# Sevcon Gen4 (G4845) Ixxat Problem with the Voltage Cutback`s



## cricketo (Oct 4, 2018)

That curve looks wrong - it doesn't take into account the regen (overvoltage). Other than that, just adjust your voltages as you need them


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## bennony (Dec 15, 2021)

Enter the new voltage and just leave the gain? unfortunately I don't understand the connection


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## cricketo (Oct 4, 2018)

gain is the decimal notation of percentage it will cut back. I want to say it's in reference to the control method being used (torque or rpm), but it may be in a refence to the max current, would need to double check. So 0.5 means only 50% torque will be allowed below that voltage. Likewise at the upper end 0.5 would mean only 50% regen output into the battery would be allowed. 

I believe a correct cutback map should visualize something like this :










Otherwise you will be getting weird undervoltage/overvoltage errors from the controller.


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## bennony (Dec 15, 2021)

Ok, I think I've got a little sand in any case ;-) Thanks for the help

Then I'll test it like this one day...

Cutback Voltage Old / New Volt ( + 4.2V = spare cells)

41,25 --- 45,45 
41,5 --- 45,7
41,75 --- 45,95
42 --- 46,2
43,25 --- 47,45
43,5 --- 47,7
43,75 --- 47,95
44,0 --- 48,2
44,25 --- 48,45

More settings in planning...
Cut-off voltage to 45 volts (2.64V = already very close (2.5 volts is cell minimum)

I will try to increase the system voltage of 48 volts to 51.2 volts (otherwise there will also be conflicts because the cutback voltage is higher than the system volt)

Maximum permissible voltage is 62.05 volts (I don't reach it, I only charge up to 3.45 volts per cell / 58.65 volts total) according to experience, they are then almost full, and save a lot of time when balancing.


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## bennony (Dec 15, 2021)

More or less it worked so far, after the changeover there was an error, it disappeared by itself after I restarted the controller. the controller itself wanted to change the last values in the cutback ...
47.4375
47.4575
47.4775

These values were probably too close to each other / the idea was to remove 2 values and fill them in with 0, but I was very unsure whether it would not cause problems elsewhere.

The basic setting of 48 volts cannot be changed, although the start of the cutback of 47.4375 volts is unfortunately not optimal. as soon as the cutback takes effect, the cells are actually almost empty.

Well, with the knowledge that you should only go to 48 volts under load, it will work, so I hope, there is still no test to see how it will make itself felt and how deep the weakest cell was (cell drift)


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