BATTERY SWITCH

[Sea Wolf]

Dave-

Nice job both ways!

The rewire looks excellent and the automatic combiner (Automatic Current Regulator) sounds like it will really do the job.

Nice modifications with the switch and indicator light, too!



Dave's Rewire Job- Nice!


Joe.

[Minnow]

Just a comment on wiring the auto charging relays. If you digest the wiring diagrams for the Blue Sea and the BEP units, you'll notice that the Blue Sea emergency parellel switch connects the two loads, while the BEP parellel switch connects the two batteries.
Both setups allow you to connect two batteries together, but only the Blue Sea allows you to isolate a dead battery and still power both the start and house loads from the good one.
I can't for the life of me figure out why I would want to connect a good battery to a bad one, other than to charge the dead one.
I have the BEP unit, but have moved the jumpers on the back of it to the Blue Sea way. The other beneficial difference to the Blue Sea unit is that it has a current limiting feature, while the BEP, when connecting to charge a depleted house battery, will cave down the start battery voltage to below the threshold voltage, and cycle on and off until the house battery comes up a bit. The BEP directions suggest that the charging system isn't big enough for the load, but there isn't anything I can do about that.

[Falco]

A tangential comment to Minnow's post (and an earlier one by Sea Wolf. If the isolated starting battery won't work (presumably battery selector switch position #1), you should switch to position #2 (house battery) to start the engine - not "Both" as what will happen immediately is the house battery voltage will cave in to equalize that low voltage of the cranking battery and you may not get enough juice to start the engine - even if you subsequently switch to position #2.

Also, I know the Blue Sea selector switches are make before break and I switch all the time - even at high RPMs. I'd bet the BEPS are too. Another problem with switches which are not "MBB" is they may send power surges to sensitive electronics - not good. Quality components are the key.

Check your engine literature (or a shop manual). At least some outboards (eg, Suzukis) have built-in Alternator Field Disconnects so its almost impossible to fry the alternator diodes.

Finally, although I don't have a Wallace (and so can't comment on its particular power needs), I am not a big fan of having anything connected directly to the battery, even if fused. Instead, everything should come to a central bus with its own switch. This means a human (generally) knows when something is powered on and this prevents Alzhiemeric battery drain.

[dogon dory]

Sorry, Folks - Post Deleted By Author

[Robbi]

All of this informative advice about batteries and wiring systems reminds me of the Far Side cartoon about what a dog hears- blah blah blah Ginger, blah blah Ginger, blah Ginger. This is to say that I wish I new a tiny bit more about electronics. It is just a mess of wires to me. Blah blah blah battery, blah blah blah Alternator Field Disconnects, blah blah "MBB"....Well, not quite. I have done some wiring of new electronics, but by reading this thread I realize that my limited knowledge is probably going to get me into trouble. So, I am going to buy a book that will help me out. Either "The 12-Volt Bible for Boats," or The 12-Volt Doctor's Practical Handbook". Any advice as to which book would be the best for an almost novice?
Thanks to you all for your sharing of imformation. I did look up in my Suzuki owner's manual about an alternator field disconnect and couldn't find anything. When I looked at the wiring diagram page, I had an strong desire to get out my colored pencils and spend an hour coloring between the lines! Robbi

[dogon dory]

Sorry, Folks - Post Deleted By Author

[lloyds]

I think one of those books was written by Nigel Calder, and I used it quite a bit. It has all the basics and a lot of the stuff that is progressively more complex. But either book should be good.

[Robbi]

Thanks for the replies. I think that I will start out with The 12 Volt Bible For Boats.

Robbi

[Falco]

OK, Robbi:

blah blah blahblah, blah blah. (LOL)

It turns out this Blue Seas battery selector switch has AFD (forget about what it means - you need it) built in:

http://www.bluesea.com/product.asp?Product_Id=31165

I just put one on my boat and plan to swap out my other no-doubt-soon-to-fail Guest switch with another. I like it alot. Very compact, solid.

Let us know what you learn from the book...

[Salmon Slayer]

This thread has been very helpful to me and I must confess that I am often mystified over the whole 12 volt wiring scheme.

Here is another basic question that has bugged me and I am sure someone will be able to help me out. I have dual batteries, one on each side of the motor well (I have an 81 Classic) and they are both in battery boxes. The plastic battery boxes dont seem to have much in the way of ventilation but my batteries are always dry even in this wet climate (they are tied down and under a plywood seat I have on either side)..

Should I be worried that they do not have adequate ventilation? I have never had a problem but its one of those nagging things I have never settled in my mind

[barefoot]

Re: battery switching, a unit that looked suspiciously like a Ford starter relay had been added underhood to a mini-motorhome I once owned. The salesman called it a poor man's battery switch. I believe the activating side was wired to the ignition switch (On only, not Starter or Accessory) and the coach battery was on the switched side of the relay. That way, the coach battery was isolated from drawing current from the alternator or starting battery until the engine fired, then both charged as needed, all automatically. My 16 Cruiser will come with just one battery as I have the other, a box, and a relay that I planned to wire as above. What do you think of this apparently elegant system and do you think I understand it correctly?

[Sea Wolf]

Salmon Slayer-

Seems like there's always a new twist to the old ball game!

Traditional wisdom was always to well ventilate any battery charging area because the process also inadvertently liberated some hydrogen and oxygen gases as the battery was charged.

This was a result of the electrolysis of water, which is simply using electricity to split the hydrogen and oxygen atoms apart that are in the H2O water molecule.

Water had to be added to the battery periodically to replace the water that was lost to electrolysis.

The problem was that the gases could explosively recombine if a spark was present.

A few decades later, we notice that most all batteries are sealed and don't ever require the addition of water. This means that there is no water being consumed in electrolysis, no gases being liberated, and no explosion danger.

So if you're using sealed, modern batteriess, there's no danger from the gases, and you can just keep the box pretty much sealed up and everything will be fine.

I'm actually sleeping on the dinette berth over two big group 27 deep cycle batteries in boxes in the storage locker under the front seat in my boat as a result of this change in tecnnology.

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

This is similar to the old dictum of " don't leave the batteries stored on a cold cement floor over the winter because they'll discharge through the bottom of their cases with the humidity from the concrete", etc.

The modern plastic battery cases found on today's batteries eliminated that problem quite a few years ago, too!

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

Now if I could just get a similar technological up date for my aging body.........???

Joe.

[Sea Wolf]

barefoot-

Sounds like you have a good understanding of the system! The device used as a switch is a solenoid relay, like the ones used as the big amperage switch on a starter.

If it's wired as you suggest, the vehicle and coach batteries are linked together whenever the key is "ON", allowing the two batteries to work together to start the vehicle and get charged back up as well.

I've also seen a similar system where the wire that activates the solenoid, closing the switch, was linked to the alternator output.

This second system isolates the vehicle from the coach battery until the alternator begins to put out current, then closes the solenoid to charge the coach battery.

You should be able to tell the difference easily from where the activating (small) wire lead comes. Sounds like you have the first type.

For a boat with an outboard, the alternator output will be connected with the starting cable inside the engine, so the first system would be your easiest (maybe only practical) choice.

You will wind up with a system that parallels your batteries whenever the ignition key is "ON". I'm OK with such a system, just be sure both of your batteries are strong and in equal condition.

It would be possible to insert a switch in the activation wire to turn off this system if, for some reason, you seriously discharged the house battery, so that you could start on just the starting battery alone. I would do this because paralleling the batteries together when one is fully discharged can result in a huge amperage flow from the good one into the weak one, which can boil the electrolyte in the weak one (Old Faithful with battery acid!) and draw down the strong one to where it won't start the engine !

Go ahead and set it up as needed, being sure to use heavy enough battery cables to handle the loads.

Good Luck!

Joe.

[Robbi]

Falco, Thanks for the information on the battery switch by Blue Sea. The 9002E sounds like the switch to get as a replacement. I still have not been able to determine if my Suzuki has a AFD system or not, but I never move the switch while the motor is running, I always shut down first.

Is the typical C-Dory two battery system set up as a true "house" and "starter" type system with one battery meant to be the starter, and the other set up to run the house (electronics etc)or are they really interchangable? Both of my batteries are deep cycle batteries, so I have always assumed that starting on "1" or "2" was ok. Then my husband asked if I shut off my electronics when I started the engine? No. In our airplane, there are two master switches. One is the starter and one is the radio (all of the electronics). You never start the engine with the radio switch on. This is to protect the instuments from electrical surges. So, he got me thinking, am I putting my electronics at risk? I think not, but thought I should ask. Thanks for any information. Robbi

[Salmon Slayer]

Thanks Joe, gives me piece of mind.