Had a strange issue with my new Ultrex yesterday. This was actually my first trip out with it and I was really just checking it out and getting familiar with it. Stopped out in the middle of the lake, synced with the heading sensor and calibrated the motor. Tested spot lock and some of the other functionality. Everything worked great with both the remote and the pedal. Picked up and went to another spot to check out the new live scope. Dropped the TM, hit spot lock and all was good. Tried the jog forward feature and it seemed to be working. Then started getting out a rod and after a minute or two I notice I'm drifting away from my spot. Remote still shows it's in anchor mode. When I tried to manually steer the motor, both with the remote and with the pedal, it wouldn't turn. If I turned the prop off I could turn the motor with the remote and the pedal but it turned very slowly. The remote showed an icon of a battery with an exclamation point inside it for the boat battery. So I figure I've got a bad battery. Or, possibly my charger has gone bad and didn't fully charge the batteries and the little bit i used the motor drained the battery. I get back to the house (several hours later) and get the volt meter out. All batteries test good. 12.6-12.8 volts. Test the TM leads going into the pedal and I'm getting 24.9V (24V system). Deploy the TM, turn everything on and it's working perfectly.

Now I know there are any number of things that can cause this from a battery that's not performing under load to bad wiring/connections to water intrusion in the TM to a whole host of other things. My question is, has anyone seen this issue and can point me to where to start?

Checking battery voltage with no load (open-circuit, essentially) is rather meaningless. You need to watch the battery voltage when the standard load is applied. If you have a bad battery, the voltage will fall drastically as amps are pulled by the load. Running the TM with the prop in air is still not a lot of load, but a bad battery may be evident even in that scenario.

Load test batteries at an auto parts store, or go back to the water and have someone run the TM as you check the voltage on each battery. Also check for corrosion on all connections, which is as much of a problem as a loose connection - both cause high resistance, so the TM gets lower voltage than it needs. I'm going to put the odds on the voltage dropping rapidly as soon as the prop begins to rotate under load.

The odds say the problem is not the new TM. For starters, unplug the charger for a bit so it goes back to step 1 of the charging profile. Plug charger in, then check the voltage at each battery right away. You should see 13.x volts initially, where it will be closer to 14 than 13 depending on what charger you have.

Spot on. Follow these suggestions and you’ll find the issue.