Explain this battery switch / is it ok to have diff sized house batteries?

[Enyar]

Still learning this boat and it appears I have 2 dead batteries. The boat has a 8D house battery under the galley sink. In front of the motor is 2 Group 31s. The two group 31s are only putting out 5-7 volts and so for the last few trips we've been combining all batteries to start ( I thought only 1 was dead, not 2). I'm wondering if I fried these batteries with the switch set to ALL and the charger trying to charge 2 different types of batteries that were connected.

For some reason I thought the two group 31s were used for starting but now I'm thinking that's a bad idea. If you look at my diagram I think going forward I will keep the battery switch to OFF which means only battery 1 is used for starting (not the most obvious of things....). If that battery is dead I can set it to 1 which will use #1 and #2. If I need all the above I put it to ALL and I get 1+2+House. Does this make sense?

I believe the 2nd switch on the boat will allow me to select what to feed the DC panel with, hopefully #2 battery and/or the house instead of just one. When on shorepower, I should probably keep this on OFF for charging? ALL when on the hook and need the power? If #2 and House are connected when on shorepower wont that mess with the charger?

[OldManMirage]

For what it's worth, my plan in your particular case would be to use the 8D as the House Bank and hook it up to position 1. Leave your switch in that position. An 8D will start just about anything likely to be on a sailboat, and it will not hurt it one bit to use it that way.

Get an ACR. This is a device that will charge a 2nd battery whenever there is enough voltage to do so. In other words, under almost all normal operating conditions. You will use this to charge Battery #2, which in your case I would just buy 1 NEW Group 31 and use this as your backup, which you will wire to Switch Position #2.

So you basically will be able to leave your battery switch alone UNLESS there is a problem, such as if you weren't paying attention and your frig pulled your house bank too far down to crank the engine. Then you'll switch to position #2 and crank it up and let it charge the house back up.

Here is website that explains things like this really well.
https://marinehowto.com/

Make a donation while you're there, it's for a good cause.

[smac999]

That switch makes no sense. And should be rewired.

Drop the boat to 2 banks. Start and house.

Where do the house loads come from?

You need an engine switch between the battery and starter.

If the batteries are at 7v then the need to be replaced.,, Also you need to figure out why all 3 batteries are not charging.

[Enyar]

Originally Posted by OldManMirage

For what it's worth, my plan in your particular case would be to use the 8D as the House Bank and hook it up to position 1. Leave your switch in that position. An 8D will start just about anything likely to be on a sailboat, and it will not hurt it one bit to use it that way.

Get an ACR. This is a device that will charge a 2nd battery whenever there is enough voltage to do so. In other words, under almost all normal operating conditions. You will use this to charge Battery #2, which in your case I would just buy 1 NEW Group 31 and use this as your backup, which you will wire to Switch Position #2.

So you basically will be able to leave your battery switch alone UNLESS there is a problem, such as if you weren't paying attention and your frig pulled your house bank too far down to crank the engine. Then you'll switch to position #2 and crank it up and let it charge the house back up.

Here is website that explains things like this really well.
https://marinehowto.com/

Make a donation while you're there, it's for a good cause.

Thanks for the site. So I lied, the 8D is actually a 4D with 1050 CCA and 290 min reserve capacity. I haven't finished sorting through the wiring to see if there is an ACR but I don't think there is. The boat has 2 alternators but I'm not sure which alternator is feeding which battery.

Why do you like the house battery to position 1? I'm relatively new to this but I would have thought you would want your starting battery to be #1 and to make sure this one gets charged first. Then let the bigger 4d handle all the house DC loads at sea leaving your starter battery alone.

[Stu Jackson]

The way you have shown the switch wiring makes little sense.



Here are some more specific references for you to peruse:


OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4....html#msg30101

1-2-B Considerations (New 2020 - Rod finally got around to diagramming what I had done in the above link in 2009 )
https://marinehowto.com/1-2-both-bat...onsiderations/

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

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.sailboatowner...d.php?t=137615

This is a newer primer for boat system wiring design with a thorough diagram: Building a Good Foundation (October 2016)
http://forums.sailboatowners.com/ind.../#post-1332240

The Short Version of the 1-2-B Switch Stuff: http://c34.org/bbs/index.php/topic,5....html#msg38552 This is a link to the Electrical Systems 101 Topic, reply #2

How to properly wire & switch a DCP switch - Maine Sail's "workaround" explained Replies #28 & 29
https://forums.sailboatowners.com/th...9932137/page-2

What are ACRs, Combiners & Echo Chargers? (by Maine Sail) [scroll to the top]
http://forums.catalina.sailboatowner...d.php?p=742417 and http://c34.org/bbs/index.php/topic,9....html#msg70131

Making Sense of Automatic Charging Relays (2019)
https://marinehowto.com/automatic-charging-relays/


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


These come from this:


Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html

[Enyar]

Originally Posted by smac999

That switch makes no sense. And should be rewired.

Drop the boat to 2 banks. Start and house.

Where do the house loads come from?

You need an engine switch between the battery and starter.

If the batteries are at 7v then the need to be replaced.,, Also you need to figure out why all 3 batteries are not charging.

There is another switch below it that lets you select which battery to pull the house loads from. It can pull from the 4D(normal) or the starter battery. Or if the top switch is set to 1, then the house load would pull from starter battery 31 and the extra group 31 that's now missing.

Basically if the top switch (pictured) is set to OFF - Battery 1 starts the motor.

If it's set to 1 - Battery one and battery 2 start the motor

If it's set to 2 - Battery one and the house 4D start the motor

If it's set to ALL - Battery 1, 2 and the House 4D start the motor


Dropping it to 2 banks - how should I split that up? I went ahead and bought another group 31 (kinda regretting that now, more later) as the starting battery.I originally was planning on keeping the 31 as the starting battery, the 4D as the house battery and then adding an anderson connector where the 2nd group 31 was. Then I wanted to build a little Lifepo4 battery kit that I could plug in when I needed the extra Ah. When I park the boat I take the Lifepo4 with me and use it in the RV or my truck or my other boat as needed.

Now I'm thinking I should have used the 4D as the starter and then went straight Lifepo4 for the house bank/not mix battery types.

The batteries are charging. I think I cooked them because I had the battery switch on ALL (2 group 31s and a 4d) and then the 3 bank charger was tryying to charge them all together for the past year.

[Bowdrie]

Originally Posted by Enyar

The boat has 2 alternators but I'm not sure which alternator is feeding which battery.

Tracking this down is the first step on the road to recovery.
With 2 alternators you have the ability to totally isolate starting/engine requirements and house loads, as well as the charging profiles of each.
With suitable wiring you can have a system in which "Never the twain shall meet".
Problems decrease significantly when house loads/charging and engine systems, (instruments/panel lighting/pre-heat/fuel pumps/starting/charging engine starting batts,) are not co-mingled with each other.

[Ballsnall]

Originally Posted by Enyar

Dropping it to 2 banks - how should I split that up? I

House & Start
With 2 alternators you have the basics of a good system. Check the alternative sizing and wire the smaller (if different) to the start battery. Larger alternator goes to the house. You will need a battery switch for each battery and a combiner switch which can be on one of the battery switches but personally I prefer a bank of 3 switches as it's more visual that way.

The combiner switch is always off and only used in the case of a flat start battery. When your on the boat, both battery switches set to on. Off the boat all switches are off.

The batteries are charging. I think I cooked them because I had the battery switch on ALL.

Yes, but not due to the different sizes, most likely due to having a dead battery which killed the good ones.

[Enyar]

Originally Posted by Bowdrie

Tracking this down is the first step on the road to recovery.
With 2 alternators you have the ability to totally isolate starting/engine requirements and house loads, as well as the charging profiles of each.
With suitable wiring you can have a system in which "Never the twain shall meet".
Problems decrease significantly when house loads/charging and engine systems, (instruments/panel lighting/pre-heat/fuel pumps/starting/charging engine starting batts,) are not co-mingled with each other.

Thanks, I am a bit torn on the dual alternators. Not great contact with the belt which causes a lot of belt dust. I might remove one now that I am down to 11 house battery for now. I am basically just starting out from scratch now that my Dad has passed and we haven't been able to venture farther than day trips. The goal is to hit the bahamas this summer but even then it would only be for a week and I bet we could survive with one battery/one alternator. We would likely stay in marinas for the kids.

[Enyar]

Originally Posted by Ballsnall

House & Start
With 2 alternators you have the basics of a good system. Check the alternative sizing and wire the smaller (if different) to the start battery. Larger alternator goes to the house. You will need a battery switch for each battery and a combiner switch which can be on one of the battery switches but personally I prefer a bank of 3 switches as it's more visual that way.

The combiner switch is always off and only used in the case of a flat start battery. When your on the boat, both battery switches set to on. Off the boat all switches are off.



Yes, but not due to the different sizes, most likely due to having a dead battery which killed the good ones.

I meant between the 3 batteries (2 group 31s and a 4D). I dont think combining the 4D and group 31 would be good for the life of the group 31 when on the charger.

[Bowdrie]

Originally Posted by Enyar

Thanks, I am a bit torn on the dual alternators. Not great contact with the belt which causes a lot of belt dust.

In the old days boats commonly only had one alternator, but most boats had only rudimentary electrical systems, and few had refrigeration, (the greatest power consumer,) and house/starting batts were typically of ~the same size/type.
As such, a single alternator would "more-or-less" keep things going without too many issues.
Then, boaters learned about 6V deep cycle batts and things started to change.
The deep cycle units have different charging/floating regimens than do starting batts, (chemical composition and physical plate construction are different,) and with increased power demands problems started to arise.
The alternators regulator senses the voltage of the batt it's connected to and adjusts the output accordingly.
If it's sensing an almost fully charged starting batt then the depleted house batt never really will reach a full charge even after hours of motoring.
If it's sensing a depleted house batt then the start batt ends-up being overcharged, leading to positive plate grid corrosion.
If it's sensing both, you don't get the best of both worlds, you get the worst.
Today, if one wishes only one alternator it works best if the alternator senses and charges the house batt and the start batt is charged from a DC>DC unit such as those from Victron.
You mentioned "belt dust".
From which alternator does the dust come from?
Belt dust can arise from several sources, belt too loose/too tight/wrong profile or type/misalignment/scored pulleys/too small of alternator pulley, these are the most common causes.
If things can be sorted out a 2 alternator set-up will give great service while also providing a "back up" incase of a failure, (mostly due to excessive heat).
A side note: A 4D batt is not a great choice for house use, in a boat of the size you have surely there must be a way to accommodate some 6V units to use for house batts?

[Enyar]

Originally Posted by Bowdrie

In the old days boats commonly only had one alternator, but most boats had only rudimentary electrical systems, and few had refrigeration, (the greatest power consumer,) and house/starting batts were typically of ~the same size/type.
As such, a single alternator would "more-or-less" keep things going without too many issues.
Then, boaters learned about 6V deep cycle batts and things started to change.
The deep cycle units have different charging/floating regimens than do starting batts, (chemical composition and physical plate construction are different,) and with increased power demands problems started to arise.
The alternators regulator senses the voltage of the batt it's connected to and adjusts the output accordingly.
If it's sensing an almost fully charged starting batt then the depleted house batt never really will reach a full charge even after hours of motoring.
If it's sensing a depleted house batt then the start batt ends-up being overcharged, leading to positive plate grid corrosion.
If it's sensing both, you don't get the best of both worlds, you get the worst.
Today, if one wishes only one alternator it works best if the alternator senses and charges the house batt and the start batt is charged from a DC>DC unit such as those from Victron.
You mentioned "belt dust".
From which alternator does the dust come from?
Belt dust can arise from several sources, belt too loose/too tight/wrong profile or type/misalignment/scored pulleys/too small of alternator pulley, these are the most common causes.
If things can be sorted out a 2 alternator set-up will give great service while also providing a "back up" incase of a failure, (mostly due to excessive heat).
A side note: A 4D batt is not a great choice for house use, in a boat of the size you have surely there must be a way to accommodate some 6V units to use for house batts?

Thanks for this, that was an interesting read.

Why would one want a DC to DC charger charging the start battery vs an ACR which charges the house battery once the start is full?

The belt dust is from not great pulley wrap/probably not enough tension due to the way my Dad mounted these alternators.

Before I fried the 2 group 31s, the house was serviced by the 4D and the group 31 (I assume this was a deep cycle). When my Dad was alive we mostly visited marinas or did day trips. We never got to do a night on the hook, though I want to. What I probably should have done instead of replacing the G31 start battery was move the 4D to starting duties and switched to Lifepo4 for house. Now that I already bought the G31 starting battery I think we will test this setup (without the 2nd group 31 house battery) to see how it serves our duties. I have a little Honda gen that can help charge if we get adventurous.

I just need to figure out what the 2nd alternator was charging to make sure its still charging something, it might have been hooked to that 2nd group 31

[Bowdrie]

Originally Posted by Enyar

Why would one want a DC to DC charger charging the start battery vs an ACR which charges the house battery once the start is full?

The belt dust is from not great pulley wrap/probably not enough tension due to the way my Dad mounted these alternators.

I just used "DC>DC" as a euphuism for some kind of gizmo.
Typically, when the engine is started it's batt gets charged-up pretty fast, whereas the house bank usually requires a lot more input.
Having the "Main" charging effort directed to the house bank and using "excess" power to top-off the start batt, (thru some gizmo,) is more-or-less accepted practice.
OK, I know it's not the same thing, but the amount of "power", expressed in Watt-Hours to start an "in good shape" engine is not all that much.
In starting, a typical 350ci Chevy small block uses less watt-hours of energy than is contained within an AA dry cell.
Even if our little 4-cylinder diesels used 3>4 times as much, it's still only the amount of a "C" or "D" battery.
What I'm getting at is that unless you're endlessly cranking an engine you're not using all that much power.
A friend of mine starts his 120HP Detroit with 1 group 24 batt, no problems ever.
Belt wrap is an issue that's hard to deal with on alternators that are required to crank-out a lot of power, that's a big reason for the serpentine systems.
However, there are an amazing assortment of belts available besides what one gets at the local auto parts store.
If you could take your old belt to a "Power transmission/Bearing supply" business they might have something for you.
Simply cranking-up the tension is a non-starter.