🚀 go-pugleaf

With regard to asking a DMM to measure its own battery voltage, 
Mark-Tarbell@suite.com writes:

>Any ideas?

Sure.  Charge a cap with the battery voltage and measure it.  
Linear Technology even makes a special switch IC to do this sort
of thing gracefully, if you need to do it often.  It helps if
the cap has low leakage and the DMM has an essentially infinite
input impedance on the required range.  Try a time constant of
DMM input R * C of 100 times as long as it will take you to read
the DMM, for a 1% error.

Trying to measure the battery directly is dangerous at best, since
you are shorting out some part of the guts of the DMM when you hook
the input leads back to the battery.