First 36.7 and battery wiring problem

[jarcher]

Hi Owners...

I'm adding an LFP battery bank to my First 36.7, and it will replace a FLA battery. Because the start battery will be AGM I want to isolate the batteries.

I learned that on this boat, there is a single positive bus. There are three battery switches, one black for the common negative ground and two red ones, one for each of two batteries. The battery switches are actually connected together, so turning either battery on causes that battery to do everything (house and engine start). It's more like a BATT1, BATT2, BOTH switch.

I separated the switches by removing the jumper and discovered that, to start the engine, I now have to have both switches on. If either switch is on, the engine panel is completely dead. Pressing the start button does nothing. I never even hear the solenoid.

After I start the engine I do see alternator voltage on just one battery, which is good.

So my question is, how is the engine panel control wired and what do I have to do so that it can be powered from the start battery alone?

 

[Ron20324]

Silly question, but do you have the owners manual with wiring diagram? I added a 3rd batt to my B323 and a third main switch so each batt has a red switch. I took out the black/grd switch. I strapped a large cable across the three "load" sides of the switches, so that has become my pos buss. Everything that makes or uses electricity is wired to this buss in one way or another. This way, whichever of the three batts is on, that buss supplies all onboard funchtion. Shore battery charger is wired directly to the batts. The solar/alternator/starter/windlass/inverter/brkr panel are all wired to this + buss. All switches off, and nothing works except the "always on" feeds(radio, bilge). I do not think it is wise to feed part of the boat from one battery, the rest of the boat from a different battery.

 

[Jackdaw]

This is a very common mod on the 367, and indeed on most modern Benes. Normally if you remove just the jumper, BAT1 becomes STARTER and BAT2 becomes HOUSE. If it will not start with just BAT1 on, something strange is going on. Like your engine panel being wired to the house?

Note that the switch on the picture is backward because it show it looking aft and the schematic is looking forward.

 

[Maine Sail]

If your vessel is wired like many Bene's, including most 36.7's we;ve worked on, you don't likely have "HOUSE" and "START" you simply have two battery banks that are in parallel when both switches are set to ON. Leave both switches set to ON, discharge too far, and you're dead in the water. We have a number of Bene & Jenneau customers who've learned this the hard way.

Unfortunately many, but not all Beneteau's, have a bussed switch system where by HOUSE and START switches are permanently bused (hard wired) together on the load side of the switches. Any time both red switches are turned ON both battery banks are in parallel. Many owners are unaware of this wiring scenario and incorrectly assume they have "isolated" HOUSE & START banks.. If your boat has this wiring it is best to correct this issue.

When you pull the jumper you'll need to make sure house loads stay on the house switch and the engine remains with the start switch.

Below is what this wiring typically looks like. The issues are listed on the drawing, if your boat has this wiring scenario. Link to full size image if needed: http://www.pbase.com/mainecruising/i...1/original.jpg

The diagram below (drawn for a customer) corrects for the Beneteau bused switch system and adds alternator to house bank wiring plus an emergency parallel (the old negative switch), dedicated & isolated start and house banks, full isolation of each bank and full cross over and an ACR etc...

 

[MikeHoncho]

An amazing amount of information. This is why this forum is so valuable. Nice work Maine Sail.!

 

[jarcher]

Silly question, but do you have the owners manual with wiring diagram?

Yes, I reviewed the wiring diagram in the manual and it was not helpful. Not enough detail about the starter circuit.

... Everything that makes or uses electricity is wired to this buss in one way or another. This way, whichever of the three batts is on, that buss supplies all onboard funchtion. Shore battery charger is wired directly to the batts...\

Right, this is exactly what I'm trying not to do. I want a battery bank for starting, and a battery bank for house, and the two need to be isolated.

 

[jarcher]

This is a very common mod on the 367, and indeed on most modern Benes. Normally if you remove just the jumper, BAT1 becomes STARTER and BAT2 becomes HOUSE. If it will not start with just BAT1 on, something strange is going on. Like your engine panel being wired to the house?

Yes I removed the jumper, exactly. The engine panel does appear to be wired on the "house" circuit but if so it is not at the battery switches. But, the problem seems to be be more than that. I would expect that even with the engine panel not powered the blower and tach and such would not work, but the solenoid would. Apparently I need to move the entire engine panel from the house battery to the start battery.

As far as I know the wiring is still original so I was hoping someone can confirm that this is indeed how the factory wired it and hopefully tell me where the engine panel is wired and the easiest / best way to move it to the start battery.

 

[jarcher]

If your vessel is wired like many Bene's, including most 36.7's we;ve worked on, you don't likely have "HOUSE" and "START" you simply have two battery banks that are in parallel when both switches are set to ON. Leave both switches set to ON, discharge too far, and you're dead in the water. We have a number of Bene & Jenneau customers who've learned this the hard way.

Right, a terrible system and I'm surprised it came out of the factory this way.

When you pull the jumper you'll need to make sure house loads stay on the house switch and the engine remains with the start switch.

Right, hence my original question. Have you ever seen how the engine control panel is wired in a 36.7? Mine is a 2004. I can see that the power for the engine panel does not come to the battery area, I assume it must come to the breaker panel. I have not had any luck locating it yet.

I like the idea of using the neg switch (which currently does nothing) as an emergency jumper, I may do that. I may not, since uninformed crew members may someday decide to fiddle with it. My plan is to have an LFP bank for house and an AGM batt for start, and jumping them together for any length of time would be bad.

My plan is in the attached file.

Thanks to everyone who replied!

 

[Maine Sail]

Most every marine engine ever shipped has its gauge panel power essentially pulled from the starter post. This allows builders to drop the engine in, plug in the panel to the engine harness, connect the 12V positive to the starter lug, and it works.

If you're considering an LFP build then figuring out where engine gauge power is coming from should be a rather easy task. I've not yet seen a Bene or Jeanneau that had the engine panel power wired differently? Perhaps you just blew a fuse when messing with it. The back side of those switches is a horrid mess and it could easily happen...

There is also nothing wrong with an "emergency" cross connect switch. If concerned, then simply install an ON/OFF battery switch close to the LFP bank to allow the use of the start battery as a "reserve" bank. We run a Firefly as our reserve bank and do everything off the LFP but your chosen contactors are too small for that.......

 

[Jackdaw]

I think Maine might be onto something with the blown fuse. Our 2006 model worked as described above without any addition changes.

 

[jarcher]

I think Maine might be onto something with the blown fuse. Our 2006 model worked as described above without any addition changes.

I will certainly check, but everything works fine if I turn the house bank on along with the starter battery. Unless both switches are on, nothing works. Not even the blower. It's strange. This is after I removed the jumper across the two switches.

 

[Jackdaw]

I will certainly check, but everything works fine if I turn the house bank on along with the starter battery. Unless both switches are on, nothing works. Not even the blower. It's strange. This is after I removed the jumper across the two switches.

I agree... with further refection I can't see how a blown fuse would effect only one of the situations. Here is a pic of the area on the 367 with the jumper removed. One of the smaller red wires might be the panel wire (which IIRC is code) attached here instead of at the battery. Is one not on?

But it is strange. The fault would imply that the panel wire was powered by one switch behind a relay energized by the other.

 

[jarcher]

But it is strange. The fault would imply that the panel wire was powered by one switch behind a relay energized by the other.

Hm, I had not thought of that. Maybe they did that as some kind of safety, but are you telling me that it didn't come from the factory this way?

Looking at your picture, you have two red wired with inline fuses I don't have. The small red wires with white fuses, I'm pretty sure, are for the voltage meter on the breaker panel. You then have two other red wires with black inline fuses, I don't have those. I attached a pic of my switches. The orange wire with the fuse was added by me, it's for my auto pilot RAM.
Sorry for not posting the image inline, I can't figure out how...