# 1200 lb three-wheeler, Warp 9, Curtis 1231C



## Paxterra (Mar 12, 2012)

Hi, this is my first time on here so I apologize if I'm in the wrong section for these questions.

Can anyone tell me why---->The forward/reverse contactor coils must match the vehicle’s battery voltage when using the Curtis 1231C.

I am building a direct drive vehicle and I am reversing the motor for reverse travel. I don't understand why the coil voltage for the Albright SW202 must match the pack voltage. 

When I ordered everything the 202 came with 12v coils. I'd like to use it and power it from the same source as the main contactor.

ALSO Netgain docs says you shouldn't apply high power if the motor is advanced in the CCW, as mine is. They don't define how much that is however. Backing the vehicle out of the garage or a parking space shouldn't require much power given the 1200lb weight of the vehicle but I'd like to know if some reversing will damage the motor.

Thanks in advance for any help you can give me. I'm pretty good with mechanicals but I am no EE.

Carmelo


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## Woodsmith (Jun 5, 2008)

Hi, welcome to the forum. I'll move your thread to the controllers section.
Any photos of your vehicle?

I can't see why the coils should be pack voltage, though the contacts must be.

The only thing I can think of is if there is any similarity to the Curtis 1214 I am using on my tractor.
The 1214 is 48V but routes all the controls through a multipin plug on the controller. The controller will not operate unless it can sense both the forward reverse switch and both contactor coils. As such the controller operates the F/R contactors using pack voltage. I have 48V coils on my F/R contactors for this to work.

I tried to remove the F/R switch and contactors when I changed to a trans with reverse gear but the controller refuses to work unless they are properly connected to the controller and the motor so I still have them, redundent, in the circuit.

However, looking at the Curtis data for the 1231C it only seems to have three spade terminals, for the throttle and the power supply, and nothing else. Can you link to where it says the contactors have to pack voltage?

From looking at the manual I think it might be the case for linking the F/R contactors to to the main contactor via the F/R switch to interupt the controller to prevent switching under load to to operate the plug braking system. Everything then is at pack voltage.

If you are driving on the road you should really wire it not to use plug braking and then you can have the control circuits for the KSI contactor coil and F/R contactor coils at 12V.

Use the wiring in Fig 10 of the manual and just add 12V controlled F/R contactors into the field connections.


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## Tesseract (Sep 27, 2008)

Paxterra said:


> ...
> Can anyone tell me why---->The forward/reverse contactor coils must match the vehicle’s battery voltage when using the Curtis 1231C.
> 
> I am building a direct drive vehicle and I am reversing the motor for reverse travel....


First off, the contactor coils CAN be 12V with the Curtis 1231C. Other Curtis controllers - those intended for golf carts and forklifts - do have internal contactor control logic, but not the 1231C.

That said, what you are proposing to do is *extremely dangerous* because you have no means of preventing the direction switch from being flipped when the vehicle is already moving. The way you reverse a series motor is by flipping the polarity of the field in relation to the armature. If the motor is already turning in the forward direction when reverse is engaged (or vice versa), however, then the motor will act as a generator. The problem here is that the freewheeling diodes inside the controller will start conducting, shorting out the motor-as-generator. At the very least this will result in strong braking, but the more likely consequence is rapid and total destruction of the controller.

The way I have previously suggested this be handled is to route the power to the reversing contactors through a NO pressure switch on the hydraulic brake line which closes above a certain pressure (say, 100 psi, but with a burst rating of at least 500 psi). This will prevent the motor direction from being changed unless the brakes are firmly applied. It's not a foolproof method of ensuring the motor is at a dead stop when the direction is changed, but it's better than nothing at all.


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## Paxterra (Mar 12, 2012)

Thanks for the replies, it sure is nice to have help. I'll get a photo on here as soon as I figure out how. 

On the coil/pack voltage issue: Page 11 of the Curtis manual states: The forward/reverse contactor coils must match the vehicle's battery voltage.

About the Plug braking: I definitely don't want plug braking enabled. According to the Curtis manual (pg.16 Freewheeling: Wiring To Inhibit Plug Braking) 

Freewheeling: Wiring to Inhibit Plug Braking
If your controller has the HPD option, this feature can be used to inhibit plug
braking by brieﬂy turning off the controller’s KSI input when the forward/reverse switch goes through neutral. As shown in Figure 11, another set of contacts is added on the forward/reverse switch. Therefore, a double-pole, double-throw (DPDT) center-off switch must be used for this setup. A “hesitation switch” is recommended, to ensure the switch is in neutral long enough to actuate HPD and inhibit plug braking. Plug braking can be reactivated during freewheeling by releasing the throttle
and reapplying it.

Now this all sounds fine until the last sentence. This makes it sound like normal on throttle/off throttle driving "reactivates" plug braking.

While the Curtis manual is beautiful to look at I don't find it all that well written. (of course I don't speak EE)

My plan of the f/r switch is to force a hesitation of several milliseconds by a mechanical complication of the f/r control. According to the above this will inhibit plug braking. What I really want to know is how to wire this up so plug braking will NEVER occur.

Thanks for any help you can offer. Next time I'm going with a controller that is only designed for on-road use.

carmelo


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## Paxterra (Mar 12, 2012)

Now I see your point on the brake pressure inhibitor. I definitely don't want to switch motor direction when the vehicle is moving in the opposite direction.

With the brake pressure switch enabling reversing contacts do I have to latch the relay. My logic says when you let off the brake circuit goes back to NO and now the relay shuts down again.

Sorry if I'm dense about this.


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## Woodsmith (Jun 5, 2008)

You don't have to have plug braking at all. It will only mean not including the extra cable from the controller to the motor. Loose that and there is no plug braking.

I agree the manual isn't well written, it took me many attempts to make sense of it and it still isn't clear.

For my Trike, which will also have direct drive and a F/R switch, I am intending to have a mechanical interlock that prevents the switch being activated while there is movement. I am not sure how yet but our taxi cabs here have a system that locks the doors when the taxi moves and then only unlocks when it stops, to stop passengers exiting a moving cab. I can use a similar set up to inter lock the F/R switch.

However, I am also using a mechanical F/R switch removed from a milk float. That, for me, is easier to interlock then an electric system.


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## Paxterra (Mar 12, 2012)

Thanks again. 

Well the Curtis only has three terminals (not including the HV part) two are for the 0-5K throttle the other is power to the unit (KSI-keyswitch input). Running the KSI through the throttle microswitch causes the KSI to open whenever you let up on the throttle. THIS is what inhibits plug braking on the 1231-c. 

In my set-up I will run this through a low voltage relay circuit to avoid having the full pack voltage running all over the interior. KSI needs to be pack voltage since that is how the 1231 does over/under voltage protection.

I guess my big question still remains: Why does Curtis say you MUST use pack voltage the coils for the fwd/rev. relays.


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## Paxterra (Mar 12, 2012)

I love the idea of a manual reversing switch. How did you find yours. I don't know what a "milk float" is. I've been looking at designing one from scratch.

Manual f/r switching is superior in several ways I can think of: Less cost, has built in human factors, no current required to keep the relays energized (that part kills me, I hate clicking sounds in a vehicle, less complexity.

The thought of changing the vehicle direction with a tiny little switch is bad human factor design in my opinion. I've been in an electric production vehicle where the rocker switch for f/r is no different from the on/off for the wipers. yikes!!


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## Woodsmith (Jun 5, 2008)

If you have a look at my trike thread from this post onwards you will see the reversing switch as I got it and in bits being cleaned.

A milk float is an electric vehicle from the 50's to the 80's in the UK that was used to deliver milk door to door. Weighed up to 4 tons and had a range of up to 30-40 miles. It was a backwards step when milk deliveries changed to 'modern' diesel vans.


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## Paxterra (Mar 12, 2012)

Thanks Woodsmith. I checked out your trike thread. Sorry you're having the health issues. And you still have the energy to help others. Wow.


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