posted 07-12-2010 09:31 PM ET (US)        

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?

Thanks,

Sarge

posted 07-12-2010 10:26 PM ET (US)            

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.

posted 07-14-2010 08:05 AM ET (US)            

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:

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.

posted 07-14-2010 09:32 AM ET (US)            

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:

posted 07-14-2010 09:44 AM ET (US)            

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.

posted 07-14-2010 10:15 AM ET (US)            

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.

http://www.bepmarine.com/home-mainmenu-8/product-270/dual-sense-voltage-sensitive-relay-125amp-vsr-

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.

posted 07-14-2010 05:20 PM ET (US)         

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.

posted 07-15-2010 12:14 AM ET (US)            

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.

posted 07-15-2010 12:30 AM ET (US)            

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).

posted 07-15-2010 09:45 AM ET (US)            

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.

posted 07-16-2010 01:43 PM ET (US)            

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.