How to wire dual batteries?

Wakebrad · Ladies Man Joined: 11 Dec 2003 Posts: 12257 City: Dallas

I bought the boat and the guy before me already had this setup installed but I don't think they're installed right. The problem is I get too much voltage going to the batteries when the boat runs. It shoots up to 17 volts when running. I had the alternator checked and it's only putting out 13.5-14 when run at a good RPM. I'm wondering if this wiring is just completely screwed up or what. Any thoughts on what could be causing this or how to fix it?

The red wires on the inside run directly to a 200 watt amp pushing 4 6x9s. The red outside wires go to power the rest of the boat.

joedirt00 · Posted: Oct 13, 2004 5:35 pm Post subject:

I think you need something like a battery isolator to regulate the charge to the batteries or something like that. Confused

BigDeal · Soul Rider Joined: 18 Oct 2003 Posts: 477 City: Orlando

Personally, I'd like to see two things before I comment further about your wiring.

1 - Mark up the pic you posted with (+) and (-) for both pair of battery terminals.
2 - Provide a better description about what each wire coming off both batteries is going to.

Battery isolator, Perko, or whatever, you may indeed have a wiring issue to resolve. I don't want to comment further though until I get a little more info.

-Mike-

882001 · Posted: Oct 13, 2004 6:13 pm Post subject:

all pos together all negs together. looks ok to me. if it were run in series it would be 24v. have you checked it w a multimeter? or are you just going by the guage?

salmon_tacos · Posted: Oct 13, 2004 6:25 pm Post subject:

BigDeal,

You can see the polarities of the terminals in the picture. The negatives are connected to each other. The dark red wires go to the amp with the the wire going to the positive terminal of one battery.

The positive terminals of each battery go into that switch. I don't know what happens from there.

torquetowers · Criminal Joined: 03 May 2004 Posts: 95 City: pasadena

it looks correct, pos from switch goes to eng (2 gag.). 2 reds (4 gag) go to
batt pos. neg are conneceted(4 gag) together then go to eng block (2 gag). As long as one of those red (8 gag) are going to the amp pos and one neg, it is wired up ok. Could be gauge, dash harness. Gauge are not always correct, you need to put it on one batt and see, the disconnect one batt and see if it changes.

BigDeal · Soul Rider Joined: 18 Oct 2003 Posts: 477 City: Orlando

baggyman · Soul Rider Joined: 19 Aug 2004 Posts: 331 City: Vegas

Wakebrad, have done this a few times and the set up is ok. the wire gague is fine also. not sure why you are getting 17v out. the batteries to be ran in sequence would have to be hooked up pos to neg to give you 24 volts. (dont all freak out and say that will blow your batteries out cuz it doesnt i do it all the time).

Prob would be a good idea to atleast do some better marking on the pos or neg to the amp just to save you some time and headache.

baggyman · Soul Rider Joined: 19 Aug 2004 Posts: 331 City: Vegas

actually just found the perko switch paperwork on the desk. installed one in my brothers boat a few weeks ago (i am a paper slob what can i say.... ) it showes the Positive of each battery going to the switch like you have it and the negatives of each battery together and going to a common ground.

Wakebrad · Ladies Man Joined: 11 Dec 2003 Posts: 12257 City: Dallas

Ok well I guess that solves this part of the problem. I have no idea why I am getting 17 volts out. I did check it with a multimeter.

Doing this test at speed (2500 rpms):
When I set the switch on 1 battery and ran it it measured at 17+ volts and the other battery read something like 12.5. So I'm assuming the other battery wasn't being charged when it wasn't set to it. But when I set the switch on 'all,' one of the batteries registered at 17 volts and the other one was 13.5-14 which I'm assuming would mean it's being charged. I don't know if that makes a difference..

Everything works: amp, speakers, and whatnot but I keep frying my batteries by sending so much charge to them. It kills the CCAs. They are under warranty so it's not directly costing me any money but I would still like to get the problem fixed.

So I guess this is something behind the switch. I guess I will dig through and try to draw up a diagram of what the wiring looks like. Maybe I'll try to take off the amp to isolate it to either the sound system or the power system. If someone with practical knowledge of electrical systems wants to swing by and help me out with it that'd be awesome Mr. Green

my electrical knowledge is all pretty academic.

salmon_tacos · Posted: Oct 13, 2004 8:16 pm Post subject:

I don't know where you're measuring but it sounds as if somehow the alternator and battery are ending up in series or something. Otherwise, I don't know how you'd get the extra voltage. The battery isn't putting out 17V. You said the alternator isn't putting out 17V. It's obvious that the batteries are not in series. So that leaves the combined voltage of the alternator and a battery. Without thinking too hard about the possibilities, I'd suspect that something is wrong with the switch.

I looked up the switch and noticed that it's only rated for 360 intermittent amps. It seems like if you started the boat on both batteries, you could exceed that by far. Maybe something is fried in there?

They also sell a heavy-duty switch that costs 3x as much but is rated for 850 intermittent amps.

Wakebrad · Ladies Man Joined: 11 Dec 2003 Posts: 12257 City: Dallas

salmon_tacos, interesting thought. I hadn't considered the switch to be bad. Is there a way I can test that. Or could there be something wired wrong on the side of the alternator (when I had it tested I took it out and took it to an alternator repair place)

Maybe I'll disconnect the switch and see how it reacts. I wonder if that thing has a warranty.

baggyman · Soul Rider Joined: 19 Aug 2004 Posts: 331 City: Vegas

if not they are cheap like under 30 bucks

wesgardner · Posted: Oct 14, 2004 3:52 am Post subject:

Hey Wakebrad,

Here's a thought - the Perko switch cannot "make" electricity as in increasing the amount of voltage, the only way to do that is as others have suggested - wiring your batteries in series which clearly by your set-up, you don't have....you have a parallel set up (which is what you want)

My guess - voltage regulator...

Wes

882001 · Posted: Oct 14, 2004 4:17 am Post subject:

wesgardner, yup

KristianB · Posted: Oct 14, 2004 4:51 am Post subject:

If your batteries are wired in parallell, and the switch is only a main on/off switch, you will have leakage from one battery to the other. That is, one of the batteries is doing all of the work as well as losing power to the other battery.

My generator produces about 16 volts (according to the gauge) when it is loading, which I think is boarderline. 17 V is a bit high.

A good switch would let you choose one and use a relay for loading the the weakest battery.

nashvillematt · Addict Joined: 15 Jul 2004 Posts: 823 City: Nashville

If I am not mistaken (which I could be) will this voltage (17V) not harm the amp? If it is made to run at 12V and you are putting an extra 5V to it...is may be working overtime!

Again....I may be mistaken!
MS

Wakebrad · Ladies Man Joined: 11 Dec 2003 Posts: 12257 City: Dallas

Well if there is some sort of short in the switch it could be doing some wierd things to the voltage but I don't know.

I have had the alternator checked multiple times and I actually watched then test it and at 2500 rpms it was only putting out 13-14 volts. It can't be the regulator which is built on the alternator.

And yeah 17v is not good for the amp but it still works. It's got a built in shutoff so it won't get damaged if the voltage goes too high.

Could it be possible that the alternator isn't wired in correctly? I'll take a picture and see what you guys think. If that's not it I guess I'll try using a single battery and removing the switch, to see if I am still getting 17

KristianB · Posted: Oct 15, 2004 12:09 am Post subject:

As wesgardner implied, unless you've got a magic switch here I cannot se how it could increase your voltage! It's a DC system and changing upping the voltage in a DC system without adding a powersource is a complex issue.

Where exactly have you measured the voltages? Where the batteries still connected when you measured the voltage? Your sure you havn't got a 24V battery there Confused

?

Wakebrad · Ladies Man Joined: 11 Dec 2003 Posts: 12257 City: Dallas

They're standard optimas. I measured the batteries across the terminals. Battery 1 pos to battery 1 neg and battery 2 pos to battery 2 neg.

wesgardner · Posted: Oct 15, 2004 6:58 am Post subject:

Hey Wakebrad,

I'd do the single battery test....as tacos, has suggested, even if the battery and alternator were working as one, you'd still have a parallel situation where you'd just get no more than 14V (assumes voltage is being correctly regulated at the alternator)...it's a bit of a head scratcher...there have been "fast charge" systems on the market where YOU can regulate the alternator's output, but I think you'd know if you had one....

Wes

Wakebrad · Ladies Man Joined: 11 Dec 2003 Posts: 12257 City: Dallas

Well if the fast charge system is built directly into the alternator then I don't have one but I haven't traced all the wires to see if there's something fishy going on. I doubt there is one but you never know.

I'll test the alternator output while it's hooked up to the boat and see if it's giving the same readings as it was when hooked up at the shop and see how it acts with no amp hookup and single battery. Hopefully that should narrow it. Thanks guys.

Wakebrad · Ladies Man Joined: 11 Dec 2003 Posts: 12257 City: Dallas

I found out the problem!

It was the switch. I took it off the switch and wired it to one battery and everything came out alright at 2500 rpms it was only going 14.5-15 volts. So I went to the store and bought a new switch and put it in. Stupidly I wired my tower lights backwards but luckily they didn't blow or anything. The only thing I'm concerned about is when I put the switch in at idle it was at 13 volts and when I reved it, the voltage actually dropped back closer to 12. I don't know if this has to do with the fact that one of the batteries that was hooked up with it is bad (only like 100CCAs) or that I wired my tower lights up backwards. I wonder if I messed up my alternator when I did this or something. Or is dropping to 12-12.5 volts at 2500 rpms not something to worry about?

DiyGuy · Soul Rider Joined: 26 Dec 2003 Posts: 460

Unless you are using a common ground to your tower lights, it doesn't matter. Only LED's would only light one way.

I'll admit, this is a strange one.

What are your voltages off the batteries, NOT connected to anything? Undo all leads + and - and what voltage? If one is putting out 17v engine running, one would think one of the batt's would be at least 15v or something?

~~~~~~~~

Wakebrad · Ladies Man Joined: 11 Dec 2003 Posts: 12257 City: Dallas

The batteries not connected are putting out 12.5-12.7 when they're not connected.