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Old 09-30-2016, 04:08 PM   #1
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Boat Battery problem Help!

Boat Battery problem Help!

OK - This is what I need help with:

There are two (2) banks of batteries on the boat - 1 House - 1 Engine start.
They each go to a 4 position Battery switch: Position 1 - Both - 2 - Off. The switch has been disconnected & tested for the propper continuity & working when cycled. There is no continuity between positions 1 & 2 and it’s off when in that position.

Here is the problem, it doesn’t matter which position the switch is in, both banks are connected to all loads. The house circuits can be used when in the “start” (position1) & the engine can be started from the “house” (Position 2). It’s as if the switch is always in the “Both” position.

Again the switch itself works and positions 1 - 2 - Both are isolated in the switch.

On the battery banks the Neutral terminals (“Minus” - ) are joined & then go to ground. I can’t see any other joining of the positive terminals.

Where do I start looking?
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Old 09-30-2016, 04:15 PM   #2
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Sounds like you have a parallel switch in the on position.
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Old 09-30-2016, 04:35 PM   #3
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It sounds to me (and I could be wrong) like the switch is wired wrong. Normally, the load is switched between the batteries. If one of the batteries is connected where the load should be and the load is where the battery should be, you might get that result. Trace the cables and make sure they're on the correct terminals on the battery switch.

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Old 09-30-2016, 04:58 PM   #4
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It may be that the switch instead of switching load is switching the charge output from the engine meaning that the battery lead from the starter is the common pole of the switch and just switches the bank that gets charged. In this case with the description from the OP the house bank would be wired direct to the load....
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Old 09-30-2016, 05:57 PM   #5
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Quote:
Originally Posted by 1Sailor View Post


There are two (2) banks of batteries on the boat - 1 House - 1 Engine start.
They each go to a 4 position Battery switch: Position 1 - Both - 2 - Off. The switch has been disconnected & tested for the propper continuity & working when cycled. There is no continuity between positions 1 & 2 and it’s off when in that position. NORMAL

Here is the problem, it doesn’t matter which position the switch is in, both banks are connected to all loads. ABNORMAL If the battery switch is truly working correctly, then there has to be an external connection such as a Combiner, Voltage Sensing Relay, or Emergency Parallel solenoid connecting the 2 banks which have failed closed. My question is how do you know there is a problem?

The house circuits can be used when in the “start” (position1) & the engine can be started from the “house” (Position 2). It’s as if the switch is always in the “Both” position. NORMAL

Again the switch itself works and positions 1 - 2 - Both are isolated in the switch. NORMAL

On the battery banks the Neutral terminals (“Minus” - ) are joined & then go to ground. I can’t see any other joining of the positive terminals. NORMAL

Where do I start looking?
Go to Blue Sea Systems catalog and download it.
Normally, 2 batteries and one switch are setup like this diagram. The switch selects which battery feeds ALL loads.
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Old 09-30-2016, 08:20 PM   #6
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Originally Posted by Ka_sea_ta View Post
It may be that the switch instead of switching load is switching the charge output from the engine meaning that the battery lead from the starter is the common pole of the switch and just switches the bank that gets charged. In this case with the description from the OP the house bank would be wired direct to the load....
This is the only reply that may be the case. I know that on the battery switch terminal 1 goes to the starter battery & 2 goes to the house bank. If this is true, how do I isolate the batteries so, when away from shore power at anchor, I can have the house bank run the load while preserving the power in the starter bank?
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Old 09-30-2016, 11:28 PM   #7
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This is the only reply that may be the case. I know that on the battery switch terminal 1 goes to the starter battery & 2 goes to the house bank. If this is true, how do I isolate the batteries so, when away from shore power at anchor, I can have the house bank run the load while preserving the power in the starter bank?
The best way is to use an ACR between the starting Bat and the house bank... leave the battery switch wired as is... Just leave the switch to the start batt... The ACR will isolate the house bank once the charging source is removed..
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Old 10-01-2016, 09:02 AM   #8
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Could be the house loads are directly connected to house bank, and engine connected directly to start bank. Batt sw then connect the two when in all.

Does house loads and engine work when batt sw is off?

If so, start engine and turn charger off. Measure batt volts at batt terminals, if getting charged volts will be around 14. If not getting charged it will be under 13.

Nothing replaces drawing an accurate schematic in these situation.
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Old 10-01-2016, 10:42 AM   #9
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Originally Posted by 1Sailor View Post
This is the only reply that may be the case. I know that on the battery switch terminal 1 goes to the starter battery & 2 goes to the house bank. If this is true, how do I isolate the batteries so, when away from shore power at anchor, I can have the house bank run the load while preserving the power in the starter bank?
And this is how my Prairie was wired. I left it that way. As long as you have your generator start battery isolated you will have redundancy. I also carried jumper cables in case generator start battery died. Never had to use them.

When I put my inverter in I ended up doing this all over again. I did not see that it was necessary to run the inverter off of 2 Group 31s....seeing as I only had 4 total. So the entire house bank is also the start bank...with the generator battery isolated. I am not saying this is ideal. But it is simple and it was a solution when installing an inverter without a huge amount of batteries.

PS....the generator is the 5th battery and it was the same high quality Odyssey Group 31 as the rest. I have since added it to the battery bank and bought a smaller Group 24 for the generator.
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Old 10-01-2016, 01:19 PM   #10
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Be careful of running the engines with the switch OFF in case it isolates the alternator charge and blows a diode.
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Old 10-02-2016, 06:23 AM   #11
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"Be careful of running the engines with the switch OFF in case it isolates the alternator charge and blows a diode. "

YES!, but a properly chosen and wired rotary switch will have a field cut off built in, so fried diodes should not become a problem
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Old 10-02-2016, 06:45 AM   #12
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"Be careful of running the engines with the switch OFF in case it isolates the alternator charge and blows a diode. "

YES!, but a properly chosen and wired rotary switch will have a field cut off built in, so fried diodes should not become a problem
One in ten wired this way at best.
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Old 10-02-2016, 08:35 AM   #13
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One in ten wired this way at best.
I wired my alternator output to #1 post on the 4 way switches, this way rotating switches never will disconnect the alternators from a battery. I also have an 80 amp Blue Sea fuse inline to the alternator close to the 4 way battery switch. You can fit a 100 amp fuse in that holder.
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Old 10-02-2016, 10:47 AM   #14
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Had a similar problem on our last sailboat. No matter the switch position, the house load was always energized. Checked the wiring, starter battery went to direct to starter and one input of the switch. House bank to the other input on the switch. Why was the house load always hot? Then I noticed there were two cables on the starter solenoid, one to the starter battery but where did the other one go? Turns out it was connected to the output terminal of the selector switch, hence the starter battery was always connected to the house load.
Why did someone do that? It's one of those things that you know is wrong, doesn't make sense, yet somebody did that. You try to think of what you are missing here but can't come up with an answer. Disconnected that cable and all was well.
On our current boat there was supposed to be an isolated start battery for the genset, start battery for the engines and house battery. Turns out all three were connected together somewhere. Don't ask how we found out.
The point is, on an older boat trace and document all battery cables. There is no telling what a PO might have done.
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Old 10-02-2016, 05:15 PM   #15
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I would be wondering if both banks are tied together at the alternator.
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Old 10-02-2016, 05:32 PM   #16
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On our current boat there was supposed to be an isolated start battery for the genset, start battery for the engines and house battery. Turns out all three were connected together somewhere.
Wonder if you bought yours from the same guy as I did. Mine had the same arrangement. An earlier PO installed a battery combiner that allows you to (optionally) charge all banks from one source. My PO had jumpered them all together at the combiner terminals so they were always all connected.

Genius. Pure Genius. No more worrying about which bank to select
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Old 10-02-2016, 05:38 PM   #17
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"Be careful of running the engines with the switch OFF in case it isolates the alternator charge and blows a diode. "

YES!, but a properly chosen and wired rotary switch will have a field cut off built in, so fried diodes should not become a problem
Or a make before break selector switch, like my big old Guest.
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Old 10-02-2016, 07:06 PM   #18
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Or a make before break selector switch, like my big old Guest.
The problem with that one is if it gets switched to OFF, you just fried your diode.

To avoid this, I hard-wired my alternators to my batteries with 4AWG (IIRC) and use my switches to control load only. It's a much simpler system for me to manage and is similar to an airplane where the charge and load sides are split and controlled separately. My boat manufacturer saved money, as many do, by using undersized wires on the alternator charge output which is connected to the starter hot cable which carried the charge through the switches to the batteries. (insert head scratch here)

I recabled with my load side with oversize aviation-grade APU cable that was being discarded due to a 1-inch length of broken cable insulation from a cable clamp. This wire is as fine as a redhead's hair and is capable of carrying over 3500A/28V. It should be fine for my lil' boat.
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Old 10-02-2016, 07:16 PM   #19
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The problem with that one is if it gets switched to OFF, you just fried your diode.

To avoid this, I hard-wired my alternators to my batteries with 4AWG (IIRC) and use my switches to control load only.
Come to think of it... I did the same thing when I repowered. Duh.

Also went from a 2 start/2 house batteries to a 1start/3 house battery setup.
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Old 10-02-2016, 08:17 PM   #20
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I suppose It just makes too much sense to wire the alternator output to the battery, which is why more people don't do that.

I recognized this issue years ago and made the switch. It is one of those KISS principles.
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