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Old 08-08-2012, 06:27   #1
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Split Charge Diode Installing

I work currently on a friends boat with complete messed up electric and following question came up:

The small Yanmar (3GM20) has just two cable come out of the engine room. They serve as starter and charge cables in one (at least there is higher voltage provided as soon the engine runs).

We would like to install now a split charging diode to charge both batterys (start and house). The manuals of the diodes say not much as connect it to the alternator.

So can I feed this only positive trough the diode and still start the engine or not? Thanks.
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Old 08-08-2012, 07:53   #2
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Re: Split Charge Diode Installing

No, you will want a separate cable from the battery to the starter. Disconnect the cable that runs from the alternator to the starter. Make sure the alternator sense wire comes from the house battery.
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Old 08-08-2012, 08:10   #3
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Re: Split Charge Diode Installing

what you are trying to do will not work, even if you run a separate wire. The split charge diodes have a 0.6 volt loss across the diode and the yanmar alternator has an internal regulator, so you will not get a proper charge. Better for you to put in an echo charge relay device to charge the starting battery once the voltage has increased in the house battery.
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Old 08-08-2012, 08:32   #4
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Re: Split Charge Diode Installing

Ok Thanks, was getting clear to me as well - how stupid as diodes are suposed to blocking the way back...

Nevertheless, I consider an Echocharge solution now, would you say that ruff drawing is OK? Do I still need an additional sensing cable?

Sorry for the dumm questions - 12 V was never a problem for me but as soon it involves the engine part I loose somehow my common sense, scared??
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Old 08-08-2012, 08:37   #5
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Re: Split Charge Diode Installing

Yes, that looks okay.
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Old 08-08-2012, 08:39   #6
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Provided the alternator has an internal regulator your drawing looks good. Only thing missing ( and subject to some debate as to the necessity) is a "both" switch between the start and house battery.
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Old 08-08-2012, 08:46   #7
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Re: Split Charge Diode Installing

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Originally Posted by ExRonin View Post
Only thing missing ( and subject to some debate as to the necessity) is a "both" switch between the start and house battery.
Necessity? Hardly. If the start bank dies, then one would have to replace battery wiring to get the engine going. A simple 1-2-B switch would do that easily, rather than moving physical wires just when the sh&t hits the fan. Or he could simply add another I/O switch in between. Three switches or just one.

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
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Old 08-08-2012, 09:08   #8
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Stu

I agree with you that this is the proper way ( a both crossover switch) and would not have a boat without one, which is why I pointed it out. Just observing that I notice in other posts not everyone agrees to the necessity, but this is not my view.
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Old 08-08-2012, 09:34   #9
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Re: Split Charge Diode Installing

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Originally Posted by Stu Jackson View Post
Necessity? Hardly. If the start bank dies, then one would have to replace battery wiring to get the engine going. A simple 1-2-B switch would do that easily, rather than moving physical wires just when the sh&t hits the fan. Or he could simply add another I/O switch in between. Three switches or just one.
Thanks all. I agree with the crossover switch (I have one in my boat). We dont do it in this case on purpose. The owner had always trouble with this switches as the boat is used by different people. And someone always left the boat with the switch in the both position. Since there will be just two small Batteries (House and Start) in one compartment we just place a jumper cable in the batterie box for that emergency. But we more confident that that emergency will not happen anymore due the missing 2-B switch.

Thank you all for the (once more) professional help!
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Old 08-08-2012, 13:42   #10
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Re: Split Charge Diode Installing

That's exactly why proponents of the simple 1-2-B switch feel that West Marine's (and others) suggestion to use two or three switches is a tad over-the-top compared to the single useful 1-2-B switch.

Even if it was MY own boat, if I had more than one switch, I'd post HOW TO USE instructions - for myself!
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Old 08-08-2012, 16:13   #11
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Re: Split Charge Diode Installing

Swisscraft-
You will also need a fuse (two total) in the conductors going to the two batteries from the Echo Charge. Recommend Blue Sea Marine Rated Battery Fuses (MRBF), a compact fuse on its fuse holder that can mount directly on the battery B+.

If you don't want to use a 1-2-B-Off switch, you can achieve the same protection by installing a simple On-Off switch between the house B+ and the load side of the battery switch that isolates the starting battery from the engine starter. If the starting battery fails, open the starting battery isolation switch and close the emergency start switch to bring house battery current directly to the starter. I usually use a Blue Sea 6005 switch with a removable plastic key that I cable tie next to the switch.

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Old 08-08-2012, 16:59   #12
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Re: Split Charge Diode Installing

Actually, three ON-OFF switches makes a lot of sense and is very easy to understand. No need for crib sheets.

Here's one I did recently:

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Normally, you just use the HOUSE switch (it's shown as ON). When you plan to use the engine, you turn on the ENGINE switch. And, if either the house bank or the engine start battery fail, you can combine them with the EMERGENCY COMBINE switch.

It's wired so that you can use EITHER the house or the start battery for all loads, including starting, and you can switch a bad bank out of the system if desired.

Simple. Fully functional. Not expensive. These Blue Sea Systems #6006 switches are very robust (300A capacity, 3/8" studs) and cost just about $20 each.

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Old 09-08-2012, 09:02   #13
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Re: Split Charge Diode Installing

A Combiner100 would be a better choice than an echo charge. Costs 1/2 the price and can handle up to a 100 amp alternator without the 15 amp limit of echo charge so charging time is reduced. It is also bi-directional so if you put a shore power charger on the house battery the starting battery gets charged if needed.
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Old 09-08-2012, 09:11   #14
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Re: Split Charge Diode Installing

Andina,

You seem to be assuming that the alternator is wired to the start battery. Yes, many boats are wired this way.

However, when you employ an EchoCharge, normally the alternator -- as well as ALL OTHER CHARGING SOURCES -- are wired to the house battery bank.

The EchoCharge draws current from the house battery when voltage exceeds 13VDC, and passes it to the start battery.

Starting batteries require very little charging, typically using way less than one amp-hour to start a small-med size diesel. That is replaced in a few minutes, and the 15A limitation of the EchoCharge really isn't relevant. Nor would a larger charging current capacity help, because the start battery is going to take what it's going to take, and at nearly full charge will take only a few amps.

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Old 09-08-2012, 09:36   #15
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Re: Split Charge Diode Installing

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Originally Posted by Andina View Post
A Combiner100 would be a better choice than an echo charge. Costs 1/2 the price and can handle up to a 100 amp alternator without the 15 amp limit of echo charge so charging time is reduced. It is also bi-directional so if you put a shore power charger on the house battery the starting battery gets charged if needed.
Hi Andina,
thanks for the hint. First I was very impressed, cheap and it looks it does the work. But reading the data sheet http://www.yandina.com/acrobats/C100Data.pdf it raised a few questions:
The Echocharger has at least a kind of charging curve, the combiner 100 just "parallels" the battery if there is enough power. I assume now thats a bad thing in the long run - I really looks there is no control despite the Voltage of the higher battery Voltage. I think that may somehow work if you use the same Batteries - but mostly start and house batteries are different things....just my toughs....
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