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Old 07-05-2014, 16:26   #1
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Automatic Charge Relays - Good or Bad

I am going to redo the electrical system on a Bavaria 42 and must decide how I want to charge the house bank and the start battery. I think that there are three main choices:

1. Uses switches to connect batteries as desired to charging source or to combine. I doubt that I will go this route because it takes more "watching" the system and I would prefer something more automatic.

2. Connecting both banks to the charging system and using diodes to prevent current from flowing from one bank to the other. This is pretty standard. The only negative is that there is a voltage drop across the diodes that reduces the charge rate.

3. Installing a automatic charge relay such as the Blue Sea Systems SI-ACR. The charging source is attached to the house bank and the starting battery is connected via the charge relay. The electronics in the relay senses the voltage of the batteries and will only open if both batteries need charging. As I see it, the start battery will typically be charged quickly because the total drain on starting is small (high current for shot time). Most of the time the relay will be open and only the house bank gets charged. The advantage over the diodes is that there is no voltage drop.

There is much more to this, e.g. the voltage at which the relay switches, but too complicated to try in explain (and I might not say it correctly).

I know the diode system is well proven with its one short-coming; the voltage drop. The automatic charge relay sounds better and I heard about it from the Lifeline rep at a boat show. Does anyone have any experience with the automatic charge relay or other informative information???
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Old 07-05-2014, 16:40   #2
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Re: Automatic charge relays - good or bad

Charge relay is the way to go imo. Another advantage is that they allow a proportion of the second bank to contribute to the house bank until the voltage drops to a preset level. In my experience they are very reliable. I've used them in my dual battery four wheel drive and on previous boats. I'm going to keep the manual switch and add a charge relay in parallel to my current boat once I install the second bank as my only complaint is that most are rated to 100A which is a bit low for switching to the house bank for engine starting.
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Old 07-05-2014, 16:50   #3
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Re: Automatic charge relays - good or bad

The relay is the most efficient way to insure full voltage goes to house battery from the engine alternator. You can do this very economically by using a relay and wiring the coil to operate in conjunction with your ignition switch without a lot of bells and whistles. Been doing this for years with a 100 amp 12v relay from grainger.
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Old 07-05-2014, 16:52   #4
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Re: Automatic charge relays - good or bad

I like them and have installed them recently. They also do well to allow solar to keep start batteries charged in addition to the house bank

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Old 07-05-2014, 16:59   #5
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Re: Automatic charge relays - good or bad

Diodes are Dumb.

I should get a T sahirt with this.

Why even bother, you know the voltage drop issue...

There's a fourth option: wire the alternator and all other charging sources to your house bank, and use B on a simple 1-2-B switch.

Yes, it's just like an ACR but you have to turn the switch to charge the reserve bank, and if used for starting a 60 ah bank will give you 30 starts before getting to 50% SOC.

If you can run a sailboat, why can't you remember to turn a switch?

If you run the AO to the house bank, you can turn the switch OFF without frying diodes, so no issues with turning the switch with the engine running.

Good luck.

Simpler is an echo charger. Or a combiner.
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Old 07-05-2014, 17:48   #6
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Re: Automatic charge relays - good or bad

Quote:
Originally Posted by Stu Jackson View Post
Diodes are Dumb.

I should get a T sahirt with this.

Why even bother, you know the voltage drop issue...

There's a fourth option: wire the alternator and all other charging sources to your house bank, and use B on a simple 1-2-B switch.

Yes, it's just like an ACR but you have to turn the switch to charge the reserve bank, and if used for starting a 60 ah bank will give you 30 starts before getting to 50% SOC.

If you can run a sailboat, why can't you remember to turn a switch?

If you run the AO to the house bank, you can turn the switch OFF without frying diodes, so no issues with turning the switch with the engine running.

Good luck.

Simpler is an echo charger. Or a combiner.
I had not heard of the echo charger and am fascinated after reading about it on Xanterx website. I had not expressed my thought that since the start battery gets little use, that I could easily manually switch it in and out of the charging circuit when necessary thus eliminating the charge relay.

But the echo charger essentially keeps the batteries separate and in real time allows the start battery to charge when necessary. I really like this.

I think that I would also add switches so that I can manually set the start battery to charge separately.
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Old 07-05-2014, 18:04   #7
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Re: Automatic charge relays - good or bad

Quote:
Originally Posted by mlibkind View Post
I had not heard of the echo charger and am fascinated after reading about it on Xanterx website. I had not expressed my thought that since the start battery gets little use, that I could easily manually switch it in and out of the charging circuit when necessary thus eliminating the charge relay.

But the echo charger essentially keeps the batteries separate and in real time allows the start battery to charge when necessary. I really like this.

I think that I would also add switches so that I can manually set the start battery to charge separately.
Yes. You're essentially reinventing the wheel.

Try these:

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

Echo Charger Use Warning from Maine Sail: Xantrex Echo Charger Rant - SailNet Community
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Old 08-05-2014, 08:51   #8
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Re: Automatic charge relays - good or bad

Quote:
Originally Posted by mlibkind View Post
I had not heard of the echo charger and am fascinated after reading about it on Xanterx website. I had not expressed my thought that since the start battery gets little use, that I could easily manually switch it in and out of the charging circuit when necessary thus eliminating the charge relay.

But the echo charger essentially keeps the batteries separate and in real time allows the start battery to charge when necessary. I really like this.

I think that I would also add switches so that I can manually set the start battery to charge separately.
The echo charger has a maximum current rating of about 15 amps and you have to re-wire your alternator.

For less than half the cost of an echo charger, a Combiner100 will handle the output of alternators rated up to 100 amps, requires no boat re-wiring and is compatible with selector switches, it draws NO current when not combining and it is the only one on the market with over 20 years experience and UNLIMITED warranty.
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Old 08-05-2014, 09:18   #9
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Re: Automatic charge relays - good or bad

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Originally Posted by mlibkind View Post
Does anyone have any experience with the automatic charge relay or other informative information???
Have been using BlueSeas ACR for 4 years now. Works so good I forgot all about it until I had starter problems last week.
(Problem was corroded connector at starter solenoid.)

I wish I had more systems that transparent.

Definitely the best way to go!
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Old 08-05-2014, 11:01   #10
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Re: Automatic charge relays - good or bad

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Originally Posted by rdempsey View Post
Have been using BlueSeas ACR for 4 years now. Works so good I forgot all about it until I had starter problems last week.
(Problem was corroded connector at starter solenoid.)

I wish I had more systems that transparent.

Definitely the best way to go!

Yep I think I am. 7 years with this setup. No issue. Battery's still seem good


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Old 08-05-2014, 11:26   #11
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Re: Automatic charge relays - good or bad

Blue Seas ACR for 6 years and no problems. Send Charge to house bank.
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Old 08-05-2014, 11:55   #12
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Re: Automatic charge relays - good or bad

15 years with one of her combiners, Great product. Battery acceptance determines how much the start battery will, uhm, accept, so the differences between combiners and echo chargers is essentially moot.

There are three things on the market:

combiners and ACRs

echo chargers

duo chargers - not necessarily applicable or necessary for folks with similar/identical type battery banks

This stuff has been around for over 15 years, surprised why it's still such a secret to many. Yes, I understand folks with new or bigger boats, but this is basic electrical 101, included in books and all over the internet.

Your boat, your choice.


Quote:
Originally Posted by Andina Marie View Post
The echo charger has a maximum current rating of about 15 amps and you have to re-wire your alternator.

For less than half the cost of an echo charger, a Combiner100 will handle the output of alternators rated up to 100 amps, requires no boat re-wiring and is compatible with selector switches, it draws NO current when not combining and it is the only one on the market with over 20 years experience and UNLIMITED warranty.
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Old 08-05-2014, 19:39   #13
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Re: Automatic charge relays - good or bad

The 4 links provided above in reply #9 are outstanding. Put it in a book.

Based in great part on that information i was able to update my boats power distribution.

House is charged via solar, shore charger or generator and once full the start bank is topped off via the no thought, no effort, no switching relay.

I like to drink beer and sail, not do math.

Start bank is charged via alternator and quickly topped off, then house bank takes the charge thru the relay. The banks are combined when voltage of either is above 13.0v. Isolated when below 12.4v.

The SI-ACR has a continuos rating of 120A and an ignition isolation switch which prevents start loads from passing thru.

With very little experience I was able to replicate a simple no switching no remembering no forgetting system that works flawlessly thus far.

I tried to make it harder then it was, threw my hands up in frustration and then followed the lessons provided.
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Old 08-05-2014, 20:49   #14
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Re: Automatic charge relays - good or bad

I have installed about 100 blue sea acr's. 2 this week already. as long as the banks aren't hugely mismatched it's a great device. (like a 800ah+ house bank and a group 27 start, then you want something like a proisocharge)
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Old 09-05-2014, 00:08   #15
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Re: Automatic charge relays - good or bad

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I have installed about 100 blue sea acr's. 2 this week already. as long as the banks aren't hugely mismatched it's a great device. (like a 800ah+ house bank and a group 27 start, then you want something like a proisocharge)

Why does a large size mismatch matter?
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