Battery Switch Confusion

[Dudenhoeffer]

Hi All!

Picking up our "new to us" C-30 on Tuesday (thanks to everyone that chimed in on my prop question last week) and would appreciate a little feedback on a piece of information I got from the P.O... He's suggesting that we should NOT switch the Battery from Run / 1 to 1+2 while the engine is running. His concern is that the Alternator will spike and that could cause damage in the time the switch travels from 1 -> 1+2. He even put a sticky below the switch to help prevent this action.

If this is the case, I do not see how anyone could charge the house batteries via the alternator. And, I've never heard of a disconnected alternator being damaged when an engine is running.

Wondering if this is born of an abundance of caution and perhaps a known issue?

Thoughts? Thanks!
Don

 

[Davidasailor26]

The 6007 is a “make before break” switch. That means switching from 1 to 1+2 makes the connection to 2 without breaking the connection to 1. Definitely do NOT switch to Off while the engine is running. That does risk a voltage spike which could blow the diodes in the alternator.

Specs for that switch are at https://www.bluesea.com/products/6007/m-Series_Mini_Selector_Battery_Switch_-_Red

A really good article about the various considerations of the 1-2-B switch is at 1/2/BOTH Switch Considerations

 

[Don S/V ILLusion]

It’s possible to burn out the alternator diodes under a no-load condition which is the basis for this warning.
Some old switches were designed so as to not make-before break connection but it’s easy to determine if you have that type by a simple test - slowing switch while checking for continuity with a VOM.

 

[jviss]

And, I've never heard of a disconnected alternator being damaged when an engine is running.

Well, then you haven't been reading enough. Disconnecting the load from an alternator that's supplying current can damage the rectifier (diodes).

It’s possible to burn out the alternator diodes under a no-load condition which is the basis for this warning.

I have never heard of this. Can you please elaborate? I take it that what you are saying is that just running the alternator with no load can damage it. That's just not so.

 

[Don S/V ILLusion]

Well, then you haven't been reading enough. Disconnecting the load from an alternator that's supplying current can damage the rectifier (diodes).


I have never heard of this. Can you please elaborate? I take it that what you are saying is that just running the alternator with no load can damage it. That's just not so.

Just as you explained saying “ disconnecting the load….can damage the diodes”, that is the “no load” condition to which I refer.

 

[Johnb]

As you can see there is a warning right on this switch to stop engine before switching off. The reason for this is the voltage spike that comes when a current carrying inductor is open circuited. The solar controller is now an additional device that has an inductor in it, hence the added requirement that the panel be switched off.

I know that the switch is a make before break and therefore switching between 1/ALL/2 should not result in a problem, however
1 If the wiping action results in a momentary break or
2 If someone misoperates the switch
you just scored an own goal, so I have laid down the rule - no changes unless panel and engine are off.

 

[Stu Jackson]

It is critical to get to the basics:

OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams

1-2-B Considerations (New 2020 - Rod finally got around to diagramming what I had done in the above link in 2009 )
1/2/BOTH Switch Considerations

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

This is a newer primer for boat system wiring design with a thorough diagram: Building a Good Foundation (October 2016)
Building a DC Electrical Foundation

The Short Version of the 1-2-B Switch Stuff: Electrical Systems 101 This is a link to the Electrical Systems 101 Topic, reply #2

*************************

These links all come from this main thread:

Electrical Systems 101 Electrical Systems 101

You would be wise to read them all.

 

[jonelli]

Read what Stu just posted, that's all the info you need.
I re-wired my system like this. It solves the issue about how to charge everything and not worry about the battery switch.

 

[jviss]

Hmmm, I'm not following the logic of your wiring, @jonelli . It is such that whatever battery is powering the panel is also powering the starter. So, no dedicated starting or engine battery. Battery 2 is just a backup battery. Is that so? Is that the intention?

 

[Stu Jackson]

Hmmm, I'm not following the logic of your wiring, @jonelli . It is such that whatever battery is powering the panel is also powering the starter. So, no dedicated starting or engine battery. Battery 2 is just a backup battery. Is that so? Is that the intention?

Read what Stu just posted, that's all the info you need.

jviss, what jonelli said is very apt, and what I suggested is that folks read the links I provided. One of the important parts of the texts that are an inherent part of the links is that they show MULTIPLE and DIFFERENT wiring diagrams. jonelli chose to pick a very popular and easy to implement one. There are OTHERS.

The answer to your question is obviously YES. The second battery is considered a reserve battery as compared to a dedicated start battery.

 

[jonelli]

Jviss, I “fixed” my starting issue by replacing the corroded #4 wiring to 1/0 marine wire. Then there was no issues starting on one battery as some have with old wiring.
next I added a battery combiner and ran the alternator to battery #1. When it runs it charges both batteries always. My battery switch is now a real batt1/batt2 switch. I leave it on batt1 100% of the time and ONlY switch if I’ve ran it down a little too much over the weekend and use batt#2 to start as a reserve battery.
but now that I’ve got a 100W solar panel, it’s rare I run down batt1 unless I use my espresso machine for 4 people to make 8 shots each morning.
But I love knowing that batt2 is always ready to go.

 

[Dudenhoeffer]

Great thread and learned alot about how my new to me boat's system is wired.... Alternator runs straight to House.

Another question for the pros here... Is it important to keep the house pack batteries all the same? I was gifted a new deep cycle but it is a different make / size battery. Any reason I should not add the 3rd battery?

 

[kappykaplan]

Is it important to keep the house pack batteries all the same?

I think so, but others may disagree.

 

[dlochner]

All the batteries in one bank should be of the same type, manufacturer, and age.

 

[jssailem]

@Dudenhoeffer Dave speaks wise words.

But why you may ask.
Batteries are very helpful. When one is struggling the others give a little and try to pull the lackard along. Pretty soon all tend to find balance based on the lowest denominator. Your. New battery would, before long be of the age and power capacity of any mates.

Thus it is best economics to get a match fresh set.

That being said, boat owners not wanting to throw a gift in the bin have and will mix and match and eventually be faced buying a new bank of batteries. Who knows how long that might be. Only you can be the judge. It is your boat and you are free to do whatever meets your needs. None need be the wiser.

 

[dlochner]

I admit, I got lazy and didn't give the explanation.

There are degrees of bad mix and matches. When batteries have very different chemistries, i.e., FLA, AGM, Gel, LFP, Carbon Foam, they have have very different charge profiles. Inevitably, one of the mismatched batteries will be chronically undercharged and another chronically overcharged.

With that said, there are bigger and lesser sins. LFP and anything else is really problematic. On the other hand, 2 FLA batteries of the same size, but of different ages will be less problematic. As you add the variables, size, age, type to the mix the problems will increase.

The simplest advice is just don't do it.

 

[Ward H]

I agree with @jssailem and @dlochner that best practice is not to mix batteries of different ages and sizes.
In @Dudenhoeffer s case, if he follows that advice, he may never be able to use the new gifted battery. (without rewiring as a single dedicated start/reserve battery).

Instead of not using the battery I would go ahead and connect to the current batteries as long as all three are the same type flooded lead acid. Yes it won't last as long as a fully matched set but even if it settles down to match the other two batteries he would have a larger capacity bank which may delay when he needs to replace his batteries. If it does, he got some positive use out of the gifted battery.

Of course, now he is better prepared to follow best practice when he does go to buy a new battery bank.


I have a friend who uses nothing but used batteries with "some life" left in them. Says he "never had a problem so why not."

@Dudenhoeffer Just make sure they are FLA ( flooded lead acid batteries).