When your range is from nano amps during sleep to spikes of several tens of amps you will not find a voltmeter with a range big enough to work with a single shu

When your range is from nano amps during sleep to spikes of several tens of amps you will not find a voltmeter with a range big enough to work with a single shunt. You need several shunts and switch between them very fast. That's what devices like the Joulscope do and why they are expensive.