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Author Topic:   Battery usage and switch
prxmid posted 02-08-2003 12:27 PM ET (US)   Profile for prxmid   Send Email to prxmid  
This should be easy to check but my boat is in storage. I have a 1999 OR 18 that has two batteries. I never thought about whether they are two batteries in series or a starter battery and an "accessory" battery.
Does anyone know what the setup is? Also how should the switch be used? On both so they both recharge or 1 on way out, and 2 on way back? Also typically is #1 the starter battery?
jimh posted 02-08-2003 12:49 PM ET (US)     Profile for jimh  Send Email to jimh     
It is hard to make any accurate statements about how your boat is wired without having a chance to look at it and trace the cables, etc. We don't know how many batteries you have, how many charging sources (engines, battery chargers, etc.) you have, or any notion of how they may all be interconnected, and if there is any switching equipment.

In general, however, one can say that it is extremely unlikely that the batteries are arranged in series. I have never heard of this being done on an outboard powered boat. In the case of very large diesel engines that need enormous amounts of current to start them with electical motors, 6-volt cells are often used. They are connected in series. The use of 6-volt cells keeps the weight of the battery manageable.

There is a one-to-one correlation between the number of people you ask and the number of different theories you will get on what is the proper technique for battery charging and management.

On my twin engine outboard boat I have no switches. Each engine connects to its battery. Each engine charges its battery. Additional load is spread between the two batteries. Instruments run off one, the bilge pump runs off the other. It is very simple.

If you want to make things complicated, I offer some suggestions in a Reference article I published some time ago. See

jimh posted 02-08-2003 12:58 PM ET (US)     Profile for jimh  Send Email to jimh     
Oops--you do clearly state you have two batteries, but we don't know if they are identical types. Sometimes people use starting-current batteries and deep-discharge batteries in a mixed application. There are also now exotic batteries that need different charging characteristics than the common lead-acid starting battery. It gets complicated. The people that make switches and battery things have about 50 different diagrams on their website to help you. (In that sentence there should be quotation marks around "help".)

You might also find some comments interesting in this thread:

prxmid posted 02-08-2003 02:18 PM ET (US)     Profile for prxmid  Send Email to prxmid     
I will check the threads, there are two batteries, one engine (Merc DFI 150), one switch (1,2,both,off), Can't check to see if batteries are identical, boats not here.

They are as originally set up by Whaler (or dealer). Assuming the, starter and deep cycle, what's the best use of switches?

prxmid posted 02-08-2003 02:27 PM ET (US)     Profile for prxmid  Send Email to prxmid     
Read the thread. It's like talking in tongues.

Can I get the "Batteries for Dummies" version?

prxmid posted 02-08-2003 02:40 PM ET (US)     Profile for prxmid  Send Email to prxmid     
I went back and read the reference article and think I've got it.

Although in the absence of using both, as they may never fully charge, should you switxh between 1 and 2 in the middle of each trip. Do you leave it in OFF in the slip, I've always left it in 1 or 2 to keep the bilge pump going.

kingfish posted 02-08-2003 02:45 PM ET (US)     Profile for kingfish  Send Email to kingfish     
Isn't an OR18 self-draining/bailing?? (With the plugs pulled)
JBCornwell posted 02-08-2003 03:48 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Howdy, prxmid.

Haven't seen this mentioned lately, but I was cautioned about it.

Never switch or disconnect battery or batteries when ignition is ON with a computer controlled engine. Transients are deadly on 'puters. That would include your Merc.

Red sky at night. . .

prxmid posted 02-08-2003 04:01 PM ET (US)     Profile for prxmid  Send Email to prxmid     
I've heard never switch it to or through off with engine on, are you saying don't touch it at all once started?
JBCornwell posted 02-08-2003 06:19 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
If you are certain that your switch is a "make before break" and in perfect condition you can probably get away with that.

Considering the price ofa new ECM I wouldn't risk it.

Red sky at night. . .

Drydock posted 02-09-2003 12:40 AM ET (US)     Profile for Drydock  Send Email to Drydock     
I have a dual battery setup that was original from the dealer on a Ventura 18.
Both batteries are starting type batteries. wired in parallel through a off,1,both,2 switch. All house loads bilge pump, livewell, lighting and accessories are wired directly off of the forward battery and are not switchable. So the battery with the accessories on it does not get charged unless I run with the #1 position or Both. I'm not sure what the logic was but I guess it would have the advantage of keeping a starting battery fully charged if you didn't operate in the Both position.
prxmid posted 02-09-2003 11:41 AM ET (US)     Profile for prxmid  Send Email to prxmid     
Interesting that they would both be starting batteries.
Drydock posted 02-09-2003 12:02 PM ET (US)     Profile for Drydock  Send Email to Drydock     
It did seem odd that both were start batteries. I think the way jimh shows his first dual battery, single engine setup makes the most sense to me. I don't know how (complete) the boats are when they come from the factory but it does seem like different dealers set them up in different ways.
prxmid posted 02-14-2003 05:15 PM ET (US)     Profile for prxmid  Send Email to prxmid     
I guess in hindsight, I never did get an answer. Do most people with i motor/2 batteries. Alternate between 1 and 2? Use BOTH?, Leave 1 OR 2 on when in slip/mooring? And what about when underway?
Drydock posted 02-15-2003 12:49 AM ET (US)     Profile for Drydock  Send Email to Drydock     
I guess I was talking too much about the wiring to answer the question. My answer. I use position 1 on odd days, Position 2 on even days. Just to try and equalize the use.
If I had an electric trolling motor i would replace one of the starting batteries with a deep cycle and only align the alternator to the deep cycle after the engine was started to charge back up the deep cycle after trolling.
prxmid posted 02-16-2003 12:50 PM ET (US)     Profile for prxmid  Send Email to prxmid     
last question on this, promise. Then when would you use BOTH?
jimh posted 02-16-2003 08:13 PM ET (US)     Profile for jimh  Send Email to jimh     
Use BOTH to start an engine when neither battery can do it alone. Then run on 1 or 2 to recharge. The charging will probably work better if only one battery at a time is connected to a common charging source.
JohnJ80 posted 04-02-2003 04:25 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
I came across this slick charging thing. My application is to use it to charge a trolling motor battery. However, if you have a cranking battery and a deep discharge battery for house use (the way it should be done). This thing would work great and make the 1-2-both-off switches not needed.

I always worry on boats about switching the load when the engine is running. It doesn't take alot to blow up a regulator and that is one great way to do it.

Check out:


jimh posted 04-05-2003 10:23 AM ET (US)     Profile for jimh  Send Email to jimh     
The "slick charging thing" appears to be a device which uses one battery to charge another. It also appears to be intended for use with 24-volt or higher trolling motors. I don't think this device has a wide application among owners of Boston Whaler boats.

There may be specific instances where the "slick charging thing" is an excellent application, but I don't think I would recommend it as a general solution to the battery installation and wiring on a Boston Whaler, particularly a late model boat still set up as it came from the factory.

JohnJ80 posted 04-07-2003 09:47 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
This thing doesn't use 'one battery to charge another'. It watches the voltage level of the charging battery and when it hits the fully charged voltage, then and only then, the current is diverted to the second battery (trolling). Its a big voltage controlled switch - exactly like watching your cranking battery charge on position 1 and then flipping to position 2 when it is fully charged.

It works with 12V and 24V systems (depending on how its wired up - there are jumpers for different voltages).

The other application for these is to connect a solar panel to the cranking battery. When the cranking battery is charged, the solar panel then charges the secondary panel (switch flips).

The other benefit to this is that if you need to pull current from a battery, due to the V-I (voltage-current characteristic) of a battery, is that as you use Amp-Hours from the battery the voltage drops. As it goes over the knee of the curve (voltage drops faster after a point) then the current required from the battery goes up fast in order to supply the watts required by the accessory.

Its operating batteries in this region of the curve that is when the most destruction in the battery occurs (I believe when the most sulfates are formed) - a common problem with trolling motors. If you keep the battery charged then you can dramatically reduce this.

So, if you want to preserve your batteries and keep their capacity from degrading, or if you would like to use a solar panel to maintain batteries (trolling or otherwise), or if you have a difficult time getting an AC charger to your boat on a dock etc... then this device is applicable.

Hope that helps - if you are considering a switch for isolator, then this device is similar to both.

JohnJ80 posted 06-04-2003 11:29 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
I thought I would update this thread after I had some use on my Stealth One charger.

I have used this for several days of extensive fishing - typically ride to a location, fish the area extensively for an hour or more and then move on.

My rig is a D15 with a Minnkota 55AP autopilot trolling motor, 12V connected to a 105Ah battery. There is a volt meter on both the charging and cranking batteries, plus the motor has a 5 step battery voltage indicator. The boat motor is capable of 35A current output (max).

Starting out with a fully charged battery and after fishing for 2 hours with the motor throttle set at about 35-40% the battery shows about 20% depleted on the trolling motor gauge and just under 12V on the console meter.

After moving the boat and running for about 20 minutes, the battery voltage shows 13.8V on the console and 5 bars on the motor (100%). This cycle continues througout the day.

Qualitatively, it appears to charge the battery back up to voltage quickly. Probably could figure this out by doing the math on Ah consuption and current output of the alternator.

It is now apparent to me that I will never need to charge my battery with an external charger, since the alternator of the motor keeps it up to full charge. I also have never run my trolling battery below about 70% of full charge - a fact which should extend the life of the battery vs the heavy discharge/charge pattern I have had before.

While I didn't try it, I am sure it would work, but if you are trolling for long times without stopping, I believe I could run the engine charge the trolling battery concurrently with operating the trolling motor.

So, this thing operates as advertised and virtually eliminates the hassle of having to connect an external charger. Time will tell, but I also believe that it will help to get max life out of the trolling battery.

Good applications for this are where the boat is at a dock full time or not near AC power often.


bsmotril posted 06-05-2003 12:04 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
A trolling motor/deep cycle battery is only good for a finite number of charge - discharge cycles. Your many shallow cycles per day as opposed to a single deep cycle at the end of the day is likley shortening the battery life by a good bit.
hauptjm posted 06-05-2003 12:58 PM ET (US)     Profile for hauptjm    
Another set-up, to add some confusion: three batteries/one motor. I have two for the engine (one start, one deep cycle) and one just for the electronics. The engine batteries (which the live bait well and bilge pump run on as well) are located in the stern and the third (deep cycle) is located in the console dedicated to stereo, VHF, fish finder and running lights. All are kept fresh by a three bank charger also mounted up high inside the console.

You may be surprised at how long I can run all electronics at once on that battery before needing recharge. I've never run out of juice. And I have fished and run her all day and partly into the night and came in with running lights shinning and Grover Washington, Jr. bringing it home.

JohnJ80 posted 06-05-2003 10:51 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
I'm not sure I agree about your charge/disharge cycle limitation. I think that means complete discharges because as the voltage drops the chemical reactions (sulfates?) begin to become irreversible and do damage to the battery. Anyhow, I need to research that to figure it out.

At any rate, once I figure that out, it is just a matter of managing the on/off breaker for the Stealth One device.

The main point here is that no AC outlet is needed, ever.


JohnJ80 posted 06-06-2003 11:54 AM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
I looked up on an Exide website at

for some information on marine deep discharge batteries and recharging.

Important points:
- recharge within 24 hours after use.
- unhook charger when battery is fully charged.
- fully recharge
- storage on concrete is not an issue.
- storing for extended period with out use or recharge causes sulfates to form (hurts battery).
- measure charge state by battery voltage or specific gravity measure.

So, what i get out of this is to fully charge a battery after use, store if fully charge and do not continue to charge after fully charged.

As has been my experience with lead/acid flooded cells, the number or recharge cycles is really not an issue as much as making sure that the battery is charged and stays that way for storage.

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