Blue Sea ACR Wiring Question

[DiploStrat]

Do you think the accessory fuse panel should reside in the seat box with the batteries or do you think I should install it next to the stock fuse panel?

Doesn't really matter. I would place the accessory fuse box close to the accessory loads.

What wire gauge/thicknesses should I be using for these various connections?

The main wires from battery to battery should be sized for the maximum output of the alternator. You want the smallest voltage drop you can achieve without breaking the bank on copper. Most of us are happy if we can get the loss down to 0.5v. Courtesy of dwh, here is a handy calculator: http://www.calculator.net/voltage-d...ce=10&distanceunit=feet&amperes=100&x=47&y=13

Am I good with just one MAXI fuse or should I also ad one to the starter battery?

You want a fuse at each end of the cable that runs from battery to battery through the ACR. Remember, this line is live at BOTH ends so it does no good to fuse only one end. Size your fuse to protect your wire. You want the fuse to blow before the wire melts.

 

[dwh]

Winch should be on main battery to draw power from the alternator by the shortest path.


I don't really worry about voltage drop. I just size the wire for the expected load it will have to carry.

If you are using welding cable for the big wire, then use the wire size chart from Lincoln that I posted on the previous page. If you are using pretty much any other wire, I'd just use a standard AWG chart (all over the net).

Figure out the max load the wire will have to carry, and size for that. Fuses are sized to protect whatever the wire is that you use.

Since you already have an 80a fuse - then you'll have to use wire for that circuit that can carry at least 80a.

 

[AndrewP]

There is a mistake in your diagram. You don't want the + cable from the aux battery to the ACR fused with an 80amp Maxi fuse like you show. That needs to be a heavy duty fuse that can protect whatever sized wire you decide on.

The 80 amp Maxi to feed your aux loads sounds about right assuming you are using sufficient sized wiring. Make sure you order a couple of spares since most folks don't carry trail spares of Maxi fuses.

If you use a bus bar for your grounds, you'll need one capable of more than 100 amps. The Blue Sea 250 amp one would be better. And even then a dedicated ground for the Aux battery with the same 2/0 cable would be smart. Or you can ground the aux battery to the post of the engine battery which presumably already has a good ground.

And to repeat, you don't show your + feeds to the ACR being fused. They need to be fused at the battery and ANL fuses work well for this and are fairly standard.

 

[DiploStrat]

I don't really worry about voltage drop. I just size the wire for the expected load it will have to carry.
...
Figure out the max load the wire will have to carry, and size for that.

A properly sized wire will have minimal voltage drop, no? Isn't that one of the definitions of properly sized? Obviously, one definition of undersized would be a wire so small that it melts.

Battery charging speed depends on many things, but one of the more important is that the voltage of the charge source be higher than the voltage of the battery. Once the voltage differential drops low enough, charging effectively ends.

Using a shore charger that will be connected for 24 hours? Charge rate isn't that important. Using your vehicle's alternator and driving for only six hours, it matters a lot. This is why you want to assure that there is as little resistance as possible in the circuit between the two batteries.

 

[dwh]

A properly sized wire will have minimal voltage drop, no?

Generally yes - over the wire lengths in a vehicle.

A properly sized wire will carry the amperage load it is expected to carry. At higher voltages, there is less voltage drop over distance, at lower voltages more voltage drop over distance. It matters when rigging a solar array on a building and dealing with wire lengths like 30', 50', 100'. Same with large boats.

Over short distances - even at a very low voltage (like 12v) - if the wire is sized to carry the expected amperage load, the voltage drop isn't going to make much difference.

 

[dwh]

There is a mistake in your diagram. You don't want the + cable from the aux battery to the ACR fused with an 80amp Maxi fuse like you show.

Good catch. The wire from the ACR should normally go to the aux battery on the other side of that 80a fuse.

Of course, if the alternator is 80a or less, it won't really matter.

 

[Tiktaalik]

Thank you. Can you give recommendations for what type and brand of HD fuse I should get instead of the MAXI? Is this the ANL type that you mention? How many Amps? Should I have one for each battery? Is the bus bar unnecessary? I'm all for simplifying. So as an alternative I could just connect the two grounds of the two batteries assuming the starter battery already has a good ground? I have a 100A alternator that I plan to install at the same time. Does this affect any of what I'm doing here? Thanks!

There is a mistake in your diagram. You don't want the + cable from the aux battery to the ACR fused with an 80amp Maxi fuse like you show. That needs to be a heavy duty fuse that can protect whatever sized wire you decide on.

The 80 amp Maxi to feed your aux loads sounds about right assuming you are using sufficient sized wiring. Make sure you order a couple of spares since most folks don't carry trail spares of Maxi fuses.

If you use a bus bar for your grounds, you'll need one capable of more than 100 amps. The Blue Sea 250 amp one would be better. And even then a dedicated ground for the Aux battery with the same 2/0 cable would be smart. Or you can ground the aux battery to the post of the engine battery which presumably already has a good ground.

And to repeat, you don't show your + feeds to the ACR being fused. They need to be fused at the battery and ANL fuses work well for this and are fairly standard.

 

[AndrewP]

Of course, if the alternator is 80a or less, it won't really matter.

Actually it will. In any combined high current situation, that 80 amp fuse will blow as soon as the current exceeds 80 amps.

The way I see it, the Maxi Fuse could feed the aux panel. That's a good way to do that.

But the big lead from the battery to the ACR needs to be much higher capacity. I'm sitting in an airport and not looking at a chart right now, but seat of the pants, assuming 1/0 cable, I would think the battery to ACR cable would need to be fused around 200 amps.

I like the Blue Sea ANL fuse holders, but there are less expensive ones available. ANL fuses are available everywhere, often associated with car audio. Amazon is a good source too. They are not that expensive. There is another style of fuse that would work too called MEGA fuses. Use what you can easily get and install.

 

[dwh]

Actually it will. In any combined high current situation, that 80 amp fuse will blow as soon as the current exceeds 80 amps.

Fuses don't blow quickly - they have to hit a certain overload point for a certain time before they blow. According to Blue Sea, their 80a ANL will blow instantly at 194a, and the average blow point would be 155a for 500 seconds.

https://www.bluesea.com/support/articles/Circuit_Protection/95/Choosing_Circuit_Protection


The only high current situation would be winching or jump starting. Winching could potentially blow the fuse, but it's unlikely with most of the current coming from a cranking battery (flows more amps faster than a deep cycle) plus the alternator.

Jump starting might blow the fuse, but it's also unlikely as A) the starter probably doesn't actually draw as much as most would imagine, and B) probably won't run long enough to blow the fuse.

Still, you are correct, to be proper, the fuse(s) between the batteries should be bigger.

But the big lead from the battery to the ACR needs to be much higher capacity. I'm sitting in an airport and not looking at a chart right now, but seat of the pants, assuming 1/0 cable, I would think the battery to ACR cable would need to be fused around 200 amps.

I like the Blue Sea ANL fuse holders, but there are less expensive ones available. ANL fuses are available everywhere, often associated with car audio. Amazon is a good source too. They are not that expensive. There is another style of fuse that would work too called MEGA fuses. Use what you can easily get and install.

George point out VTE Warehouse in his posts. I took a quick look, but didn't check prices:

https://www.vtewarehouse.com/content/electromech/fuse/fuse.php

 

[Tiktaalik]

Ok. Thanks! An ANL fuse it is. Should I just get rid (replace) of the MAXI fuse? Would you also recommend an ANL fuse between the starter battery and the ACR? It would make sense to keep them all the same, wouldn't it (for spares, backup)? I'm a little confused by my own diagram. You're saying that I need a 200AMP ANL fuse between the + on the Aux Battery and the CL. Understood. The way I have drawn it though is that the + cable to the aux fuse box would also end up being fused. Is this correct? Is there another way to do it? If I would like to eliminated the bus bar for the grounds I would just keep the starter battery ground, connect the grounds between the batteries and run a cable to the ground cable on the ACR, right?

Last question. How do you deal with cable management when you have several (2-3) cables going to the + terminal? I'm asking because I'd like to install quick disconnects (see attached) on both batteries in order to quickly disconnect and remove them. How could I have 2-3 cables connect to one of these Quick Disconnect connectors? If I eliminate the ground bus bar perhaps I could have a bus bar for each battery? Is that overly complicated? The current install I have (done by PO) is a mess and has several cables connecting to the battery. I'd like to have one if that is realistic. Thanks again for your patience with all my questions.

 

[dwh]

Move the winch to the starter battery.
Move the wire that runs from the ACR to the aux battery, to the aux battery + post (ahead of the Maxi fuse).
Put a fuse in the wire from each battery to ACR (at each battery's +).

Instead of bus bars, you could just use a power post and stack all the wires on a single post:

http://www.amazon.com/Positive-Insulated-Battery-Power-Junction/dp/B00784HYI2

 

[DiploStrat]

These are a handy way to fuse; you can't get much closer! https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A Simply install the fuse of the size you need.

 

[AndrewP]

Move the winch to the starter battery.
Move the wire that runs from the ACR to the aux battery, to the aux battery + post (ahead of the Maxi fuse).
Put a fuse in the wire from each battery to ACR (at each battery's +).

I totally agree. separate the ACR feed from the Aux panel feed.

 

[James86004]

There is a lot of good information in this thread, I am glad I used the search function. I have a question about setting up my ACR which I didn't see covered. The generalized cartoon Blue Sea uses to show how to set it up looks like this:



The geometry of my engine bay is that the alternator is across from the starting battery, but right next to the house battery. I was wondering if there were any issues with wiring the house battery through the ACR directly to the alternator, and also leave the connection between the alternator and starting battery? Like this:

 

[DiploStrat]

Unless dwh jumps on me on some point I missed, both of your diagrams are the same electrically. (Assuming that Battery 2 is, in all cases, the camper/house/domestic battery.)

Be careful about changing your alternator to starter battery, but that said, you may want to consider this: http://www.smartgauge.co.uk/alt_how.html
N.B. If this is not completely clear to you, you may want to make sure that you are working with a competent auto electrician.