Wiring 3 Batteries: 1 Main, 2 Trolling w/ 1 shared to House

How do I wire three batteries...
Main Battery: feeds engine, charged by alt and 110v charger
Trolling Batteries: feeds 24v trolling motor and one battery is tapped for 12v panel feed, including electronics, charged by alt and 110v 3-bank charger

Basic questions:

1. Is is wise to tap one of the two trolling batteries (wired in series to produce 24v) for a 12v panel feed? This will feed all my electronics (GPS, sounder, VHF, stereo, etc.)

2. Can I use a ACS device to charge all three batteries sequentially from the engine alternator? If ACS is proper name for device that takes power from running outboard engine's alternator and sends it first to main battery, then when it is fully charged, to the other batteries (one at a time, possibly in one minute increments) until the other (two) batteries are fully charged.

3. Do I need to use switches to disconnect batteries from 'seeing' each other during 110v smart charging? I'm thinking that ACS may 'see' a charging voltage from 110v charger and try to send it sequentially to the three batteries. This would seem to thwart the 110v smart charger from charging each battery individually according to its need. The batteries will likely be discharged at varying levels and I want the 110v changer to not have its dedicated smart charging of each battery overridden by the ACS trying to send charge to one battery at a time sequentially. I'm thinking that a switch on the battery side of the ACS would prevent it from interferring with the 110v charger's operation.

Clear as mud?

Any help would be greatly appreciated. I have searched for info on this and can't find this specific issue addressed.
Mike

Re: Wiring 3 Batteries: 1 Main, 2 Trolling w/ 1 shared to House

After 30 viewings but no responses, it seems that I have asked a question that 30 people want to see an answer to but no one seems to know.
Or did I format the question improperly for answering? If so, let me know and I'll respond.
Thanks for any help.
Mike 919-812-8188

Re: Wiring 3 Batteries: 1 Main, 2 Trolling w/ 1 shared to House

Well sir, first of all we have no idea what size engine you have, whether it is an outboard or I/O so the first issue is what is the alternator output rated at. If you hope to charge three batteries with an alternator that has say 20 amp output you are beating a dead horse as you would have to run for hours at wide open throttle to make dent in the system. Even a 100 amp alternator on an I/O would require a fair amount of long distance running at high speed to keep things topped off.

Since you apparently have a 24 volt system and have a 12 volt feed off that system, which is ok by the way PROVIDED you have taken 12 volts from the battery that has the 24 volt ground lead on the negative cable. If you take 12 volts off the other battery, an accidental ground to the chassis of the boat (assuming is aluminim) means you just put 24 volts on all 12 volt accessories. One minute intervals of charging are a mere blip on a charging curve and absolutely meaningless. Hours is a better measure.

Because of this grounding situation, you cannot charge a 24 volt system from the engine alternator, On board chargers can be used because the charger outputs are totally isolated from each other so the grounding is not an issue.

Do you see how easy it is for people to "battery themselves" into electrical problems. Why not keep the accessories on the starting battery like the manufacturer intended and let the engine take care of that load. Unless you have a killer stereo the battery will not go dead over a several hour period. A sett of jumper cables or a jump start box would take care of emergency starting should it arise. Then a two or three bank charger is all that's needed for charging at the dock.

Re: Wiring 3 Batteries: 1 Main, 2 Trolling w/ 1 shared to House

Thanks Silvertip for the response.

My fiberglass boat has one Evinrude 115 ETEC engine. I don't have the alternator output handy, but the ACS unit feeds the alt output to one battery at a time, sequentially starting with the main battery, which should work fine for the 12v main starting battery, but seems problematic in charging the two trolling batteries wired together in series to produce 24v. But I must be missing something because it seems a lot of fisherman use a 24v trolling motor on their boats and must use the alt output for charging.

I could probably install a disconnect switch between the two trolling batteries that would separate them while running at speed (to allow the ACS to charge each battery separately, consecutively) then reconnect them with the engine shut off to feed 24v to trolling motor.
The same disconnect switch would also seem to allow smart charging from a three bank 110v battery charger plugged in at dock.

I'm not sure what would happen if I forgot to use the disconnect switch to separate the two trolling batteries when I cranked the engine and ran the boat. 12v charge sent to 24v connected batteries!

Makes me want to go to a 12v trolling motor (with two batteries connected in parallel), but I would still seem to need the disconnect switch since I need to feed the 12v alt charge to the two trolling batteries separately. And 12v trolling motors aren't as efficient as a 24v setup, so I've been told.

I hesitate to tap the starting battery for electronics use since I have a power hungry side-scanning sonar with an 8000W transducer.

Thanks also for the tip about which of the two 12v batteries (wired in series for 24v trolling motor) to tap for 12v feed to electronics. If I'm reading you correctly, I tap the 'second' battery whose pos terminal is wired to neg of 'first' battery.

I investigated using a battery integrator to automatically separate the batteries but the integrator separated the batteries during discharge (when I need the two trolling batteries connected) and connected them during charging (when I need them separated for 110v smart or sequential ACS alt charging.

I guess it this stuff were easy, anyone could do it.

Re: Wiring 3 Batteries: 1 Main, 2 Trolling w/ 1 shared to House

Here is a 24 volt series system.



Current needs a ground path to the charging system for the charging system to work. Now then, if you connect the alternator output and ground to the left battery it will charge normally. What happens if you move the charge output to the positive terminal of the battery on the right???????? You have 24 volts on the engine do you not??? And would you risk a couple thousand dollar ECM by making that connection?? The ONLY way you can charge two batteries independently in a 24 volt system is if the ACS (as you call it) can also switch the ground lead the same time it switches the positive lead. Even then, grounding becomes an issue because grounding the negative lead on the battery on the right means the POSITIVE terminal on the battery on the left is also grounded. If for some reason the trolling motor or the ground lead on the left battery reaches ground (as in the first scenario) you have a very nice arc welder. I have not seen a device that will switch both the positive and negative leads but then because I've not seen it does not mean it doesn't exist. Using two separate devices also would not work because the grounds from the those units would still end up being common back at the engine. Multi-bank on board charges can be used because the grounds are totally isolated electrically from each other. In other words they appear like 2, 3, or 4 totally separate chargers all in one package. Point us to the ACS system you reference. Perhaps we have something to learn. The factd remains, alternators will have a tough time fully charging a deeply discharged 24 volt system with short runs between fishing spots. Will it prolong on-water time -- Certainly. But I'll bet their on-board charges work pretty hard when they get back to the dock and plugged in.

Re: Wiring 3 Batteries: 1 Main, 2 Trolling w/ 1 shared to House

What if you install a switch in the red wire between the neg post of right battery and the pos post of left battery? This switch would break the connection between the two batteries, then the ACS charger from alternator could charge each of the 12v batteries separately.

Re: Wiring 3 Batteries: 1 Main, 2 Trolling w/ 1 shared to House

You are hell bent on creating a problem sir! The very moment you forget to flip that switch is time you fry an ECM and other electronics. Now if you want me to design an automatic electronic switching system for you I would be glad to do that. But you would not like the price. Show us this ACS you keep talking about and perhaps we can help you incorporate it. Until we see what that is, we (I) have no idea what type of charging system you are trying to incorporate. I understand fully what you want to do but you can't do it safely the way you want to. Lots of people do lots of "creative" wiring in a boat and seemingly get away with it. But failure can be extremely costly.

Re: Wiring 3 Batteries: 1 Main, 2 Trolling w/ 1 shared to House

SilverTip
Thanks for the reply.
The device I'm looking at to send a engine alt supplied charging voltage to the trolling / house batteries after the starting battery is topped off is:

The Dual Pro CRS2 Onboard Charger is a marine unit which takes engine alternator output from the starting battery when the engine is in use, and passes it to two auxilliary 12 volt batteries, which may be wired in series for 24 volts, as in a typical trolling motor installation, or wired in parallel.
This maximizes run time available from the auxilliary batteries.
The unit does not start the current flow until the starting battery reaches a
factory preset voltage, and then monitors the starting battery, and shuts off
current flow to the secondary batteries, if the starting battery starts to lose voltage.
When the auxilliary batteries reach a preset voltage, the unit shuts off.

Once home, I'll use a 110v smart batt charger to charge each battery individually:

Dual Pro 3 Bank PS3 Marine Battery Charger
12/24/36 Volt 15 amp 3 bank waterproof marine charger.

The Dual Pro 3 Bank TRI PRO marine battery charger is a 3 bank, 15 amp 12 volt per bank, temperature compensation charger. The Pro series are
heavy duty, microprocessor controlled, waterproof, and fully potted vibration proof battery chargers.
These independent output battery chargers have a separate positive and negative terminal for each battery bank, and a separate microprocessor for each which controls the charging profile. With this design, they can be used on batteries which differ in state of charge, age, size, or type
(sealed, flooded).
This works well in applications with a starting battery and a trolling setup.
It also is suitable for series strings of 12 volt batteries for 24 or 36 volts.
Once each battery has its individual positive and negative terminals connected, the microprocessor for each output does not care if the batteries are in series or parallel.
This is useful in 24 - 36 volt applications where one of the 12 volt batteries
in the string supplies some 12 volt loads and the other batteries do not.
The batteries in this situation end up with an imbalance condition.

Seems like the CRS2 would work to send excess charging voltage to trolling batts once starting battery is fully charged. I know that several posts say this is not of much help in charging the trolling batteries, but my experience is that my starting batt stays nearly fully charged after starting the engine, so there is considerable excess charging voltage coming off alt when I am moving at planing speeds between fishing spots. Any voltage bump this gives my trolling batteries during a run is helpful.
The TRI PRO 110v charger will then charge each batt individually when I get home to bring them to max charge with 'smart' charging.
MikPhilips

Re: Wiring 3 Batteries: 1 Main, 2 Trolling w/ 1 shared to House

I checked the alternator output from my Evinrude 115 ETEC 2 stroke outboard; it is 50amps.
MikPhilips