# How to up the voltage on Curtis 1204, where did the post for dual curtis's go?



## Tesseract (Sep 27, 2008)

rmay635703 said:


> There was a very informative thread here several months ago from an individual that took 2 curtis 1204's replaced mosfets and combined them into a single controller.


http://www.diyelectriccar.com/forums/showthread.php?t=28857

Don't forget about the freewheeling diodes and input capacitors!


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## rmay635703 (Oct 23, 2008)

Tesseract said:


> http://www.diyelectriccar.com/forums/showthread.php?t=28857
> 
> Don't forget about the freewheeling diodes and input capacitors!


Thanx for the heads up! The threads 2xcurtis messed up my searches, I would assume any part that is not rated at least double my goal voltage of 96 volts would have to be replaced with higher rated components I plan on doing a 2 rail power input so I can bypass dc-dc issues.

jsodemann is in wisconsin, he sort of dissappeared, I wonder if he ever did get that up and running in a real non-lab environment.

Also I might borrow his "lab" for tests if he is nearby.


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## Amberwolf (May 29, 2009)

How has your project gone so far? 

I ask because I just received a 1204-410 in a "care package" from one of my blog readers, and it's been opened up (it's not potted) by one of it's previous owners. I've not tested it yet but assume there is probably something wrong with it if it had to be opened up. No obvious blown parts.

I've been looking at Otmar's reverse-engineering of a different model, to get some idea of what they might have done in creating this one; it's probably not identical anywhere but possibly similar enough to get the idea of their engineering style without tracing it all out myself. 

I'm considering using this, once tested (and/or repaired) to run some of my ebike testing, to see how it compares with my 2QD in operational style, etc. At some point, I would like to go beyond 48V on my ebike (to make using my treadmill motor more effective), and if I did I'd need to do what you set out to do. Knowing how yours turned out would be helpful. 

EDIT: BTW, since from your previous posts in this thread it doesn't look like you've actually gotten one yet to do the experiments on or see stuff inside, I can contribute pics, info, etc to you if you like. I"m also more than willing to experiment on mine, as long as I already have the parts around here somewhere (I have no money to buy new ones).
________
Leather Cams


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## rmay635703 (Oct 23, 2008)

Amberwolf said:


> How has your project gone so far?


Nowhere, I got recalled to my job, lots of OT and I'm back to living out of a small apartment so I haven't had time to do anything.

I would estimate the 1204 would be moderately easy with the right equipment and parts since it is more simplistic than some of the other models.

Good Luck
Ryan


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## rmay635703 (Oct 23, 2008)

http://ferromit.com/controller.html

Hmm, I still haven't sourced a 1204 to play with but it appears it may be good to 60v AS-IS once you disconnect the logic section and provide 48v to it independantly.

Looks well fairly simple, but alas things rarely are, I wonder how mosfets behave when you get quicker HV units? Likely the resistors would need to be changed to slow them down a bit for the weak caps.

Ah well, good luck I would love to see someone find a use for all these 1204's floating around. There are more of them than anything else on the market.


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## Amberwolf (May 29, 2009)

rmay635703 said:


> http://ferromit.com/controller.html


That is an interesting page. 



> Hmm, I still haven't sourced a 1204 to play with but it appears it may be good to 60v AS-IS once you disconnect the logic section and provide 48v to it independantly


.
Funny--what ultimately ended up being wrong with mine was that there were cracked solder joints between the logic and power boards. Once fixed, I ran it succesfully on CrazyBike2. 



> Looks well fairly simple, but alas things rarely are, I wonder how mosfets behave when you get quicker HV units? Likely the resistors would need to be changed to slow them down a bit for the weak caps


.
Not sure about that part. But another option is to replace ALL the MOSFETs with IRF4110 parts, which are good for 100V, and probably don't need any more gate current than the existing ones. Replacing the caps with higher voltage units would also be an option. 




> Ah well, good luck I would love to see someone find a use for all these 1204's floating around. There are more of them than anything else on the market.


The big catch with them is that due to the heatsink not being a part of the case itself, but rather an electrically-insulated part within the casing. That electrical insulation also makes a thermal barrier, so heat can't be transferred out fast enough for really high sustained currents that most car-sized EVs would need, so the caps and other heat-sensitive parts in there are going to die faster. 

Leaving the case off, and bolting it to a heatsink that is insulated from the vehicle chassis but not the MOSFET heatsink, and actively cooling the core of the 1204 where the caps are would help a lot in extending it's life and reliability, I suspect.
________
LIVE SEX WEBSHOWS


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## jehan12413 (Feb 4, 2010)

I have also been upgrading curtis controllers for several years now and have had great success running single and multiple power sections off one control board. For voltages around 72v I use IRF3710 mosfets and for high voltage IRF 740. I do have one question which Tesseract may be be able to answer judging from the technical discussion last year on this subject. That question is if the current limit will be damaged by the higher voltage? On my control boards I use a seperate supply or regulator to supply the power and disconnect the plug brake. The current limit however senses voltage drop across the MOSFETS and is only enabled when they are turned on. Will this be damaged by the higher voltage (120-300v) while they are turned off. If I remember correctly this connects to an LM339 and I'm not sure what it can handle. Any information would be appreciated.


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## Tesseract (Sep 27, 2008)

jehan12413 said:


> ...That question is if the current limit will be damaged by the higher voltage? ... The current limit however senses voltage drop across the MOSFETS and is only enabled when they are turned on. Will this be damaged by the higher voltage (120-300v) while they are turned off. If I remember correctly this connects to an LM339 and I'm not sure what it can handle. Any information would be appreciated.


Sensing the voltage drop across the switch is a pretty sloppy current limiting method and it depends, of course, on the Rds[on] of the mosfets.

A diode that is reverse-biased when the 'fets are off protects the current sensing circuit. You will likely need to replace it with one that is rated for a higher voltage as well. It needs to be an ultrafast recovery type. UF4007 is a good general purpose choice for this application.


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## jehan12413 (Feb 4, 2010)

That helps thanks. A circuit diagram or at least parts layout description for the control board for a curtis 1205 would be very helpfull if anyone has one. Due to the fact that curtis does not provide a schematic I have been trying to figure it out with a magnifying glass and by trial and error.


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