, If battery change interval is above 3, or better 5 hrs, manual battery change might be feasible, at least for early experimentation.

On the other hand, if I could meet the challenge of an autonomous battery changing system, the plough itself may be the lest complex part of the system, so it were easily extended to other machines.

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Re: Ideas for EV farm machinery

Post by wjr » Nov 23 2019 7:52am

As a consequence, I think motors and control units were fixed to machinery.
I'd leave the traditional tractor-attachment design pattern.
A standard async industrial motor is usually cheaper than a simple angle gear - and even provides an axle with a bearing, which you would need any way.
You save a lot of complex transmission gearing, if you can supply torque right where it is required.
Cables are much cheaper and more flexible than gears, chains, belts, PTO gimble shafts...

Standard motors call for standard controllers, which are frequency converter in industrial drives.
If it comes to > 5 kW, they are attached to 3P-400V, but have an internal intermediate DC-circuit with capacitors that operates at somewhere ~ 600V. Most converters can be fed directly by this DC-circuit.

So maybe the battery could be designed to meet this voltage.
This would come out to 260S LTO, 167S LiIon or sw inbetween LiFePO
Maybe a security nightmare, but feasible.

I also encountered DC-DC-converters for feeding lower batt voltages to 600V converters intermediate circuit,
But this adds cost and losses as well.

600 V is also the magnitude of roof scale PV string voltages.
So maybe direct battery loading without the intermediary AC grid could further increase efficiency.
I haven't yet encountered a DC-DC-MPP tracker for such high voltage.
But photovoltaic AC inverters have an intermediate DC circuit as well.
So maybe this can be tapped to short way load a 600 V battery pack?

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Re: Ideas for EV farm machinery

Post by nicobie » Nov 23 2019 5:36pm

That would be an ambitious project, but one that will have to be conquered eventually as sooner or later we will run out of fossil fuels.

I wish you the best of luck on this. We need more folks like you. :thumb:
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May your tote always stay tight and your edge eversharp :wink:

my eTownie build thread: http://endless-sphere.com/forums/viewto ... =6&t=23701

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Re: Ideas for EV farm machinery

Post by wjr » Nov 23 2019 7:42pm

Thanks for the flowers :wink:

I think all the large manufacturers are working on projects like those, as some universities do as well.
But when it comes to delivering, I expect them to try any available option of "customer lock in".

So we'd expect a lot of propietary solutions, not compatible with each other, heavily overengineered.
Much worse like the situation with charging connectors for public EV charge stations, I'm afraid.

Lets hope I'm wrong. Time will tell us.

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Re: Ideas for EV farm machinery

Post by billvon » Nov 23 2019 7:52pm

wjr wrote:
Nov 23 2019 7:36am
My next idea was to use LTO as the Chinese use in their buses, since they allow very fast charging (10C, maybe even 20C) and provide elctricity cables to the field edge aka headland.
With a fixed pattern for plowing, why not run power directly to the tractor? A good reel system with a high voltage cable could avoid the need for mobile batteries.
--bill von

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Re: Ideas for EV farm machinery

Post by wjr » Nov 24 2019 1:50pm

billvon wrote:
Nov 23 2019 7:52pm
A good reel system with a high voltage cable could avoid the need for mobile batteries.
Hm... interesting idea.

Not sure how reliable this were.
I run an irrigation machine that pulls the pipe towards a fixed drum.
Needs quite some effort to control it.
Well, technology from the 1980ies, and moving pipe.

If it were possible to carry the reel on the tractor, there were no need to move the cable over the soil.

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Re: Ideas for EV farm machinery

Post by wjr » Nov 24 2019 2:35pm

Just did a quick hack to check feasibility.
(Used some online tool in German language)
10 kW, 400V-3P -> 14,43 A
500 m cable lengt, 10 mm²
-> 5,3 % voltage drop
This is more than recommendet for fixed installations in DIN 18015, but still OK I think.
I even might live with more,

4mm² -> 13,25% , 226 kg, 1400 €
6mm ² -> 8,84%, 278 kg, 1900 €
10 mm² -> 5,3 %, 500 kg, 3350€
16 mm² -> 3,31 %, 715 kg, 4900 €

25 mm² -> 2,12 %, 1048 kg ??

weight is for 500 m of 5G H07RN-F
price is for 500 m just a quick ebay lookup
current carrying limit is OK even for less than 4mm²

So - yes, feasible in terms of weight and cost.

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Re: Ideas for EV farm machinery

Post by wjr » Nov 24 2019 2:44pm

The challenge of reeling and unreeling doesn't sound that complicated in the first instance.
If I have GPS guided track and speed, I have reeling rate to compare against,
I can check the cable tension and compare real reeling rate with real speed - to check for problems.

I'm sure that's not a wheel to be reinvented - there are reeling specialists alredy lingering somewhere, I'd expect.

Mmh, begin like the idea. :bigthumb:
looks easier - and maybe even cheaper - than batteries.

Of course, I need grid acces in any field.
Depending on the distribution, this may be the game changer.
I managed to get water for irrigation to a large portion - so what.

Might have a second reel on the headland that slowly moves along the parallel tracks
but that's already detail planning

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Re: Ideas for EV farm machinery

Post by wjr » Nov 24 2019 5:46pm

still playing with the cable loss calculator.
Losses scale inverse to the square of voltage, and DC is more effective than whatever fluctuating stuff such as AC.
I think I should go for DC at max of the cabling rate.

If I stay with H07RN-F - which is a standard cable type, produced at high volume discount prices
it's "rated " 450/750 V, and google revels that DC is allowed at a factor of 1.5 upon those
So we can operate 650 V wire-earth and 1125 V wire-wire.

At 1000 V, even 4 mm² suffices to keep losses as low as 4.46 % / 500 m
And we need 2 wires only, not up to 5 as in a proper compliant 3-phase system.
I think I should consider a transformer for galvanic isolation to get rid of the grid companies regulations.

Had speculated about a DC-DC bridge in some other context and was advised to implement this with a star-delta-transformer, 12-point rectification and feed the resulting DC into some standard off-the-shelf solar inverter.
So why not recycling this idea and just add a long reeled DC-cable between?

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Re: Ideas for EV farm machinery

Post by Hillhater » Nov 25 2019 1:17am

Just a comment..
Why do you need to Plough ?.... it is not considered to be necessary for modern farming techniques.
Also considered undesirable for the atmosphere (if that is a concern ?) as it releases much more CO2 from the soil.
Look up “no Till” cropping methods.
But, if you have to , ploughing is all about torque, not kW, so gearing is your friend.
Your typical 20kW small tractor can produce as much as 10,000 Nm of torque at the wheel.
It may be difficult to find a direct drive electric drive to match that
Initially, a simple EV conversion on a small conventional tractor to utilise the proven gearing and other systems

PS... 1.0 ltr of diesel is equivalent to 10.0 kWh ! :shock:
So your 10,000 ltr usage would be equivalent to 100,000 kWh
Ignoring losses etc, and assuming a typical CF of 0.15, you would need at least 80 kW of solar to produce it.

Ahh .. sorry, i forgot, your ploughing will be concentrated into the autum/winter months i assume ?
If so, that means your power consumption (and generation) will also be concentrated in that period rather than spread evenly through the year....which happens to be a poor time for solar PV generation also .
Even if only 50% of your fuel consumption is ploughing that still suggests you need 50,000 kWh generated in a 3 month period... 500+ kWh per day..!..... :shock:
You sre going to need your own Solar Farm ........and backup !
Last edited by Hillhater on Nov 25 2019 3:09am, edited 1 time in total.
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Re: Ideas for EV farm machinery

Post by jonescg » Nov 25 2019 3:05am

Unfortunately no-till agriculture and organic don't really work together (glyphosate and all that ;) ) but yes ploughing will still take a tremendous amount of energy. However if you spend most of your time on the tractor slashing grass, carrying hay or generally doing odd jobs, an electric tractor is entirely reasonable.

10,000 litres of diesel might equal 124,000 kWh, but the tractor would only make use of about 20% of that. So you would need about 25,000 kWh per year, or ~70 kWh a day, on average. You'll need twice this battery size though, charging at night and all that ;)

But yeah, I'd love to build one for shits and giggles. Most mixed farms don't do much ploughing, mostly light duties.

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Re: Ideas for EV farm machinery

Post by Hillhater » Nov 25 2019 3:29am

Looking at it another way, ...
A 20 kw tractor will use a maximum of 480kWh per day ( continuous 24hr Automated operation)
But probably more realisticly a 12hr day and 240kWh is likely
.. still alot of power to generate from PV in winter time.
So somewhere there will need to be a decision on which limitation is key ..
Generation capacity ?
Battery capacity ?
Operating time ?
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Re: Ideas for EV farm machinery

Post by Hillhater » Nov 25 2019 5:20am

jonescg wrote:
Nov 25 2019 3:05am
.
.....
10,000 litres of diesel might equal 124,000 kWh, but the tractor would only make use of about 20% of that. So you would need about 25,000 kWh per year, or ~70 kWh a day, on average. You'll need twice this battery size though, charging at night and all that ;)
You would be a brave person to base any energy forecast on a 20% conversion factor for a modern diesel.
Current automotive diesels are commonly over 40% efficient, with slow marine diesels over 50%.
A tractor which is designed to operate at peak efficiency (IE constant speed) will also be in the 40-50% range.
https://theicct.org/blogs/staff/ever-im ... sel-engine
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Re: Ideas for EV farm machinery

Post by jonescg » Nov 25 2019 6:47am

Maybe, but how do you define the efficiency of a tractor lifting rocks and sods? I mean there's some complicated physics to account for - it's not just mass and distance travelled over time anymore. I guess the fuel consumed is all you have to go on.
Since you'll have torque from low speeds, it changes the nature of the gearing and differential massively - dual motors with planetary reductions? Lots of options to keep a mechanical engineers busy.

And I'm guessing most farms don't have the latest and most efficient machines.

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Re: Ideas for EV farm machinery

Post by Hillhater » Nov 25 2019 7:56am

We can only generalise.
IE. ploughing established farmland is generally a steady load , barring hills ,wet areas etc.
An experienced operator knows what rpm and ground speed gives the best result and work rate, whilst minimising fuel consumption (lt/ha),
Most diesel tractors are designed to operate in a specific rpm band (peak torque) for optimum efficiency and have been so for 50+ yrs.
And there is this..
https://www.futurefarming.com/Machinery ... or-4419WP/
And for more giggles..

Wjr’s machine would have to be ancient to only return a 20% energy utilisation.
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Re: Ideas for EV farm machinery

Post by Hillhater » Nov 25 2019 7:41pm

It appears that much of this is already being developed..
https://www.farmweekly.com.au/story/621 ... c-tractor/
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Re: Ideas for EV farm machinery

Post by Hillhater » Nov 26 2019 2:44am

An intro to organic, No Till , farming..
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Re: Ideas for EV farm machinery

Post by jonescg » Nov 26 2019 5:39am

Very cool. Some observations though - Illinois cornbelt is some of the most amazeballs soil on the planet. They report rye yields in the order of 15 tons per hectare. In the WA wheatbelt, 1.4 tons per hectare is a cracker of a year. I'm surprised he pushed over all that straw just to grow pumpkins. Pumpkins must be worth a lot over there :?

I take issue with organic agriculture - why deliberately go about things the hard way to produce a crop you can sell to rich hippies? And their opposition to genetically engineers crops is as bad as opposing nuclear on safety grounds (that is, the science doesn't back up their claims). https://www.abc.net.au/news/rural/2017- ... gm/8302458

Love the tethered tractor :) I think the Russians had something similar in the late 50s... I

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Re: Ideas for EV farm machinery

Post by Hillhater » Nov 26 2019 5:54am

Yes, agree, but just pointing out that No Till and Organics can be combined to some extent.
NoTill seems a logical advance in cropping for many reasons, not least of which is reduced energy required.
https://agex.org.au/media/no-till-organic-farming/
BEV Tractors could be viable for non tilling work, but before any heavy duty equipment can be electrified, we will need a new generation of batteries
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Re: Ideas for EV farm machinery

Post by wineboyrider » Nov 26 2019 9:56am

ES IS SAVED! THANK YOU JUSTIN.

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Re: Ideas for EV farm machinery

Post by billvon » Nov 26 2019 1:29pm

jonescg wrote:
Nov 26 2019 5:39am
I take issue with organic agriculture - why deliberately go about things the hard way to produce a crop you can sell to rich hippies?
There's a lot of good things about parts of organic agriculture (i.e. agriculture that doesn't rely heavily on natural gas or petroleum based pesticides) but some of the aspects of it are just silly, and don't contribute to either energy efficiency or food safety.
--bill von

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Re: Ideas for EV farm machinery

Post by wjr » Nov 26 2019 2:33pm

Hillhater wrote:
Nov 25 2019 1:17am
Why do you need to Plough ?.... it is not considered to be necessary for modern farming techniques.
Yes, of course, you can use Glyhosate aka Roundup, of course.
But I'm in organic farming, so well, let's say - I don't like that - OK :wink:

I've been watching no plugh systems in organic farming coming and going for decades.
Maybe in some areas it may work - in my area I don't know anybody sustainig it for more than 10 years.
After all, the plugh has the lowest specific energy requirement per volume of soil moved.

But anyway, I think this question in all its deep considerations is beyond the scope of this forum.
Hillhater wrote:
Nov 25 2019 1:17am
ploughing is all about torque, not kW
of course I can slow down.
But you have to get your act done when winter is coming.
Hillhater wrote:
Nov 25 2019 1:17am
PS... 1.0 ltr of diesel is equivalent to 10.0 kWh ! :shock:
That's the raw energy content, isn't it?
But the second law of thermodynamic is EV's friend in this case, since electric energy is alread equivalent to mechanic, no need to go the lossy 30..40 % thermal cyles any more.

My rough estimate is 5 l/HP and hour, but I think with slower speed, lower weight, motors close to the axle w/o complex transmission stuff, I came to my estimte of 3 kWh to replace one l diesel fuel.
Just a rough order of magnitude.
Hillhater wrote:
Nov 25 2019 1:17am
500+ kWh per day..!..... :shock:
Currently I have 150 kWp on my roofs, maybe will be double the next years.
so, no need to be shocked.
Time of ploughing depends on the system a little bit, can partly be shifted to summer month. July, August...

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Re: Ideas for EV farm machinery

Post by wjr » Nov 26 2019 2:45pm

jonescg wrote:
Nov 25 2019 6:47am
Since you'll have torque from low speeds, it changes the nature of the gearing and differential massively - dual motors with planetary reductions?
My Idea was to use ordinary standard industrial asynchronous AC induction motors.
They are designed for 24/7 and quite cheap.

Simplest design would be to attach each wheel to a simple worm gear motor.
Had the advantage that I don't have to design for a brake.
But worm gear may not be the best in efficiency.

If somebody sells me a chap planetary gear - fine.
For sure I'll not go and design my own.
But maybe I can just use a common tractor's front axle?

Well, the alternative might be to use modern EV-style motors, such as the QS 138 I wanna try on my bike conversion.
Add a gear, operate it in the sustainable power range, add a cooling fan and maybe replace chinese bearings by high quality long life bearings.

Depends a little bit on the voltage.
So, a battery might tend for EV-Motors, a cable reel might tend for AC induction motors.

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Re: Ideas for EV farm machinery

Post by wjr » Nov 26 2019 2:57pm

regarding the question of till vs no till:
That's not the point for me here.
If can drive an electric gadget in parallel tracks over the field, I can let do it pretty much anything I want.
So I'd like to leave evergoing agricultural discussions where they belong - they have their place there, no doubt.

But here I'd like to focus on the technical challenge to get the mains plug to the field.
jonescg wrote:
Nov 26 2019 5:39am
I take issue with organic agriculture - why deliberately go about things the hard way to produce a crop you can sell to rich hippies? And their opposition to genetically engineers crops is as bad as opposing nuclear on safety grounds ....
Same with this discussion.
Valid in itself (should we have a beer together - or maybe even more than one :lol: on this issue ) - but not related to the technical challenge at hand.

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