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12v vs 24v ??

8608 Views 22 Replies 8 Participants Last post by  Oldfart9999
Ok, got a question about 12 volts and 24 volts ( batteries ) for trolling motors.

I was talking to a guy and he is running a 12v trolling motor BUT he says is useing 2( two ) 12v batteries. Now, to me that would be a 24v system.

Seems to me he would burn that trolling motor up, useing 2 batteries since it is a 12v system.

So, how can you use 2 ( two ) 12v batteries on a 12v trolling motor without any damage to it ??
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What he is doing is just using the two batteries in parrelell to make the trolling motor last longer through the day. You can hook up 100 batteries together and still only have twelve volts as long as all the positives are hooked together and all the negatives are hooked together. He will get more running time by the way he is hooking two batteries together. To get 24 volts from two batteries you need to hook the positive from one battery to the negative of the other battery and then the outside positive and neg will give you 24 volts and that is called wired in series. I hope this makes since
Thanks BB :)

I was thinking of doing it, since I run a 12v system BUT I didnt want to burn anything up.
You will not burn up anything by doing it that way and you will get more trolling time but it will take longer to recharge the two batteries.
I used to have a 55lb thrust trolling motor that ran on both 12V and 24V by flipping a switch in the foot pedal. I would flip it to 12 if I wanted it to last and wasn't fighting allot of wind. I used to like that option and wish my trolling motor would still do that. The down side is that you run one battery down while the other is still strong. The advantage is even if you are using 24V system and 1 of your batteries is bad or not real good and poops out on you then with a true 24v system like I have I am dead. Even if one of my batteries is good the other battery which is dead makes the whole set up fail.

That is why I liked the option to switch to a 12v in certain circumstances.
That is a big problem and there are some guys out there that use four batteries the same way you use two for a 12 system. They will actually double up on each side to make the trolling batteries last through the day.
bigbear said:
You will not burn up anything by doing it that way and you will get more trolling time but it will take longer to recharge the two batteries.
Is there a special way to hook the battery charger up ? ( example, do you have to hook one lead from the charger to one battery and the other lead from charger to the other battery ? OR hook them up to the battery not having the trolling motor directly wired to it ? )
It should not matter either way should be fine. It really depends on how good the charger is and how good the batteries are. They should just equalize themselves.
I have that exact setup in my jonboat. The two batteries are hooked up parallel, as has been said. I usually hook the pos end of the charger to one battery, and the neg to the other, while they are still connected. So far so good, but my charger is wearing out.
With todays digital pulse trolling motors battery life is doubled. The 24 volt system provides more thrust per amp draw hour and that is why most pros opt for the 24V or even 36V systems. You have better boat control with a variable rheostat type power control that goes from stop to full power with a rotary switch (wheel).You should charge each battery separately or use a multiple bank charger that performs that task automatically. The reason is if one battery has a bad cell, the charger will over charge and damage the plates on the good battery before reaching 13V and shutting off. The cranking battery should always be separate from the trolling motor batteries and be used to run your electronics, running lights etc. The cranking battery should also have a Easy breaker, switched 40 amp breaker, that is switch off whenever you are charging the cranking battery or storing the boat to protect the electronics. The trolling motor 27 to 31 group size deep cycle marine batteries, should be on separate 50 amp breakers, one for each battery. Hopes this helps.
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Thanks yall :)

When I get back from my cruise, I'm gonna rig up the two ( 2 ) batteries.
There are some other issues you need to consider. The two batteries ought to be a matched pair and of the same age & condition. As soon as one begins to age it will drag the better battery down, so if you are using unmatched batteries don't leave them connected when not in use. It like water finding its level. The full one drains into the weaker. If one develops a bad cell (shorted or open) and left connected to the other, the other will discharge and can fall so low it can't take a charge. Both battreries try to arrive at a common voltage. If one is 12 volts and the other 11 volts, both will go to 11 volts.

Most new boats have the electronics hooked to the cranking battery. Over time an outboard can get out of tune yet seem to work fine, and plugs foul, alternator gets electrically noisy. Older boats are much more prone to electrical noise which passes into the main boat wiring bus and from there into electronics like radio and sonar. Specks begin to show up on screen, then dots, then lines and eventually the unit will begin shutting off and on, especially whenever starting up. When that happens it's time to wire directly to a trolling battery. However, an old trolling motor has brushes that wear down, and that can cause even worse noise. If you have noise you would hear it on a radio (buzzing) on the system before seeing noise on a sonar screen.

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Thanks Jim
Ditto Jim on the batteries should be the same size and should be the same brand too but even then that doesn't guarantee anything. Most important is to make sure you take care of the batteries with clean tight connections and well just good maintenance and you will be glad you did.
Here is a question for anyone willing to running a 24v trolling motor(2 battery setup) and third batt for everything else...I am running a 3 bank charger.can i hook the charger up pos-pos neg-neg on all batterys without disconecting the trolling motor, or do i need to disconect it before charging the system.

also if i plug the charger in while im working on the boat in the garage while listening to the radio in the boat, i get a lot of interference. Is that normal?
First question is the three bank charger marked for which bank is for trolling battery and which one is for the start battery? Each bank should hook to each battery plus to plus and negative to negative. The part about the radio is yes if the charger is on you are going to get static from the charger through the speakers.
Yes there is one set of leads the is marked specifically for the starting batt. That much i know i did right. my question was hooking the charger to the trolling batterys in a 24v systemand if i could hook the charger up in the normal fashion pos-pos and neg-neg, with the trolling motor still hooked up 24v or do i need to disconect the trolling motor cables to properly charge the batteries.

Thanks for the feedback though
i really appreciate it
Dave is the trolling motor wired straight to the batteries or are they plugged in. If the trolling motor is plugged in at the bow then most charger companies say that you should unhook them before you plug in the charger. If they are hard wired then you can do two things. Put a swicth on one wire or do what most of the anglers do, just plug the charger in and don't worry about it. I have not heard of anyone ever having a problem by doing it that way. I just know most trolling motor companies say you should unplug them first. I guess you can ask the others on the site and see if they unplug theres. Be honest all
Yeah that is what i have always done but i just worry about that stuff all the time so i figured i would ask about it. Too much money involved in all my stuff. we all do for that matter

Thanks for the input
If your trolling motor switch is turned off & the pedal is in the off position then you should not have to unplug the motor. The charging system would be 1 that charges each battery, it has a seperate cicuit for each. The charger would also have a fast charge mode that slows up when the battery gets near full charge, it would also have a desulfiding phase & a maintence phase when done charging. Todays quality onboard chargers do that & are worth the money they cost. Also proper maintence of the battery is needed, cleaning, checking water levels as needed, & making sure all connection are clean & tight.
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