Batteries in parallel question............

[BmacBmac1]

I am fixing to wire up my trolling motor in parallel. (2) 12 Volts + to + / - to - to gain longer AMP time.

question is do I run a "splitter" off the (2) positives and then run the positive off of the trolling motor and draw of of both batteries at same time or do I hook to one battery and let them draw from each other? I "could" purchase a Perko crossover witch and switch over when needed?

Anyones input would be appreciated!


"BmacBmac1"

Bill McGuire

[Bill]

If you don't have any sort of circuit that allows you to recharge both, but only draw-off one (like in a camper dual battery), electrically if you put in a Y to both +s and another to both -s, or do a pigtail from the 1st + to the second, electrically it's the same.

I'd eliminate any extra connections, since connections are the source of problems most of the time. I'd clamp a second wire in the battery terminals on the 1st battery, and run it to the second. Put in the heaviest gauge battery wire you can find at the auto parts store (sold in the battery accessories area), not the thin stuff for lights, etc.

The bigger the wire, the lower the resistance, and you loose less current to heating the wire.

[dv9296]

You probably already know this....but hooking two batteries in parallel to the trolling motor will double the amperage to the motor.

Hooking two batteries in series will double the voltage to the motor. I had a friend who thought he could hook two batteries in series and make a 12v trolling motor a 12/24. It will not, because, contrary to his belief, the motor windings are different....it burnt up the motor.

I'm just wondering what the max. amp. rating your trolling motor has on it? If I were you...I would just wire up with a switch....when one battery gets weak...switch to the other. Don't use both at same time....

[texag93]

You probably already know this....but hooking two batteries in parallel to the trolling motor will double the amperage to the motor.

You lost me on this one. Your motor is drawing(determining) the amps....battery isn't sending amps to the motor. Batteries in parrallel will extend the run time of the motor by approx. 2x. In series, well 24v to a 12v motor is a bad thing.

[dv9296]

Battery Question....

The Batteries "are" sending amps to the motor. If you pull the motor out of the water with no load on it...won't it run? Of course it will, and it runs off the amperage the batteries are supplying. If you hook two batteries in parallel, you are doulbing the Amperage to the motor, which could damage it. If you want a longer run time on a 12 V "only" motor, then simply use one battery until it becomes weak and hook a switch up to make it simple to switch to second battery.

[dv9296]

You are right in the sense that the motor creates a draw on the battery, but what I am saying is that the motor can be damaged by too much current, especially when it gets in a bind...like in some weeds.

[Bill]

I respectfully disagree. With a fixed voltage (1 or 2 12V batteries), the current the motor will draw is strictly a function of the resistance of the motor.

Ohms law, E=iR.

The potential (voltage) is given in the battery, with a lower resistance (like shorting the 2 wires together, not a good idea) the current will shoot up higher (and flame-out the insulation on the wires). It's like water in a pipe, at 100 psi (V) the amount that flows (i or current) is determined by the resistance (say a valve open 1/8 the way or all the way).

Eliminate an extra T connection in the wires, and you eliminate something else to break, corrode, come apart or give you trouble.

You could put 100 batteries in parallel, and the motor will draw the same amount of current. Since each battery is rated in some number of amp-hours, you'll be able to run your motor for longer than on a single battery.

[dv9296]

Hmmm...

I hear what you're saying, but doesn't it depend on how the trolling motor is built. Aren't all trolling motors shunt wound motors? If so, the following statement is true:

Shunt wound motor
A shunt wound motor has a high-resistance field winding connected in parallel with the armature. It responds to increased load by trying to maintain its speed and this leads to an increase in armature current. This makes it unsuitable for widely-varying loads, which may lead to overheating. (See DC motors on Wikepedia)

increased load being....in tough conditions
increases current draw across armature, and
may cause overheating.

I'm going to check with MinnKota on this....I'm curious and confused.

[Bill]

I believe regardless of how many batteries you have in parallel, the motor will draw the current it will draw- more batteries will give you more run time before you have to paddle (been there, done that- that's why I always insisted we duck hunt starting going upriver with my son's john boat and electric motor).

[bearintex]

It absoluteley depends solely on the motor. Battery capacity has zilch to do with it. All the capacity dictates is the amount of time that the motor will run at a given current draw. Say your battery is rated for 100 amp/hours. Your motor draws 10 amps nominally. You should get approximately 10 hours of run time on that battery. Now hook the same motor up to a 7.5 Amp hour gel cell (common 12V feeder battery), and you only get to run about 45 minutes. You can run a trolling motor on one of these at full speed, I've done it in a pinch when my deep cycle crapped out on me.

Wire the batteries in parallel (positive to positive to load, etc) and you sum the amp/ hour capacity. Wire them in series (positive to negative to load, etc.) and you sum the voltages, while retaining the capacity of the lowest rated battery in the circuit.

[txhuntingguide]

Ya'll have me confused now.

Could you take marine two batteries. Connect positive to positive and negative to negative with battery cables and the run the trolling motor wires to the wing nuts on one battery and pull off of each battery equally on 12 V. Is this true or false ?

[refugioco]

I have considered going to 2 6v golf cart batteries in series. I have heard they will last longer and are cheaper?

[Cropduster]

6 volt golf cart batteries are "commercial grade" batteries and have a better deep cycle set then does the other batteries. They will last longer and do area good job. Just hook them up a positive to negative with a relative large cable. I usually make up my cable from a local store that sells welding supplies. Then all you do is hook up to the positive and negative with you troling motor that is not connected by the cable and you are ready to go for 12 volts and approximately 110 amp hours.

[Bill]

Autozone sells the heavy-duty battery cables and clamps. Doubtful you'll ever draw as much current as an auto starter motor, but heavier = more durable.