charging batteries with trolling motor connected

A previous post mentioned that newer trolling motors should not be connected to batteries while they are being charged. I assume that is because the new electronics can not handle the extra 1-1.5 volts necessary to charge a battery. If that is the case then is it also necessary to disconnect fish finders that are recommended to be directly connected to the battery to reduce interference? And related to that doesn't cut out switches on any wire leading to any electronics increase the possibility of interference just by having extra connections, etc.

I don't know about MK but MG shut off switch essentially unhooks it. A master shut off is the easiest way to go. Just a flip of the switch shuts down the whole boat.

I back my boat in the shop and plug in the charger. Been doing it this way for 40 years and never had a problem.

^^^This^^^ Not saying it's correct, but that's the way I've done it as well.

SE Kansas grass grower

Although I've never had a problem apparently with MG's Xi5 is can cause issues with the GPS system.

Most DC powered devices can handle an extra 5 volts without being damaged. Unless you Battery chargers shorts out and is dumping high voltage into your batteries your motor and devices will work just fine. I wouldn't think MK or MG electrical engineers would be that stupid to make voltage sensitive equipment.

I've been told that it should be unplugged. My manual tells me to unplug it. Trolling motor 40 years ago didn't have the same electronic components that you find in the new ones today and they didn't cost $2500.

I unplug mine because why gamble? If I don't, they might not repair it under the warranty and even if they do, I don't want to be without a trolling motor for weeks when I could have prevented it. I just went thru that and it isn't fun.

I don't unplug my fish finders because I can't get to the connector easily. I've already been thinking about putting a power shut off switch to just kill all power in the boat.

Ive installed cutoff for Xi5 and, whole boat electronics. It's an easy install for the DIYer. And again, many thanks to Flipping Out on this forum for his sage advice regarding this subject.

Depends on how your trolling motor is wired and what type charger you are using. On a 12/24 hookup and using two automotive chargers it can smoke some equipment. This is eliminated with most onboard chargers. bg

It just seems with all the information out there on what the majority of fishermen do, how everybody likes to just pull in the garage and plug in the batteries to charge, that both trolling motor and other electronic boat equipment engineers would to make it safe. What is one more volt or two to allow for when you are actually designing something. They make stuff electronic that runs a lot higher voltage than that.

Reads the installation: "Your Minn Kota trolling motor is designed with an internal bonding wire to reduce sonar interference. Most alternator charging systems do not account for this bonding wire, and connect the negative posts of the trolling motor batteries to the negative posts of the crank/starting battery. These external connections can damage connected electronics and the electrical system of your trolling motor, voiding your warranty. Review your charger’s manual carefully or consult the manufacturer prior to use to ensure your charger is compatible. Minn Kota recommends using Minn Kota brand chargers to recharge the batteries connected to your Minn Kota trolling motor, as they have been engineered to work with motors that include a bonding wire."
It reads like the recommendation to unplug while charging has to do with the negative side of the various batteries when you have one charger for both trolling and cranking batteries. If your brand of charger brings all the negative battery connections together inside the charger, you may have problems. My charger has 3 pairs of wires for charging 3 batteries, but I can't say I have ever tested the negatives to see if they all have continuity.

OK, the digital trolling motors draw current entire time that they are connected to the batteries -- just as your outboard, power poles or Talons do. The Depth finders do not. On Motorguide Tours, the on/off switch on the side of the footpedal disconnects the power wire going to the digital electronics. On a MinnKota, the mom/off/con switch is part of the control board and does not disconnect power from the batteries. Charge current is typically 1.5V to 2V per battery above battery voltage, which in a 36V/3 battery circuit could be as much as 6V above what the control board is designed to have input, so to avoid damage to the control board, the digital MinnKota has to be disconnected from the batteries. A 5-speed motor that is available today and has been the "norm" for the past 40yrs do not have the same electronics and it doesn't hurt them to stay connected, however disconnecting will avoid things like the cat setting on the button, causing the prop to turn and hang on the gunnel and burning up the motor (you get the idea, even if you don't own a cat).

Don't know about the new equipment, I am running a MG Brute 12/24, probably 25 years old. When the 12/24 switch is on 24V If I connect two automotive type chargers to the batteries it creates a direct short circuit across battery #2. This is I believe because the two chargers are tied together on the minus side by the electrical (120v) system. This is not a problem with the on board chargers. bg

Ive ALWAYS UNPLUGGED my TM as a precautionary measure. I would never direct wire a TM either.
Just the way I prefer to do it. Takes 2 seconds to unplug or plug it in & don't have to ever worry or deal with IF it does or doesn't cause problems.

I suppose a manufacturer would also be concern with electrical spikes or lightning strikes could create damaging situation.

I’m going to unplug my tm from now on after reading this

I would also never recommend to wire direct to the batteries. With the new electrical steer trolling motors there is always the possibility of the head unit going crazy and start spinning out of control. I have had this happen with my legacy terrova a few times. All I had to do was unplug the trolling motor. If it had been directly wired I would have had to go to the back of the boat and turned it off with the switch. With the time it took to get to the back of the boat it could have really damaged the cables that were twisting along with other things