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Discussion Starter #1
I have a Simple Cycler and have never been able to get it to read the correct battery voltage consistently. Mine always varied quite a bit with temperature. I've recently fixed mine, and now it reads the high voltage battery consistently. Here's how I fixed it:

The culprit to the incorrect voltage readings seemed to be the U4 K817P9 opto coupler, so I removed it and R8 and C5 from the PC board to free up ADC IN. I don't use the FANPWM output to run my HV Battery fan, so I added a resistor, LED, and transistor to have FANPWM control a 12v DPDT relay instead.

For measuring the high voltage, I added two 1% resistors as a voltage divider to drop the HV battery voltage down to 5v or less. This lower voltage charges a small capacitor that's attached to the relay's terminals. I modified the software to sample the voltage by triggering the relay. The relay switches the capacitor leads from the HV Battery voltage divider to the ADC IN of the PIC. The PIC then reads the capacitor voltage, keeping the HV battery isolated from the car.

It works!!! Now my Simple Cycler tracks the voltage of the HV battery perfectly, remains electrically isolated, and displays the correct voltage on its LCD screen. The fix sounds a little complicated, but really isn't that bad to do. Here's a pic of the mod:

83788


What's great is I can now set the Cycler to charge, discharge, or cycle the battery and it now operates without any intervention from me at all. I just set it and forget it!!

Awesome!!!
 

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Nice work. I'll have to update mine and redo the schematic..

What is your sample rate?

Once a minute would be ample and the relay would last a long time.
 

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Discussion Starter #4
Software updates the voltage once per minute. I'll share the code when I get home from work today. (I also have a diode across the relay's coil that I didn't mention in the original post)
 

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Discussion Starter #5
For the voltage divider, I used 100k and 2.7k ohm resistors. It assumes a max battery/charger voltage of 190vdc

Attached are the software modifications to operate the relay and read the voltage. You'll need to rename the CyclerFlyingcap-V01.pdf to CyclerFlyingCap-V01.hex. The website wouldn't let me upload the file with a hex suffix, so I changed it to pdf. If you change it back to a hex suffix after downloading it, you should be good to program your pic.

I've also attached the modified source code as a text file, so it can be changed and compiled for different charge/discharge parameters as needed.
 

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Discussion Starter #6 (Edited)
Here's a schematic for the Flying Cap version to modify the Simple Cycler: It is necessary to first remove the other components to free up FanPWM and ADC IN as described previously in this thread. I drilled a small hole in a clear area of the board to allow easier access for connecting the 2.7k 1 watt resistor to the HV Negative connection. All the resistors used are 1% tolerance. The LED is standard red 3mm.
84165
 

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@davismltc I'm thinking of changing the charge output voltage of the Simple Cycler from 180V to 30V to use it to charge one 24-cell LTO battery pack by substituting a 30V cc/cv Mean Well LPF 16-30 supply with the two APC 35-350 supplies. I would change the divider circuit to a 330k and a 64.9k resistor.
I'm finding it difficult to reconcile the pin-out of the relay with your pic. It looks as if the 10uf cap is connected to pins 6 & 11 and I can't tell where R1/R2 junction goes. Silly question but does your picture agree with the pin-out on your schematic?
@snikrepretep Can I assume the SC will work if the code is changed to a 30V hi and 26V low limit
 

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@snikrepretep Can I assume the SC will work if the code is changed to a 30V hi and 26V low limit
It might, but I would not assume anything, it wasn't designed to operate at those low voltages.

You also need to be reducing values in the divider not increasing them.
 

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@retepsnikrep do you mean the @davismltc divider? He uses a divider with 1W resistors. I don't want to use 1W resistors therefore I want the divider to use high resistance. What is high? What's the reasoning to use lower resistance? Is a reduction by a factor of 10 acceptable?

Is reducing SC divider input R5 and R7 necessary too? Thanks
 

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Discussion Starter #10 (Edited)
The picture and the schematic agree. However, the relay's coil in the picture is on the right side of the relay. The schematic happens to show the relay coil toward its left side. A schematic is an electrical diagram of the circuit, and doesn't necessarily correspond with physical orientation. (The 10uf cap in the picture is attached to pins 4 & 13 as shown in the schematic)
 

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Discussion Starter #11
One reason for lower resistance for the voltage divider network would be to allow the capacitor to charge in a reasonable amount of time.
 
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