Ultrex shut down - safety mode?

[bassmasher]

Ultrex 112, Lithium batteries, fishing an electric only lake all day no problems. Towards the end of the day going across the lake on number 10 the motor shut off (ran earlier in the day on number ten across the lake with no issues). Turned it off then back on and it was hard to steer and the prop would only spin as if it were on number 2. Shut the breaker for a few minutes (breaker was not tripped) turned it on and it ran fine for about 2 minutes and did it again. I repeated the shut down again and same thing. Drove the rest of the way back to the dock which seemed to be like a safety mode . Any suggestions on what you think this could be? Never had any issue before. Thanks for your input in advance

[Neighbor]

I've heard Ultrex will do that when low battery power situation arises.
Do you have a battery charge meter on board?

[Bradrodfish]

You have a power problem. You probably ran the batteries down. Lithium will cause issues went gets drained

[Erie660]

I’ve read that you should not run a Ultrex over 8.5 for extended periods of time. I’m pretty sure this is with Lithium batteries.

[Erie660]

SELECTING THE CORRECT BATTERIES
The motor will operate with any lead acid, deep cycle marine 12 volt battery/batteries. For best results, use a deep cycle, marine battery with at least a 105 amp-hour rating. Maintain battery at full charge. Proper care will ensure having battery power when you need it, and will significantly improve the battery life. Failure to recharge lead-acid batteries (within 12-24 hours) is the leading cause of premature battery failure. Use a multi-stage charger to avoid overcharging. We offer a wide selection of chargers to fit your charging needs. If you are using a crank battery to start a gasoline outboard, we recommend that you use a separate deep cycle marine battery/ batteries for your Minn Kota trolling motor. For more information on battery selection and rigging, please visit minnkotamotors.com. Minn Kota trolling motors can run on Lithium Ion batteries. However, they are specifically designed to run on traditional lead acid batteries (flooded, AMG or GEL). Lithium Ion batteries maintain higher voltages for longer periods of time than lead acid. Therefore, running a Minn Kota trolling motor at speeds higher than 85% for a prolonged period could cause permanent damage to the motor.

[bassmasher]

I'm not sure it's the batteries due to when I got home that day I put them on charge and they read 39.8 volts. When the charge was complete it read 40.3 volts. I'm running two 36v lithium's parallel. I do not know anything about these batteries but that doesn't seem like I used much juice. I'm not sure if this helps narrow down my issue.

[fishnfireman]

Melted wires inside shaft from running on high ?

[MichAngler]

I believe in the manual it says not to run the Ultrex above 8-1/2 for long periods of time

Now with wet cell batteries this wasn’t as important as the batteries voltage and current begins to drop as the batteries draws down

But with the advent and popularity of lithium batteries this has become a bigger issue

The motor most likely shut down from a thermal issue and there is a good chance you have done some damage

[Erie660]

Ultrex 112, Lithium batteries, fishing an electric only lake all day no problems. Towards the end of the day going across the lake on number 10 the motor shut off (ran earlier in the day on number ten across the lake with no issues). Turned it off then back on and it was hard to steer and the prop would only spin as if it were on number 2. Shut the breaker for a few minutes (breaker was not tripped) turned it on and it ran fine for about 2 minutes and did it again. I repeated the shut down again and same thing. Drove the rest of the way back to the dock which seemed to be like a safety mode . Any suggestions on what you think this could be? Never had any issue before. Thanks for your input in advance

Reply #5 is taken right out of the Ultrex manual.