battery info: apm cannot attach to mainbus: compiling kernel error

[fire%firecrow.com@localhost]

Hi,
Having some difficulty adding getting battery information from my 
laptop, I tried adding apm to a custom kernel as

    #APM
    apm0            at mainbus?

running config fails with

   $ config MYKERNEL
   MYKERNEL:206: apm cannot attach to mainbus

when my computer boots up I see a message about acpibat0 to the effect 
of "charging state" and it's accurate to where the battery is at the 
time.

I'm not married to apm, was reading about how it's the recommended way 
here.https://www.netbsd.org/docs/power-mgmt/index.html#configuring

what is the best way for me to get apm to work, or an alternative to 
solution to accessing battery information such as via acpibat

thanks
~fire
fire%firecrow.com@localhost