I went down cellar and checked my Hobbico digital against a good multi-meter and a Tower/Hobbico analog ESV. THe Hobbico was bang on with my Multi-Meter. Both read 5.34v on the pack I tested.

In checking, however, I did have to select to turn off the load on the Hobbico. You're not comparing a loaded circuit against an unloaded one are you? The Hobbico puts a load on unless the three-way switch is centered. The loaded Hobbico was on again with the Tower ESV, which is always a loaded circuit (I think both use a 250 ohm load).