Overvolting by 6v inline (not just in series)

[kitsune]

I'm in the process of rebuilding a 12v TM (more of a Frankenstein custom build from parts) and before I finish wiring up the head to the motor, I was thinking about over volting the motor by having a 6v battery inline with just the positive from the head to the motor. I might have to toss some DC regulations on the head to make sure it stays at 12v internally. At the same time it might be a better idea to just wire the 6v directly to the motor, and have it controlled via switch like a booster as well as able to be stand alone power.

DC motors should usually be able to 50% more of their rated voltage without too much issue, and since I'd be bypassing the controllers 12v relays and not adding more heat to the wiring, I *think* it wouldn't cause too much issue. I'd check things before hand on the meter, because even though the controller should be able to take 6v more if it did need a voltage regulator and I didn't add one, it'd be nice to know.

Im not worried about frying the parts since as they are at the moment, they're useless anyway so experimenting and failing isn't a huge worry. Usually when I overvolt a DC motor, I build a controller that can handle 24v off the bat, but I don't wanna.

Why not just try the above and answer my own question? Because that's future me and present me wants to see if anyone else that does this sort of insanity with electric stuff has tried before. If I'm a pioneer here, I'll record and edit a video of the process and results lol.

 

[amberwolf]

I'm in the process of rebuilding a 12v TM (more of a Frankenstein custom build from parts) and before I finish wiring up the head to the motor, I was thinking about over volting the motor by having a 6v battery inline with just the positive from the head to the motor

I don't know what you intend based on your word choice, but the only way to "overvolt" a motor by putting another battery in there with the existing one is to put it in series with the original battery.

You can't put it in parallel, because it'll short out the higher voltage battery, and probably start a fire in the wiring if one of the batteries doesn't catch fire or explode.

There aren't any other ways to connect another battery--series and parallel are it.

It doesn't matter where in the wiring you put it, assuming there are no electronics between main battery and motor--it still has to go in series, so that it's negative connects to the positive from the main battery, and it's positive connects to the motor (or put in the negative main battery wire in the reverse polarity).

If there are electronics, such as a motor controller, you cannot put it anywhere in there *except* directly in series with the main battery, in the feed going to the controller. If you try to put it between controller and motor you may damage the battery *and* the controller.

I might have to toss some DC regulations on the head to make sure it stays at 12v internally.

If you do that, then putting the 6v in there is pointless, as it will do nothing beyond adding some Wh to the total capacity, and the regulator will be wasting power as heat so not all that capacity can be used.

At the same time it might be a better idea to just wire the 6v directly to the motor, and have it controlled via switch like a booster as well as able to be stand alone power.

You can't wire it directly to the motor (+/- of 6v to motor +/-) unless you first disconnect the rest of the system from the motor, or you are shorting out the rest of the system and asking for a fire.

Wiring it in series to one side of the motor directly is covered in previous part of this reply.

DC motors should usually be able to 50% more of their rated voltage without too much issue,

Many, yes. Keep in mind that brushed motors will have more brush arcing and so more heating in the brushes and commutator, wearing them out faster (not just from the higher speeds, but the greater intensity of plasma arcing that occurs within brushed motors there).

Motors do have RPM limits, however, so if you use a voltage that causes it to exceed it's physical RPM limit (whatever that is for that specific motor), the commutator will grenade, and its' segments come off and at the least destroy the motor, ripping off the brushes and potentially giving the windings on that end a bad hair day as they are shredded. If the walls of the motor at the comm end are thin enough, the segments will actually fly thru them and out into the world beyond--exposed motors that do this can injure or kill if the comm segments then puncture a living being in the wrong place.

and since I'd be bypassing the controllers 12v relays and not adding more heat to the wiring, I *think* it wouldn't cause too much issue. I'd check things before hand on the meter, because even though the controller should be able to take 6v more if it did need a voltage regulator and I didn't add one, it'd be nice to know.

To know if the controller can take a higher voltage (by putting the 6v in series with the 12v main feeding into the controller input), you'd need to open up the controller and check every part inside it that connects across the battery bus for voltage ratings, and make sure you are not reaching their limits or exceeding them. If it's a an electronic motor controller you'll need to draw up a schematic for it so you can be sure you are checking all the parts on the battery bus.

Exceeding the voltage ratings at all will usually damage the parts (sometimes in non-obvious ways), and often destroy them, depending on the specific failure modes of those parts. FETs typically fail shorted, so a brushed motor would then be stuck on at full speed, and could not be turned down or off except at your main power switch (the throttle wouldn't work anymore).

Relays also have voltage ratings, and exceeding those at all can cause them to weld shut, preventing shutoff. If it's a complex relay system where some contacts have to disengage before others engage, short circuits can occur and start a wiring fire.



Note also that increasing voltage on the system, with the fixed resistance of the motor, will increase the power the motor, controller, etc has to handle, and if it doesn't have sufficient cooling can fail, or if enclosed with no airflow can even start a fire.

 

[floydr]

a 12v TM

For people that don't know what you are talking (me). What is a 12v TM?
later floyd

 

[fill]

Travelling Machine DOH!, well thats what i guess floyd ..

 

[amberwolf]

12v trolling motor

There's a few threads about them, mostly under "minnkota" or "minn kota" brands, around this subforum, if you want to see some pics.

 

[floydr]

Slaps himself with a large trout, duh I should have looked at the subforum.

Later floyd

 

[E-HP]

Why not just try the above and answer my own question? Because that's future me and present me wants to see if anyone else that does this sort of insanity with electric stuff has tried before. If I'm a pioneer here, I'll record and edit a video of the process and results lol.

Normally I’d recommend that you follow amberwolf’s advice, but in this case, I believe a video would be far more beneficial to the forum.