Absolute maximum voltage on Curtis controller

[Pat911]

Hi,

I have a Club Car with a Curtis 1221B-6601 controller that is specified as 48v-72v. No absolute maximum rating is given in the specs. I’m assuming they’re system voltages and not absolute maximum voltages.

I want to power the cart with Nissan Leaf modules and want to know the absolute maximum voltage that the controller can sustain so that I can decide whether to go with 9 modules (18s @75.6 max volts) or 10 modules (20s @84 max volts).

The cart currently has 9x8v FLA batteries that would be providing around 79v when fully charged.

Cheers
Pat.

[ThreeCW]

I also was not able to find those limits online.

But I did find this interesting article on the Curtis 1221B.
https://www.cafeelectric.com/curtis/curtis.php

Linked to the above article was another interesting article on your controller:
https://www.cafeelectric.com/curtis/FirstFeet.html

I’ll let you draw your own conclusions.

[Pat911]

That’s some great information there ThreeCW. Thanks.

It certainly highlights the limitations of the 1221B controller when using motors that are too powerful for it. The motor I’m using is well within the specs of the controller though, continuous current of 83A with a peak of 230A. These are at 72v. The maximum current of 500A should never be reached.

Would still like to know the absolute max of B+ though. Surely this value should be published somewhere.

Cheers
Pat.

[Pat911]

From the 1221B installation manual,

Overvoltage cutoff inhibits the PWM and opens the contactors, preventing operation when battery voltages are too high for proper function................. The cutoff voltage and re-enable voltage are percentages of the battery voltage and are set at the factory.

These voltages or percentages are what I’m after.

Cheers
Pat.

[ThreeCW]

I had a look through your controller manual and the overvoltage setting does not seem to be published. I had a quick look at a few other Curtis controller manuals online and was not able to find anything on other 72 volts models.

For reference, my Curtis 1219-8405 is rated at 36 to 48 volts nominal with an overvoltage setting of 60 volts ... which was detailed (hidden) in my manual (see attachment).

You might have to contact Curtis directly to find out what this setting is supposed to be. Let us know what you find out!

Curtis PMC 1219 Overvoltage Setting.JPG

[Pat911]

Thanks ThreeCW,

Since Curtis described the overvoltage function as a percentage, and extrapolating the information you posted above,

36v -> 46v max = 27.8% overvoltage
48v -> 60v max = 25% overvoltage

72v + 25% = 90v
Or more conservatively,
72v + 20% = 86.4v

Both under the 20s maximum voltage of 84v.

Would this be a reasonable assumption?

I’ll try emailing Curtis for a more definitive answer.

Cheers
Pat.

[ThreeCW]

It sounds reasonable that if the 10 module pack maximum voltage is 84 volts, that it would be within a safe operating window for your 72 volt controller.

Hopefully Curtis can confirm the controller maximum voltage for you to give your a real number to deal with.

If your lithium pack maximum static voltage is 84 volts, what would the maximum charging voltage be? I "assume" that you would want that to be under the maximum controller voltage limit as well. I am thinking from a lead acid analogy where 48 v LA batteries are charged to 65 volts during the finish stage and then after charging, will rapidly decrease to about 55 volts at which point they will slowly drop in voltage until a stabilized voltage is reached. I have jumped in my LA cart many a time after charging with 55 volts on the battery pack ... which is safe with a controller overvoltage setting of 60 volts.
Maybe that is not a factor in lithium cells ???

[Pat911]

Hi ThreeCW,

The maximum charge voltage is 84v (4.2v/cell) and that is also the pack fully charged voltage. The lithium discharge curve is very linear compared to FLA. To lengthen battery life I may reduce charge voltage to 4.1v or 4.15v per cell (82v or 83v).

I've sent an email to Curtis and I'm awaiting their response.

Cheers
Pat.

[ThreeCW]

It is not a Curtis, but it is interesting to note that the Alltrax SR48XXX controllers have a maximum voltage rating of 62 volts. The Alltrax SR72XXX controllers have a maximum voltage rating of 90 volts.

Apples to oranges for sure, but it might help you with your comfort level in case you can't get a better confirmation.

Spec sheet below for reference.

[Pat911]

Thanks, I was expecting around 90v max.