Canoe Rig Circuit Breaker Problems

[CastingClinic]

Started having issues with my breaker tripping under typical conditions.
 

75ah deep cycle 12v battery > 60a circuit breaker (manual reset) > ~10ft 8awg wire > Newport Vessels 55lb thrust trolling motor
 

This is the setup I used without any issues for all of last year.  The breaker never tripped regardless of conditions, runtime, etc.

 

Over the winter I replaced the deep cycle with a 100ah LiFePO4 12V battery, upgraded the wiring to 4awg, and added a PWM unit.  This setup also worked flawlessly until a few weeks ago when I ended up in a lake with WAY too much grass and wind to boot.  I pushed the motor trying to navigate through and started smoking the PWM.  Disconnected and went straight battery>motor and immediately started tripping the breaker.  Called it a day, pulled up the motor and started paddling my heart out.

 

Took the PWM out of the equation and had two fishing trips without issue and then at the end of a long day while cruising back to the launch had the breaker start tripping at full speed (no grass or obstructions this time) and had to drive back on setting 4 of 5.

 

Bought a brand new breaker thinking I’d pushed the last to the breaking point and the first trip out the breaker trips after a few minutes at full speed and wouldn’t reset.  I had to pull out a wrench and rewire the battery to bypass the circuit breaker and limped home as slow as I could manage.  Once home I took another look at the breaker and it would reset for me.

 

Besides the first day I started having issues in the grass, every instance of the breakers tripping has been in clean water and under full speed.  The prop shaft is clean and spins smoothly, prop is in good condition, connections are tight with no corrosion, no signs that the battery or motor are compromised in any manner.

 

Could the new breaker have just been a dud and a bad coincidence or am I missing something?  Again I haven’t had any issues running the motor at full speed for extended periods of time in the nearly 150 hours on the water with this setup.

[casts_by_fly]

could be a dud, but the chances of the old one and the new one both being bad is low I think.  I'm wondering if you burned out some of the brushes in the motor when you were trying to chop through the grass.  I would have said grass/line on the prop shaft would do it, but you say that's been cleaned.  

[padlin]

Sounds like the motor is drawing over 60A. Check all the connections first, I don’t suppose you have a battery monitor? Something like this Battery Monitor it’d show you the amperage draw,  built one into my battery box. Some lithiums have an app that shows the info.

[MN Fisher]

11 minutes ago, padlin said:

Sounds like the motor is drawing over 60A.

If it is - something's wrong with the motor. The Newport 55# is suppose to max at 52amps

[CastingClinic]

@MN Fisher @padlin

 

Almost certainly an over current situation and I plan to do a full mock-up test with my rig, a bucket of water, and a multimeter when I get a chance.

 

@casts_by_fly Is it possible for a brush to be damaged and offer no symptoms besides higher than normal current draw?

 

[Scott F]

If the battery is not in top shape and the voltage starts to drop, the amp draw will rise. Because at 52 amps you are already near the circuit breaker limit , it wouldn’t take much of a voltage drop to trip the breaker. 

[Fishingmickey]

     It really sounds like you've got something wrong either with the motor or wiring between the motor and battery. Maybe the motor shaft is bent and rubbing on the housing (you'd feel vibration if that's the case). Or is there possibly some braid wrapped tightly around the prop shaft that is causing friction and high amps when your pushing the motor hard. Maybe a bearing failing on the motor?

     I don't know if you have access to a multimeter with a clamp for measuring amps that will read DC voltage.  If your tripping a 60 amp breaker something is wrong, bad wrong. Honestly it might be the motor is going out on you and the trip powering through the weeds weakened/burnt the windings and now your amps are high.

[CastingClinic]

Well for anyone interested I ordered a battery meter that will measure DC current to 100A.  Tested at home and saw nothing out of the ordinary but would still need to test on the water for the most accurate readings.

 

Went out yesterday and logged almost 3 hours of run time without a single abnormal reading.  At full power the current draw averaged 43A with peak amperage hitting 50A only when "flooring it" from a dead stop.

 

I had the battery wired direct to the motor so the culprit now is either poor connectors or bad breaker but at least I'm confident the battery and motor are still good to go.

[casts_by_fly]

glad you're getting to the bottom of it.  43A seems a little high compared to a comparable cheap minn kota but not out of the realm of possibility.  I'd check the spec on the motor to start.  Then, as you say, work through the other components.  A bad connector where you're not getting good contact could impede flow.  You might see it show up as corrosion or darkening of the wires at the connection point.  I still find it hard to believe that you got two bad breakers, but maybe so.

[Bankc]

I'd check all of your wire connections.  When you started having this issue, you replaced the wiring, so that's a good place to start looking.  I'd also disassemble the motor and check the insides of it.  Check the bushings and commutator.  If the commutator or bushings has gotten dirty or damaged, it could be a cause.  Also check for any foreign objects and make sure you're not getting water inside it.  Plus check the windings for any charring or indications of shorts or overheating.  I'd probably measure the resistance of the windings as well, to see if any of them are off.