Hi!
Tried looking around in case anyone had already solved my problen, but only found:
http://www.element14.com/community/message/19513#19513/l/电量计在手持设备中的实现
Which was not so helpful as I do not read Chinese 
Anyway. The idea is to use a STC3100 to monitor a lead-acid battery. Previous design uses a TI BQ-chip and works well, but the idea was to be able to monitor several batteries, using a central console.
Assume that I have a 100A/50mV shunt. The full-scale reading will be +/-160A. Permissible range for a STC3100 is +/-80mV and maximum resolution of the coloumb-counter is 6.7mV. Absolute Maximum ratings for inputs are -0.3V..7V.
Problem is that if I monitor a starter battery or a bow thruster I might see up to 1000A during a split second and that will risk damaging the STC3100 in case it sees below -300mV over the shunt.
Unfortunately is one end of the input amplifier grounded.
But what happens if I turn the tables on the unit? Ie switch CG and GND? Connect CG to ground and the STC3100 ground to the shunt? I guess the following will happen:
1. The allowable range for discharge masx goes from 600A to 14 000A
2. The measured voltage on the Vin pin will be off by the voltage over the shunt, bt that can be compensated for as the current is known
3. I2C ground is no longer ground. Instead it rides on a variable voltage of +/-80mV,a galvanic isolator will fix that. This also makes the system suitable for scenarios where not all batteries share the same ground.
4. Currents in excess of 160A will not be measured correctly, but my algorithms also make an educated guess, based on battery idle voltage.
5. Charge polarity will be negative for positive charges and vice versa, but the STC3100 stores everything signed anyway
Comments?