# 12v Trolling Motor on parallel configuration



## psgreenjack (Aug 14, 2008)

I am new to this site & have just started my first jon boat conversion on my first new boat, I will post some pics.
My electrical question is, I have a 12v trolling motor and am setting up 2 batteries in a parallel 12v configuration. When connecting the trolling motor, do I have to connect the trolling motor positive to battery 1 & the negative to battery 2? I know for a 24v system this must be done in a series configuration.
Thank you.


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## Jim (Aug 14, 2008)

Welcome aboard!

Thanks for joining! :beer:

Try this link, It should help you out!

https://batterytender.com/connecting.php/#3


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## SlimeTime (Aug 14, 2008)

You want the + of battery-1 to the + of battery-2, the - of battery-1 to - of battery-2. As long as the + lead of your TM is on the + side, and the - of your TM on - side, doesn't make any difference which battery you connect to.

And welcome! 
ST


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## Waterwings (Aug 14, 2008)

Welcome Aboard! 8)


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## russ010 (Aug 14, 2008)

I never though about putting 12 volts batteries in parallel to gain more amp... but my question is will it make the batteries last longer than just using 1 at a time.


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## Mossy535 (Aug 14, 2008)

russ010 said:


> I never though about putting 12 volts batteries in parallel to gain more amp... but my question is will it make the batteries last longer than just using 1 at a time.



In general, yes. Let's say you typically drain your one 12V battery to 50% capacity during a day out. If you had two 12V batteries in parallel, under the same use, you would drain each to approximately 75% capacity. Probably even less drain in reality.

If you look at the link 12ftModder posted here:

https://tinboats.net/forum/viewtopic.php?p=43003#p43003

you will see that a battery drained to only 75% will last longer than the same model drained to 50%.

Mark


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## SlimeTime (Aug 15, 2008)

I'm assuming ( #-o lol) that your 75% figure was down to 75% of full charge, meaning a 25% discharge?

It would pay everyone to have a cheap digital voltmeter and tend to their batteries. Discharging them too much is a death-sentence to a battery....& they're too dang expensive not to take care of. 

In this link: https://www.ccis.com/home/mnemeth/12volt/12volt.htm about 1/2 way down is a chart that gives you depth of discharge related to voltage. A volt meter will tell you how deep you're discharging your batteries. Next time you fish, run your TM like you always do, when you load up at the ramp, or when you get home.....read the voltage, you might be suprised at how far you're draining your battery(s).

ST


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## Mossy535 (Aug 15, 2008)

SlimeTime said:


> I'm assuming ( #-o lol) that your 75% figure was down to 75% of full charge, meaning a 25% discharge?



That is indeed correct. I could have worded that better, couldn't I? #-o 

Mark


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## Don't Say (Aug 15, 2008)

The batteries need to be twins, not cousins. I've read, that it works if the batteries are the same age and brand. =P~


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## SlimeTime (Aug 15, 2008)

Mossy535 said:


> SlimeTime said:
> 
> 
> > I'm assuming ( #-o lol) that your 75% figure was down to 75% of full charge, meaning a 25% discharge?
> ...


I knew what you were saying, just didn't want the OP to misunderstand. :wink: 

ST


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## bassboy1 (Aug 17, 2008)

I know this doesn't follow the original post, but we seemed to have digressed over this way anyway. What is safe battery discharge? Obviously, every time you discharge it, even a little bit, then recharge it, it looses a some capability in the long run, but what is the commonly accepted safe discharge amount?


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## 12ftModder (Aug 17, 2008)

50% MAX DoD @most is what is reccomended.


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## SlimeTime (Aug 17, 2008)

I would avoid 50% if at all possible. This is why you're actually better-off having 2 batteries & swapping them out (if you fish that much). Sure, you'll have double the initial cost, but it will prolong battery life....not to mention you always have reserve power.

ST


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## bassboy1 (Aug 23, 2008)

SlimeTime said:


> I would avoid 50% if at all possible. This is why you're actually better-off having 2 batteries & swapping them out (if you fish that much). Sure, you'll have double the initial cost, but it will prolong battery life....not to mention you always have reserve power.
> 
> ST


Right, but what should my meter say that tells me to swap them out? I need a number......


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## 12ftModder (Aug 24, 2008)

There is voltage/state of charge info here its a good guideline to go by
*Deep Cycle Battery FAQS*

My 2 batteries in parallel show 13v each when fully charged and sitting overnight instead of the 12.7 so I recharge anytime below 12.4v


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## SlimeTime (Aug 24, 2008)

bassboy1 said:


> SlimeTime said:
> 
> 
> > I would avoid 50% if at all possible. This is why you're actually better-off having 2 batteries & swapping them out (if you fish that much). Sure, you'll have double the initial cost, but it will prolong battery life....not to mention you always have reserve power.
> ...



I posted a link on the 1st page of this post with a chart that gives you voltages :wink: 

"In this link: https://www.ccis.com/home/mnemeth/12volt/12volt.htm about 1/2 way down is a chart that gives you depth of discharge related to voltage."

ST


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## Waterwings (Aug 24, 2008)

SlimeTime said:


> ...This is why you're actually better-off having 2 batteries & swapping them out (if you fish that much). Sure, you'll have double the initial cost, but it will prolong battery life....not to mention you always have reserve power.ST



That's good advice. I run two independant batteries, and the one for the front tm gets a lot more use than the other one (hooked to rear tm, depth finder, bilge pump) I may swap them around. 8)


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## bassboy1 (Aug 24, 2008)

Wow. I had always thought taking them down to 12.4 was pushing my luck. Seems I am using them to the fullest extent.


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## Popeye (Sep 17, 2008)

Don't Say said:


> The batteries need to be twins, not cousins. I've read, that it works if the batteries are the same age and brand. =P~



And most importantly same capacity


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