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Old 31-12-2010, 10:44   #1
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Two Bank Charger on Single Bank ?

Hi,

I have two group 31 FLA's for my house bank, and a single group 27 for a backup/starting bank. I'd like to set it up so all my charging goes to the house bank and the start battery gets charged through an echo-charge or something similar...

So for my shore-power (or generator) driven charger, I only need a single bank charger. The problem is the single bank versions are rare and most often charge at around 6amps. Very few of them are 10 amps and I've only found 2 that are 15amps. I think the 15 amp single bank charger will be fine for my needs. BUT I've become curious.... If I where to buy a two bank 20 amp charger (10/10, or something similar, 15/15 etc..) could I both outputs on the same battery to give 20amps to a single bank? (Same question applies to larger chargers/banks as well)

Thanks.
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Old 31-12-2010, 10:57   #2
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All you need is a single two bank charger. That will keep both of your batteries banks topped up. You leave them isolated from each normally and run a positive lead from the charger to each bank.

There are plenty of two bank chargers with a variety of charging rates that start from a few amps to far more than what your boat needs. The charging capacity of the charger should not only be gauged to the size of your banks but also to how much power your house load typically consumes while at the dock.

http://www.defender.com/category.jsp?path=-1|328&id=985
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Old 31-12-2010, 11:03   #3
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So you're saying that even though the batteries are connected together in parallel. A two bank charger will charge each battery individually?

I thought because the batteries are paralleled they are not isolated at all and no matter which battery I hook the charger leads up to, it will see both batteries as one single battery (hence the "bank"), correct?
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Old 31-12-2010, 11:04   #4
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Your echo charge idea is a good one. I'd spend a little more money and get a 30 amp charger (this would provide a charging rate that is 15% of your house bank amperage). Some batteries - especially AGM - can take a higher rate.

A few reasons:

This will reduce generator run time and increase the load on the genset. Gensets don't like to be loaded at less than about 25% of their capacity. 50-75% is better. Genset fuel use per watt is also bad at low loads.

A faster charge rate (but not too fast) may reduce sulfation on the batteries plates and they will last longer.

There are a lot of good 30 amp battery chargers. Look at Victron, Charles, and IOTA. Look for one with three stage charging and a battery temperature sensor.

Carl
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Old 31-12-2010, 11:08   #5
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Your best charger is the alternator. I would also run your alternator output to the house bank. Let the echo charger handle the start battery charging. This solution means you never have to think about switching battery switches around.

Carl
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Old 31-12-2010, 11:38   #6
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Your best charger is the alternator. I would also run your alternator output to the house bank. Let the echo charger handle the start battery charging. This solution means you never have to think about switching battery switches around.

Carl

Thanks Carl,

Yes, I'll be running all charging sources to the house bank as per the simpler solution (except I may use an echo-charge instead).

It looks like Iota's 30amp charger is exactly what I'm looking for (because it's a single bank charger). Thanks.

But that still leaves the question unanswered (though, only theoretical at this point). Most of the other chargers, like the Charles, Guest, Promariner, Xantrex etc.. only provide multi-bank outputs for their chargers above 15amps or so... For example, the Charles 30amp (2000 SP) is a 3-bank charger (and their 20amp is two bank, etc..). So it spreads the 30amps across 3 outputs giving 10amps per output. The question is: is it safe to put all 3 of those outputs on a single bank?
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Old 31-12-2010, 11:46   #7
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I 2nd the iota chargers Best charger for the money
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Old 31-12-2010, 12:38   #8
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Yes, you can parallel the two charger outputs, to (both) feed a single battery bank.
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Old 31-12-2010, 12:55   #9
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I iota has a 3 stage reg that will run 2 charger
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Old 31-12-2010, 12:56   #10
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Quote:
Originally Posted by callmecrazy View Post
Hi,

I have two group 31 FLA's for my house bank, and a single group 27 for a backup/starting bank. I'd like to set it up so all my charging goes to the house bank and the start battery gets charged through an echo-charge or something similar...

So for my shore-power (or generator) driven charger, I only need a single bank charger. The problem is the single bank versions are rare and most often charge at around 6amps. Very few of them are 10 amps and I've only found 2 that are 15amps. I think the 15 amp single bank charger will be fine for my needs. BUT I've become curious.... If I where to buy a two bank 20 amp charger (10/10, or something similar, 15/15 etc..) could I both outputs on the same battery to give 20amps to a single bank? (Same question applies to larger chargers/banks as well)

Thanks.
I'm not sure what you're trying to do.

For shore power charging do you only have a limited time to charge? Even the 5/5 is going to top off the batteries in two to three days. A 15 probably in a day. Why not keep both banks topped off with the dual output charger?

John
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Old 31-12-2010, 13:12   #11
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Quote:
Originally Posted by callmecrazy View Post
So you're saying that even though the batteries are connected together in parallel. A two bank charger will charge each battery individually?

I thought because the batteries are paralleled they are not isolated at all and no matter which battery I hook the charger leads up to, it will see both batteries as one single battery (hence the "bank"), correct?
If they are electrically isolated from each other then you will need to have each bank charged separately. If they are truly parallel to each other then all you need is one charger to charge both batteries.

It's a smart idea to have your start battery and your house bank electrically isolated from each other so your house bank does not run down your start battery leaving you with the inability to start your engine. One way that automates this process is with battery combiner or a battery isolator. There are merits and disadvantages to each which has been the subject of some debate.

If all you have or want to purchase is a single battery charger with the ability to charge only one bank, then you should set up your battery switch with the ability parallel all your batteries. This would be the "All" position.
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Old 31-12-2010, 14:07   #12
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I'm not sure what you're trying to do.

For shore power charging do you only have a limited time to charge? Even the 5/5 is going to top off the batteries in two to three days. A 15 probably in a day. Why not keep both banks topped off with the dual output charger?

John
John I normally wouldn't be concerned about the amperage except it's possible I'll be using a small generator (honda 1000) to charge while at anchor/mooring for extended periods. So getting the most amperage out of the charger will be important. I'd rather run a small generator to conserve fuel compared to my 1gal/hr A4


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Yes, you can parallel the two charger outputs, to (both) feed a single battery bank.
Thanks, that's the answer I was looking for. I still haven't found any reference to doing this in any of the charger installation instructions, but it makes sense in my mind... this gives me a lot more options in choosing a charger.
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Old 31-12-2010, 14:10   #13
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I have two Iota 55 amp chargers set up on my boat. I have one of them on all the time when plugged into shore power and the other needs to be plugged into a circuit on the AC when I am using the generator. They work great both ways. I believe that you will need the IQ4 in order to make the charger work as a three stage charger.
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Old 31-12-2010, 14:14   #14
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I have a Xantrex Truecharge 40+. I talked to Xantrex tech support (nothing like getting an answer from the manufacturer). They said the three outputs would be split according to the needs of the various battery banks. If 2 battery banks are topped up, all 40 amps would be available to the third bank
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Old 31-12-2010, 14:41   #15
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I have two Iota 55 amp chargers set up on my boat. I have one of them on all the time when plugged into shore power and the other needs to be plugged into a circuit on the AC when I am using the generator. They work great both ways. I believe that you will need the IQ4 in order to make the charger work as a three stage charger.
I have the same setup except the 2nd charger is hard wired to the 2nd side of the gen set I have 110amps with the genset running
I would check the specs on the honda and buy the biggest charger it will support I iota 55 amp uses 13amps ac They make them to 90 amps and all can be used together
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