[24Seven]

The ICE is almost out and I begin to see the space availiable for the tesla motor.

There does not seem to be enough room to mount the Tesla front drive unit at the same angle as it is mounted originally.

Would it be ok to tilt the drive unit forward without creating lubrication or cooling issues?

 

[brian_]

There does not seem to be enough room to mount the Tesla front drive unit at the same angle as it is mounted originally.

Would it be ok to tilt the drive unit forward without creating lubrication or cooling issues?

There is an oil pickup in the bottom of the gear case; if you rotate the unit significantly you would need to relocate that so it still picks up properly.

 

[24Seven]

Thank's Brian!

Might be easier to mod the firewall then.

I guess turning the drive unit 180 degrees and drive the motor in reverse direction is not a good idea either?

 

[brian_]

I guess turning the drive unit 180 degrees and drive the motor in reverse direction is not a good idea either?

It can be done, by replacing the internal oil pump with one that still pumps properly when the motor is turning the other way. Zero EV has a reverse rotation pump for the large drive unit, and apparently this works okay even though the gears will be slinging oil the opposite directions to normal; I don't know if anyone has a solution for the small drive units.

 

[24Seven]

It can be done, by replacing the internal oil pump with one that still pumps properly when the motor is turning the other way. Zero EV has a reverse rotation pump for the large drive unit, and apparently this works okay even though the gears will be slinging oil the opposite directions to normal; I don't know if anyone has a solution for the small drive units.

Once again, thank's Brian!

The knowledge on this forum is amazing!

 

[Smatt]

The ICE is almost out and I begin to see the space availiable for the tesla motor.

There does not seem to be enough room to mount the Tesla front drive unit at the same angle as it is mounted originally.

Would it be ok to tilt the drive unit forward without creating lubrication or cooling issues?

Does this mean that the small rear drive unit is no longer an option?

 

[brian_]

I guess turning the drive unit 180 degrees and drive the motor in reverse direction is not a good idea either?

If you're still seriously considering turning the drive unit around, an alternative to reversing the oil pump in a Tesla Model S/X unit might be to use the drive units which Tesla supplied for the Mercedes B250e or Toyota RAV4 EV, which place the motor ahead of the axle line in front-wheel-drive vehicles. You would need to check for compatibility with whatever you are planning to use for controller replacement or modification.

 

[Evbeddy]

thats the basis of my (current) preference for fewer large format cells.... less to check. fewer connections to go wrong, and no time or expense trying to hack into a Volt, Leaf, or Tesla BMS to set parameters to a 'partial pack' at 120-160v for a DC motor.

The second issue is that the wiring in most of the OEM battery packs is designed to handle twice the voltage, but half the current I'd expect to pull with a DC motor. Pulling 1000amps out of a pack with multiple series and parallel connections designed for 500amps seems risky.



I haven't kept up in this forum for a while.... and wanted to ask if there is a new 'cookbook' with the kinks worked out to effectively use OEM packs for DC voltages.




Hi Everyone

For someone who is new to the diy ev scene this has been a very interesting build thread. Lots of info for someone trying to learn.

Without trying to take over this tread Ive got a question which I think relates to what has already been talked about. What do people is the max voltage and current you can run with a dc motor (forklift or otherwise)?

Above on this thread people are talking about running 120 to 160v but Im sure Ive read on Duncan's build that he is running 400v and 1200A from volt batteries. What are peoples thoughts?

Thanks Brennan

 

[Duncan]

Max voltage for a DC motor

You can't actually just "overvolt" a DC motor
You controller controls the motor voltage to achieve the commanded current

So it may need 10 v to get 1000 amps when stationary
But as the motor starts to spin it develops a back EMF and that adds to the voltage

When I had a 130 v battery and a controller set to 1000 amps it took off like a scalded rat - and then as the revs rose the required voltage increased

With 130 volts it topped out at 200 amps and 100 kph (3500 rpm)
Which means that the controller was at 100% but the voltage was only driving 200 amps through the motor

To need a high voltage you need high current and high rpm

My current battery is 300v empty and 340v full - I'm still accelerating at 150 kph and 5300 rpm but I have passed 100% on the controller and the current is dropping as the rpm's increase

If using more sensible numbers I would say that 150v was enough
Or you could use 400v and simply let the controller adjust it to what the motor wants

 

[Evbeddy]

Hi Duncan

Good to talk to you again.

Thanks for sharing your experiences. So just to make sure I have this straight in my head, current = torque and voltage = rpm. If you set your controller to your max current yoy have max acceleration. Then you will keep accelerating until you run out of rpm (voltage) which is like hitting the rev limiter in an ICE car.

So my next big question (and hopefully its not a stupid one), how do you decide on the best voltage for your car? I know it will depend on what you want your max rpm to be but is there a way to calculate what voltage is needed?

Just to be clear I know how to use tyre size and diff ratios to calculate speed and rpm I'm more interested in voltage.

Thanks
Brennan

 

[Duncan]

Hi Duncan

Good to talk to you again.

Thanks for sharing your experiences. So just to make sure I have this straight in my head, current = torque and voltage = rpm. If you set your controller to your max current yoy have max acceleration. Then you will keep accelerating until you run out of rpm (voltage) which is like hitting the rev limiter in an ICE car.

So my next big question (and hopefully its not a stupid one), how do you decide on the best voltage for your car? I know it will depend on what you want your max rpm to be but is there a way to calculate what voltage is needed?

Just to be clear I know how to use tyre size and diff ratios to calculate speed and rpm I'm more interested in voltage.

Thanks
Brennan

The back EMF is proportional to current and to rpm

So you then need the RATIO! - and that is down to your motor!

Which is the rub

If you have a Warp9 or Warp11 you can use the graphs they give to make a very good estimate

I am using a Hitachi 11 inch - no graphs!

But when I used 130 v the effect was "noticeably"

With 130 v - my Device topped out at 100 kph and 200 amps

So 130 v (probably sagged to 105 V) - allow 5 volts for the resistive load

100 volts of EMF = 3500 rpm and 200 amps

So to drive 1000 amps at 3500 rpm - would take 500 volts

At half of that rpm (1750 rpm) 1000 amps would take 250 volts

At the end of the 1/8th when I'm doing about 5250 rpm it would take 150 volts for 200 amps
My actual voltage of 300 volts would give me 400 amps


That is all approximations - but it gives you an idea of what is happening