http://www.powerwerx.com/techdata/Watts-UP-V2.pdf

Note the voltage drop-power consumption of this device.

This device is mostly designed for the Radio Control (RC) car, plane, boat,
helicopter hobbyist. While it can take 50 amps this is for a source that
will be depleted in minutes, not hours.  All the current going in/out of
this device is connected with those 14 gauge wires, normally used for 15-20
A/H loads. This can be a good test device but I would only for limited
load/charging current currents.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Alistair Bell
Sent: Sunday, October 14, 2012 7:06 PM
To: vanagon@GERRY.VANAGON.COM
Subject: doc wattson or watts up?

I think I might have posted about these meters some time ago, I'm sure I
mentioned them to Mark D. I'm wondering if anyone has bought either of them
and if so what their thoughts are after some use.

http://www.powerwerx.com/digital-meters/doc-wattson-meter-dc-inline.html

I'm leaning towards buying the doc wattson model.

alistair