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  1. #1

    Default Start Battery vs Deep Cycle (What should be connected?)

    Hello all,
    Currently I have 2 deep cycle batteries which power a 12/24 volt trolling motor and 1 starting battery for my merc. For now, everything seems to be attached to the starting battery with the exception of the trolling motor. (Lights, Livewell, Bilge, Humminbird FF). From my inexperienced position, it would seem like I would want more of the load on the deep cycle batteries and less on the starting battery. What is a typical configuration of the loads?

  2. #2
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Typically, the starting battery is used for the engine and engine instrument only. All other accessories come off the house batteries. BUT if you hook up your batteries in series for 24V for the trolling motor, you don't want any 12V accessories on it.
    Don S.


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  3. #3

    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Deep Cycles are not wired in series. Its 2 12 volt battery with seperate sets of wires running to a plug at the bow. Effectively the batteries are still 12 volts with 12 volts coming out of em.

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    Supreme Mariner Silvertip's Avatar
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Quote Originally Posted by mbrown2097 View Post
    Deep Cycles are not wired in series. Its 2 12 volt battery with seperate sets of wires running to a plug at the bow. Effectively the batteries are still 12 volts with 12 volts coming out of em.
    The minute you select 24 volts on your trolling motor that system becomes 24 volts period. Yes, you can pick 12 volts off a 24 volt system but you need to be careful how you do it. The NEGATIVE terminal on ONE of the two batteries serves as ground for the 24 volt system. Whichever battery that happens to be is the one you want to pick 12 volts from. If you happen to pick the wrong negative and positive wires to feed the 12 volt accessories you will feed them 24 volts. If you pick the battery which has the POSITIVE terminal for the 24 volt system your accessories will still work but all that needs to happen is an accidental chassis ground on any accessory and you again have 24 volts on a 12 volt device. Where you elect to make these 12 volts connects is complicated by the "stupid" 12/24 four wire wiring system some boat manufacturers used. They are not totally to blame since it is the troller people that came up with the 12/24 thing. If that was such a good idea back then it would still be used today. Sorry -- but I really dislike that system.

  5. #5
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Quote Originally Posted by mbrown2097 View Post
    Hello all,
    Currently I have 2 deep cycle batteries which power a 12/24 volt trolling motor and 1 starting battery for my merc. For now, everything seems to be attached to the starting battery with the exception of the trolling motor. (Lights, Livewell, Bilge, Humminbird FF). From my inexperienced position, it would seem like I would want more of the load on the deep cycle batteries and less on the starting battery. What is a typical configuration of the loads?
    why would you want more load on the batteries that are not being recharged by the engine. I felt the same way that the load should be on the trolling batteries but to be honest small loads like the livewell/ff/lights will run for hours and the bilge shouldn't be running much if any. If you decied to go night fishing alot then theres no harm in changing the wiring but you have to be real careful to get the correct hook up.

  6. #6

    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Quote Originally Posted by glenn property of pam View Post
    why would you want more load on the batteries that are not being recharged by the engine. I felt the same way that the load should be on the trolling batteries but to be honest small loads like the livewell/ff/lights will run for hours and the bilge shouldn't be running much if any. If you decied to go night fishing alot then theres no harm in changing the wiring but you have to be real careful to get the correct hook up.
    Great points, exactly the kind of discussion that I need to hear. Would love to hear other opinions as well.

  7. #7
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Just wondering but how do you fishing guys charge the trolling batteries? Do you take them off after every trip and put them on a charger back at home?
    2013 Bayliner 255CR
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  8. #8
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Quote Originally Posted by agallant80 View Post
    Just wondering but how do you fishing guys charge the trolling batteries? Do you take them off after every trip and put them on a charger back at home?
    im lazy and have a bad back (batteries are a pain to get to on my boat) so $160 for a 3 bank on board charger was my ans.

  9. #9
    Vice Admiral NYBo's Avatar
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Replace the starting battery with a deep cycle or dual-purpose battery.
    Bob
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  10. #10
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Quote Originally Posted by Silvertip View Post
    The minute you select 24 volts on your trolling motor that system becomes 24 volts period. Yes, you can pick 12 volts off a 24 volt system but you need to be careful how you do it. The NEGATIVE terminal on ONE of the two batteries serves as ground for the 24 volt system. Whichever battery that happens to be is the one you want to pick 12 volts from. If you happen to pick the wrong negative and positive wires to feed the 12 volt accessories you will feed them 24 volts. If you pick the battery which has the POSITIVE terminal for the 24 volt system your accessories will still work but all that needs to happen is an accidental chassis ground on any accessory and you again have 24 volts on a 12 volt device. Where you elect to make these 12 volts connects is complicated by the "stupid" 12/24 four wire wiring system some boat manufacturers used. They are not totally to blame since it is the troller people that came up with the 12/24 thing. If that was such a good idea back then it would still be used today. Sorry -- but I really dislike that system.
    I'm confused. If two batteries are wired in parallel, positive to positive-negative to negative, there is no way to get 24VDC out of them. Essentially, all you have created is "one" battery with a larger reserve capacity.

    What is this "stupid 12/24 four wire" thing you are referring to? Is it a system boat manufacturers used to afford an owner the ability to switch back and forth from 12VDC to 24VDC without rewiring the batteries?

    Excuse my naivete, I've only owned smaller boats pre-wired for 12VDC.

    -MN

  11. #11
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Quote Originally Posted by MN Sun View Post
    I'm confused. If two batteries are wired in parallel, positive to positive-negative to negative, there is no way to get 24VDC out of them. Essentially, all you have created is "one" battery with a larger reserve capacity.

    What is this "stupid 12/24 four wire" thing you are referring to? Is it a system boat manufacturers used to afford an owner the ability to switch back and forth from 12VDC to 24VDC without rewiring the batteries?

    Excuse my naivete, I've only owned smaller boats pre-wired for 12VDC.

    -MN
    do you have a switch up front of the boat that says 12v charge/ 12v / 24v should be next to trolling plug?
    do you have 4 wires going from the batteries to the front of the boat?

  12. #12
    Supreme Mariner Silvertip's Avatar
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    Quote Originally Posted by MN Sun View Post
    I'm confused. If two batteries are wired in parallel, positive to positive-negative to negative, there is no way to get 24VDC out of them. Essentially, all you have created is "one" battery with a larger reserve capacity.

    What is this "stupid 12/24 four wire" thing you are referring to? Is it a system boat manufacturers used to afford an owner the ability to switch back and forth from 12VDC to 24VDC without rewiring the batteries?

    Excuse my naivete, I've only owned smaller boats pre-wired for 12VDC.

    -MN
    That is true, but you need to consider what happens at the trolling motor connector, the run/charge switch, and the motor connector if it has a jumper strap in it. Just because you connected batteries in parallel at the batteries, does not mean everything is just fine at the other end. Remembeer this: In a 24 volt system one battery has its NEGATIVE terminal connected to the other battery POSITIVE. Throw some switching and plug variations into the mix and you have potential issues. Consider this as well. There are lots of two, three and four wire troller wiring system out there. Until I see a diagram of exactly the system being discussed -- I present the OP with a warning. We have not seen that diagram other than there are four wires going up front.

  13. #13
    Supreme Mariner Silvertip's Avatar
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    OK -- here goes again. A 12 volt ONLY, 24 volt ONLY,, 36 volt ONLY and 48 volt ONLY motor can run from a two wire system where the batteries are wired in series back at the batteries and only TWO wires run up front to a TWO terminal connector to which a TWO terminal trolling motor attaches to feed power to the motor via TWO wires.

    If you want to parallel batteries the same situation applies and the system does not change from back to front.

    Back in the good old days the trolling motor manufacturers decided that it would be cool to make a motor run on EITHER 12 or 24 volts. That meant the boat manufacturers needed to change the wiring to accommodate that capability and those who already owned boats needed to modify their wiring. So some manufacturers made a three wire system having various color coding but the most common (in my view) was red, orange, and black. The red and orange went to the POSITIVE terminal on each of the two batteries. The jumper between the two batteries was still needed. Black went to the NEGATIVE terminal on the battery that served as the system ground. So red to black = 24 volts, orange to black = 12 volts (unless folks turned these two around). A THREE terminal plug was used at the bow. The troller may have had a three wire power lead with a switch on the motor (stern mount or tiller bow mount) or it may have had the 12/24 switch on the foot pedal.

    Enter the FOUR wire system. TWO batteries, no connection between them, so TWO PAIRS of wires going up front. Going to what??? a) directly to a FOUR wire receptacle that feeds a FOUR wire plug that may or may not have a jumper strap in it. b) to a panel that has a FOUR wire receptacle AND a 12/24/RUN/CHARGE switch. The receptacle feeds a FOUR terminal plug that feeds a foot pedal with a 12/24 selector switch. The logic of the run/charge switch was that in the CHARGE position the batteries were paralleled so both batteries could be charged using a single output 12 volt charger connected through the trolling motor receptacle or connect the charger to one battery and charge both. In the RUN position the parallel connection was open so the 12/24 switch (wherever it was located) could function. Since most motors today are ONLY 12, 24, or 36 volts, AND are electronically controlled is it worth the risk to willy-nilly connect stuff and hope you don't muck up the electrics? Again, understand what you have before you re-engineer a system and you will likely save yourself grief and possibly lots of money. These three and four wire systems have been messed with by so many people who try to make things work that you have no idea just how or how badly they have been rearranged.

  14. #14
    Petty Officer 1st Class zippy83's Avatar
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    Default Re: Start Battery vs Deep Cycle (What should be connected?)

    I myself have the same configuration. I got lowrance, outboard, blidge, aerator, lights, and I also added a pair of LED lights for night fishing as well on the starting battry. As long as your alternator is working properly and re-charging the battery you should be fine. I've been out many times now and neverhad an issue as far as the load goes. As mentioned above by many most of the devices hooked up arent running constantly.

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