Need help from a battery / electrical expert

[Jetter]

Here is my set up. I have 4 batteries in my boat. Reason being is I have 5 amps on my stereo. Three of the batteries are dedicated to the stereo and one just starts the boat. I am having issues with two of the three that are connected to the stereo. One of the three is at the back on the port side and connected to the other two via extremely large gauge wiring. At rest and fully charged the back battery shows a 13 volts on meter. At the other end of the wires it is only returning 11.88. Is it possible to lose 1.12 volts due to an 8 foot large gauge wire? I don't know exact gauge but the wire is over 1/2 inch in diameter.

Secondly with the batteries hooked up in parallel, can I expect the boat to charge all three while it is running or is that too much for the alternator?

Any expertise would be appreciated.

[chpthril]

Theres both a positive and negative cable running between the aft house battery and forward house batteries, correct? If so, one of them has a bad connection or terminal end.

The alternator will not recharge 3 depleted batteries. You should be using a shore charger once the boat is back home.

[freeheel4life]

And not to be the nomenclature nazi, but I hope your 3 "house" batteries arent wired in series. That would be a 36v battery bank. I'm assuming they are parallel.

[Jetter]

That is correct - positive and negative posts are connected and I corrected original post. They are indeed connected in parallel NOT series. Just used wrong term. I understand alternator won't charge all three from a depleted state. Question should have been will the alternator keep them charged while boat is running? And yes, I always have the bank hooked up to a genius trickle charger/tender while off the water.

I'll post pictures of the setup.

[chpthril]

Question should have been will the alternator keep them charged while boat is running?

In this scenario, its more about the load being placed on the house bank, then the actual number batteries. Id say the 90A alternator would do fine to keep pace with most typical system. Its those four thousand watt 12's and six tower pod system that will take more from the batteries then the alt can put in.

[Jetter]

Thanks to all those who replied. I went in and tested more today to try and track down why the loss of voltage from back house battery to front ones. I cut all the zip ties holding the wire and discovered the problem! At times I am embarrassed to admin stuff like this but it certainly wasn't my doing! The donkey I bought the boat from definitely had some hidden gems in for me. The wire connecting the batteries from back to front is nice 0/1 gauge high amperage wire.
20190621_123948_resized.jpg
I traced the wire coming from the rear battery and after untying it and letting in down for inspection I find this. I am still somewhat in shock. Someone in their infinite wisdom had cut the positive wire and spliced in this little piece. It wasn't even soldered in - just held together with electrical tape!
20190621_123408_resized.jpg
So I cut the ends of the wires and stripped nice new connection points and installed this guy that I found at Princess Auto.
20190621_134054_resized.jpg
I now have a nice clean connection on my severed positive cable. I re-insulated properly and tied things back up where they belong.
20190621_142146_resized.jpg
Tested wires at the end near the front batteries and they now read identical voltage to back battery. Now hopefully the alternator will pass it's charge to all three batteries in parallel simultaneously. Will do some voltage testing next time out at the lake.


Jetter

[JohnnieMo]

That's just a poor man's fuse.

[chpthril]

Do you realize that the split loom at your finger tips is melted? Also, the cut end on the left looks like CCA.

[Jetter]

Yes I noticed the melt. That's where that little red wire was taped in a bundle right against it. You mention the cut end on the left. Both cut ends looked the same. I cut a new clean cut off each end a good inch back from the end of the insulation. I then stripped an inch off each end and connected using that connector shown. Was a good tight fit and I'm convinced the connection is as solid as I'm going to get it.

Is there a problem with copper clad aluminum wire?

[chpthril]

Less then ideal in the marine environment. Corrodes fast when exposed to the elements compared to 100% OFC. Also less conductive.

[IDBoating]

At rest and fully charged the back battery shows a 13 volts on meter. At the other end of the wires it is only returning 11.88. Is it possible to lose 1.12 volts due to an 8 foot large gauge wire?

I know you found the shade-tree splice, but I'm still troubled by your numbers. Losing 1.12VDC would only occur if some current was flowing across a resistance - Ohm's Law doesn't lie. But you said "at rest and fully charged", which suggests you weren't powering anything from the batteries when you measured this voltage difference.

Were you powering something from the batteries when you measured that voltage drop? Even a terrible connection like that splice won't drop voltage if no current is flowing. There's an unanswered question here and I would want to understand it before trusting it.

[chpthril]

ID,

I think that his amps/stereo are drawing off the 2 forward locker batteries, yet the aft the battery is likely getting some contribution from the alternator. , but do to that.......hard to even use the term splice......the forward batteries see little from the alternator.

[BrentP]

So... is It safe to say that we are all lucky that didn’t straight up start on fire? Wow




Sent from my iPhone using Tapatalk

[chpthril]

^^^^^ yes

[talltigeguy]

That's just a poor man's fuse.

Hahahaha!

I saw something like that in one of my previous boats. But this is much worse. Mine was an inline fuse meant for 8 gauge wire, but was connected with 4 gauge. So they just trimmed down the 4 gauge until it fit. So it looked like a good big wire for the amp, but in reality could only handle 8 gauge loads. Luckily no fires.

I think this just scared me to never buy a used boat ever again. @Jetter, I think you are pretty lucky that did not melt completely and start a fire.