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PBzeer 01-13-2007 10:02 AM

Selector switch or Automatic Relay
Since I'm currently in the middle of cleaning up my electrical system and the panels at the nav desk, I'm trying to decide whether to go with one of the automatic charging relays rather than the current switch I have.

The postives I see for the ACR would be a smaller footprint, not worrying about switching batteries, and a much smaller switch at the nav desk. On the negative side, I have to buy it, and it is a piece of electronics, so eventually it will fail.

With the "normal" 4 position switch, I already have one, it isn't as likely to fail, but it has a much larger footprint.

So, I'm wondering if any of you use an auto combiner and if so, how you like it, and how well it works?


hellosailor 01-13-2007 10:22 AM

John, I'd agree with you that anything you add can become another failure point but the Yandina/West units seem to be robust and faithful, at least knock wood so far this one is.<G> Whether I'd trust a new solid-state one to be better or worse, dunno. But so far so good, it goes on, it goes off, there's a reasonable time delay to prevent it from chattering, and LED so you can eyeball it once in a while to "trust but verify".<G>

sailingdog 01-13-2007 02:19 PM

I have one on my boat, and it is a nice thing to have. I have it setup so that if either side is charging, it will bridge and both banks will charge off of the single source. For instance, the starting bank is connected to the alternator, and if the boat is under power, the house bank will be connected so that the alternator will charge both house and starting banks. The solar panels are connected to the house bank, and if they come on-line, the ACR will bridge both banks and allow the starting bank to charge off the solar panels.

camaraderie 01-13-2007 05:07 PM

John/SD/HS... I'm not really familiar with ACR's so hold my hand a bit here. I understand that they direct available charging current to the individual battery banks as needed. How does that eliminate the need for a battery selector switch (4 position 1-2-both-off)? How do you choose which bank you want to RUN off of and which to hold in reserve.
Old 4-pos switch're running under engine offshore under battery bank #1. All of a sudden all of your instruments go out and you trace the problem to a faulty alternator and a now dead battery bank #1. Spare alternator is installed and you switch to battery #2 to re-start the engine.
How does this work with JUST an ACR...I thought they would allow BOTH batteries to drain leaving you unable in the same scenario to re-start.
Don't you still need a 4-pos switch with an ACR to prevent such a situation?

PBzeer 01-13-2007 06:26 PM

The ACR charges both/all banks, but on discharge, only uses from the (user) designated bank, ie: house bank. They also have a 3 postion switch for auto, off and combine. You can get the big Perko type switch, or (at least with the Blue Sea model I'm looking at) a toggle type switch in a flush mounted plate. They are also user adjustable for max voltage, load shedding (will turn off high draw items if battery gets too low).

hellosailor 01-13-2007 06:39 PM

The automatic combiner doesn't necessarily eliminate anything *except* the need to select batteries while you are charging. Not using--just charging.
The Yandina/West unit is normally installed in a system where there is one engine-mounted alternator, one starting battery, and one house battery. In that application, when you run the engine it will wait until it sees 13.5V at the starting battery, indicating the starting battery has a reasonably full charge or is getting one. At that point, it automatically adds in the house battery, allowing both to charge as long as 13.5v is still available.
When the engine is off, the voltage on the starting battery (even fully charged) will drop below 13.5 in a minute or so, at which point the batteries are isolated again. That means you can run house loads off one house bank, and know the starting battery was charged first and kept separated so it is available again for starting.
There's no provision for switching or multiple house banks in that scheme.

If you have two house banks, instead of one starting battery plus one larger house bank...yes, some type of switching to a/b or combine your banks would still be a good idea. (Dare I say "needed" ? <G>) And obviously, even with a combiner you might want the option of an a/b/all switch since something like a bad alternator diode could still wipe out your starting battery, even when isolated from the house bank. There are still many options. The advantage to the combiner is simply that, in its most basic installation, it ensures that the "Number One Wife" gets full and prompt attention whenever the engine is running, and is left in splendid isolation the rest of the time. As a means of protecting Number One Wife, and doing nothing more, it can still be a good idea.

Incidentally, there are also three extra contacts on the combiner, which can be manually jumpered, or connected with two switches, so that you can manually FORCE the batteries to be combined--or isolated--regardless of engine operation. So in theory, you could add two small panel switches ($1-2 each kind) and add some manual switching with it as well. In practice...that's just more switches to accidentally trip and "oops" with, isn't it?<G>

I went online looking for aircraft type switch safety covers, the kind you have to lift in order to flip on a switch? Ouch, ten bucks each, surplus, even without the switch!

PBzeer 01-13-2007 07:47 PM

In my case, I'm looking at an ACR not so much for not having to switch manually, but to clean up my electrical system. My present setup is alternator to the both terminal, with wind generator directly to the house bank. Since the terminals, switch and other paraphenalia are placed willy nilly on the bulkhead, I'd like to clean up the whole mess and make it neater and more compact. It would also take the big 4 pos. switch out of the nav desk area and replace it with a smaller switch to fit in with the changes I'm making there.

camaraderie 01-13-2007 08:43 PM

Thanks guys... understand now I think!

sailingdog 01-13-2007 09:22 PM


If you didn't have a 1/2/both four-position switch, then all the ACR would do is combine the banks when the primary bank is being charged, to charge both banks, even if the switch is not in the both position. If you connect a wire to a terminal on it... it will combine the banks if either bank is being charged....which is how I have it setup.

However, without a four-position switch, you can't combine the banks, in the case of dead starting bank.

The ACR has pots that you can set on it to adjust the charging voltage trigger level and the voltage at which the batteries isolate at.

As hellosailor said...there are also terminals on the ACR which will force combining or isolating the banks.

There is a new, smaller type electrical switch that might be a nice choice for you PB. It only has three positions IIRC... Off, start and combine. It is a good deal smaller than a traditional four-position switch.

PBzeer 01-13-2007 10:16 PM

SD - Blue Sea has a 3 position switch (large Perko type) and a remote panel with a toggle type switch for their ACR. That's the one that interests me the most. I know a lot of people recommed combiners, but I hadn't seen much actual feedback on how well they worked, hence my question.

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