2G wrote on 8/9/2018 9:10 AM:
The only one I could find specifically designed for aircraft is the MGL BAT-1 (anything else was only a voltmeter or ammeter):
http://www.mglavionics.com/BAT1.pdf
It does not have a coulometer, however. I have specified this for my new ASH31.

Pilots that are don't require the alarm function can find small panel mounted
volt-amp meters like these from Amazon for about $15:

- WATERWICH DC12-24V/0.1-10A Dual LED Digital Multimeter Amp Voltage Meter
- TOOGOO(R)Dual LED Digital Voltmeter Ammeter DC 0-100V 10A Panel Amp Volt Meter

I'm not suggesting those two are the best choices, but I have used similar units
that worked well.

There are panel mounted units that include amp-hour/watt-hour readings, but are
larger. I use a charger for my instrument battery that shows amp-hour/watt-hour
readings during charge, so I can see the battery did accept the expected charge.
That's be satisfactory for years, so I haven't felt the need for amp-hour readings
in the glider; generally, my current drain in-flight varies only a little.

--
Eric Greenwell - Washington State, USA