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Hi, I have just joined this group in the hope of getting some expert guidance, I am converting a Ford model T 1911, and whilst of the work is now completed, I am adding an electric brake, no regen, just resistance, I couldn't find any rheostats man enough to do the job and so looking to build my own, wondered if anyone has already achieved this, my motor is a 7kw brushed at 48 volts DC, the whole project is one of simplicity ie repairable at roadside unlike my Nissan Leaf which is marvelous View attachment 120703
 

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Some controllers offer "plug" braking which I think may be used in forklifts to slow down. I have no real clue other than the fact that it's sometimes mentioned in literature. BTW, what are your performance goals for this vehicle?
 

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Regenerative and dynamic braking are not feasible with a series DC motor.

Some controllers offer "plug" braking which I think may be used in forklifts to slow down.
That would be all you could do with a series DC motor, but in its basic form it is a severe and uncontrolled braking method. The version implemented in a controller is better, but this should still not be the primary braking method for the vehicle.

An old but still valid discussion from the EVDL list, copied here in DIYElectricCar:
[EVDL] What is plug braking vs. dynamic braking?

There are lots of online descriptions, once you know to search for "plug braking".
 

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Regenerative and dynamic braking are not feasible with a series DC motor.


That would be all you could do with a series DC motor, but in its basic form it is a severe and uncontrolled braking method. The version implemented in a controller is better, but this should still not be the primary braking method for the vehicle.

An old but still valid discussion from the EVDL list, copied here in DIYElectricCar:
[EVDL] What is plug braking vs. dynamic braking?

There are lots of online descriptions, once you know to search for "plug braking".
Really?? I have been using both dynamic and regenerative braking on series motor EV conversions since the 1980's. For dynamic or regenerative braking, place a lithium cell through a contactor across the motor field. When the field contactor is closed, the lithium cell will enerize the motor field. For dynamic braking place a resistor comprised of 10 feet of nichrome wire wound in several round turns with another contactor across the motor armature. To energize dynamic braking, energize the field contactor and the armature resistor contactor and instant resistance dynamic braking. For renenerative braking, replace the dynamic braking resistor with the your traction 2 loop paralled battery for 1/2 voltage and the motor will charge up the batteries.

In my working days I performed service on large industrial cranes using series motors with four quadrant SCR motor controls. Of course, cranes operated in motoring and regenerating modes. Each time the crane hoist goes down, it becomes a generator and feeds its energy into the AC line. And that is regenerative braking with a series motor.-

Easy.
 

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Really?? I have been using both dynamic and regenerative braking on series motor EV conversions since the 1980's. For dynamic or regenerative braking, place a lithium cell through a contactor across the motor field. When the field contactor is closed, the lithium cell will enerize the motor field...
You're separately exciting the field winding, so you are no longer operating it as a series motor. Yes, a separately excited motor works fine for regenerative (or even just dynamic) braking.
 

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Sure, but the OP asked about his series motor.
Right, and your fix is to not run it as a series motor for braking. Okay, and maybe that will be the chosen solution, but it doesn't change the fact that if the field is just in series with the armature, controlled regenerative braking is not available.
 

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Could you explain what this is?
Use an even number of cells. Split the back into two. Example: Pack was 144 volts; split pack into two sets of 72 volts. For motoring place a contactor in series BETWEEN the two set of cells. Close the contactor for motoring for 144 volts. For regeneration open the above series contactor and close two smaller contactors placing both modules negative to negative and positiveto positive in PARALLEL for 72 volts. This allows stronger regeneration than using the series 144 volt pack. Also reduces having to downshift transmission.
 

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Use an even number of cells. Split the back into two. Example: Pack was 144 volts; split pack into two sets of 72 volts. For motoring place a contactor in series BETWEEN the two set of cells. Close the contactor for motoring for 144 volts. For regeneration open the above series contactor and close two smaller contactors placing both modules negative to negative and positiveto positive in PARALLEL for 72 volts. This allows stronger regeneration than using the series 144 volt pack. Also reduces having to downshift transmission.
That made sense when motors had brushes and controllers were sets of switches and resistors. If I recall correctly, it was used by some drag racers year ago, who later abandoned this method; they also tried using two motors and switching them between series and parallel with each other. Now, just configure the pack for the highest desired voltage, and let the controller do its work.

By the way, to implement this properly the "two smaller contactors" are not any smaller, because they take the same current - they just operate at half of the voltage of the main contactors.

If you really like using contactors, you can wire the battery this way, wire each motor to switch between series field and some other field configuration, wire each motor field to reverse polarity for reverse direction, and wire the motors in series and parallel. It should be possible to find places for a couple dozen contactors, plus the many relays used to control them. ;)

The GM Ultium system as implemented in the GMC Hummer EV has a pack which can reconfigure this way (two halves in parallel or series), so it can charge from up to 400 V sources (common fast DC charging stations, presumably using a 360 V nominal battery configuration) but run at up to 800 V (presumably 720 V nominal). They do not switch configurations during operation because there is no benefit - they drive in the series configuration at all times, using the parallel configuration only to enable charging from 400 V sources without the use of a charging voltage boost converter.
 

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Really?? I have been using both dynamic and regenerative braking on series motor EV conversions since the 1980's. For dynamic or regenerative braking, place a lithium cell through a contactor across the motor field. When the field contactor is closed, the lithium cell will enerize the motor field. For dynamic braking place a resistor comprised of 10 feet of nichrome wire wound in several round turns with another contactor across the motor armature. To energize dynamic braking, energize the field contactor and the armature resistor contactor and instant resistance dynamic braking. For renenerative braking, replace the dynamic braking resistor with the your traction 2 loop paralled battery for 1/2 voltage and the motor will charge up the batteries.
Use an even number of cells. Split the back into two. Example: Pack was 144 volts; split pack into two sets of 72 volts. For motoring place a contactor in series BETWEEN the two set of cells. Close the contactor for motoring for 144 volts. For regeneration open the above series contactor and close two smaller contactors placing both modules negative to negative and positiveto positive in PARALLEL for 72 volts. This allows stronger regeneration than using the series 144 volt pack. Also reduces having to downshift transmission.
With out getting into the extreme complexity and dubious practicality of what you are describing, let's just say it is very difficult to regen from a series motor. So difficult, I never seen it done successfully in a road going EV in 40 years of waiting for it to happen. If you have actual examples of this sucessfully being done, please show us.
 

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With out getting into the extreme complexity and dubious practicality of what you are describing, let's just say it is very difficult to regen from a series motor. So difficult, I never seen it done successfully in a road going EV in 40 years of waiting for it to happen. If you have actual examples of this sucessfully being done, please show us.
Well, yes, years ago when I converted a 1965 VW Bug into a dune buggy, I had driven around town and on Hiway 101 north of San Francisco and the regen system worked fine around town on on freeway exits. You could watch the ammeter swing negative of zero when regenerating. Since then I've converted 4 more cars to EV, all without regen. My driving is mostly flat, so regen does little good. If one had to go down a one mile long continual grade, regen would be needed. And yes, one of my regen setups used a GE shunt motor with field shunt current control which tracked armature current. Regen was automatic, no contactors required. But that's another story. Today, just go with an AC system if you desire regenerative braking.
 

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With out getting into the extreme complexity and dubious practicality of what you are describing, let's just say it is very difficult to regen from a series motor. So difficult, I never seen it done successfully in a road going EV in 40 years of waiting for it to happen. If you have actual examples of this sucessfully being done, please show us.
Back in the nineties, there were two scientist in Southern California, call Litte Guy Racing, or something similar that used an Advance series motor, 6.7", I think, in a Geo Metro for racing. They used the parallel battery, 6 volt lead acid field battery system for regeneration similiar to the one I described above. They published a booklet describing how to do it, which I have somewhere. So, it has been done.

Found it, pictures enclosed. It's 67 pages long. It's copyrighted, so only get 2 pictures enclosed
Publication Book Font Material property Paper
Rectangle Font Material property Parallel Handwriting
.
 

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I stand corrected. I too have found an example:


123448
Organism Font Rectangle Art Pattern



Seriously, is it worth getting people's hopes up about how practical this is? For crying out loud, we've got gullible people taking horse medicine to prevent covid virus infections. This, when you only did it once, and never again:

Well, yes, years ago when I converted a 1965 VW Bug into a dune buggy, I had driven around town and on Hiway 101 north of San Francisco and the regen system worked fine around town on on freeway exits. You could watch the ammeter swing negative of zero when regenerating. Since then I've converted 4 more cars to EV, all without regen. My driving is mostly flat, so regen does little good. If one had to go down a one mile long continual grade, regen would be needed. And yes, one of my regen setups used a GE shunt motor with field shunt current control which tracked armature current. Regen was automatic, no contactors required. But that's another story. Today, just go with an AC system if you desire regenerative braking.
 

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Back in the nineties, there were two scientist in Southern California, call Litte Guy Racing, or something similar that used an Advance series motor, 6.7", I think, in a Geo Metro for racing. They used the parallel battery, 6 volt lead acid field battery system for regeneration similiar to the one I described above. View attachment 123444 .
Thanks for the illustration, which shows that the regenerative braking configuration operates the motors with separate field excitation.

This is why I said:
You're separately exciting the field winding, so you are no longer operating it as a series motor.
and
Right, and your fix is to not run it as a series motor for braking.
The reconfiguration for regenerative braking splits the battery pack into two sections (90 V and 6 V, nominally; 45S and 3S lead-acid), then discharges the 6 V section to excite the field while regeneratively charging the 90 V and 6 V batteries in series; an immediate result of this operation is imbalance between the two sections, which are normally operated together as one battery. This is okay for the braking phase of a drag racing run (the "racing" in this example is only drag racing), because after each run the car gets attention in the pits, which can include separately charging portions of the battery to fix the imbalance. As the note on the drawing confirms, it is completely unsuitable for normal use.

It would be vastly superior to just keep the armature and field separate, operating them from the armature and field outputs of a SepEx controller, or from two separate but coordinated controllers. The only difference between a series motor and a shunt (SepEx) motor is that the series field is designed for high current (same as the armature) and low voltage (a small fraction of the armature voltage), which a shunt field is designed for high voltage (same as the armature) and low current (a small fraction of the armature current).
 

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Thanks for the illustration, which shows that the regenerative braking configuration operates the motors with separate field excitation.

This is why I said:

and


The reconfiguration for regenerative braking splits the battery pack into two sections (90 V and 6 V, nominally; 45S and 3S lead-acid), then discharges the 6 V section to excite the field while regeneratively charging the 90 V and 6 V batteries in series; an immediate result of this operation is imbalance between the two sections, which are normally operated together as one battery. This is okay for the braking phase of a drag racing run (the "racing" in this example is only drag racing), because after each run the car gets attention in the pits, which can include separately charging portions of the battery to fix the imbalance. As the note on the drawing confirms, it is completely unsuitable for normal use.

It would be vastly superior to just keep the armature and field separate, operating them from the armature and field outputs of a SepEx controller, or from two separate but coordinated controllers. The only difference between a series motor and a shunt (SepEx) motor is that the series field is designed for high current (same as the armature) and low voltage (a small fraction of the armature voltage), which a shunt field is designed for high voltage (same as the armature) and low current (a small fraction of the armature current).
OK, true. The book has other drawings where the 6 volt field excitation battery is seperate for street driving. The book also has a diagram for splitting and halving the battery pack for systems of 144 volts. Let's just call it a seperately excited motor field. High current and low voltage field and high voltage equal or lower to field current armature specs.

End of my discussion.
 

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Let's just call it a seperately excited motor field.
Agreed. :)(y)

The book has other drawings where the 6 volt field excitation battery is seperate for street driving.
Yes, that's an approach. One from this century would use a dedicated controller for the field, running from the same battery, to avoid the ridiculous complication of carrying and charging two separate batteries for the traction drive.
 
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