Confusion about 24V to V-MOS

[jace]

I'm deploying a Scylla with a 24V primary rail and 48V for motors. I have battery backup on the 24V rail with an 8S LiFePO4 pack. This means the 24V rail can go as high as 29V when the battery is discharging from full capacity. I'm auditing all my 24V components for safety margins and have some questions about the Scylla.

Relevant notes from the manual:

1. Product Profile
   1. Feature Highlights (page 5)
      • 3 Power inputs supporting from 24V to 56V with reverse polarity, over voltage and over current protection. One input is for Motor supply, another is for auxiliary MOSFET output supply and the final one is for logic supply.
      • 8 Voltage selectable, optoisolated inputs for endstops or otherwise.
      • 3 Voltage selectable, optoisolated, high-current, FET driven auxiliary outputs
        to drive external devices.
2. Interface Overview
   1. Pin Description (page 8)
      • V-MOS highlighted:

V-Probe, V-Tool and V-Lim have regulated outputs for 12V and 5V but not for 24V. That's just V-MOS unfiltered. Spindle outputs V-DIR and V-EN also have a choice of 12V or V-MOS. Further in the manual:

3. Interface Details
   9. Probe & Tool Interface
   1. Tool Interface Description (page 15): "Both the tool setter and the optoisolator have their operating voltages defined by the state of the Vtool jumper as shown in the image below. Do not use the VMOS setting if the voltage supplied to VMOS is greater than 24V as this may cause damage to the controller."
   2. Probe Interface Description (page 16): "Both the probe and the optoisolator have their operating voltages defined by the state of the Vprobe jumper as shown in the image below. Do not use the VMOS setting if the voltage supplied to VMOS is greater than 24V as this may cause damage to the controller."

Section 3.10 "Spindle/VFD interface" does not have a similar warning. Some doubts here:

1. Since section 1.1 explicitly allows 24~56V to V-MOS, will the 12V and 5V outputs work with any input?
2. What is the risk of damage to the controller if V-MOS exceeds 24V? Is it because the optoisolators are only rated for 24V?
3. Does this risk apply to the spindle V-DIR and V-EN outputs?
4. What is the tolerance range for 24V? ±5%? ±10%? ±15%? My 24V PSU will be within 26.4~27.2V for ideal battery float voltage (80-98% battery capacity). This is in the +10-15% tolerance zone for 24V. Is this okay for the Scylla's optoisolators (or whatever component is sensitive to 24V)?
5. There is a minor risk of a fully charged battery putting out 28.8~29V (theoretical max capacity for 8S LiFePO4). Is 29V within tolerance?

At the moment I'm considering three mitigations:

1. This is all within acceptable tolerance and there is no problem here.
2. Use 12V for the toolsetter (just a microswitch) and probe (to be checked).
3. Use a DC-DC PSU to supply regulated 24V to V-MOS. This adds to the cost but de-risks the AUX0/AUX1/AUX2/Mist/Cool outputs.