DAISY CHAINING BATTERIES... and keeping it 12v???

[zuke1]

i was told by the guy at cabellas that i could hook my two trolling batteries together and they would drain together so i could troll for twice as long...

my question is, how do i connect them together with out them turning into 24v i would like to keep my system 12v since that is what my trolling motor requires...

also, i have an onboard charger hooked up to one of the batteries, would having the two batteries connected affect how they were charged???

and does it matter that one of the batteries is a deep cycle trolling motor while the other one is just a regular marine battery???

thanks
zuke

 

[ZmOz]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

First of all, you shouldn't do this if the batteries are not of the same brand, type, age, and size. If your other battery is not a deep cycle then you definately shouldn't do this. If you have two batteries that are similar, you can wire them in parallel by connecting positive to positive and negative to negative. They will charge the same as any other 12v battery this way.

They will actually last more than twice as long this way with a trolling motor, because the load is divided between the two batteries and a smaller load makes the battery last longer.

 

[Silvertip]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

Here's how two batteries are wired in parallel to provide 12V with twice the capacity of a single battery -- assuming both batteries are of the same type, capacity, and age. The second picture shows how to charge them using a two bank charger. A single bank charger can be connected to one battery and both will charge. However it will take twice as long.

 

[Silvertip]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

Scratch that -- I grabbed the wrong diagrams.

12V Parallel wiring:

12V Parallel Charging:

 

[Texasmark]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

Boy Silvertip I'm glad you corrected that......was beginning to wonder. 8)

Agree with ZM. If you don't have identical batteries, the one needing the most current will get it and the other won't charge properly, or if one has a different "full charge" voltage, you will overvoltage it while trying to pump up the other one which will boil your water out and ruin your battery.

But if balanced loads, you can, and people do all the time, run em and charge em in parallel.

Mark

 

[Texasmark]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

And if anyone asks, daisy chaining (series wiring) is how you get 24 volts which is not what you are doing; you are wiring in parallel to double your capacity at 12V.

HTH

Mark

 

[Silvertip]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

Tex -- the first pictures were a test!!! 8)

 

[Barnacle_Bill]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

While I certainly agree that identical batteries are the best, the newer smart on-board chargers compensate for this. For instance if you have a 2 bank charger hooked up and one of the batteries is charged, it will put most the amperage on the one needing charged while just going into maintenance mode on the charged one. Hope I explained that right.

 

[Silvertip]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

He has a single bank charger so battery differences might be an issue.

 

[zuke1]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

ok, so i have two identical batteries, so that solves that problem, now as far as my charger goes... i have only a single bank one, but i have two of em, so can i hook em both up at once? or can i dissconnect them and charge them seperately???
and in order to make these two batteries my trolling batteris i have to make my trojan deep cycle battery my starting battery... so i wonder, is it a bad idea to have a deep cycle as your starting battery???

thanks for the great diagrams.. that first one had me a little worried, so i guess its a good thing i waited for the second one before i do anything...

ill wait till you guys tell me about charging possibilites before i hook em up together...

also is there a kit for the cables i should use, ill probably just check the auto store for em...

thanks again.
zuke

 

[Silvertip]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

You can use the single bank to charge both batteries at the same time without disconnecting them. Remember, in parallel, you are using two small batteries to create one big one. With a single bank charger it will just take twice as long to charge both batteries. You can hook the charger to either battery. As for wiring, auto stores will have battery cables but you really don't need them that heavy. Buy 6 gauge wire and add whatever terminals you need. You can get the terminals in the electrical department at any home improvement store. Wiring should be marine rated and is available at most places that sell boating equipment and supplies (like right here on iBoats).

 

[Texasmark]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

Ok silver, 10-4 on your test. 8)

Mark

 

[Texasmark]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

Hey behile. Before you are going to convince me (and anyone else that knows what you are supposed to be talking about) of what you said, you have to provide the viewing audience with the mechanism that allows this to happen.

The battery charger has two things to monitor (V and I) and since the batteries are in parallel, it monitors the average of both batteries. It has absolutely no idea which battery is getting what amount of current and which battery is providing the voltage it is using for it's charge reference. :'(

Unless, they are set up on separate circuits and if so, they cease to be in parallel. :|

Mark

 

[tommays]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

Well there are about 7 billion pallet jacks ,floor scrubers and all other types of multi-battery operated machinery that are wired parallel or series running on a single charger and it seems to work


Tommays

 

[zuke1]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

ok, so i bought the battery connecting cables...

after reading some of the responses above,

should i connect the two batteries or not???

cuz i want to do it tonight, so i can use em tomorrow..

thanks
zuke

 

[Silvertip]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

For heavens sake connect them and stop worrying. Stop at any GM dealer and ask a mechanic how the two batteries in GM diesels were wired. If he/she is old enough to remember the late 70's and 80's diesel cars he/she will tell you they were wired in parallel and charged by the alternator just as they would be using a your single bank charger. Since the batteries are wired in parallel, and since no two batteries are identical, they will float until both are charged or discharged to the same level. How do I know this. I've owned more diesels than the average Joe and I can assure you it works just fine. Even if you used a two bank charger, once charged the two batteries will still seek a common level so there is no advantage to a two bank charger other than charge time. The one caviat is that a weak battery will suck the life out of the good one. Now connect them and go boating.

 

[Tom Scully]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

Silver tip is correct you can charge two identical batteries which are connected in parallel with one charger. Two identical batteries in parallel appear as one load to the charger. Since they are connected in parallel the voltage on each is the same and as a result the charging current will be split between them.

 

[Barnacle_Bill]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

Texasmark, that come out of my owner's manual for a ProMariner XPS 5/5/5

 

[ZmOz]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

and since no two batteries are identical

Wrong. The only batteries that should ever be in parallel are two that you bought on the same day from the same store that are the same size and brand. You can get away with using two batteries that are just similar, and not identical, but you shouldn't.

As for the original poster, he says one battery is a deep cycle and the other isn't, so NO they should NOT be connected together.

 

[Texasmark]

Re: DAISY CHAINING BATTERIES... and keeping it 12v???

I guess we are splitting hairs here. On the pallet jacks and diesel cars and trucks there is charged and there is charged. Hard to tell the difference between 85% of capacity and 100% on any given day.

I was being a purist and talking about 100%, where the charging current drops to a trickle.

But I also know that there is a different full voltage associated with different types of batteries containing different chemicals besides H2O and H2SO4, and that they have different internal resistances which determine how fast they will accept recharge from their current state of discharge.

Mark