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House vs Engine Loads / ACR Question

Old 08-28-2014, 01:54 PM
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Default House vs Engine Loads / ACR Question

HI! Long time listener, first time caller, Love the show.

Hey, I have a question and I've tried to search and just can't quite come up with the answer.

I am getting ready to add a second battery, with the Blue Sea ACR and Switch (7650), My only real interest is having the stereo seperated. However, the stereo requires the key to be on, and the key being on.. Well, I assume other things are powered up (ignition coil, etc).

So with that in mind, what do most people do? Run everything at the helm from the house battery? I'd have to get the house battery really low to be too low to switch on the engine electronics, right? I might be overthinking this. (I probably am)

This is on a 1990 Sylvan 209, it's a 350 mercruiser with thunderbolt ignition. I don't have an automatic bilge, boat never stays in the water except an occasional overnighter. No other electronics (depth, fish finder, trolling, etc)
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Old 08-28-2014, 02:12 PM
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Originally Posted by nester View Post
HI! Long time listener, first time caller, Love the show.

Hey, I have a question and I've tried to search and just can't quite come up with the answer.

I am getting ready to add a second battery, with the Blue Sea ACR and Switch (7650), My only real interest is having the stereo seperated. However, the stereo requires the key to be on, and the key being on.. Well, I assume other things are powered up (ignition coil, etc).

So with that in mind, what do most people do? Run everything at the helm from the house battery? I'd have to get the house battery really low to be too low to switch on the engine electronics, right? I might be overthinking this. (I probably am)

This is on a 1990 Sylvan 209, it's a 350 mercruiser with thunderbolt ignition. I don't have an automatic bilge, boat never stays in the water except an occasional overnighter. No other electronics (depth, fish finder, trolling, etc)
These basic concepts helped me;

starter/engine battery powers the ignition switch (and pretty much NOTHING else)

House/stereo battery powers EVERYTHING else. (if you have non-engine systems currently being energized by the key/ignition, REMOVE them from the ignition, and move them over to the house system, COMPLETELY seperate from the ingition.

run two completely seperate systems, each system has its own dedicated battery,

The only connection between these two SEPERATE systems is the ACR. (and a way two parrellel the two batts in an emergency situation, like "both" on a 1/both/2 switch.
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Old 08-28-2014, 02:31 PM
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Originally Posted by Rico2 View Post
These basic concepts helped me;

starter/engine battery powers the ignition switch (and pretty much NOTHING else)

House/stereo battery powers EVERYTHING else. (if you have non-engine systems currently being energized by the key/ignition, REMOVE them from the ignition, and move them over to the house system, COMPLETELY seperate from the ingition.

run two completely seperate systems, each system has its own dedicated battery,

The only connection between these two SEPERATE systems is the ACR. (and a way two parrellel the two batts in an emergency situation, like "both" on a 1/both/2 switch.
I guess that makes sense. Everything else is not connected to the ignition switch. Bilge/Nav Lights/Courtesy Lights/Blower are independent of the key. Only thing that's key on is the radio. I guess wire the radio direct and just turn it off at the battery on/off switch at the end of the day?
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Old 08-28-2014, 03:40 PM
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Originally Posted by nester View Post
I guess that makes sense. Everything else is not connected to the ignition switch. Bilge/Nav Lights/Courtesy Lights/Blower are independent of the key. Only thing that's key on is the radio. I guess wire the radio direct and just turn it off at the battery on/off switch at the end of the day?
Like Rico2's boat, the only device powered by my starting battery is the engine (pre-start, then the engine charges the starting battery). Everything else on my boat is powered from the house battery bank. An ACR connects the two banks when either one is being charged.

You should move the radio feed from the ignition circuit to the house feed circuit. If you want to (and if your radio draws less than ~15A), you can insert a simple (SPST) switch between the radio and the house distribution point. That would allow you to switch the radio off, even if the other house devices are powered. If your radio draws more than 15A and you need to switch it off separately, you may also need a relay.

In any case, your radio should be powered by the house battery.
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Old 08-28-2014, 06:34 PM
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Yeah, the switched wire of the radio only pulls ~1amp. The main lead is 10 amp, but it needs constant power to retain it's settings, clock, etc.

I wanted the radio powered by the house battery, but I like the convience of having it on the key. I guess a toggle is the same as a key. In stead of being worried about leaving the radio on, I could just as easily leave the lights or the bilge running...
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Old 08-28-2014, 08:12 PM
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Originally Posted by nester View Post
Yeah, the switched wire of the radio only pulls ~1amp. The main lead is 10 amp, but it needs constant power to retain it's settings, clock, etc.

I wanted the radio powered by the house battery, but I like the convience of having it on the key. I guess a toggle is the same as a key. In stead of being worried about leaving the radio on, I could just as easily leave the lights or the bilge running...
well if you leave it on, unlike now, the engine will still start... the whole point of having a separated start and house battery.
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Old 08-28-2014, 08:17 PM
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Point taken
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Old 08-29-2014, 06:41 PM
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Spent all day gathering parts. Still don't have everything. For some reason, I had it in my head that main cables to the starter and the block were 4 gauge. So I bought everything 4 gauge, only to realize that they're 2 gauge. Wife left me with the kid tonight, so keeping him alive didn't allow for me to get much done. This is a bummer since I was planning to get out early tomorrow and try to beat the rain.

Guess I'm going to get up real early and try to knock this out before the heat takes over.

I couldn't locally come up with a bus bar for the negative side. I can't imagine that tying the negative posts of the batteries together for weekend would make that big of a deal. Anyone want to chime in on that thought while both my fire extinguishers are still charged?
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Old 08-29-2014, 07:05 PM
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The grounds should all be connected together.........not separate.
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Old 08-29-2014, 07:42 PM
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I get that, running a wire from the neg post of each battery to a bus bar, then all the devices to the bus bar, versus all the devices are connected to the battery terminal now and running a cable from the new battery to the old.. I can't see the difference.

IE:

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Old 08-29-2014, 07:57 PM
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Originally Posted by nester View Post
I get that, running a wire from the neg post of each battery to a bus bar, then all the devices to the bus bar, versus all the devices are connected to the battery terminal now and running a cable from the new battery to the old.. I can't see the difference.

IE:

Well, I guess I don't understand your previous post. Either of your drawings will work, as long as the batteries are tied together.The post that confused me was when you said would tying the batteries together hurt something.
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Old 08-29-2014, 08:38 PM
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Originally Posted by 270Handiman View Post
Well, I guess I don't understand your previous post. Either of your drawings will work, as long as the batteries are tied together.The post that confused me was when you said would tying the batteries together hurt something.
If I confused you, it's because I was confused myself. Blue Sea makes a big deal about using a bus bar, and while I can see the advantages from a structured wiring stand point, and a clean install, etc,etc,etc.. I can't see the technical benefit.

But because my internet persona allows me to ask stupid questions (in real life, the boat would burn to the ground) I thought I would ask other people for their opinions.
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Old 08-29-2014, 10:18 PM
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Originally Posted by nester View Post
Blue Sea makes a big deal about using a bus bar, and while I can see the advantages from a structured wiring stand point, and a clean install, etc,etc,etc.. I can't see the technical benefit.
One technical advantage to a bus bar is that it minimizes the stacking of multiple connectors on battery studs. Stacked connectors can compromise the quality of the electrical connection between the connectors and the stud.

For what it's worth, the ABYC (American Boat & Yacht Council) electrical design standards state "No more than four conductors shall be secured to any one terminal stud." A bus bar typically allows you put only one connector on a stud, maybe two.

One practical advantage of a bus bar is that you only have to disturb one ground connection when you service a battery or a device. With stacked terminals, you disconnect (and reconnect) all the connections every time you service any of them. The bus bar saves service time (cleaning multiple connectors) and increases reliability by disturbing only the connectors that need service.

The cleaner wiring and expandability are just bonuses, in my opinion.
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Old 08-30-2014, 06:30 AM
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Ok, that make sense. I like the over engineered approach, so I will get a bus bar soon.
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