DIY Electric Car Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1 (Edited)
Hello from the republic of ireland. I am a farmer and drive a pivot steer telescopic loader every day which is powered by a naturally aspirated ford d400 380 series, about 80kw or so, coupled to a clark torque converter.

Recently I found a newer similar version for sale locally which is missing its engine and torque converter. since I just do yard work with it, there is no certification needed and the motor could be reversed electrically, replacing the function of the torque. I have never worked with ac before, but have built a 12v rf amplifier for ham radio.

I do not exceed walking speed currently as the torque is worn out and I am happy to drive an ev like that, with one gear only. I do however, need lots of grunt for pushing around piles of dung and lifting 2 tons via hydraulics.

I had a look around here and everyone says not to use a mains motor as the battery voltage is too high, however using a tractor pto/ 540 rpm generator as a motor/gearbox combi in reverse would give me that low end grunt I need.

I would also be interested in implementing an electrical brake, by shorting the motor windings, if that would work, as a safety backup.
I would prefer to use 3 phase motors to avoid issues with brushes.

I have metal fabricating experience, having built numerous agricultural trailers and implements, some arduino and teensy 8 bit experience, if that is a help for making a PWM 3 phase controller.

The loader needs to operate for 3 hours every day. eventually I hope to charge it from solar panels, and may need to, when oil becomes uneconomical.

Some questions I have:

In this motor controller, it requires a rotary encoder on the motor, why is that since every motor I have seen can run on 3 phase or single phase alone, at a constant speed?

https://github.com/catphish/stm32_vfd/blob/master/main.c

Is it possible to reuse battery packs from scrapped evs or do those use incomprehensible battery management systems and proprietary chargers. I do not know anything about the design of such systems, and I am not particularly clever to be able to learn.

I feel like I could just about tackle a lead acid dc build, but the reliability of such a system would be poor, and expensive due to battery replacement.
 

·
Administrator
Joined
·
6,120 Posts
Hi
I won't answer the motor questions but I will answer the battery

You can use the battery from a crashed EV - they are all made of "modules" of several cells

The Charger and the Battery management System from the EV will probably be too difficult to use

But you don't need them

The cells in a production EV will be very well matched and simply won't drift - and you can simply be your own BMS with a voltmeter - 10 minutes and you can check the voltage of each cell

You can also use a dead simple device
http://www.evdl.org/pages/battbridge.html

This will tell you if you have a dead or damaged cell

For what you are doing that is all you need
 

·
Registered
Joined
·
6 Posts
Discussion Starter #3
that's an interesting link, somewhat like the wheatstone bridge but as it is passive all it will do is run down the batteries slowly (and tbh the batteries will be from multiple cars to have enough capacity so they won't be balanced anyway)

maybe I should start collecting old laptop batteries from computer shops and go the diy tesla powerwall route. At least I could repair that myself, and charge it with a tp4056 on each cell and atx power supply for charging.
 

·
Registered
Joined
·
197 Posts
maybe I should start collecting old laptop batteries from computer shops and go the diy tesla powerwall route. At least I could repair that myself, and charge it with a tp4056 on each cell and atx power supply for charging.
That'll take you a lot of time and effort to reach a useful capacity and get all the niggles ironed out. OEM packs from an Ampera, Leaf, Renault or one of the recent plugin hybrids should give you at least 10 kWh already assembled and tested. I know Damien (evbmw.com, @Jackbauer on here) has had some luck finding complete packs at scrapyards in Ireland. I think he's based somewhere in the bottom half of the Republic.
 

·
Registered
Joined
·
4,791 Posts
I am a farmer and drive a pivot steer telescopic loader
Interesting... telescopic loaders here all seem to have steered wheels, instead of articulating (pivot steering).

... powered by a naturally aspirated ford d400 380 series, about 80kw or so, coupled to a clark torque converter.
Fortunately it probably doesn't use the whole 80 kW of engine output often if at all. 80 kW is a common power rating for recent EV motors.

I do not exceed walking speed currently as the torque is worn out and I am happy to drive an ev like that, with one gear only. I do however, need lots of grunt for pushing around piles of dung and lifting 2 tons via hydraulics.
Just like a forklift :)
This seems like a reasonable EV application.

I had a look around here and everyone says not to use a mains motor as the battery voltage is too high, however using a tractor pto/ 540 rpm generator as a motor/gearbox combi in reverse would give me that low end grunt I need.
By a "mains motor" I assume that you mean an AC motor (probably induction) designed to run on 50 Hz 230 V power. That's a reasonable voltage by the standards of current EVs.

If you feed power into a 540 rpm PTO, the motor would only be turning 540 rpm at full load... which is way too slow to do the job with a reasonable size of motor.

I would also be interested in implementing an electrical brake, by shorting the motor windings, if that would work, as a safety backup.
That's a feature of at least some controllers.

The loader needs to operate for 3 hours every day.
Is that three hours in total over multiple sessions as you do different jobs, or does it need to work for three hours without recharging?

In this motor controller, it requires a rotary encoder on the motor, why is that since every motor I have seen can run on 3 phase or single phase alone, at a constant speed?

https://github.com/catphish/stm32_vfd/blob/master/main.c
You have probably seen only induction motors for use directly on 50 Hz AC power; they settle at a speed determined by the frequency and to a lesser extent by the load. In a vehicle that needs to vary the motor speed, the controller needs to know how fast the motor is turning (in the case of an induction motor), or the rotational position of the motor (in the case of a synchronous motor such as the permanent magnet motors used in most EVs). A synchronous motor requires the encoder even for constant-speed operation.

I feel like I could just about tackle a lead acid dc build, but the reliability of such a system would be poor, and expensive due to battery replacement.
I think most people here would agree with that. :)
 

·
Registered
Joined
·
6 Posts
Discussion Starter #6
@emyr I tried to get in contact with damien but didn't pay the 10 euro he was asking for tech emails. No response anyway, I guess he gets plagued with n00bs like me. Either way, damiens stuff is too high tech for me to repair in any event. It sounds cheap though compared to the low tech route. I have subscribed to his patreon at the 2 euro level. emails require paypal which is out of order ever since my debit card got renewed. I'm not a friendly person in general so I don't want to fall out with him if I need to buy something so i'm not going to push it.

@brian_
Well matbro in the uk made the first pivot steer brought to market and theres a lot of them still running because they use generic parts. I sought it out because I was frustrated with stub axle issues. In general other brands would be too new, or high horsepower, i.e. pricy to become common on small farms

>50 Hz 230 V power
correct

>the motor would only be turning 540 rpm at full load... which is way too slow to do the job with a reasonable size of motor.

I assume the differential has a 4:1 ratio so 540:4 would be 135 revolutions per minute at the axle. with an off the top of my head wheel circumference of 3 meters( it uses 24 inch rims) that comes to 24.3 km/h which is likely too fast for me, but maybe workable. Much of my work is done at a crawl, so the slower the better. I do not know what rpm the motor is turning at when driven to 540 rpm at the pto. There would likely be little torque at low speeds so I would have to use an oversize generator, 40kva or larger.

I like the idea of a drop in reliable unit though, saves making adapter plates etc.

does it need to work for three hours without recharging?
yes.
 

·
Registered
Joined
·
197 Posts
I would also be interested in implementing an electrical brake, by shorting the motor windings, if that would work, as a safety backup.
I would prefer to use 3 phase motors to avoid issues with brushes.
I assume that by 3-phase you mean an industrial induction motor..?

Shorting the windings only works with rotors that have magnets in them, so either brushed or brushless dc motors (the latter also being called PMAC in some circumstances). AC motors that are induction motors, not PMAC, don't have magnets in the rotors. Change in the magnetic field of the stator windings induces current in the squirrel-cage rotor, causing another magnetic field around the rotor. If the stator field rotates faster than the rotor, you have positive torque. If the stator field is slower than the rotor, you have negative torque and hence regen. Without the input frequency, there is no rotor field, so it would continue to spin.

The reliance on input frequency is why induction motors make for good grid-connected generators, since if the shaft is spun faster than the if the motor were fed mains AC, the motor acts as a generator without needing adjustable gearing to sync the frequencies, or needing to rectify and re-invert as would be required when generating with a brushless dc motor. (a more educated member than me could explain what influence an induction motor in regen could actually have on grid frequency)
 

·
Registered
Joined
·
6 Posts
Discussion Starter #8
I assume that by 3-phase you mean an industrial induction motor..?
I don't know what I mean tbh, this is all new to me, despite using motors for work for years. I didn't set them up though. I assume this pto generator is induction because if it was ACPM then it would degrade over time. I'm not against using a regen controller, but it makes a diy controller less feasible, in order to keep costs down.

https://www.donedeal.ie/tractors-for-sale/40-kva-3-phase-amp-26-kva-1-phase-perkins-generator/21128754

Am I correct in thinking that if the slip is set in the opposite direction to generate a slow stator field with that diy controller in the github link then that would act as a primitive regen? I don't actually need to charge the batteries from it.

Do i need a resistive dummy load to dump the generated power into or is it sufficient to short the windings (so long as attention is paid to keep a stator field).

I assume a working regen would make demands on the battery pack and increase complexity and cost greatly.

damien mentioned in one of his videos that the advantage of using a 3 phase motor (idk what type) was that it could be used to charge his car while stationary, simplifying his charging setup. Could someone clarify what was going on.
 
1 - 8 of 8 Posts
Top