Issue with typeof voltage in script

RouterOS Scripting
1

Hello,

I have an issue retrieving the voltage from my HAP. I simply want to do the following: if the voltage is lower than 10.8 V, then perform one action; otherwise, perform another action.

The problem comes from the return type, which I can’t convert to make a comparison (ROS 7.18, 7.15.3):

:local health [/system health get 0]
:local volts ($health->"value")

log info message=$volts; <-- return : 11.6
log info message=[:typeof $volts]; <-- return : str

:local volts [:tonum "$volts"];

log info message=$volts; <-- return nothing
log info message=[:typeof $volts]; <-- return : nil

log info message=[:typeof 10.8]; <-- return : ip (why ?)
local alert [:tonum 10.8];
log info message=[:typeof $alert]; <-- return : num

:if ($volts >= $alert) do={
    action...
} else={
   other action...
}

Thanks for your help !