Dual Battery question...

[Skillet]

I am doing the simple and manual system that Boston Mangler posted a while back.

http://www.yankeetoys.org/mangler/dualbats.htm


My reason for doing this is the pure simplicity of it and I don't mind popping my hood to switch back and forth. (plus it is cheap)

Anyhoo, this may be a stupid question but, what should stay permenently hooked up to the main battery?

I noticed on Manglers hook up schematic, it shows the ECM hooked up to the common fuse block.

Should this be? I am not an electrical ghuru buy any stretch of the imagination so just looking for a little advise on this.

I want to have as many things as possible hooked to the fuse block but do not want to mess up the operation of the vehicle by some goofy blunder.

 

[dfmorse]

All three fuse links need to be connected to the main battery. The "MAIN" fuse link powers the ECU and keeps the memory up.

...

 

[Mike S]

If you are going to use a manual switch, I would first make sure that the switch has the alternator field disconnect feature, which will protect your alternator when switching. The switch should be rated for the maximum combined peak load anticipated.

I would leave everything except the winch connected to the primary battery. I would cable the secondary through the switch to the primary, and leave the switch OFF (no connection) when winching. I would connect the batteries when running in normal use.

This is a bit more trouble than an automatic switching system, but cheaper, and if used properly, effective.

It is better to have two like batteries of the same age, and be sure to ground both to the engine or frame. Use 1/0 welding cable for the positive side, and number two for the grounds, and solder the connections as well as covering the join with marine shrink tubing. Give some thought, also to where you route the connecting cable, since you don't want to rick a break - and resulting probelms from a high amp short. Some people protect the battery to battery connection with a marine type fuse of about 150 to 200 amp rating at the secondary battery.

M

 

[Rich]

All three fuse links need to be connected to the main battery. The "MAIN" fuse link powers the ECU and keeps the memory up.

I don't see any reason why the entire vehicles electircal system can not be switched between either battery, with the requirement that the switch being able to handle the full current for the entire system. There is no loss of connectivity when switching between batteries if one is using a proper dual bank battery switch.

 

[Rich]

I am doing the simple and manual system that Boston Mangler posted a while back....
...what should stay permenently hooked up to the main battery?...

If you want to achieve full redundency between the batteries, I.E. either battery can supply all circuits, and the complete failure of a single battery does not impact the operation of any electrical device, then wire it just like the diagram.

One thing you do want to avoid is switching off both batteries while the engine is running, as doing so can damage the alternator, and possibly other devices due to the large voltage spike that may occur.

The alternator field disconnect, as referenced by Mike, can be used to disable alternator charging, automatically, prior to the batteries both being switched off. Utilizing this would require phyically modifying the voltage regulator, which is internal to the alternator.

 

[Rich]

...Use 1/0 welding cable for the positive side, and number two for the grounds...

Why the recommendation for using different size positive and negative cables? From a practical standpoint the same amperage flows equally through both the positive and negative connections.

 

[Skillet]

Rich,

Do you propose that the alternator cable be completely moved to the fuseblock and both batteries connected from there?

 

[Rich]

Rich,

Do you propose that the alternator cable be completely moved to the fuseblock and both batteries connected from there?

I will share that is how I will wire mine. I published a design, quite some time ago, in the Outfitting forum, that, with respect to feed to all circuits, is set up like that.

There are two major advantages to this approach: 1) Both batteries are fully redundant, 2) The battery switch now enables you to totally disconnect all power to the electrical system. Many engine service jobs start with the instructions "remove battery cable". With this setup, the instructions change to "Turn battery switch off".

The only disadvantage I see is the risk of somebody switching off both batteries with engine running. This may or may not cause a problem, but is definitely to be avoided.

On your part, I suggest that you decide what capabilities you desire from a dual battery system, and then chose a design that delivers those capabilities.

 

[Mike S]

I will share that is how I will wire mine.

Still in planning stages???

The only disadvantage I see is the risk of somebody switching off both batteries with engine running. This may or may not cause a problem, but is definitely to be avoided.

This is why you need a 'make before break' and the alternator field disconnect feature on the switch.

On your part, I suggest that you decide what capabilities you desire from a dual battery system, and then chose a design that delivers those capabilities.

Looks to me like he is running a winch. Good enough reason to have separate batteries for vehicle systems and winch.

M

 

[Rich]

Still in planning stages???...M

Finished planning prior to completing the design I sketched in outfitting. Haven't started executing. Excecution will be trigged by buying a 60 qt Engel fridge or installation of the winch which has been sitting on the shelf for longer than I have owned the cruiser. Of course, installing the winch is dependent on finding a bumper that meets my needs. May need to go custom.

 

[Rich]

...Looks to me like he is running a winch. Good enough reason to have separate batteries for vehicle systems and winch...

If the design enables chosing between running the winch and everything else together, on either individual battery, and on both batteries combined, what is the disadvantage?

Having any circuit (winch, fridge, whatever) dedicated to a single battery means if that battery fails completely, say due to an internal short, then those circuits are down until the battery is replaced.

FYI, my OEM Toyota supplied Panasonic battery failed due to an internal short.

 

[Mike S]

If the design enables chosing between running the winch and everything else together, on either individual battery, and on both batteries combined, what is the disadvantage?

Having any circuit (winch, fridge, whatever) dedicated to a single battery means if that battery fails completely, say due to an internal short, then those circuits are down until the battery is replaced.

FYI, my OEM Toyota supplied Panasonic battery failed due to an internal short.

Good practice not to winch on your starting battery. Unless you are doing really short pulls. The second battery fails, I suggest that you COULD move the winch connections to the other battery...

I am not suggesting that this is the best way to do the wiring - it would be marginally better to have an automatic circuit, power posts, fused (or breakered) cross connections, etc. I think the poster is lookig for simple, functional and inexpensive. He's on the right track.

M

 

[Rich]

With a dual battery such as being discussed, where either battery, by itself, and also both together combined can start the vehicle, either battery by itself can be the starting battery.

With this as a given, I am failing to see what the drawback is in operating the winch connected to a battery that is also connected to the starter.

The operater gets to choose to either run from battery 1, run from battery 2, or run from both. If one battery gets drawn down to insufficient charge to operate winch or anything else, operator gets to choose to switch to the other battery or to combine both. If operater winches with both batteries combined, operator knowningly takes the risk of draining both batteries.

What am I missing?