New guy with electrical config question?

[ssobol]

[smckean (Tosca)]

You may already know this, but be aware that multi-channel chargers usually divide their stated output among the channels. So for example, you want a 30 amp charger. If it has 3 channels, then only 10 amps will get delivered to any one channel. So if you only hook up one channel, your 30 amp charger just effectively became a 10 amp charger.

There are chargers (the more expensive) that will sense this situation and direct all the available charging power to whatever channel needs it, but you have to look for that feature.

[Gene Morris]

I have the Xantrex Pro 40. It charges 3 bank at 40 amps each. It has been very adequate for my two Optima start batteries and the 4 6 volt golf cart batteries for the house.

Gene

[smckean (Tosca)]

Gene,

Perhaps your battery charger does do this, but I have never seen a consumer model that does. Every battery charger I've looked at can only deliver its rated charge (40 amps in your case) in total. When the manufacturers rate them at, say, 40 amps, they do not mean that each of the 3 outputs can deliver 40 amps simultaneously, but rather that the 3 outputs will share the total capacity of 40 amps. This limit is not often made clear in their documentation....for marketing reasons I presume.

Some chargers divide the total output equally across the outputs such that each output can only deliver a maximum of its share (for example, a 60 amp charger with 3 outputs, each can only deliver 20 amps max ever). Other units are smart enough to share the total amps dynamically (for example, a 60 amp charger with 3 outputs could deliver 60 amps to one output if there is no draw on the other 2 outputs).

Perhaps there is a charger advertised as a 40 amp charger with 3 outputs that can deliver 40 amps to each of the 3 outputs at once (i.e., a total of 120 amps), but I've never seen one in the typical consumer market.

[thataway]

[Micahbigsur@msn.com]

I still don't understand why with a paralleled house bank and the start battery linked in with a VSR or a ACR you would need more than one channel, seems like wasted complication and money to me.

[thataway]

[smckean (Tosca)]

As I understand it, it is never a good idea to combine 2 banks (I'll assume 2 banks) via ACR etc unless you need to overcome a temporary problem (i.e., dead start battery).

As long as you separate the banks via an ACR (and why have an ACR if you don't), then the 2 banks will be in 2 different states of charge (i.e., say, start battery at 95% and the house battery at 60%). If combined (non-emergency) the higher state of charge battery will feed charge to the lower charge state battery because the higher state of charge will be at a higher voltage (electron always flow from higher voltage to lower). This is not good for battery life.

Indeed, the entire purpose of an ACR is avoid this situation by isolating the 2 battery banks.....although the ACR does give you a "combine" option if you should ever need it. For myself, I have never combined batteries via an ACR.....no need to.

[smckean (Tosca)]

P.S. It just occurred to me.....I don't know this for a fact, but I presume that the ACR does combine the 2 banks once both banks are at 100% state of charge so that the charger can maintain all the batteries properly with a trickle charge or float charge (or whatever the term for that "steady state" at the end of the charge cycle is called).

[Stearmandriver2]

All good discussion.

I've been debating myself as to whether I need (or want) a 3 bank charger, but 15a seems a reasonable output capacity, and the ones I'm looking at seem to be 3 bank chargers. The Promariner Promarine series are smart chargers, so they will divide current between banks, send all current to one bank etc. as necessary. So that still seems like a reasonable choice?

I was wondering whether I even needed to use two banks of the charger, since it seems with the VSR I could just wire one bank of the charger to whichever battery is the closest and both batteries would charge? (The batteries are on opposite sides of the boat, is why I'd be tempted to do this... less leads to run). AGM batteries, if that's relevant.

And now a new question: on a 22 cruiser, where would this charger typically be located? I'm thinking port side battery locker, since that's where I have the most room. I don't see a way to mount it without drilling holes in the side of the boat though (the inside wall of that battery compartment, facing the splash well). This I've never done, and am not entirely comfortable with it, out of water intrusion concerns. Clearly there's a right way to do this... but I don't know it. Could anyone point me towards an explanation of what I'd need to ensure an absolutely watertight seal around the mounting bolts?

Thanks again for indulging me... I'm sure this is all extremely basic knowledge. All I've owned previously was a Catalina 27 with a shore power system already installed, and while much tinkering was necessary to keep the Atomic 4 behaving, I never cut or drilled any holes, and surprisingly in the 10 years I had her she never needed any electrical work, so I just used everything as it was.

Joe

[Micahbigsur@msn.com]

Joe, you can use the full output of your charger in one channel into your house bank and have your ACR, (VSR) manage the charging between your house and start banks.
I have been using a Balmar and Blue Seas ACRs on 3 boats for 15 years. They are smart enough not to overcharge a charged start battery, they cut off the charge above a set voltage so I've always had perfectly charged start batteries, and the motor has always perfectly charged my house batteries through them. I have always wired in a manual combine switch that I have never had to use. Using separate channels on a battery charger takes more computing power to keep things balanced and more ways to fail and you still need to have a manual switch or ACR to charge from your motor to your house bank. (I hate those cheap solution, manufacturer installed 1, 2, both, off switches). Then you also need more heavy guage wire runs for your multi channel charger.
Using more than 2 banks, house (multiple balanced batteries in parallel) and start on our small boats with conventional batteries is absolutely not necessary and a waste of time and money.
I still think a smart ACR combine (not the older dumb ones that were inefficient) is far better and simpler solution to 2 bank balancing than using a multi channel charger, the Balmar version was basically a 12v to 12v charger that keeps the banks balanced, I now prefer the Blue Seas ACR to keep my system smart charged.

Just my opinion for what it is worth.

[Micahbigsur@msn.com]

On the subject of having separated instead of paralleled house batteries and why it makes no sense.
Conventional lead acid batterys will lose longevity if the discharge goes down to 60% very often. So if you separate your house batteries, discharge 1 in half the time that battery will not last as long as it would have if it had been in parallel with its twin and only discharged by half as much. Battery chemistry changes over time and having 2 separate house batteries, over time will not be balanced and balanced is better if you ever combine them with a switch. More rapid Sulfation is likely to occur in the more heavily discharged battery which can also lead to shorter battery life.
Some larger boats run a whole extra bank linked with an ACR for the anchor windlass and thrusters that is not necessary on our boats.

[smckean (Tosca)]

I had a re-think about all this overnight. Micah's insights have raised questions in my mind about just how all this works. I thought I understood it all (or almost all), but now I realize there are holes in my understanding. I'm going to do more thinking about all this. For one thing, it now occurs to me that I have not given sufficient thought to the various scenarios batteries are subjected to. For example, at times, there could be no charging going on; at other times charging is occurring from the alternator on the engine; at still other times charging is occurring from a charger plugged into 120v. Overlay all of that with the circumstance that the battery switches could be on or off under most or all of those scenarios.

One thought that has occurred to me is concerning the need for multi-channel chargers. Micah makes a good case that single channel is all you need since the ACR will insure that both banks are connected while being charged. However, I can think of one case where multi-channel is a benefit; namely, when the boat is in its boathouse (or whatever) and the battery switches are turned off. In that case it is recommended that the charger provides a float charge to all the batteries to keep them topped off and therefore healthy. A single channel charger would not be able to do that with the batteries cut out of circuit with their on/off switches. OTOH, does the ACR typically connect the 2 banks upstream of the on/off switches such that both banks can "see" the single channel charger when they are at full charge and the switches are off?

I am beginning to think that as thataway suggests above it might be best for me to remove my ACR since I have a multi-channel, smart charger that has independent connections directly to the battery posts of both banks. OTOH, it seems to me that I would still need the ACR when the engine alternator is providing the charge and the battery charger is out of the picture. Hmmmmmmm......

Like I say.....I gotta think more about this. Ironically, I thought I had answers to this stuff (and I do have some), but now I have more questions than answers

P.S. BTW, one thing I've noticed as I've been doing some reading on this stuff is that the battery charger manufacturer materials tend to not mention or diagram the engine alternator source of charging; whereas the engine folks tend to draw diagrams etc leaving out a possible charger. Of course, in the real world of the boat owner like you and me, we do have both.

[Micahbigsur@msn.com]

smckean, I believe I did wire my ACR from the strip of studs that are the first thing that my house and start battery are connected to before my main house and start batterys so they stay balanced. (along with the bilge pumps on the house side). An ACR if I remember correctly does use a few milliamps so it must have at least a small charging source.
To make my charging system even more of a complicated mess I have a 3 stage solar controller in a solar system that can put out up to 15-20 amps that is tied into the TRIPLE charging system. In an earlier system on another boat if I left the solar on when motoring it would apply enough voltage at a few amps when motoring on a 600 AH house bank that my 80 amp alternator decided the batteries were charged and went to float charge leaving my batteries mostly uncharged.
This is where my lack of technical knowledge limits my ability to solve the problem, so now when I am motoring I have to turn off my solar manually.
Electricity is fun to plan out the wiring for but it can throw a few curves and weird feedback at you as I am an amateur at it and when Dana asks why something isn't working as designed I just tell her it is MK I, I'll have it sorted by design MK II or III!

[smckean (Tosca)]

Micah,

I did some research today. I won't say "I got it figured out", but I will say I've made progress. I certainly learned some things. I also snagged a couple of useful diagrams -- which I may try to post in this thread later.

One consideration is that there is definitely 2 basic ways of hooking up a ACR: on the load side, and on the battery side (as the pros called them) of the switches. If you place the ACR on the battery side, then putting a charger on either battery will charge both batteries regardless of how one sets the on/off switches; and a one channel charger is all you need. OTOH, if you place the ACR on the load side, a single channel charger can only charge one battery at a time if either switch is turned off; so you then need a multi-channel charger unless you manually intervene while charging. A load side installation with a smart multi-channel charger is preferred (though less common) since then the charger can manage each battery separately....each according to its individual needs. OTOH, if you want to use a single channel charger then you must install the ACR on the battery side, but then the smart charger can't see that there are 2 different batteries, so it charges them as if they were one giant battery. This single channel charge might not be good if the two batteries don't accept charge in the same way (for example, one battery might be weak even tho there are both the same model).

I'm not sure I understand your 1st sentence above, but it sounds like you have a battery side installation.