External Switch To Lower Input Resistor Value / Any Voltage?

[icecube57]

Is it possible to wire an extra resistor with a switch parallel across the input resistor slots to lower the resistance to allow more current to flow through the MCU at lower voltages. I current have a Infineon XC846 72V 45 Amp Controller that workes between a programmed LVC of 58v-100v. The input resistors are to high to allow enough current under load at lower voltages I understand if this mod is possible I would have to lower the programmed lvc of the controller to a new number. I want to be able to run a 36-48v pack with a new lvc of about 29v.

I always run 88v nominal. There are times I just wanna take it down a notch. I have 6 Bosch packs that I run at 3 parallel and 2 series 74v nominal 6.6AH. I have a 12v 15AH ping booster pack. For a voltage of 88v nominal. This gives me 516wh to use.

I want to be able to put my bosch packs in a 6 parallel config and wire my ping booster in series for a solid 48v 13.2AH setup. But this will also increase my 602w. I could theoretically extend my range 5-10 miles. Depending on how I ride.

Could this be an alternative solution to knuckles any voltage mod or is the a FAILED wet dream.

 

[methods]

It is on the first page of my 100V 100A thread

This is assuming you are working with a 116 starting with three 1.5K resistors in parallel
Basically for 50V to 100V you want about 600 ohms total
For <50V you want about 400 ohms - so you "switch in" another resistor in parallel


The principles apply to the 846 design (but not the exact values of course). The 116 is actually much more tolerant due to the regulator design.

I dont know off hand but IIRC the 846 uses a 317 variable regulator. The way you tune in a 317 is by making sure you never drop more than 40V across its terminals - while making sure you have enough voltage at its input to supply your target output. You can calculate this since you know the input voltage, inline resistance, idle current, and loaded idle current.

If you want to do it the lazy man way just hook up your lower voltage (say 30V) and measure the 14V buss. Try laying a few different parallel resistors to see how the voltage changes.

I am sure it has been calculated before - or just find a 36V - 48V board. Whatever total parallel resistance is there, that is what you want to create when you close the switch.
Makes sense right? It will probably just involve laying a 1.5K ish resistor in parallel with the rest.

I can do the calculation if you need me to buy my guess is that someone can get you the resistor values faster and easier. Even just a picture search would do it.

-methods

 

[icecube57]

I have to check my input resistors on my controller with my VM tommorrow but I think my current input resistors are at a little over 500 ohms. If i parallel a 1500 ohm resistor across them it will drop me down to around 375 ohm which would allow me to run the controller down to 24v @ 65ma and but since my lvc is 29v this combination provide the MCU with 78ma of current @ 29v. Which should be more than enough to satisfy it under load. My goal is an lvc of 29v. So your resistor value sounds like a good plan to me plan to me.

Since i did the R12 Mod this changed my lvc. My LVC multiplication factor is 1.391. So I need to program a new lvc in my controller of 21v. This will give me a new lvc of 29.211v

If I do this mod I will more likely run two wires outside the controller and crimp a connector. I would plug in the connectors to parallel the resistor with the existing input resistors and run in a lower voltage band. I would unplug it to run above 60v. I will use my CA to set my LVC when running packs above 36v.

 

[methods]

Sounds like you are on the right track.

as an aside -
As a rule of thumb I never rely on controllers to handle my LVC.
They are often (kelly for instance) off by a "volt or two"
No big deal with lead acid - but doom for Lipo

I have Gary/Fechter LVC boards but in reality 99% of the time I just never let the packs get there.

-methods

 

[icecube57]

I finally did the Any voltage mod. My r01 and r02 added up to 635 ohms. I added a wire across r01A and r01b. I soldered a 1k ohm resistor to 1 wire and ran a wire outside the case. The other wire was a straight shot outside the case. I added a connector so when i plugged the two wires together it drops the input resisor value down to 388 ohms. Unplugged returns it to 635 ohms. Now i can run 36v to 100v battery packs. I also reprogrammed the lvc to 29v.