How to wire a "two batteries with switch" setup

[Sculpin]

I just had the Bluesea add a battery system installed this summer with the automatic charging relay switch. Works like a hot damn and I am very pleased with it.

 

[Charlie]

Wow. It seems you are really determined to prove me wrong on this one.

Not really!

It appears you know (as well as I), we are saying the same thing. You are focusing on the "charge." I am focusing on the "discharge"!

I am actually tired of towing people in due to nothing more than dead batteries. Most are due to leaving that switch in the "both" position. Some people just really don't understand. One particular week I towed a friend in three times and finally asked why he kept running in the "both" position. Ready for this answer? He had wired his two downriggers directly to his separate batteries. When he ran on one battery, the other battery kept running down to the point the downrigger would quit working. So, when that happened he figured he needed to switch to "both" position to keep using both downriggers. End result - two batteries without enough charge to start his main.

If one run a battery switch in the both position - here is what WILL eventually happen. One day:
1) Engine will be started by the using the start battery.
2) Battery switch will be put in "both" while running out to fishing area.
3) Individual will continually forget to switch battery to isolate one of the batteries.
4) Will fish all day on kicker. (which is only supplying 6 AMPS @ WOT - to two batteries).
5) Will be fishing an area with no shore power.

After many times of doing this at the end of one of those days that starting batter (not designed for multible discharges):
6) The individual will be a few miles offshore and goes to start main engine.
7) Switch is found in "both" position as individual once again forget to switch it.
8) Both batteries found discharged to the point neither will start main (which by this time the "starting" battery has gone bad) and the deep cycle has equalized to it's level - dead.
9) Individual now learns just how long it really takes for a deep cycle battery to absorb enough charge (at LESS than 6 AMPS an hour) to start the main engine.

It takes a loooong time to run in using that kicker with an outgoing 3 KT tide!

For the average boater who will forget to switch those batteries around and like to run in that "both" position - Do us all a favor just go ahead and buy a 'Bluesea add a battery system'. It actually will and is designed to charge both batteries at the same time!
http://bluesea.com/viewresource/93

 

[TenMile]

I just had the Bluesea add a battery system installed this summer with the automatic charging relay switch. Works like a hot damn and I am very pleased with it.

Installed one on my last boat, and put one in this summer on my new boat. Would never go without one again.

From Blue Sea:

What is an ACR, and how does it work?

What is an ACR? An ACR parallels (combines) batteries during charging, and isolates them when charging has stopped and after battery voltage has fallen. An ACR is intended to keep a load from discharging both of the batteries.
How does an ACR work? An ACR senses when the voltage of either of the batteries rises to a level indicating that a charge source is active (13.0V for 2 minutes). The ACR′s contacts then connect and the ACR applies the charge to both batteries. If the voltage on both of the batteries subsequently drops to 12.75V for 30 seconds, the ACR will disconnect, isolating the batteries.
Why do I need an ACR? An ACR allows two battery banks to be connected so that they can share the output of a single charge source, allowing the user to charge more battery banks than the number of charging outputs. For example, an ACR can be used with a single-output charger, resulting in a simpler system at lower cost than a dual-output charger.
How many ACRs do I need? To combine two battery banks, one ACR is needed; to combine three battery banks, two ACRs are required.
What are some features of ACRs?

What does “Dual Sensing” mean? A dual-sensing ACR will sense an active charge source on one or both batteries and not solely on a designated battery. The ACR will operate if the measured voltage on either of the terminals is of a level to initiate a connection or disconnection.
How does an ACR differ from a battery isolator? Battery isolators use one-way electrical check valves called diodes that allow current to flow to, but not from, the battery. ACRs use a relay combined with a circuit that senses when a charging source is being applied to either battery. ACRs are more efficient than battery isolators because they create little heat and consume minimal charging energy.
Will an ACR manage the charge of my individual battery banks? An ACR does not direct the charge to the battery that “needs it the most” or has the lowest terminal voltage. If there is a charge present on either battery, indicated by a high enough voltage, the ACR will combine the batteries. To read more about this subject click here to download the ADD-A-BATTERY Sales Sheet (1000kb - PDF file).
What Charge Sources will an ACR work with? An ACR will work with all charge sources, including an alternator, AC charger, or solar panel. However, low current charge sources might not produce the voltage rise required to force the ACR to combine.
What else do I need to know about my ACR?

What are the minimum number of connections I need to make my ACR work? Three: One wire to each battery, and one for a ground (GND) connection. For safety reasons, remember to disconnect the negative battery connections before beginning any ACR installation. See this article for more information on selecting the right fuses for Blue Sea Systems ACRs: See Selecting the Appropriate Fuse Rating When Installing the 120A SI ACR
What does “Undervoltage Lockout” mean? As a safety feature, some ACRs prevent combining into a severely discharged battery. A dual-sensing ACR will monitor the voltage on both batteries and will not connect if either battery is below the undervoltage lockout level. Use caution when combining into a battery with extremely low voltage, because this might represent a faulty battery or a problem elsewhere in the system.
Why doesn't my ACR automatically combine every time my engine is running? For an ACR to automatically combine the batteries, voltage and time thresholds must be reached. Although these numbers vary somewhat from one ACR product to another, if ACR terminal voltage is greater than 13.0V for 2 minutes, the ACR should combine.
Why didn't the ACR disconnect when my engine was turned off? The ACR will not disconnect until the low voltage threshold is reached to isolate the circuit. It may take several minutes for the voltage of the batteries to drop to this level. Since the ACR incorporates a delay, additional time (up to 2 minutes) is required before the ACR disconnects.
Where can I get more troubleshooting information? For specific troubleshooting help with SI-Series PN 7610 and ML-Series PNs 7620, 7621, 7622, and 7623 ACRs, click on the following links: SI-Series ACR Diagnostic Flowchart or ML-Series ACR Diagnostic Flowchart. For more information on specific ACR applications, please visit www.bluesea.com/resources and navigate to Application Briefs and Technical Briefs.

 

[Striker]

I use the on-board Pro-sport dual 'smart' charging system to charge and maintain my 'Start' battery and my deep cycle 'house' battery. I am an electrician and know never to parallel these batteries as they will never be at the same level. I use a 'off-1-2-Both' switch to choose which battery to use to start the motor. The motor circuit is wired to the common on the switch. The house load circuit panel is wired directly to the 'house' battery. Under normal operation the switch is set to 1 and the motor charges only the start battery. The house battery never sees the motor. If for some reason my 'start' battery were to fail, I would set the switch to 2 and start off the 'house' battery. I can't imagine a scenario where I would set the switch to both.
Back at home I set the switch to off and plug in the charger. It takes care of the batteries automatically starting with the 'start' battery. I leave this plugged in at all times and have had no issues.

Joe

 

[staying alive]

two batteries and wiring

very good thread ,made me realize i have been doing it wrong all these years and going through batteries unneceessarily.
I have a nice new Bluesea ACR that I want to install, but looking at my wiring I can see I need to re-do most of it and clean it up.-- I have a new used boat that I have had for 8 months (94 Crestliner 2360 Eagle ).It has quite a few things wired direct to battery, I can understand about having bilge pump wired direct but all the other stuff I want to put to a fused panel? or distribution panel?. What about downriggers are they supposed to be wired direct? Under the console It's a mess also with glass fuses ect.
So where can I get some info on how to accomplish this task-I can do the work I just need to be steered in the right direction ----something to do over winter

thanks

Staying Alive

 

[FishBear]

Great info everyone. Thank you for all the thought provoking discussion.

I am leaning towards the "one starter batt and one deep cycle batt with switch" configuration where the engines are wired into the startet batt and the electronics are wired into the deep cycle batt. I believe that a fully charged deep cycle should power the light load electronics for several days... and the deep cycle can be charged via the engines, with switch, if necessary.

But what about the downriggers? I presume these are wired into the starter battery since this is where the engines will be sending their charge to most the time... YES?

Thanks again.

 

[TenMile]

But what about the downriggers? I presume these are wired into the starter battery since this is where the engines will be sending their charge to most the time... YES?

Not usually. Typical configuration is to also wire them to the house battery system. When trolling, you'd switch your selector over to house to allow your engine to charge the house system while you are fishing.

 

[Charlie]

The only thing on your battery should be one large cable going to the battery selector switch and depending on what and how it is installed the bilge pump. Remember, if the bildge pump is connected to one battery it will stop working when that battery is drained. You can add distribution panel, terminal block, and/or busbar. Or all the above, depending on how much you want to spend!

You want EVERYTHING (with maybe the exception of a bilge pump) running off the battery selected. That way what AMPS being used at least has a chance of being put back in the battery it came from. If everything is wired to one battery, that battery should be the one used. They other should only be used as a back up or starting. Then switched to the one that has everthing wired to it. I would recommend getting rid of that mess! DC Main Power Distribution from Battery Management Panels
http://www.jamestowndistributors.co...r+Distribution+from+Battery+Management+Panels

A starting battery is just that, it has thinner plates and is not designed to be discharged deeply. It is designed to produce those starting AMPS. They are designed to provide those starting AMP then have the charging system (not battery) run the system. How many AMPS do you really think is being used in that 30 second start cycle? Not many, and it is quickly replaced. The problem with starting batteries is trolling with them. Slowly discharging them and if they are allowed to be discharged for any length of time, which they are not designed for that - they will end up with a shorter lifespan and - dead!

Many marine "starting batteries" have heavier plates; however, they are still not classified as "deep cycle".

Deep cycle have heavier plates and are designed for that deep cycle discharge. A deep cycle battery life is more determined by how many times it has been "deeply" discharged, not years. A good deep cycyle battery kept charged and not allowed to be fully discharged (down to 20%) will outlast a automobile and marine starting battery by YEARS! Here is a tip for longer battery life! If you do a lot of trolling and have system using more AMPS than your charging system (think kicker here) can supply - You might want to replace those "starting batteries" with "deep cycle," you can buy "deep cycle" batteries that provide the required starting amps for all marine engines.