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Author Topic:   Triple Battery Set-up
Sarge posted 07-12-2010 09:31 PM ET (US)   Profile for Sarge   Send Email to Sarge  
I use three batteries on my Outrage 18 with a single Suzuki 175-HP outboard (at elevation 6,772-feet, so it's more like a 130-HP). I've read enough to understand the problem of dual batteries--basically the weaker battery will draw on the better battery until equilibrium is reached. All three of my batteries are identical Blue Top Optima, but that doesn't mean they'll all age the same.

The original advice given to me by the dealer was to use one as a starting battery, and the other two to run electronics, which consist of:

--1,000 watt Alpine stereo, plus Sirius, iPod, etc
--Garmin GPSMAP and SONAR
--Garmin transducer, speed, temp
--two Suzuki multi-gauges
--Bennet trim tabs
-- running lights
--12v charger for phones and porta-fridge
--Icom VHF radio

The boat is buoyed too, so I may install a 20-Watt solar charger integrated with the boat cover in case driving it on the weekends doesn't keep things charged.

The problem is I can't quite sort out the best way to manage the three batteries. My thought is to bifurcate the circuit between the single starter battery and the dual electronics batteries, and then separately bifurcate the dual electronics' batteries.

Is that the best way to go? What is the best equipment, and how should it be wired?

Then there's the solar charger wiring too. Just leave the batteries in the ALL position and let it charge all at once? This would seem to be problematic if the batteries aren't equal, i.e., it might just be draining the other batteries and the charger by dumping everything into a vacuum if one battery is less perfect.

Advice from the cognoscenti?



1986 Outrage 18, Suzuki 175DF

jimh posted 07-12-2010 10:26 PM ET (US)     Profile for jimh  Send Email to jimh     
Use two batteries in conjunction with an OFF-1-BOTH-2 battery switch to be the cranking batteries for the outboard. These batteries will be charged by the outboard. Use the manual switch selection to manage battery use and charging.

Use the third battery as a completely isolated primary power source for all the electronics. The third battery will need charging current. There are three solutions for finding a source of charing current for this isolated house or electronics battery:

--fit the outboard motor with an auxiliary charging output, if possible;

--use an automatic combiner relay to steal charging current from the cranking battery when it is at a full-charge state; or,

--use a 12-volt to 12-volt convertor to create an isolated new charging output from the motor's charging output.

Some outboard motor charging circuits have provisions for providing an auxiliary charging output which can be used to charge a second, isolated battery, without having to wire that battery in parallel with the outboard motor's cranking battery. If your motor can be fitted with this accessory, it is a very good solution.

Or, fit an automatic charging relay to provide charging current to the house battery when the cranking battery is fully charged. This is a workable solution, but it adds some complexity to the vessel wiring.

Or, locate a 12-volt-to-12-volt charging convertor so that you can charge the house battery from the outboard with a separate charing output. This avoids ever putting the house and cranking batteries in parallel.

Sarge posted 07-13-2010 12:36 AM ET (US)     Profile for Sarge  Send Email to Sarge     
Thanks Jim, I'm going to check on the charge options for the SUZUKI 175 and will go from there. Pending the cost/complexity, the relay route sounds like a good idea.
jimh posted 07-14-2010 08:05 AM ET (US)     Profile for jimh  Send Email to jimh     

Here is another method of wiring three batteries to two loads. I refer to the batteries as A-B-C, and the loads as OUTBOARD and HOUSE. The only source of charging current is the OUTBOARD. There are two battery switches, S1 and S2. They are the usual OFF-1-BOTH-2 switches. All the negative terminals of the batteries are wired in common, but for clarity I do not show that in the sketch below:

Dwg: Three batteries connected to two dual-battery selector switches

Battery B can be connected to either the OUTBOARD or the HOUSE as an isolated battery, that is, without paralleling it with battery A or C. Battery A can also be isolated and connected to the OUTBOARD. Battery C can be isolated and connected to the HOUSE. For charging, we can charge one-at-a-time Battery A or Battery B from the OUTBOARD. To charge Battery C we must charge it in parallel with Battery B.

To manage all of this requires careful setting of the two battery switches, S1 and S2. There are many possible combinations of settings, which produce many resulting arrangements of batteries and loads being combined. This sounds good, but I tend to think of this system as being weak for just this reason--too much complexity. The operator has to keep a clear head and manage all the switch settings. With complicated settings possible, the opportunity to make a mistake is also present.

jimh posted 07-14-2010 09:32 AM ET (US)     Profile for jimh  Send Email to jimh     
A sample of the many combinations possible:

S1 set to 1
Battery A is connected to the OUTBOARD. S2 can be set as follows:

1 = Battery C to HOUSE; Battery B not connected
2 = Battery B to HOUSE; Battery C not connected
BOTH = Battery B and C are in parallel to HOUSE

The OUTBOARD runs from and charges Battery A. The HOUSE runs from either Battery B or Battery C or both, and there is no charging to either of them.

S1 set to 2
Battery B is connected to the OUTBOARD. S2 can be set as follows:

1 = Battery C to HOUSE; Battery A not connected
2 = Battery B to HOUSE (in parallel with OUTBOARD); Battery A not connected
BOTH = Battery B and C are in parallel and connected to both OUTBOARD and HOUSE, and are charging; Battery A not connected.

S1 set to BOTH
Battery A and Battery B are connected to the OUTBOARD and are being charged. S2 can set as follow:

1=Battery C to HOUSE; not being charged
2=Battery A and Battery B are in parallel and connected to both OUTBOARD and HOUSE, and are charging; Battery C not connected
BOTH=Battery A and Battery B and Battery C are in parallel and connected to both OUTBOARD and HOUSE, and are charging.

Sarge posted 07-14-2010 09:44 AM ET (US)     Profile for Sarge  Send Email to Sarge     
I thought I posted this, but maybe I misplaced my post b/c I don't see it above...

Here's an interesting bit I learned about the Suzuki DF150/175 motors: They have an integrated battery isolator for isolating 'starting' and 'house' batteries.

I'm still going through what you've said above, but wanted to make sure and mention the Suzuki isolator. (The engine has a 40 AMP alternator, FYI)...

Sarge posted 07-14-2010 10:15 AM ET (US)     Profile for Sarge  Send Email to Sarge     
From what I understand, the Suzuki Outboard isolation system charges the outboard battery first, and then charges the house battery.

So if I want a single 'engine starter' battery and a dual house battery setup (mainly with consideration for the 1,000 watt stereo and 600 watt transducer) then I can use the Suzuki isolator relay in conjunction with a voltage sensitive relay that will charge the batteries according to their charge level.

However, I'm not clear as to whether you can still run those batteries in parallel while using the relay to select which to charge; otherwise that relay achieves nothing if you're running the two house batteries in parallel.

If you can use the relay to selectively charge the parallel house batteries, I'd also use the 'dual sense' version of the above BEP Marine Relay and wire solar charging as the secondary charge source, with a 20W solar charge panel on the boat cover to keep the batteries up for bilge pump operation (and ready/full charge availability when going to use the boat).

The boat is on a buoy in Jackson Lake in Teton National Park, so without solar, the only time the batteries would get charged is when the engine is running, and I'd want the automatic bilge pump available while it's sitting there during the week.

The secondary question is whether I can 'daisy chain' two of those dual sensing voltage sensitive relays so that the start battery can be charged by the solar once the house batteries are full. I.E. FIRST charge one or the other parallel 'house' batteries, and SECONDLY charge the engine start battery.


I also have a 1/2/BOTH/OFF switch under the center console that would allow the engine to start from either the house or engine batteries. Under normal circumstances I'd leave this set to '1' for engine starting, keeping the house bank isolated.


hauptjm posted 07-14-2010 05:20 PM ET (US)     Profile for hauptjm    
Since, I am a strong advocate of having two batteries for the motor and knowing you have a large draw required for the house, it almost sounds like you need 4 batteries.

I don't have the need for a large house charge, but my setup is as follows:

--two batteries for outboard, controlled by a OFF-1-BOTH-2 switch. Engine is started on both, then immediately switched to 1 or 2 on rotation. This allows for one battery to receive all the charge from the alternator and remain fresh. Next time out, the other battery is chosen to be dedicated. I find this method allows me to always have one fresh battery at my disposal.

--one battery for house, wired to an onboard charger that is plugged to AC current at dock or trailer. This maintains the house battery to operate, GPS, depthfinder and stereo and occasionaly running lights: sometimes all at once, and never has been run down to a point of inoperation on any device. Sometimes used for two full days without additional charge.

Since you are on the hook, the onboard a/c charger is out, but perhaps the solar charger could be dedicated to this function. Separating the alternator from the house battery (or batteries) gives you full attention to starting and operating batteries. On a larger vessel, house batteries are a more important function of the vessel and utilizing onboard charging (alternator/generator) is more of a concern.

hauptjm posted 07-14-2010 05:27 PM ET (US)     Profile for hauptjm    

After looking at your electrical components again, you have way more than the average Outrage 18. The stereo and fridge being the largest consumers on your list. What are your experiences so far with the draw and life of your batteries at this point?

jimh posted 07-14-2010 08:05 PM ET (US)     Profile for jimh  Send Email to jimh     
Sarge--If your Suzuki outboard motor has a split alternator charging output that provides a second isolated charging output, you have the best solution.

Use an OFF-1-BOTH-2 switch to connect two batteries to the outboard. The third battery is connected to the HOUSE loads and charged with the auxiliary charging output connected directly to it.

hauptjm posted 07-14-2010 10:31 PM ET (US)     Profile for hauptjm

according to this flyer from Suzuki, your alternator is separated into two charging circuits. However, it seems to function as an isolator that allow for the charging of two batteries vs. two complete circuits. I'm not sure if there is enough "juice" for what you're contemplating.

jimh posted 07-14-2010 11:23 PM ET (US)     Profile for jimh  Send Email to jimh     
With a large outboard motor, the most important function of the batteries on the boat is to get the outboard motor started. That is why I keep suggesting you dedicate two batteries to the outboard motor.
Sarge posted 07-15-2010 12:14 AM ET (US)     Profile for Sarge  Send Email to Sarge     
Thanks guys. A few more thoughts/clarifications:

The primary 'house' draws are:

- the 1000 watt stereo (Alpine amps are supposed to be relatively low draw, very efficient, particularly at normal volumes)

- the 600 watt trasducer

- Garmin 521 (5" screen uses much juice? not sure)

There is no fridge (use a Yeti cooler). The rest of the electronics are low draw (nav lights, tabs, gauges).

I also have a portable Sears starter/charger with 1150 CCA's that I will bring with me as a 'backup', particularly the first several times out.

With that 'backup' starter battery, I feel comfortable leaving the other two batteries on the 'house' circuit, with the one for starting the engine.

They are all Optima Blue Top Batteries (750 CCA/ea, 120 reserve), however one of them has a bad cell (never even been used - I now hate Optima batteries, that's another story) so I'm contemplating replacing it with a slightly larger Die Hard platinum battery and using that one as the 'engine start' battery.

Generally you have to have identical batteries, so if I bought a different battery for the engine start, would it mean NEVER crossing the 'engine start' and 'house' banks, even briefly (if needed in an emergency to 'start'?

Lastly, I haven't had the boat in the water yet with this setup, so no experience yet to go by. I'm installing all the electronics this week and next, and plan to have it on the lake by next weekend.

I'm hoping the engine will throw enough current to keep up with the radio at regular volumes with the transducer running, particularly once the 'start' battery is recharged.

I'm not sure I understand it perfectly, but it seems the isolator circuit in the Suzi dedicates 100% to the 'start' battery until its charged, and then throws everything at the house circuit. If that's the case, I should always have a full 'start' battery.

Even with the old '86 Evinrude 150 running on one battery, no dock charging, and a modest stereo/depth sounder, I never had starting problems (due to the battery). I have to imagine the Suzuki Four Stroke starts easier than that Evinrude ever did, particularly in the last years of its life.

Given the 'engine start' charge preference on the motor, I have to think it will always start on that battery as long as the rest of the 'house' is running on the other two batteries. I'll probably carry the 'backup' charger/starter the first several times out, but I doubt I'll need it.


Sarge posted 07-15-2010 12:30 AM ET (US)     Profile for Sarge  Send Email to Sarge     
Also, does anyone have any thoughts/experience with any of the BEP Marine relays?

I'm thinking it would be best to use this dual voltage sensor relay with the dual house batteries, connected to the engine and the solar charger (used only when boat is covered).

hauptjm posted 07-15-2010 08:27 AM ET (US)     Profile for hauptjm    

in your first post, you mentioned a 12 volt charger for phone and a porta-fridge. I took that to mean you used some type of mechanical refridgeration. If so, that can be a beast of a power drain.

jimh posted 07-15-2010 09:45 AM ET (US)     Profile for jimh  Send Email to jimh     
I don't see the need for a fourth battery on an 18-foot boat. Actually, I would cut down to two batteries on an 18-foot boat.

I don't see the need to use any sort of voltage sensitive relay to parallel batteries for charging when your outboard motor has a dual charger output.

If your audio amplifier consumes more than an average of 10-watts of electrical power it is a sign that you are listening to your music at a volume that is too high.

A SONAR with a rating of "600-watts" is referring to the peak pulsed power of its output. For a SONAR to produce 600-watts of power output it would be drawing over 50-amperes from a 12-volt battery, and it would need to be connected to the battery by a cable of 6-AWG wire. You should not make any sort of inference about the average power consumed by the SONAR based on its rating of 600-watts. The average power will be more like a one-tenth of that or less, or about 50-watts.

Sarge posted 07-16-2010 01:43 PM ET (US)     Profile for Sarge  Send Email to Sarge     
The 'fourth' battery would just be for emergency starter use.

Using it on Jackson Lake, in Grand Teton National Park, we'll be using it for weekend camping trips to various parts of the lake that aren't accessible by car (camp on shore). However, we may use the stereo at various points when we aren't driving the boat - i.e. lunch, dinner, etc.

That's the reason for the RV-esque 'dual house battery' setup.

I can thusly foresee things like charging phones, someone wants to bring a minifridge, etc.

Otherwise, the boat will be used for various watersports - wakeboarding, possibly wakesurfing, and as a 'chase boat' for kite surfing. Generally those are times when the music might also be played at higher volumes, for the enjoyment of the 'athlete'. It's a large lake with almost no traffic, so no matter how loud you have the music, it's the 'tree fell in the woods with no one else to hear it' scenario.

For fishing, the stereo doesn't get used at all, or at very low volumes.

I know the Outrage is more typically a fishing boat than a party/ski boat, but this one will 'do it all', as it always has.

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