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07-05-2014, 16:26
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#1
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Registered User
Join Date: Nov 2009
Posts: 196
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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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07-05-2014, 16:40
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#2
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Registered User
Join Date: May 2008
Location: puɐןsuǝǝnb 'ʎɐʞɔɐɯ
Boat: Currawong 30
Posts: 4,897
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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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07-05-2014, 16:50
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#3
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Registered User
Join Date: Jun 2010
Location: Caribbean
Boat: Corbin Ketch 39ft
Posts: 302
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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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07-05-2014, 16:52
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#4
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Registered User
Join Date: Dec 2010
Location: Western Caribbean
Boat: 38/41 Fountains pajot
Posts: 3,060
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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
Sent from my LG-LS980 using Cruisers Sailing Forum mobile app
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07-05-2014, 16:59
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#5
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Registered User
Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 9,764
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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.
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Mill Bay, BC, SR/FK, M25, Rocna 10 (22#) (NZ model)
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07-05-2014, 17:48
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#6
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Registered User
Join Date: Nov 2009
Posts: 196
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Re: Automatic charge relays - good or bad
Quote:
Originally Posted by Stu Jackson
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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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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07-05-2014, 18:04
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#7
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Registered User
Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 9,764
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Re: Automatic charge relays - good or bad
Quote:
Originally Posted by mlibkind
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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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
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Mill Bay, BC, SR/FK, M25, Rocna 10 (22#) (NZ model)
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08-05-2014, 08:51
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#8
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Marine Service Provider
Join Date: Dec 2003
Location: South Carolina
Boat: Philip Rhodes Custom
Posts: 414
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Re: Automatic charge relays - good or bad
Quote:
Originally Posted by mlibkind
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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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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08-05-2014, 09:18
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#9
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Registered User
Join Date: Jul 2007
Location: Ladner, BC, Canada
Boat: Newport 30
Posts: 131
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Re: Automatic charge relays - good or bad
Quote:
Originally Posted by mlibkind
Does anyone have any experience with the automatic charge relay or other informative information???
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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!
__________________
SV Lorelei
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08-05-2014, 11:01
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#10
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Registered User
Join Date: Aug 2008
Location: Wash DC
Boat: PETERSON 44
Posts: 3,165
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Re: Automatic charge relays - good or bad
Quote:
Originally Posted by rdempsey
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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Yep I think I am. 7 years with this setup. No issue. Battery's still seem good
Sent from my iPhone using Tapatalk
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08-05-2014, 11:26
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#11
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Registered User
Join Date: Nov 2007
Location: Southern California
Boat: Cal 48 Wainui
Posts: 295
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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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08-05-2014, 11:55
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#12
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Registered User
Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 9,764
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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
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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__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Mill Bay, BC, SR/FK, M25, Rocna 10 (22#) (NZ model)
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08-05-2014, 19:39
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#13
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Registered User
Join Date: Mar 2014
Location: Casco Bay Maine
Boat: Mariner 36
Posts: 170
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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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08-05-2014, 20:49
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#14
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Registered User
Join Date: Jun 2013
Location: canada
Posts: 4,790
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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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09-05-2014, 00:08
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#15
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Registered User
Join Date: Sep 2013
Location: Poulsbo, Washington
Boat: Spirit 28
Posts: 245
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Re: Automatic charge relays - good or bad
Quote:
Originally Posted by smac999
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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Why does a large size mismatch matter?
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