Eliminating the 1-2-Both-Off Battery Switch

[Q Xopa]

Originally Posted by john61ct

I agree there is no "one true way", room left for other owner choices, but
is more precise than

In your setup, what is the scenario where the B is genuinely helpful?

What protection is there from running both banks down in the event B is switched accidentally or forgotten about?

Yes either a 12B or a 3 seperate system can work fine or misused.

If you already have the 12B as many do as it was the way it was done for a long time.

That doesnt mean its the only way or the best way. Particularly since ACRs have been on the scene.

If your starting from scratch I prefer 3 individual switches. But as mentioned is not idiot proof, as isnt a 12B.

To me its like parallel fuel filters using a 3 way selector valve ie Racor duo. Its fine and it works but why not just use 2 regular valves.



To me its just a question of keeping things as simple as possible by using the simplest and most common components.

[Stu Jackson]

Aaargh...


What you folks are really talking about are OPTIONS and CHOICES.


FUNCTIONALLY many of them are identical.

[john61ct]

And Blue Sea switches, if proper ampacity is selected, really do last a long long time.

[smac999]

Originally Posted by john61ct

In your setup, what is the scenario where the B is genuinely helpful?

What protection is there from running both banks down in the event B is switched accidentally or forgotten about?

I would use both to crank an engine with a weak engine battery. very rarly do you need to actually isolate or remove a bank. which is why the dual circuit blue sea switch works fine 99% of the time.

no different then leaving the parallel switch on in the 3 switch setup.

[Q Xopa]

Originally Posted by smac999

I would use both to crank an engine with a weak engine battery. very rarly do you need to actually isolate or remove a bank. which is why the dual circuit blue sea switch works fine 99% of the time.

no different then leaving the parallel switch on in the 3 switch setup.

Well yes you might get away with it.

But what about when-

The switch has been left in B and both are flat (I know that would never happen right). Or
The Start batt has an internal short, you dont want to be dragging down your good House batts, or
The Start is dead and the House is marginal.The starter batt will pull the House bank down the little it has left.

This is where the 3 seperate On/Off switch configuration has it over a 12B switch.

But many manufacturers have done, still are using 12B switches.

Im not saying they are bad. But IMHO is there a better alternative, yes ie seperate Bank switches, with ACRs or FET Combiners.

But practicaly speaking just adding an ACR on the charging side and a bit of self education will have you way ahead of the average blissfully unaware boater.
It is arguable if going to the expense and trouble to change from a 12B to a seperate switch setup is worthwhile.

Your boat, your call.

[parkstone bay]

The last post from QXopa is absolutely spot-on, except, I suggest, for his second-last sentence. I , personally, disagree that it's "arguable" about going to the expense and trouble of a 2 separate switch set-up v a combined O12B switch. I believe, and having done it, there's no argument at all - it's well worth doing! (My coolbox eats amps (about 4 - 5 amps when running), 6 hours on anchor with it on can very seriously compromise the volts available to start the engine.). Separate batteries, with the house battery electrically isolated from the starter battery, is the answer. For sailing boats, a 10 - hour night passage with lights on, instruments running, etc, will give a similar issue.

[Q Xopa]

Originally Posted by parkstone bay

The last post from QXopa is absolutely spot-on, except, I suggest, for his second-last sentence. I , personally, disagree that it's "arguable" about going to the expense and trouble of a 2 separate switch set-up v a combined O12B switch. I believe, and having done it, there's no argument at all - it's well worth doing! (My coolbox eats amps (about 4 - 5 amps when running), 6 hours on anchor with it on can very seriously compromise the volts available to start the engine.). Separate batteries, with the house battery electrically isolated from the starter battery, is the answer. For sailing boats, a 10 - hour night passage with lights on, instruments running, etc, will give a similar issue.

Ok guilty, you caught me being too diplomatic.

[Q Xopa]

Originally Posted by parkstone bay

The last post from QXopa is absolutely spot-on, except, I suggest, for his second-last sentence. I , personally, disagree that it's "arguable" about going to the expense and trouble of a 2 separate switch set-up v a combined O12B switch. I believe, and having done it, there's no argument at all - it's well worth doing! (My coolbox eats amps (about 4 - 5 amps when running), 6 hours on anchor with it on can very seriously compromise the volts available to start the engine.). Separate batteries, with the house battery electrically isolated from the starter battery, is the answer. For sailing boats, a 10 - hour night passage with lights on, instruments running, etc, will give a similar issue.

Ok guilty, you caught me being 'diplomatic'.

[c.spots]

I don’t get why you want a reserve, unused battery. It seems wasted, and complicates your system. Add it to your house bank.
Consider all charging sources to the house bank. Keep your start battery charged (automatically, daily) from your house bank by a VSR, battery combiner. In case of battery bank disaster, the VSR will separate the batteries, leaving good emergency reserve for your start battery. Very simple, reliable, and automatic. No switches to forget.

[guyrj33]

Originally Posted by c.spots

I don’t get why you want a reserve, unused battery. It seems wasted, and complicates your system. Add it to your house bank.
Consider all charging sources to the house bank. Keep your start battery charged (automatically, daily) from your house bank by a VSR, battery combiner. In case of battery bank disaster, the VSR will separate the batteries, leaving good emergency reserve for your start battery. Very simple, reliable, and automatic. No switches to forget.

You say a reserve battery is a waste and complication and then describe a system with an isolated extra battery.
Kind of like having your cake and eating it too.

[Junglebike]

Gently asking if these switching schemes are really necessary anymore on a vessel with solar and a fairly large house bank like my trawler doing easy coastal family cruising in SoCal?

I have 6x 6V US2200 GC batteries, for almost 700Ah nominal capacity (12V), and am installing 750W of solar. Voltage drop/spike seems to be a non-issue, but I switch my electronics on after starting anyway (2x Lehman 120's). I have a Balmar battery monitor, so am unlikely to accidentally run my bank down. If I do, it'll be recharging upon daybreak.

Why do I need more than one bank at all? Only situation I can think of is a battery failure, which can be pretty easily remedied by disconnecting that string's negative lead. Almost certainly I'd spot the failure with the battery monitor, and even if not, the remaining four GC batteries could easily start an engine even when extremely discharged. I suppose I could carry a Lithium emergency starter as a backup if needed.

I know a lot of you are vastly more experienced than me - am I missing something?

[Stu Jackson]

Originally Posted by Junglebike

>>>>>>>>>>>>>>>>>

I know a lot of you are vastly more experienced than me - am I missing something?

No, you are simply suggesting another OPTION. It's not unreasonable and certainly works.

[Junglebike]

Originally Posted by Stu Jackson

No, you are simply suggesting another OPTION. It's not unreasonable and certainly works.

Thanks. Surprised I don’t hear more folks bringing it up. Good to know there’s not some hidden issue with it that I’d missed.

[a64pilot]

Originally Posted by Junglebike

Gently asking if these switching schemes are really necessary anymore on a vessel with solar and a fairly large house bank like my trawler doing easy coastal family cruising in SoCal?

I have 6x 6V US2200 GC batteries, for almost 700Ah nominal capacity (12V), and am installing 750W of solar. Voltage drop/spike seems to be a non-issue, but I switch my electronics on after starting anyway (2x Lehman 120's). I have a Balmar battery monitor, so am unlikely to accidentally run my bank down. If I do, it'll be recharging upon daybreak.

Why do I need more than one bank at all? Only situation I can think of is a battery failure, which can be pretty easily remedied by disconnecting that string's negative lead. Almost certainly I'd spot the failure with the battery monitor, and even if not, the remaining four GC batteries could easily start an engine even when extremely discharged. I suppose I could carry a Lithium emergency starter as a backup if needed.

I know a lot of you are vastly more experienced than me - am I missing something?

For six years I have had what amounts to one large bank, it’s actually two banks as they all won’t fit in one location, but as I leave the switch to ALL always, it’s in effect one large bank, but if a battery shorts, I can isolate the bad bank by merely switching to the good bank from ALL.

I can’t understand how the same people who can’t imagine not having multiple banks and separate starter batteries can run around with one engine and one fuel tank.

[Pizzazz]

Clearly, if you have one large deep cycle bank, it is good for everything, house loads and starting most of the time. However, there are these times...

- Your house bank is low and you need to restart the engine (happens all the time when sailing). All the electronics will reboot.

- Redundancy. If you have only a starter pack that is not well integrated, you will forget to charge it one day when you need it the most.

The best way to eliminate the 1-2 battery switch is to have a charge relay, that combines the batteries when charging, then have the starting battery connected to the starter and the house to everything else. The system will not require user input unless your starting battery dies and then you will need to manually rewrite house to starter. I hope you do not end up doing this right when entering the marina and you need to start the engine.