# Curtis 1209B upper voltage limit?



## Woodsmith (Jun 5, 2008)

With many thanks to Greyballs I now have a pair of Curtis 1209B controllers.
They are rated at 48-72V.
With some very basic calculations I can have a theoretically comparable range using 72V 200Ah as I would have using a 96V 160Ah. The 160Ah pack is a little better but the 200Ah pack would do my commute.

I have been looking at the potential voltages available from LiFeP04 cells and with an assumed nominal voltage of 3.2V I can have either 22 cells giving 70.4V or 23 cells giving 73.6V.

Now, allowing for the increased voltage at full charge should I be looking at 22 or 23 cells in this pack?

I am working on the basis that the torque of the motor would get me to cruising speed anyway is it is an 80V 11" fork truck motor on direct drive but I can still have the option of changing to an open revolt and buying a few more cells in the future.

Thank you.


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## grayballs (Aug 27, 2008)

The first pack, I ran one of the 1209's on, was lead. I'm not certain, but I think the float on my charger was 80v.


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## EVfun (Mar 14, 2010)

I think you could run 24 cells without a problem. People use Curtis controllers with golf cart batteries all the time and with 12 of them the peak voltage on charge could reach 94 volts. It would be quite possible to turn on the controller with a pack voltage of 84 volts if you unplugged and jumped in. Those limits wouldn't be exceeded with 24 LiFePO4 cells charged to 3.9 volts or starting the car with the cells still at 3.5 volts.


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## Woodsmith (Jun 5, 2008)

Excellent!

That gives a really good overvolt range. I knew there would be some scope but wasn't sure by how much.

I recon it would be worth building the trike around the Curtis and designing a good heatsink for it.

Thank you.


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