Battery Wiring question

[riverrate]

Re: Here are the wiring diagrams

I too am an electrician and the batteries will charge better, a more even charge to each battery, in the proposed diagram.

First time posting. Love this forum. I have learned so much here. Thank you all for all your input.

Todd

 

[jviss]

I too am an electrician and the batteries will charge better, a more even charge to each battery, in the proposed diagram.
Todd

The difference will likely be too small to measure, but in the theory the existing wiring scheme, assuming equal length, same size wiring, and same type, age and use history of batteries, will charge more evenly because the batteries will see the same terminal voltage. In the proposed scheme the batteries will not see the same voltage because of the resistance of the coupling wires; because the voltages are not the same, assuming the same battery condition as above the current for each battery will not be the same either.

None of this will matter if the interconnection resistance can be driven to a negligible level for the current involved. Generally the largest currents for any significant time will be the charging current. At 60 to 100A even short runs of 4 AWG wire with crimped lugs can present significant resistance. I had a couple of batteries separated from the other two by eight feet of 4 AWG and they showed signs of chronic undercharging over the long term.

 

[Stu Jackson]

jviss, is right about the wire size, unless everything is very close. #4 is undersized for 60-100A loads. Check the wiring ampacity charts or graphs.

 

[jviss]

jviss, is right about the wire size, unless everything is very close. #4 is undersized for 60-100A loads. Check the wiring ampacity charts or graphs.

Just to clarify, when you star-wire the current is only what one battery sees; so with 60A of charge current and four batteries, the current is only 15A per pair of battery wires, and the drop with 4 ga. wire much, much less than 3%. Connect the regulator sense line directly to one battery post (properly fused) and the batteries will charge evenly and very well. For the other, 'daisy chained' wiring scheme, the wire must be much larger.

To the o.p., you might want to consider connecting the Link shunt between the two negative bus bars (which is what I did), just for wiring neatness and convenience.

 

[Stu Jackson]

To the o.p., you might want to consider connecting the Link shunt between the two negative bus bars (which is what I did), just for wiring neatness and convenience.

It looks like he needs to do it this way 'cuz he has a Link 20, two banks. He cold eliminate the two ground buses though. Only one wire from #1 to #2, but it could be a space issue.

 

[Alex 2740]

Thanks Stu, and everyone else.

I think in addition to my additional intentions of changing the batteries from home run to daisy chain I now I have a better handle on rewiring the charging system inputs. I took another look at the links that you sent Stu and they seem pretty clear. I'll need to think about whether I will use use an Echo style charger for the starting battery or just leave it to the Alternator and shore charger. Given our boating profile that should be good enough.

Of course once I pulled the batteries out of their well I found some wood rot that I will need to deal with first. After re-configuring the wiring I will test for ground faults etc.. and check back in with results.

Again thanks for all the support.

Alex

 

[Me and Boo]

Start with your ground side. This will be the same electrical point for your entire system. All your batteries and power source(s) (alternator or generator) have the same ground. The reason for this is safety. If you have one set of batteries with one ground and another set with a different ground, you could possibly have a different potential between them. You could be touching one instrument on one set and then grab something else (like a radio) that is on another and get a very nasty jolt. Also, it could cause a fire if there is a short (say water from a heavy rain coming in the hatch).

You need a good size wire for the main ground and then the wires sized for the load coming off it it. The positive side is balanced with the negative, like 18 gauge going to and from an instrument, if it is not grounded to a common piece.

The hot or positive side you are getting a lot of good advice on what to do.

 

[LloydB]

Make an complete and accurate wireing diagram BEFORE you make any changes.

 

[Fly_H23]

Make an complete and accurate wireing diagram BEFORE you make any changes.

Now that is the best darn advice yet! I have found that taking photos before I disassemble a wiring bundle is very helpful as well.

 

[Debra B]

You might want to think about adding some on/off switches. They are similar to the A-B-Both battery switch. I can disconnect any of the batteries that make up my house bank. I also like the idea of a circuit breaker or big fuse to cut out the batteries in the event there is a short somewhere before the main breaker panel.

 

[Alex 2740]

I am not certain if this is the best way to revisit the previous discussion or if I should have opened a new posting but we'll try this first to see if it works

After making the battery compartment flooring repairs that I found were needed I then did the rewiring previously discussed to bring our installation more in line with traditional recommendations for wiring of marine 12V DC systems. Thanks to all who helped previously with their feedback. In addition to doing this to eliminate possible unknown issues this hopefully would give me a good starting point to diagnosis for ground faults/stray voltage etc..

When I completed the wiring (see attached diagram of completed work) I began to test for ground leaks. First I disconnected the shore power cable from the boat. Secondly I disconnected all electrical equipment bypassing the DC panel that was wired to the batteries directly (stereo always hot/on lead, auto bilge pump, battery monitor, etc... I Then removed the positive battery clamp and placed a voltmeter between the post and the clamp for the house bank and then later for the starting bank. The result in both cases was voltage ranging up to 5 volts.


I have tried testing for voltage with the battery switch in the Off position as well as in the On position for each bank to try to determine which side of the switch the leak(s) are on with limited success. There is always voltage on the line.

After many attempts to isolate the leaks by leaving the battery switch in the on position and disconnecting individual pieces of equipment at the panel with no results I noticed something very odd. I had physically disconnected the house bank from the switch and boat ground and only left the starting battery connected to the switch. I had the volt meter still running from the positive post of the starting battery to the clamp that connects the starting battery to the switch. Even with the switch end of the cable disconnected from the switch the meter shows appx. 2 volts still. I have tried another meter to be certain but get the same results.

Additionally I did notice that as I was tightening the positive clamp back on to the battery I was also holding on the the stainless steel wheel and received a mild shock.

I have read about stray current coming from outside the boat but could that account for so much Voltage? Similarly as it related to Galvanic current, could it generate this much voltage? If anyone has any suggestions I would appreciate it.

 

[Don S/V ILLusion]

You'd probably be better served starting a new thread; it was only by accident I stumbled upon your dilemma.

One very simple thing to check before you go further - depending on the type voltmeter you use, try holding both leads, one in each hand and check the voltage. Some mutlimeters confuse capacitance with stray voltage which can obviously mislead you.

 

[Alex 2740]

Will do and then I'll start a new thread once I check it out. Thanks Don.

Alex

 

[Stu Jackson]

Alex, remove the wire connecting the starter and alternator output. The starter and the DC distribution panel should come off the C post of the 1-2-B switch. The bilge pump as wired is not always on.

 

[Alex 2740]

Good morning Don and Stu,

I will go back and post the request as a "New" post to make it easier for others to find.

I did check the voltmeter by holding the probes in each of my hands and the voltage only indicated .02 volts so I think that it is probably working correctly.

In terms of the Cable to the starter and alternator I did in fact remove it in one of the iterations of tests and it did not change the voltage reading that I got. The reason that I disconnected the Bilge wire was in the event that the float switch kicked on and additionally to test if there was a short in that circuit. I'll update the diagram on the new post to show the switch terminals labeled.

Thanks,

Alex