Do you think qs138 with Max 80nm can work or you need 100nm with qs180, would plan to run 1 motor so maybe 180 to aim for? Did the 850a controller work well, would you use bigger smaller after, what was highest pwr peak you saw?

 

For the size and weight of my tractor I think the QS180 is a bit small. I'm lucky that our property is flat and not too big, so I get by with the power it delivers. If our property was hilly and bigger (so need more speed to get around efficiently) then I thinks I'd want something with more power. So, if you're using the QS180 for everything (PTO as well as traction) then you may struggle. 850A controller is fine - not sure on what the peak power is, I can get it to draw up to about 150A from the battery (so 150A x 72V equates to 10.8kW less losses), but most of the time it's drawing less than 100A.

 

Adore your project! Doing similar and figuring out the motor, when you were driving with that behind you drew 8kw did the qs180 get warm with only that, have heard it got lot of torque at 72v. Did you ever use it at that voltage? Was first thinking of qs138 but maybe torque to low and get to warm, heard 180 was a monster so surprised at your don’t work that well. Would love to hear more about your opinion

 

Thanks Philip. Yes, the QS180 can get a bit warm when worked hard for a while. Definitely better now I'm running at 72V than when I was using 48V. I have a temp sensor on the motor and just keep an eye on it - I try not to go above 60degC, even though I know it can handle being hotter. Interesting that the 10kW Golden Motor motor on the PTO doesn't get as hot (has a bit of fan cooling I think), but the GM motor controller runs hotter than the QS180's controller.

 

Right, time for a project wrap up, and... I bet you'll be keen to see what it cost!

Ok, let's start with the cost bit first. Total project cost me NZ$24,536 (US$15,600), including the cost of the old diesel tractor (NZ$2,600).

However, the total cost includes the cost of 6x 2nd-hand SLA batteries I used for testing, plus the cables to hook them up and 12V chargers to charge them all, and a Golden Motor VEC500 I bought that I didn't need (thought I needed it when I changed from 48V to 72V). So, excluding these costs, the build cost NZ$21,428 (US$13,660). Here's the breakdown:

Base Costs:
Item	Cost (NZ$)	NZ$ to US$	Cost (US$)
1967 David Brown 880 Donor Tractor	2600.00	0.67	1742.00
QS-Motor QS-180 & ND72850 Controller	2007.70	0.68	1360.00
Cycle Analyst CA3 for PTO	229.26	0.69	157.11
1-3/4" Pillow Block Bearing	82.00	0.69	56.58
7/8" Pillow Block Bearing	36.00	0.69	24.84
Golden Motor 10kW + VEC500	3160.35	0.66	2085.83
Cycle Analyst CA3 for Transmission	338.14	0.64	215.13
Various Switches & 12V Relays	161.17	0.64	103.15
300A Shunts	70.28	0.63	44.47
100Ohm 10W Precharge Resistors	20.91	0.62	12.87
10k Potentiometer (x10 turn)	11.22	0.61	18.39
600A Main Contactors (12V switched)	228.99	0.61	140.76
Battery Cables (battery to contactor then to controller)	291.08	0.65	189.20
T10 Timing Belt Pulleys (x4)	477.71	0.64	304.78
T10 Timing Belt Steel	36.89	0.62	22.89
T10 Timing Belt Steel	48.22	0.62	29.92
Machined steel Motor Brackets	1008.55	0.62	625.30
Hall Effect Foot Controller	57.90	0.62	35.90
Hall Effect Angle Sensor (Hand throttle)	51.03	0.61	30.89
T10 Idler Pulley	20.43	0.54	11.03
Timing Belt Pulley Machining	1101.70	0.57	627.97
200A Circuit Breaker	117.50	0.61	71.68
Shaft Collars (to hold pulleys in place)	155.60	0.62	96.47
160Ahr LiFePO4 Battery Pack & Charger	7980.24	0.62	4947.75
Kevlar replacement Timing Belts	90.30	0.63	56.89
Steel for battery mounting	251.90	0.62	156.18
Replacement front Tyre	100.00	0.62	62.00
Misc Nuts, Bolts, cables, cable ties, etc	693.34	0.62	429.87
NZ$	21428.41	US$	13659.84
Testing Costs:
Item	Cost (NZ$)	NZ$ to US$	Cost (US$)
4x Trojan T-1275 Batteries	750.00	0.62	465.00
Battery Balancer	93.38	0.61	57.30
13pin Plugs & Sockets	61.00	0.63	38.43
4x 12V Battery Chargers	128.50	0.63	80.96
2x 120A Batteries	400.00	0.57	228.00
Heavy cables (for test batteries)	156.16	0.61	95.26
Replacement 140A battery (replaced 1x Trojan)	405.13	0.62	251.18
Golden Motor VEC500	1047.38	0.65	680.80
2x 12V Battery Chargers	65.98	0.65	42.89
NZ$	3107.53	US$	1939.81

So, if this tractor got stolen (or someone offers me a great price for it 😄), would I do the same as a replacement?

Yes, I think for our needs and the cost and effort involved that this conversion works out well. It is a bit noisier than I expected though, so perhaps I'd explore a more modern donor tractor (one without straight-cut gears and final drives). However, the David Brown 880's ability to lock the 3-point link arms in the up position is perfect for electric operation - means you don't need to keep the PTO motor running unless you're actually raising or lowering the arms. I guess if you converted a tractor that didn't have this then you could design and install some sort of arm locking mechanism.

Is there anything on this build I'd do differently next time?

Yes, definitely. It was a good experience trying two different motors and controllers, but for any other build I'd recommend just going with one model. In my case, I'd go for two Golden Motor 10kW motors and VEC500 controllers. The GM motor is quieter, runs cooler and the controller is simpler to configure.

Using two Golden Motors means I could've kept the voltage at 48V too. As a side-note, I've now found that most hybrid solar inverters only support batteries up to 48V. So, my plan to use the battery to bank some of our solar power on the days I'm not using the tractor has got quite a bit more complicated now that I'm using a 72V battery (if anyone has any ideas on how to use my 72V battery for solar storage please do let me know).

All the best, everyone! It's been fun sharing my build. Cheers!

 

It's cool how you figured out that battery voltage slumps when it's cold, but good thing you got healthier numbers at 15 degC!

 

Oh


Sent from my iPhone using Tapatalk

 

Congrats on the nationwide media exposure!

How I converted a diesel engine tractor to electric for just $20,000

An old engine tractor in Waikato is the latest to join the electric revolution.

www.stuff.co.nz

 

Have done a bunch more testing with the LiFePO4 battery pack and it's working out really good. The BMS's reported battery SOC is based on the Ah used, not battery voltage as I thought above. The BMS's Ah used matches pretty much what the Cycle Analyst displays say too.

Also, found that the battery voltage slumps more when the battery is cold - the numbers I mentioned above were with a battery temp of 8 degC. Testing with the battery temp at 15 degC showed much healthier numbers. Will see how my winter use goes - I might need to get an electric heat wrap sorted for it

Anyway, battery is now fitted with a frame to the tractor (took the opportunity to clean and paint the front of the tractor too), so looking forward to doing more testing...

 

Thanks for the discussion, team. Yes, the battery supplier agrees. The BMS's SOC display is not accurate until the battery pack has had a number of cycles. I thought the minimal drop in capacity was too good to be true

 

David, the discharge curves I've seen show a LiFePO4 SOC of only about 9% at 3.0V. Why would it be 73%??

 

Charge to 3.4V to 3.45V per cell 24s ~ 81.6V- 82.8V let the battery rest for a half hour after battery is taken off charger. use meter as you said. Discharge to LVCC 3.0V or 3.1V/cell 24s LVC 72V-74.4V this assumes the battery is balanced.
A coulomb counter meter is often used to determine Ah in/out of a battery ,smart bms have a coulomb counter least the Ant bms has one. how accurate it is I am not sure.
later floyd

 

LifePO4 2.97V is about empty.
Full resting voltage 3.33V- 3.4V
80-90% of energy from ~3.4V to 3..00V
Charge the battery soon.
LiFePo4 has a flat discharge curve so you can't use voltage to base the SOC
Later floyd

 

LifePO4 2.97V is about empty. Full resting voltage 3.33V- 3.4V 80-90% of energy from ~3.4V to 3..00V Charge the battery soon. LiFePo4 has a flat discharge curve so you can't use voltage to base the SOC Later floyd

How would it best be estimated? Start from full charge and meter amp/hrs consumed from that point?

 

Quick update (I'll post a more detailed update soon): I decided on a 77V 160Ah 24S (24x 3.2V 160Ah cells in series) LiFePO4 battery pack with 200A BMS for my tractor:

Battery arrived with 91% SOC and running the tractor for about 1/2 an hour yesterday (just taking it easy - about 30A avg) and then for about 90 mins today (moderate loads, but a couple of times at high speed - peaking 110A) and the battery has only dropped to 73% SOC (cells avg 2.97V). Now to make a cradle to mount the battery securely to the frame...

 

It's all straight cut gears and backlash, all mounted on iron, in a tractor, lol

 

Seems quite noisy for an electric machine - gear box noise?

 

Surprising lack of poisonous slithery things and giant bird-eating spiders in that video.

Suggestion: black out the "S" in "selectamatic" 😉 maybe put a lightning bolt where it was? Vinyl sticker maybe, as the paint and badging looks pretty clean.

 

And, here's a test run I did yesterday pulling a heavy groundhog implement that levels, aerates and seeds paddocks:

 

Finally completed some test runs. Here's a video of one run using a 1.5m rotary slasher to mow some grass. Shots of the gauges didn't show very well in the original video, so I did a second identical test run and added the gauge videos as overlays. Hope this helps to show the electric running performance.

Apologies for my commentary where I keep over-estimating the Amps being used. I was remembering usage from previous 36V test runs, but now it's using 72V the Amps are lower

 

Hey, I was wonder about your project yesterday so thanks for the update. Looking forward to test results.

 

Quick update on progress. Turns out the 48V VEC500 controller and motor (Golden Motor 10kW) I have can run at 72V. Just needed to program the controller for 72V. So, the whole project is now running at 72V and everything is working well.

I now need to find some time (and clear weather) to do some some decent test runs, including mowing grass, towing a laden trailer, etc, so that I can better measure the power requirements for sizing the final battery configuration (and type). Will post the results at some stage.

 

OK, (I don't know where the Surrettes came from. ).

Are you thinking LAs or maybe Lithium for future?

 

Are you thinking LAs or maybe Lithium for future?

I haven't really researched that area yet. I believe the costs are high for some options, so that will be a factor!

 

Sorry, I'm only using the 6 LA batteries (4x Trojan T-1275 and 2x Century 120ah AGM - all secondhand that I got cheaply) for initial testing. Once I'm happy with the motor and controller set-ups, I'll then use the test data to properly size the battery requirements. I'll then see what suitable battery, BMS and charging options are available here in New Zealand.

But, yes, I have each controller set to limit the max line current to 120A at present. So, with a battery set-up that can handle a larger peak power draw then it should perform better still.

 

Sounds like a nice improvement. Do you think more could be realized, apart from replacing the weak battery, by upgrading to batteries with higher current capacity i.e do the Surrettes have enough to drive the motors to full output?

I ask in part because I've found that a battery bank, either LA or Lithium, capable of fitting in my possible Yanmar conversion can only provide about 100A continuous which is insufficient to drive the motor that would be required.to give full continuous output.

 

Ok, so I scrounged up a couple more batteries and hooked up the QS-180 main drive motor to 72V (increased from 48V) and that has made a definite improvement. Tractor is quite lively now and from the couple of short tests I've made the motor doesn't seem to be straining as much as it was at low RPM and it's definitely got more high-RPM speed in top gear. One battery is quite tired though, so I'll try and get a replacement, do some more testing and then post the measured results for you soon. Looks like I'll need to buy a 72V VEC500 controller for the PTO motor now though

 

No, there's nothing wrong. It's just a very unusual way to operate a farm tractor.

 

Nothing wrong I can see with shifting a non-synchro on the fly as long as w/o gear grinding or popping the clutch.