Battery "combiners" any good at all??

[geoleo]

My 1984 boayt has a West Marine 'battery combiner' . Looks very old. Came with boat from some prior owner.Seems sometimes in the distant past I faintly remember that these devices actually do more harm than good. Is this true?

[knottybuoyz]

They do use some of the charge voltage from the alternator so your batteries might not get properly charged. I think the new Automatic Charge Relay's are a better choice. I pulled the combiner from our old boat and put in an ACR. Worked as advertised.

[Reefmagnet]

They're still quite popular. I don't have an opinion either way on them as I've had boats (and offroad vehicles) with both manually switched and combiner systems and both worked Ok, although I would tend to install a combiner in preference to a manual switch if starting with neither.

[pcmm]

Originally Posted by geoleo

My 1984 boayt has a West Marine 'battery combiner' . Looks very old. Came with boat from some prior owner.Seems sometimes in the distant past I faintly remember that these devices actually do more harm than good. Is this true?

Battery combiners are very popular. They have no voltage drop (compared to isolators) allow you to chard both the house and start battery as if they are one large, bank and then isolate them from each other once the charging voltage is no longer present.

[pcmm]

Originally Posted by knottybuoyz

They do use some of the charge voltage from the alternator so your batteries might not get properly charged. I think the new Automatic Charge Relay's are a better choice. I pulled the combiner from our old boat and put in an ACR. Worked as advertised.

battery combiner and ACR are the same thing.

[skipmac]

If the name "combiner" is used in the more modern sense then it will be a voltage controlled device that combines two battery banks when a charging level voltage is sensed but isolate the two banks when no charging voltage is present. It does so with no voltage drop.

I have seen older, diode based units or isolaters called combiners as in a sense they do combine two batteries to one charging source. The difference is they are "always on" and do drop the voltage from input to output, 0.7V if using standard diodes.

If it is the former then yes it does good and if it's working, keep it.

[Stu Jackson]

Originally Posted by knottybuoyz

They do use some of the charge voltage from the alternator so your batteries might not get properly charged. I think the new Automatic Charge Relay's are a better choice. I pulled the combiner from our old boat and put in an ACR. Worked as advertised.

Utter nonsense. They do NOT "use some of the charge voltage from the alternator so your batteries might not get properly charged." They use power, not voltage, measured in milliamps. Your house battery should be wired to the alternator output, and the combiner takes "care of" the start/reserve bank, which is almost always full anyway. "...might not get properly charged." is pure rubbish.

"I pulled the combiner from our old boat and put in an ACR." They are the Same Thing. What a waste of time and money to do that.

If it was an ISOLATOR, then you did the right thing. Two different issues and two different pieces of equipment.

It is truly disappointing when misinformation is bandied about.

The West Marine combiners WERE and ARE Yandina combiners sold under the WM brand. In fact, they had the same instruction manual that Yandina still has on their website for older models. Yandina still honors their LIFETIME warranty, and they are still in business.

How do I know this? Because I have a 1998 WM (Yandina) 130A combiner that has been working flawlessly for the past 18 years. So I haven't been involved in any warranty issues, but I've heard about a (very) few, from satisfied boaters who nicely posted their GOOD experiences with a company that supports their products, is still in business and cares about their customers.

[Aloft]

Originally Posted by Stu Jackson

If it was an ISOLATOR, then you did the right thing. Two different issues and two different pieces of equipment.

Just to clarify:

If it has fins it's probably a diode isolator. (Exception: there are a few MOSFET isolators with fins that are fine to keep. They'll be marked as "MOSFET" or "FET".)

If it's a small box or a bare relay, it's a combiner.

[knottybuoyz]

Jesus Stu. Easy. I probably meant isolator, see attached. No need to rip me a new one. It wasn't a malicious attempt to mislead anyone or discredit any product.

Thanks for pointing that out.

[Stu Jackson]

Originally Posted by knottybuoyz

Jesus Stu. Easy. I probably meant isolator, see attached. No need to rip me a new one. It wasn't a malicious attempt to mislead anyone or discredit any product.

Thanks for pointing that out.

Rick, sorry, rereading it I can see why you feel that way. Guess I meant it for folks who didn't know the subject matter. My apologies.

[HankOnthewater]

I got also confused with the terminology. Could I list here the various ways (I know) of combining batteries?

1. Wire all batteries parallel with thick wires. Cheap, quick, but if one battery is flat they all are, no backup, seldom used I would hope.

2. A bit safer and allowing for backup, is to put in a switch between the 2 batteries (or battery banks), a switch big enough to allow for startmotor currents (ie several hundreds of Amps). So start the engine on engine battery only, and when running add the house battery (bank). The important bit is not to forget to isolate when the engine is switched off.

3. Then an option that was popular and the norm for dozens of years: an “1-2-both-off” switch. Fairly simple to install although I think “Maine Sail’ wrote a good article about it…….can’t find it now, or was it on another forum?

4. Fairly similar to the previous option is to use 2 or 3 separate switches in place of the one switch of above. Again ‘Maine Sail’ wrote an excellent article on this. In my option this option is preferred if a non-electronic combining is needed. Note there are many ways to do it, some are very good, others to be avoided. Let us wait until someone provides a link to the article by “Maine Sail”.

5. Next easiest/cheapest option is to install is a diode isolator/combiner: current goes only one way ie from engine battery (that is charged by alternator) to house battery. Installation is easy, and can forget after that, and if the diodes are big enough will seldom fail. Disadvantage is that the 2nd battery (bank) is seldom 100% charged due to an approx. 0.7 Volt drop over the diode(s), or ~0.4 Volt if using schottky diodes. Assuming the alternator will put out 14.2 Volt, the house battery will never see a voltage higher than 13.5 Volt. Although one could build such unit at home from a few components for little money, a fancy example here: https://www.victronenergy.com/batter...tery-combiners

6. Then we move to the electronic versions like ACR (Automatic Charge Relay), as this may have been subject of the OP? An explanation is here:
https://www.bluesea.com/resources/1366
https://www.bluesea.com/products/761...12_24V_DC_120A

7. I think identical to the above is the VSR (Voltage Sensoring Relay). Just google “Stirling” or “Redarc” for examples. Yes, Yandina uses this terminology as well here Catalog Frame
Some of these (cheaper) relays do not use power when not conducting, the versions with electronics use very little power I would guess.

8. Then are the more complicated battery controllers listed often as DC-DC controllers, nearly all fully electronic. Indeed they use little power at any time. My guess is approx. 20-30 mAmps when not conducting and 200-300 mAmps when conducting and charging. However when the alternator is charging 40-140 Amps such power use is negligent.
https://www.redarc.com.au/themanager30
Battery-to-Battery DC Charge Controller 12 - 24V 140A | Jaycar Electronics

9. Lastly there is a way of NOT combining the engine battery with the house battery (bank). That can be done by having 2 alternators on the same engine. A small one (30-40 Amp is plenty) for the engine battery, and a large alternator (ie 80 to 200 Amps) for the house bank.
If one so desires, a parallel switch can be put in between the 2 banks.
This way there is a lot reduction in single failure point (ie alternator).

Other options not listed here?

[Stu Jackson]

Originally Posted by HankOnthewater

I got also confused with the terminology. Could I list here the various ways (I know) of combining batteries?

Hank, pretty good summary, although not necessarily in order.

Here are the Maine Sail posts you mentioned (I've posted these here many, many times)

OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
1/BOTH/2/OFF Switches Thoughts & Musings | SailboatOwners.com Forums

The Short Version of the 1-2-B Switch Stuff: Electrical Systems 101 This is a link to the Electrical Systems 101 Topic, reply #2

What are ACRs, Combiners & Echo Chargers? (by Maine Sail)
Battery Switch Question ? | SailboatOwners.com Forums

[HankOnthewater]

Thank you Stu for the links, yes , I read most of them over the years, maybe time to mark them as a favourite.

[Neptune's Gear]

Contrary to what some have said above, there is no problem using a diode splitter, provided a smart regulator is used with it. The alt regulator can be adjusted to allow for the voltage drop that they (diode splitters)cause. Just turn up the alt voltage so that the batteries receive the voltage they need for correct charging - check manufacturers specs. Very common install like this, and a very reliable robust solution.


Sent from my iPad using Cruisers Sailing Forum

[Stu Jackson]

Originally Posted by Neptune's Gear

Contrary to what some have said above, there is no problem using a diode splitter, provided a smart regulator is used with it. The alt regulator can be adjusted to allow for the voltage drop that they (diode splitters)cause. Just turn up the alt voltage so that the batteries receive the voltage they need for correct charging - check manufacturers specs. Very common install like this, and a very reliable robust solution.


Sent from my iPad using Cruisers Sailing Forum

And even better yet if the voltage sense is connected to the house bank, rather than just the back of the alternator. Then you don't have to "fool" anything. Better yet, please answer the question of why anyone would deliberately add a piece of equipment that when installed drops the voltage, when so many other solutions are out there?