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  #1  
Old 02-27-2009
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Electrical - How will it all work together?

I am rennovating the electrical system on a Midship 25 (later known as the Parker Dawson 26). The boat electrical system has a house bank of 2 100ah batteries and a starter battery , all three batteries are wet cells. The batteries are attached to a "1,2,both,off " switch. The previous owner had an AC extension cord arrangement, an auto battery charger attachable to a single battery at a time with alligator clips and a .9 amp solar cell wired directly to the house bank. The boat has an electric start sailmaster 9.9 connected directly to the starter battery.

My plan is to add a proper AC power arrangement, hardwire an AC charger for charging the batteries at the dock and hardwire the solar panel with a disconnect plug. I plan to use the solar panel to keep the batteries trickle charged when the boat is on the trailer or when shorepower is not available.

I have purchased a Flexcharge PV7D for the solar panel that is capable of charging 2 battery banks and I am researching AC battery chargers. I am also contemplating an ACR or battery isolator to allow the outboard to charge the house bank when the starter battery is fully charged.

I am now scratching my head about how all this will work together. I have several questions I would appreciate feedback on from the collective wisdom of this forum:

1. if I get a high end AC 3 phase charger that also conditions the batteries periodically, will an ACR or battery isolator interfere with its proper function?

2. Would it be a big improvement to get an AC charger that charges the three batteries individually vs. treating them as two banks? Will it work on all three batteries even if the two house batteries are wired together in parallel?

3. I am actually solving the same problem three ways with my approach. The ACR, Flexcharge unit and the AC battery charger are all three monitoring battery voltage and distributing power to batteries that need it and (in the case of the flexcharge and AC charger) following a charging profile that promotes battery health. Is there some economical way to solve this problem once and feed the three sources of power to that solution? Or is that a big boat only, expensive alternative.

I have gotten alot of value from this forum and I will appreciate any advice you can give me.
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I didn't read past the part in #2 in which you asked about charging individual batteries in a single bank separately. My suggestion before going further is that you may be lacking in some fundamental understanding of electrical systems. You cannot isolate batteries in the same bank.
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OK, so the answer to question 2 is no. I thought that might be the case, but I also thought that if the battery charger was connected directly to the terminals of all three batteries that the charger might sense the battery to which it was directly connected even though it was also connected to the other battery. I have read that when charging a two battery bank that one should connect the charger to the positive terminal of one battery and the negative terminal of the second battery. This implies that even though the batteries are not isolated, the charging system behaves differently depending on what batteries it is attached to.
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Talking

Quote:
Originally Posted by jhaley66 View Post
I have read that when charging a two battery bank that one should connect the charger to the positive terminal of one battery and the negative terminal of the second battery. This implies that even though the batteries are not isolated, the charging system behaves differently depending on what batteries it is attached to.

The charging system looks at a battery bank as ONE large battery. It can not differentiate between individual batteries within the bank. That said, connecting the charger to both the house bank and starter battery will charge each entity as needed but not an individual battery within the house bank......or I could be completely out of my mind!
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Just curious, why did you go with a Flexcharge PV7D. It would make far more sense to go with a single bank charge controller and use an echo charger to deal with the starting bank.

An ACR won't interfere with a charger doing a battery conditioning cycle generally, since it is just a relay. An echo charger will.

Again, I wouldn't bother going to the expense of getting a two-bank charger, since it would make more sense to use an echo charger with a single bank charger.

IMHO, you're making the system overly complex, and spending more money than you have to. There is no need to treat the house bank as two separate batteries, and very little advantage in doing so.
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Try this book. The Marine Electrical and Electronics Bible (Hardcover)
by John C. Payne (Author) or many other 12 volt books
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Just curious, why did you go with a Flexcharge PV7D. It would make far more sense to go with a single bank charge controller and use an echo charger to deal with the starting bank.

Sailingdog, thanks for the feedback.

I thought the PV7D would help me provide a float voltage to both battery banks and keep my batteries healthy. I have read that an echo charger or ACR will not provide a float voltage to the second bank because the voltage on the first bank is too low to trigger the device. That is the same objective behind getting a two bank charger.

Will an echo charger permit both banks to be maintained in float mode?

IMHO, you're making the system overly complex, and spending more money than you have to. There is no need to treat the house bank as two separate batteries, and very little advantage in doing so.

Got it, thanks.
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Try this book. The Marine Electrical and Electronics Bible (Hardcover)
by John C. Payne (Author) or many other 12 volt books


Thanks for the tip, BadSanta.

So far I have read Calder's Boat Owners Mechanical and Electrical Guide and and Casey's Sailboat Electrics Simplified. The most often discussed scenario in these books is managing the output of the engine alternator. My Midship used to have an inboard westerbeake diesel with an alternator, but one of the previous owners removed it and replaced it with an outboard that is directly connected to the starting battery.

So far I have a basic understanding about each of the parts of the electrical system but I am struggling with how they all fit together in a practical arrangement. My objective is a charging arrangement that I can set and forget for a month or more if I need to. The previous owner had the boat fill up with water at the dock and on the trailer several times because the charge on the bilge pump battery (currently the starter battery) was not managed properly in spite of the availability of shore power and a solar panel.
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Quote:
Originally Posted by sailingdog View Post
Just curious, why did you go with a Flexcharge PV7D. It would make far more sense to go with a single bank charge controller and use an echo charger to deal with the starting bank.

An ACR won't interfere with a charger doing a battery conditioning cycle generally, since it is just a relay. An echo charger will.

Again, I wouldn't bother going to the expense of getting a two-bank charger, since it would make more sense to use an echo charger with a single bank charger.

IMHO, you're making the system overly complex, and spending more money than you have to. There is no need to treat the house bank as two separate batteries, and very little advantage in doing so.
Sailingdog, thanks for the feedback.

I thought the PV7D would help me provide a float voltage to both battery banks and keep my batteries healthy. I have read that an echo charger or ACR will not provide a float voltage to the second bank because the voltage on the first bank is too low to trigger the device. That is the same objective behind getting a two bank charger.

Will an echo charger permit both banks to be maintained in float mode?
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Old 02-27-2009
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SD knows what he is talking about. The answer is yes, an echo charger will do what you want. Keep doing your homework and sometimes you will find that you spent some money that could have been better spent, just ask me
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