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Old 10-03-2015, 03:45 PM   #21
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Originally Posted by hmason View Post
...
Your battery selector switch does not determine charging--they all get charged no matter which position the switch is on.

...
Don't assume that this is true until you have checked. I owned a sailboat with the same setup (it's very common on sailboats) and only the bank that was connected being charged. To charge both (either from the charger or the alternator) require the battery switch to be set to "both".

In order to charge both all the time the charger would have to have two outputs or an echo charger would need to have been installed. Check this on your boat to be sure.

I personally do not like the two battery bank setup. It means you have to hold half of your battery capacity "hostage" just to start your engine. It's been pointed out that a relatively small battery is capable of doing the job for most engines. It also means that you tend to discharge each bank lower than you would if they were combined. On my sailboat I paralleled the two banks and added a smaller starter battery. I also installed an automatic battery combiner that ensure that all batteries were charged by either the charger or alternator without allow one to discharge into the other.

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Old 10-03-2015, 06:01 PM   #22
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Originally Posted by Britannia View Post
Don't assume that this is true until you have checked. I owned a sailboat with the same setup (it's very common on sailboats) and only the bank that was connected being charged. To charge both (either from the charger or the alternator) require the battery switch to be set to "both".

In order to charge both all the time the charger would have to have two outputs or an echo charger would need to have been installed. Check this on your boat to be sure.

I personally do not like the two battery bank setup. It means you have to hold half of your battery capacity "hostage" just to start your engine. It's been pointed out that a relatively small battery is capable of doing the job for most engines. It also means that you tend to discharge each bank lower than you would if they were combined. On my sailboat I paralleled the two banks and added a smaller starter battery. I also installed an automatic battery combiner that ensure that all batteries were charged by either the charger or alternator without allow one to discharge into the other.

Richard

Richard: Calder agrees you should have one large house bank rather than two banks at half size.


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Old 10-03-2015, 09:36 PM   #23
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Personally I like a single starting battery and a large house bank. I have a single grp 31 start battery and 4 grp 31 batteries in the house bank. They are connected by a combiner relay and also charged by a dual output solar controller that sends 10% to the start battery and 90% to the house batteries.
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Old 10-04-2015, 08:53 AM   #24
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So I'll add another question to the "Please help me understand" thread:

Why do you need two start batteries for a twin engine vessel? It seems like over-redundancy, if you isolate the start from the house bank. One the first engine is started, isn't the alternator on number one more than enough to provide charge for the battery and current to start number two? Also, shouldn't a healthy battery be able to have more than enough whoomph to start both engines?

It's a moot point for me as PH has a single engine.


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The problem is when one of the engines wont start and you run down the battery trying to start it. Then there may not be enough juice to crank the other engine.

I'm of the crowd that thinks all engines get a cranking battery and the house gets it's own bank of deep cycle batts.
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Old 10-04-2015, 12:12 PM   #25
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So I'll add another question to the "Please help me understand" thread:

Why do you need two start batteries for a twin engine vessel? It seems like over-redundancy, if you isolate the start from the house bank. One the first engine is started, isn't the alternator on number one more than enough to provide charge for the battery and current to start number two? Also, shouldn't a healthy battery be able to have more than enough whoomph to start both engines?

It's a moot point for me as PH has a single engine.


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Actually two batteries are not required. Everything, including house could be run off one or one bank. Twins offer redundancy that gets lost without two batteries.
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Old 10-06-2015, 04:12 AM   #26
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OK, I have been around boating for a number of years and this is the first boat I have owned with a battery switch. I don't quit understand the purpose of it.

Here is what I do know:
  • There is a #1 and #2 side. Each side is connected to a different battery bank. I have 2 banks with golf cart batteries.
  • I know not to turn the switch while the engines are running.
  • I keep the switch on "both"
So fill me in on the rest I am missing.......
Britannia makes a good point. Most sailboat setups as they come from the factory have a 1/2/Both/Off switch. I imagine that many of the smaller powerboats are the same. In most cases, they are wired so that the switch selects both the battery to be used, but also which battery is to be charged. Take a look at your wiring to be sure. On the 1/2/All switch there are three posts, a #1, #2, and common. If your alternator output is going to the common post, then that switch determines which bank is being charged by your alternator.

Down the road, you may want to consider a setup where you have a large house bank and a smaller start battery, much as Britannia described. If your alternator output is connected to your 1/2/Both switch, then I would keep it on both so that your alternator is charging both batteries while under way. As others have mentioned, your battery bank will tend to last longer if less deeply discharged. Having the selector on Both will do that for you. However, you have to be aware of the state of charge so you aren't stranded after being at anchor for a couple of days.

If I was you, I would get combine those 6v into 1 bank and put them on #1 and get a small starter battery and put it on #2. Run your alternator and charger directly to your house bank and install an Echo Charger to keep your starter battery charged up. Very simple wiring, much easier than a combiner, and relatively inexpensive.

You can go one better and add an Engine On/Off switch. Run your starter battery to the the On/Off switch and connect your starter to the On/Off switch. Connect your House bank to the #1 post on the 1/2/Both and your DC panel to the common post (as it is now). Then connect your On/Off switch to the #2 post of your 1/2/Both switch. Install an Echo Charger between the House bank and the Start battery and you are set.

Normal operation, you leave the 1/2/Both in the #1 position and the Engine On/Off in the On position. If your start battery fails, you switch the 1/2/Both to Both, the Engine Switch to OFF and your House bank will start your engine. If your House bank has failed and you need emergency power for nav lights or VHF, then switch the 1/2/Both to Both and the Engine Switch to On. Here is the diagram for my setup. Now, if you have a larger boat with a more complex electrical system, such as generators, inverters, etc... then this won't help at all.
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Old 10-06-2015, 11:02 AM   #27
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... Take a look at your wiring to be sure. On the 1/2/All switch there are three posts, a #1, #2, and common. If your alternator output is going to the common post, then that switch determines which bank is being charged by your alternator....
On my Catalina 36 the alternator used the starter motor +ve wire to charge the batteries. So whatever was connected to the starter motor (1, 2, both) would get charged by the alternator. Clever reuse of some thick gauge wire!

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Old 10-06-2015, 11:40 AM   #28
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Thanks everyone. Looks like I have some updating to do....
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Old 10-06-2015, 11:44 AM   #29
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On my Catalina 36 the alternator used the starter motor +ve wire to charge the batteries. So whatever was connected to the starter motor (1, 2, both) would get charged by the alternator. Clever reuse of some thick gauge wire!

Richard
Yup, but the power from the Alt went from Alt -> starter post -> 1/2/Both common post -> battery. Depending on the year of your C36, there may have been an Engine On/Off switch between the starter and 1/2/Both switch as well. I prefer a direct line from Alt to Battery.

BTW Alaskan Sea-Duction, if you are going to be making any changes to your setup, now would be a good time to ensure that you have a fuse in any Wire/cable that is connected to the house bank. Current ABYC standards call for a fuse to protect the wire within 7 inches of the battery and many older boats never had this.
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Old 10-06-2015, 02:09 PM   #30
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Current ABYC standards call for a fuse to protect the wire within 7 inches of the battery and many older boats never had this.

...and that maybe hard to achieve in some setups. At least it is on my boat. The fuse protection is after about 5' of 2/0 cable.


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Old 10-06-2015, 02:49 PM   #31
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...and that maybe hard to achieve in some setups. At least it is on my boat. The fuse protection is after about 5' of 2/0 cable.


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I wouldn't sweat it. It's not like all those boats with out them are having issues because they don't have the inline fuses.
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Old 10-06-2015, 07:10 PM   #32
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BTW Alaskan Sea-Duction, if you are going to be making any changes to your setup, now would be a good time to ensure that you have a fuse in any Wire/cable that is connected to the house bank. Current ABYC standards call for a fuse to protect the wire within 7 inches of the battery and many older boats never had this.
I know its been said a million times but here's 1,000,001. The fuse is to protect the wire, not the load it's powering. Thats why it needs to be close to the source.
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Old 10-06-2015, 08:41 PM   #33
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Why do you need two start batteries for a twin engine vessel?
Our 1973 cabin cruiser still has it's original battery system and selector switch system. The only change we have made it to change the two 8Ds for six 6vdc golf cart batteries, three of which fit in an 8D box. Four of the golf cart batteries are assigned house power duty, while the other pair is the start "battery."

We always run the boat with the Off-1-2-All battery switch in the 2 position, which is the house or 4 golf-cart battery position. This prevents the start battery (2 golf cart batteries) from being drawn down by house loads. The battery switch only serves to select the battery combination for house power.

However..... our vintage of GB is fitted with a battery combiner relay in the engine room which is activated whenever an engine start button is pushed. So regardless of the position of the battery selector switch, pushing a start button automatically connects both battery banks together to feed the starter motor. When the start button is released, the combiner relay opens.

This is a pretty nice setup and it saved us on at least one occasion when we had a cell in the earlier 8D start battery go bad.
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Old 10-06-2015, 09:55 PM   #34
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...and that maybe hard to achieve in some setups. At least it is on my boat. The fuse protection is after about 5' of 2/0 cable.
Yup, it can be very hard/impossible to do on some refits. So, get the fuse as close as you can to the battery.

I ended up using terminal fuses from Blue Sea. I couldn't find a good spot to put the ANL fuses I was going to use initially so went with those instead. The fuses now sit right on top of the terminal. It was a bit of a tight fit vertically, but that wouldn't be a problem for most power boat setups I've seen.
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Old 10-06-2015, 09:58 PM   #35
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This is a pretty nice setup and it saved us on at least one occasion when we had a cell in the earlier 8D start battery go bad.
Unless a cell goes really bad, then you don't want to parallel the good bank with the bad.

Out of curiosity, where did your alternator +out go?
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Old 10-07-2015, 12:44 AM   #36
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Out of curiosity, where did your alternator +out go?
If by that you mean where did the ammeters for the engines go I assume they didn't indicate anything until after the engines started. But to be honest I don't recall watching them at the time so I don't know what they did.

I remember that when we tested the battery the bad cell was totally dead. However, I do not recall any abnormal instrument readings once the engines were running.

Back then we put the battery selector on both before starting engines. Not because this had any effect on which batteries sent power to the starters, but to have both alternators charging both batteries (this was when we still had the stock dual 8D setup).

With the battery selector on 1 or 2, the port alternator charges the port battery and the starboard alternator charges the starboard battery. Because we use the port battery as our house battery most of the time, this means that the port alternator recharges it and picks up the ongoing house load (including our plotters, radar, radios, etc.) while the starboard alternator is just along for the ride once it"s brought the starboard battery back up to charge.

So we would always switch the battery selector to Both before starting engines, which meant both alternators were sharing the load of charging both batteries and carrying the house/instrumentation load. So we'd see the same load on both ammeters. After engine shutdown we would move the battery selector back to 2, our house battery.

When we changed from the two 8Ds to the six 6vdc golf cart batteries, we doubled our house battery capacity so now we just leave the battery selector on 2 all the time and let the starboard alternator "coast" once it's brought the starboard battery's charge back up after engine starting. So we see our house/instrumentation load on the port ammeter and very little load on the starboard ammeter once the start "bank" has been brought back up to charge.

Don't know if that's what you were looking for with your question but that's the past and present situation with the setup.
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Old 10-07-2015, 03:16 AM   #37
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I'm pleased with the battery set-up as described in post #6. Don't see the value in having two equal battery banks in boats of our type.
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Old 10-07-2015, 08:44 PM   #38
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I have 3 battery banks. One Start Batt. the port eng, one Start Batt. for the Stbd engine and then the House Batts. I set my 2 battery switches for each engine appropriately. That is, Batt Sw 1 is set for Batt. 1 which will only start my port eng from Batt 1. The second battery switch, Batt Sw 2 is set for Batt 2 which will only start my Stbd eng. In case one of my batteries dies and fails to start its allocated engine, I have the option of setting that switch for that eng to the other battery position or set it for "Both". These switch's have nothing to do with the house batteries. These switches are strictly for starting batteries. I know this for 2 reasons, one it makes sense and the other is because when you buy a battery Isolator, there are several to choose from and your choice is based on your personal configuration.
I chose a Battery Isolator designed for 2 Engines, 2 Switches and 3 battery Banks. When you look at the schematic, it is complete including the re-wiring required for the 2 switches. My battery Isolator itself is easy to wire up. There are 2 inputs, one for each alternator and 3 outputs - one for each battery bank. With this configuration, I can run on one engine if I choose to and it will charge all 3 banks from that particular engines alternator.


This is not to say that you cant do it any way you want. If you have a single engine, you should only need one switch. Batt Sw. pos 1 can be for the start battery and switch position 2 can be the house batteries and obviously, the "Both" position (sometimes Labeled as "All) would combine all of your batteries.


I am not including my Gen Start Battery in the above. It has it's own battery and is not connected to any of the other circuitry. It doesn't need to be. If I run the generator, it will automatically power my 120V AC input Battery Charger which in turn will charge all of my battery banks except for the Gen Start Battery because the Gen Set charges it's own battery.
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