Parallel battery wiring

[Bottom Rig]

Greetings. I am using 2 deep cycle interstate batteries and want to wire them in parallel for my trolling motor. Does anyone have a diagram of the wiring for this? Thanks.

 

[KaGee]

Re: Parallel battery wiring

Parallel would be red to red(+) and black to black(-). Hook up the motor to either battery.<br />This only gives you 12 volts, but twice the avaiable current from just one battery. <br /><br />Is your motor 12v or 24v?

 

[LubeDude]

Re: Parallel battery wiring

KaGee is right, but you want to use good heavy cables to do it, you can get them at an auto parts store ready made up in different lenths and are reasonably priced. You can charge them together at the same time without separtating them. and also, you want to start off with two identical brand new batteries. Might I suggest Trojans.<br /><br />You will have 12 volts with lots of reserve, I run my 12 volt trolling motor batteries this way and they last forever.

 

[Reel Poor]

Re: Parallel battery wiring

They are both correct on the parralell connection. <br /><br />Another note:<br />When connecting the trolling motor connect the + lead to #1 battery and the - lead to the #2 battery. This makes the trolling motor think you have one larrrrge battery. Also connect a battery charger the same way.

 

[--GQ--]

Re: Parallel battery wiring

 

[jhebert]

Re: Parallel battery wiring

I would not connect the two batteries in parallel unless your trolling motor pulls so much current that a single battery cannot supply it. However, I doubt that is the case.<br /><br />It would be better to keep the batteries separate. Drain them separately. Charge them separately. When batteries are connected in parallel they tend to behave more like the weaker of the two, not the stronger. One can discharge the other.

 

[jtexas]

Re: Parallel battery wiring

I run my 12volt trolling motor on 2 batts parallel connection, hooked up just like Reel Poor described, charge 'em together like that as well. I went with 10gauge wire, couldn't see the need for heavier than the wiring to the motor.<br /><br />jhebert is right in his assessment but I opted for the convenience of not switching batteries during the day, trusting myself to keep 'em identically discharged & recharged.<br /><br />My last three-day camping trip, I fished three days on Lake Texoma (big reservoir, heavy T/M use) without rechargine and could have gone another. My observation is simultaneous use yields more power than sequential...no science to back that up, though.

 

[Silvertip]

Re: Parallel battery wiring

JT -- the trolling motor decides how much power is drawn from the battery(ies) not the other way around. If the motor is demanding 15 amps, thats what the batteries supply so simply hooking them in parallel does not provide more power. It only provides the same power longer with one exception. If one of the batteries is weaker than the other, it will suck down the better battery until both are equal. Hence, the switch is a better deal.

 

[LubeDude]

Re: Parallel battery wiring

I agree with upinsmoke up to the point of "a switch being a better deal".<br /><br />Thats the reason for starting out with identical new batteries. I dont want to run each individual battery down tell it wont power the trolling motor and then start on the other one. I would rather run them down together and that way they never get ran down much past 75%.<br /><br />What I mean by that is that the batteries still have a 75% charge left at the end if the usage.

 

[Silvertip]

Re: Parallel battery wiring

Both batteries may not accept a charge, discharge, or hold a charge in identical fashion. They may for a time when new, but over time they will not degrade at the same rate. Will there be a significant difference? Maybe so -- maybe not. As a prior owner of diesel powered vehicles with parallel batteries I can assure you batteries do not deteriorate at the same rate. Once either one is on its way -- the other simply feels sorry for it and lends its life blood to the dying battery. A switch prevents that from happening. If that's an inconvenience then direct connection is the way to go. If you want the most for the longest - add the switch.

 

[--GQ--]

Re: Parallel battery wiring

oops....I apologize. Wrong diagram....

 

[18rabbit]

Re: Parallel battery wiring

If you want the most power from a pair of batteries, wire them directly together, omit any switch. The reason is the less the amp load, the longer a battery will cough up power. A 100a/hr battery will support a 5amp load for 20-hours. It will not support a 50amp load for 2 hrs. When you wire a couple batts directly in parallel, you effectively reduce by 50% the amp load on the batts and thus increasing the power available from a batt.<br /><br />Example: <br /><br />A typical 100a/hr batt with a 15amp load will reach 80% discharge in about 4hrs. Switch to a second 100a/hr battery and you get another 4hrs; total 8hrs of trolling.<br /><br />Wire those same two 100a/hr batts in parallel, apply the same 15amp load (now distributed as 7.5amps per batt) and you will reach 80% discharge in a little under 9hrs. You’ll get about 10% more trolling.

 

[ricksrster]

Re: Parallel battery wiring

I went with the switch plus isolator. The weaker battery wont discharge the stronger battery. the weaker battery charges first, then the other battery.

 

[Silvertip]

Re: Parallel battery wiring

18R -- batteries in parallel act just like one bigger battery (twice as large if both are identical) so it doesn't matter what current draw the troller demands from those batteries. They will discharge together when paralleled and you will get the same discharge time running them singly. The advantage with a switch comes when one battery begins to degrade (not discharge) differently than the other. The switch gives you control -- it does not take away from run time and in fact as the batteries age, may actually extend run time because the dying battery does not suck life from the better one. Without a switch, park your boat for a week and unless the charger is on continuously, neither battery will ever be full charge if one of those batteries is weaker than the other. They simply seek a common level of charge. Why stress the good battery when its to simple to isolate it.

 

[18rabbit]

Re: Parallel battery wiring

Yes, it does matter. That’s why all batteries are rated for capacity based on a 20-hr standard, i.e. 5% of the battery’s capacity. The only way you will ever get 100 amps out of a 100 amp battery is to NOT exceed a 5% (5amp) load. less load is ok. Any load more than 5% and you don’t get 100amps.<br /><br />As I showed in the example above, combining the two batts effectively makes one big battery, and the 15amp load is a smaller percentage of that bigger battery’s capacity. Hence the extra 10% of power available from them if combined.

 

[Silvertip]

Re: Parallel battery wiring

No disagreement -- so long as both batteries are in the same state of degradation. Once one battery becomes less efficient it begins to affect the other. Prove it to yourself by replacing one of your good batteries with one that you know has one or more bad or weak cells.

 

[tommays]

Re: Parallel battery wiring

its very common on bigger 24 volt motors and gives the best run time to use a 4 X 6 volt battery setup.<br /><br />I have a LOT of machines that are done this way and they get a LOT more use than a trolling motor.<br /><br />its rare to have one battery go bad before the rest are ready for the old battery home<br /><br /><br />tommays

 

[LubeDude]

Re: Parallel battery wiring

What upinsmoke is trying to beat into our heads is absolutly true, however, according to my local battery expert, when two batteries are wired together and one doesnt prematurely weeken, they will become one battery. Obviously the weeker will prevail, but it wont damage the other because its very slight. He recommends doing as I am and I am going to follow his advice. He said that I will know if there is a problem with one of the batteries because the charger will not shut off.