ACR Battery Selector Switch - WHY???

[Not For Hire]

Because I was redoing wiring anyway, and because I was going to a three battery, two engine setup I put in two VSRs (ACRs by another maker). There are also three switches incorporated into the circuits plus I kept one of the original on off all switches.

I like it for all of the reasons Joe said, and for what Mike said comparing it to the chime for lights left on (by the way this becomes more important with each passing year).

Also sort of covered by Joe's point number 5 - but, my deep cycle house battery is charged by both engines when both are running so it is recharged faster. Also without throwing any switches etc. my house is kept charged when I troll with either engine alone for extended periods.

My onboard 110v charger is three banks and is separate from the vsrs and switches.

Joe wrote and I find all are true:

1. Isolation of house and starting batteriess, including starting batteries from each other in twin engine applications.

2. Allow the use of specialized starting, deep cycle marine, combination, and various other types on the same boat.

3. Keep at least one battery in reserve for staring purposes.

4. Isolate voltage sensitive electronics from starting circuits which introduce voltage spikes into the electrical system.

5. Allow selective prioritized charging of batteries by any of the the motors, generator, or shore power.

6. Sell more fancy electronics with very expensive "black boxes" that defy understanding by the mortal souls who pay exorbitant prices for them.

Previous boat with single engine (and much larger alternator) always ran with two batteries and single on off all selector switch. Never had a problem.

Regards,

Mark

[Dreamer]

Mark, I originally planned to charge a single house battery with both engines through ACRs. The problem, as it was explained to me by a marine electrician, is that each charging source senses the elevated voltage caused by the other, thinks the battery is topped off and drops to float. He said he has found no way to charge a house battery from two sources. It would be nice to combine the alternator outputs for a higher charging rate. Have you tried this system and tested charging rates?

[mikeporterinmd]

An ACR will not help with the problem of two simultaneous charging sources.

A 7600 can be used with two sources that are not generally expected to be in use
at the same time. You could, with the appropriate jumper put your alternator
on one bank and the charger on a second bank. When voltage is high on
post A, the relay will combine. Additionally, if you run a sensor wire
from the 7600 to bank B, the relay will combine if the voltage goes up on
that side. So, you could connect your alternator to post A and your
charger to B.

If both charging sources were active at the same time, then the one of the
charging sources will probably drop to float.

I have a two bank charger wired as such. When the charger is on, it is good
to disconnect the ACR using its manual override switch to prevent the charger
from charging through one bank.

I plan to make a relay cutout that will cause the ACR to open when the charger
is on. This falls under the department of "unnecessarily complex yet cool".

I think there are devices that uses diodes that will combine charge sources effectively,
but there is a votage drop across the diodes. So, you need to sense the battery
voltage at the battery. This can be done with some alternators, but I don't know
how to do that with an outboard. It wouldn't be easy.

Mike

[Bill3558]

I have read this thread 2 times but I still have a question or 2 that maybe you all can help me with. I have a new CD 22 and I am in process of adding a "house" battery. I found with 4 foot cables I can put one down where the bilge pump is and reach the other battery and switch.

I have the shore power and battery charger package on the boat. I have purchased a blue sea 1+2+both switch but havent installed it yet.

Question 1 is if the engine is running, can I safely switch from battery 1 to 2?
Will the alternater automatically adjust to the different charge draw?

Question 2, If I have the battery switch on both at dock with the battery charger on, will it charge both ok? The batterys are NOT the same. One is a starting battery and the other is deep cycle.

Thanks for any advice.....

[colobear]

Bill,

Everybody has their own ideas but I am personally uncomfortable with putting a battery down on the sole of the boat. Mainly because I want my power supply (for the bilge pumps, etc.) up higher where a single big wave into the cockpit won't swamp and short it out. I also don't want it where it can be kicked, have things dropped on it, etc. I have a 22' cruiser and Les put my house battery plus the battery control switch in the starboard lazarette and the two engine batteries in the port lazarette. They are a little in the way when I am trying to get to fuel filters, etc. but otherwise they are neatly tucked away. I just took a hose to the cockpit as part of my spring commissioning routine and I'd be really leery of doing that if my battery was exposed back there by the bilge. YMMV.

[thataway]

I don't see a problem putting a battery in the bottom of a boat like the C D 22 (the battery goes into a box. If you have 11 inches of water in the boat, you are going to have a lot of problems, and placement of the batteries may not be the most important. Batteries down low, keep the weight low. However, in the 22, I did have one battery in a lazarette and the second, was under the sink.

If the battery switch is make before break or has a field disconnect, you can safely switch the battery from #1 to both. You have to have the ouput of the alternator going to a load/resistance, or cut alternator output (field disconnect). Double check the switch--most of the combine switches are make before break, so they are safe.

There is a potential problem with the battery switch on "both" when you have unequal batteries. The assumption is that one battery will have a lower capacity than the other. The lower capacity battery can be overcharged and thus boil off water. It would be better to have a dual output battery charger, which isolates the two batteries with diodes.

[ffheap]

Hi Folks,

Knowing ALMA's ONLY, I have to agree with him.

I am a firm believer in the KISS Principle, Kep It Simple Sir (or stupid). I some times forget which it is.

I believe that we sometimes get caught up with all the new gadgets and have to have them, when our boats are really very simple machines. I like to keep it as simple as I can, and add a new gadget when I see that it can really make my boating simpler. A windless was added after I had to raise an anchor when both current and wind going the same way, and I found that it was a tough job, and that maybe I am not as young as I was.

Fred