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Re: Curtis Controllers

Posted: Wed Aug 08, 2007 9:29 pm
by EVguru
electricvehicles wrote:They are sealed for a purpose --- To stop tinkering fingers tinkering with them. Thats why the only way into them other than Curtis is via the programmer. Just leave them as they are !!! They work fine and exceed their specifications.
If you tinker with a combustion engine to get a bit more, as we all know you will you will reduce its life, same with a Curtis




I've modified many production engines, often for power, sometimes for economy (not always exclusive), but often to correct well known life limiting design defects that were not adressed during the production life of the engine. Triumph straight six engines for example, where the oil drains out of the filter when parked, so they're always oil starved when started cold.


Curtis pioneered transistor based controllers, first with bipolars and later with Mosfets.

THERY' RE GOOD CONTROLLERS and I've used them several times with sucess.

But they have their limitations and in our applications, which despite your opinion, really ARE often harder on controllers. Forklifts don't often climb a hills for several minutes at 50% PWM duty. They're not typically driven in traffic and so don't missjudge a gap and have to acclerate very quickly.

Several people have taken them apart after their second or third controller (whose application was recommended by a Curtis engineer) has failed. They've usually then decided they need to use another product.

Curtis controllers fail often enough, even in ordinary golf car applications, that there are several specialist firms offering a repair, exchange or outright purchase service for them in the US. They upgrade them becuase there are OEM only components inside and also because better components have been developed and are often cheaper.

The 12xx series have rather too many mosfets in parallel, are rather short on freewhweel diode current capacity, don't have high frequency filter capacitors, don't have a linear overheat shutdown, have taken an 'easy' approach to EMC compatability (increased switching losses), and have a slow current limiting scheme that causes failed controllers when driving low impeadance motors. The latter by the was is why Curtis introduced the 1221 and 1231C series controllers where the frequency is reduces to 1.5KHz below 10% PWM.

They were pretty much state of the art when introduced, but time marches on. Judging by the current ratings and on state resistance the uProcessor logic versions of the 12xx series are using the old power stages (But why do they no longer list the 1 hour current rating?).

The Americans went through the golf car/forklift components phase about 15 years ago. Here it's taken rather longer. When I first joined the BVS some 10 years ago, many people didn't trust electronic controllers at all!

Many of us ARE tinkerers and we DO push the technology.


Edited by ChrisB to remove certain comments that are non constructive

Posted: Thu Aug 09, 2007 6:02 am
by aminorjourney
I shall drag this back on topic with news that the Curtis didn't perform as intitially required. The car went forwards and not back. Then a few hours later it did nothing.

I'm fed up with the assumption that every EV owner has to be a technician. grrrrrrrrrr.


I just want to drive the thing!

Dont Worry

Posted: Thu Aug 09, 2007 7:03 am
by electricvehicles
Hi Nikki
Please dont worry, its got to be a simple problem

1. Is the controller fitted with the SRO option ( Static Return to Off ) ?
2. Is the City E Fitted with a forward/reverse switch which has a neutral/center off position ?
3. Are the forward/reverse contactors fitted with diodes across the coils ?
4. when selecting either forward of reverse do you have full battery voltage once the accelerator is pressed at the corresponding contactor coil ?

Please let me know and I will do all I can to talk you through things.
Good luck
Dave
PS Private message me if you want to give me a call and I should be able to sort things out over the phone.

Posted: Thu Aug 09, 2007 9:12 am
by EVguru
If it's still the same as the Citi-el I worked on, the F/R switch is just an ordinary cheap rotary switch with a paddle bolted at a right angle to the shaft.

These can come loose in the dashboard, so thay you can only engage one direction, or if almost completely loose, stay stuck in neutral. The switch detent isn't strong, so it's hard to feel that the switch is turning rather than switching.

Check that the F/R signals are actually getting though to the controller. There are a lot of different connectors in the loom and it's very easy to loose a circuit. I know you haven't necessarily touched any of this stuff.


I don't recall it being an SRO controller, but it's certainly got the High Pedal lockout. Do you normally have to have the F/R switch in neutral at start up?

Posted: Thu Aug 16, 2007 9:07 pm
by aminorjourney
Well folks, it's all been sorted!

Turns out (funnily enough my instincts were right) that a diode had blown on the reverse contactor. The result was that the Curtis was sure there was a stuck contactor and didn't complete the circuit to ground as doing so may have blown the thing up.

So, a new diode in place and I've just got back from my trip to Sainsbury. The Bristol Two are back on the road! Weeeee! (And no, I'm referring to my City El and the Mini El belonging to a certain photographic whiz nearby - not any other "two" you may happen to think of! :Shock: )

Thanks to John, who helped me diagnose and fix the problem I am back on the road and happy again.

Stupid car's like a drug to me. I really get fed up when I can't drive my EV!

Posted: Thu Aug 16, 2007 11:39 pm
by qdos
Excellent news! Well done John :) Wonder if the Red one is fixable too? That'll make 3 ;)

Posted: Fri Aug 17, 2007 3:51 pm
by anachrocomputer
Should I mention the other fault? The one that took out the dashboard and battery monitor power supplies? Something to do with a 3A fuse, which was blown even when "all the fuses are OK"?

As for the diodes, the City-El has 1N4007 diodes in inverse parallel with the contactors for back-EMF protection. One of these had gone short-circuit, so the controller sensed it as a shorted contactor and switched off. The 1N4007 is a standard 1A, 1000V diode, so it's easy to find a replacement.

Anyway, glad to see the yellow City-El back in business!

Posted: Fri Aug 17, 2007 5:01 pm
by qdos
You know we once had a photocopier that was a bit like this. Should I mention what happened to it? Nah best not to me thinks ;)