BUS Bars and Dual Batteries

[tdonoughue]

Totally agree with @ctyke . The Blue Sea Add-a-Battery kit is one of my favorite upgrades. Turn the single switch on and forget it (until you come off the water and turn that single switch off...).

I looked at the Perko site. I now understand what they did in the 2-engine, 2-battery, 2-switch setup. But I would not want mine set up that way. The presumption they are using is that you have 1 battery for each engine (not a battery for the starters and a battery for the house). So they benefit they are providing there is that they have it wired so that you can start one engine from the other engine's battery (and vise-versa) or pool them together. Very flexible, very complex and does not really meet most of our use cases (where we run for a while, then float and listen to the radio, then want to leave again). If I had a larger fishing boat with twin screws and a separate house system, I might do something like this...

 

[Ronnie]

It took me a while to appreciate the DSR system that came stock in my 240 but once I set it up / did a few mods I realize this is the system to have along with an onboard charger. Adding bus bars really allowed me to clean up the wiring, which I had to do when I added a bunch of amps and 12v/usb ports last off-season. Still after a full day on the water, if I don’t charge the six battery/house battery over night my boat throws low aux power warnings the next day. As a result I keep a spare battery on board when I know I will be staying overnight to boat the next day and I don’t have shore power.
It’s much easier to switch the batteries out with the bus bars since there are only two cables (+ and -) going to each battery.

lol, I just realized the time don’t have a more recent pic, it looks a lot better now.

 

[djtech2k]

Totally agree with @ctyke . The Blue Sea Add-a-Battery kit is one of my favorite upgrades. Turn the single switch on and forget it (until you come off the water and turn that single switch off...).

I looked at the Perko site. I now understand what they did in the 2-engine, 2-battery, 2-switch setup. But I would not want mine set up that way. The presumption they are using is that you have 1 battery for each engine (not a battery for the starters and a battery for the house). So they benefit they are providing there is that they have it wired so that you can start one engine from the other engine's battery (and vise-versa) or pool them together. Very flexible, very complex and does not really meet most of our use cases (where we run for a while, then float and listen to the radio, then want to leave again). If I had a larger fishing boat with twin screws and a separate house system, I might do something like this...

So how does that add a switch thing work? I assume it has one of those relays, I think it’s called ACR or something like that, that charges the battery that needs it most automatically.

Does it isolate the motor vs house battery? I’m just trying to figure out the advantage to that thing vs using perko switch. I mean other than manually flipping the switch when you start vs anchor listening to music.

 

[tdonoughue]

Basically, it avoids you manually flipping the switch.

An ACR is going to detect when there is a charging current and link the batteries together when that charging current is there (e.g. when you are running the engines). Then, when there is no charging current (e.g. when your engines are off), it is going to separate the batteries, so that your house battery powers your stuff and your starting battery is reserved separate for you to start later. The ACR is not going to figure out which battery needs more and flip charging back and forth--it is just going to link everything together when there is charge (now, by physics, the battery with the lowest charge will get the most charging effect when you link everything together, but that is not the ACR's doing).

In truth, you get exactly the same effect if you have one of your Perko switches, wire one battery to A, one battery to B, and then everything up to the other side of the switch. Then when you start, switch to A. When running, switch to Both/All. When you turn off the engines, switch to B. Problem is that unless you mount the switch up at the helm (don't do that--the wiring--ugh), that means you need to run back to the switch at all of those times. I found I frequently forgot and left it on all while I was floating, or started up and forgot to switch it to all (thus charging only 1 battery), etc. The ACR does that automatically.

For a number of years, I also had a trickle charger (a little, cheap but semi-intelligent one). I wired it so that the ACR would detect that (put it on that other side) and link the batteries together. Worked fine. When I upgraded to a two-bank charger, I wired that directly to the batteries. Because the charge is on the other side, the ACR keeps them separate and the two-bank works as intended.

So, you can do the same thing with your existing switches. Just more convenient with an ACR.

 

[djtech2k]

Also how would this acr setup work with a dual battery charger like the noco that I have? I see that the acr relay allows the alternator to charge the battery that needs it, but what about when I want to charge both batteries

Basically, it avoids you manually flipping the switch.

An ACR is going to detect when there is a charging current and link the batteries together when that charging current is there (e.g. when you are running the engines). Then, when there is no charging current (e.g. when your engines are off), it is going to separate the batteries, so that your house battery powers your stuff and your starting battery is reserved separate for you to start later. The ACR is not going to figure out which battery needs more and flip charging back and forth--it is just going to link everything together when there is charge (now, by physics, the battery with the lowest charge will get the most charging effect when you link everything together, but that is not the ACR's doing).

In truth, you get exactly the same effect if you have one of your Perko switches, wire one battery to A, one battery to B, and then everything up to the other side of the switch. Then when you start, switch to A. When running, switch to Both/All. When you turn off the engines, switch to B. Problem is that unless you mount the switch up at the helm (don't do that--the wiring--ugh), that means you need to run back to the switch at all of those times. I found I frequently forgot and left it on all while I was floating, or started up and forgot to switch it to all (thus charging only 1 battery), etc. The ACR does that automatically.

For a number of years, I also had a trickle charger (a little, cheap but semi-intelligent one). I wired it so that the ACR would detect that (put it on that other side) and link the batteries together. Worked fine. When I upgraded to a two-bank charger, I wired that directly to the batteries. Because the charge is on the other side, the ACR keeps them separate and the two-bank works as intended.

So, you can do the same thing with your existing switches. Just more convenient with an ACR.

Thanks that’s very helpful. Could I add an Acr with my perks switch(es)? I want this to be right but I also want it to be simple to use and troubleshoot.

One thing I wonder about is how the acr isolates the starter battery from the house battery. Everything else makes great sense. That part makes me wonder how it does it. I have to admit that this conversation does almost make me want to get one, especially if I can confirm it that it isolates the batteries.

 

[tdonoughue]

That is the difference between getting just the ACR and getting the Add-a-Battery kit. The kit comes with a switch that has on/off/emergency. On turns everything on. Off turns everything off. Emergency hooks the batteries together (overriding the ACR, basically) in case you can't get enough juice from one battery to start.

You could just get an ACR and then wire the Perko's to mimic the switch in the battery kit. For me, I found it easier to just get the kit, where it has all the right sizings and ratings, single switch, labels, etc. And the kit was not that much more than just the ACR. The switch in the kit is basically a single-throw double switch (when you turn from off to on, it shorts two independent sets of poles) with the additional 'emergency' functionality (where it then shorts out all 4 poles). This is not far off of the reverse of what you presently have with your Perkos (except yours are keeping each engine separate, rather than keeping the house and start systems separate).

So, you can do it with what you have, definitely. But I would (and did) do the ACR with the add a battery thingy.

 

[djtech2k]

Thanks a lot. I am getting ready to order bus bars so I may add the kit on to the order.

I wish I knew how the acr isolates the batteries, start vs house, but if you guys can validate that it works that way, then that’s enough for me.

 

[djtech2k]

Btw, would the 120amp version be the right one for my setup?

 

[tdonoughue]

I have the 120A version; I have since learned that the 60A version (65? anyway, the smaller one) would probably have been sufficient for my needs.

The way the ACR works is really pretty simple. Basically, it sits between the battery and the load on one side (start) and the battery and the load on the other side (house), leaving each of those linked together, independently. Then it has a circuit and a relay that detects when there is charge coming from the load side. If it detects that charge, it activates the relay to short between both of those independent sides (allowing that detected charge to flow back to both batteries). When the charge disappears, the relay deenergizes and breaks the connection between the sides and you are back to normal (with the house running from the house battery and the engine start running from the engine battery).

 

[bbollinger]

I also just bought the add a battery kit with the ACR and do not plan on using the bus bar. I am lost because all the diagrams show the bus bar. Can anyone help me with a diagram and how I hook all this up without one?

 

[Ronnie]

@bbollinger , you don’t really need to use bus bars/they are not required but they really to make adding devices easier and cleaner where wiring is concerned. If you decide not to use any just attach all the positive and negative leads from your devices directly to the switch or battery, mostly like the switch and common ground. To determine these points simply follow the leads from the bus bars in the diagrams back to the source powering the bus bar and the ground connection to the negative bus bar.