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Old 13-08-2013, 13:24   #1
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Size of Battery Charger

Folks,

I need a gut check.

I need to replace my battery charger. I currently have a 270 AMP (90x3) battery bank, the charger, and a 90 AMP alternator.

I want to move up to a 500 AMP battery bank to support our future cruising wants.

When I talked to our local Electronics guy at the marina he advised Lifeline AGM's (4 x GPL-31XT) but also advised that I would need a 100 AMP charger to appropriately charge that battery bank.

Question: is a 100 AMP charger really necessary? If I am going to be hooked into a marina I'll be there at LEAST overnight, so 8 hours with a 30 AMP charger to top up 250 AMPS isn't really a problem. Is there something I am not getting? Am I getting sold on a Bill of Goods?

- z
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Old 13-08-2013, 13:35   #2
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Re: Size of Battery Charger

Your current set up should be fine (assuming that it is working properly). I would not recommend upgrading but it wouldn't hurt anything either. the lower the amperage of the charger the longer it takes to charge, also your charger is not putting out 90amps all the time it is putting out only the amount of amps the battery requires based on charge state and battery temperature. I have a (under powered) charger on my boat that works just fine over night. My house bank is 168 total amps and my charger is only 5 amps max output. It takes longer to charge them if I bring them down too far but as long as I have the time they come right back up to where they need to be. Now all this is also assuming that you have a 3 stage smart charger, (bulk phase, top off phase, and a maintenance phase). if it is not a smart charger then yes I would recommend up grading, if it is a smart charger you will be fine
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Old 13-08-2013, 13:38   #3
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Re: Size of Battery Charger

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Originally Posted by zboss View Post
Folks,

I need a gut check.

I need to replace my battery charger. I currently have a 270 AMP (90x3) battery bank, the charger, and a 90 AMP alternator.

I want to move up to a 500 AMP battery bank to support our future cruising wants.

When I talked to our local Electronics guy at the marina he advised Lifeline AGM's (4 x GPL-31XT) but also advised that I would need a 100 AMP charger to appropriately charge that battery bank.

Question: is a 100 AMP charger really necessary? If I am going to be hooked into a marina I'll be there at LEAST overnight, so 8 hours with a 30 AMP charger to top up 250 AMPS isn't really a problem. Is there something I am not getting? Am I getting sold on a Bill of Goods?

- z
i currently have a 24v 75 amp charger for my 120 amp (total) house batteries,any setting over the lowest and the batteries fizzz!
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Old 13-08-2013, 13:44   #4
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i currently have a 24v 75 amp charger for my 120 amp (total) house batteries,any setting over the lowest and the batteries fizzz!
Yes in bulk mode the charger is too powerful typically charge between 1/10 to 1/5 C

Dave
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Old 13-08-2013, 14:02   #5
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30 amps times 8 hours leaves you at 240 amp hours. But the last 50 amp hours will go in much slower. So, no you won`t have charged batteries in the morning. But then you could complete the charging while crusing the next day.
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Old 13-08-2013, 14:02   #6
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Re: Size of Battery Charger

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Yes in bulk mode the charger is too powerful typically charge between 1/10 to 1/5 C

Dave
it's great it works like a reverse dimmer switch, if i turn it to boost i can make my led's very bright

currently only have the 2x60amp leisure batteries ,as opposed to the normal 1200ah bank!
my other charger is 90 amp!
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Old 13-08-2013, 14:03   #7
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Re: Size of Battery Charger

If your battery bank is 500 amps and you don't let it get below approx. 12 volts (this will extend battery life) then you are only needing to charge 200-250 amps not the whole 500. With a 90 amp charger the bulk of the charging will be done in 2-4 hours and the longest part of the charge (the top off) can add anywhere from 2-6 hours on top of that depending on the batteries and the charger. so even if the top off phase does not complete you still have 90% or more of your batteries. Also the OP said that they are planning for this system to be used overnight at dock which will give them ample time for what they need
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Old 13-08-2013, 14:29   #8
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He stated that he has a 30 amp charger.
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Old 13-08-2013, 14:57   #9
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Re: Size of Battery Charger

I currently have a 30 amp charger that has failed and I want to take this opportunity to increase my battery bank size and charger. However, I am reluctant to invest in a 100 AMP charger if a 30 AMP charger will suffice for 500 or more amps of AGM battery power when hooked up to shore power for a day or two.

The electrician gave me the impression that even if I were to be hooked up to shore power long enough for the 30 AMP charger to fill the batteries, that I would somehow be degrading the batteries by not hitting them with enough juice.

How may 12 volt amps does one get out of a Honda 2000 generator?
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Old 13-08-2013, 14:59   #10
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Re: Size of Battery Charger

Sorry my bad I was going off of the OPs statement of the 90 amp charger... the 30 amp is a little low but compared to mine it would still be a huge improvement over what I have. Ultimately I would say no you don't need to go to 100 amps if you don't want to spend the money but 30 amps will take you a while to get to full charge but as long as you don't drop the bank below 12 volts it should be plenty to get you up to speed by morning.
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Old 13-08-2013, 15:00   #11
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Re: Size of Battery Charger

the only difference the amperage makes is the amount of time it takes to charge, it will not hurt the batteries by taking longer.
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Old 13-08-2013, 15:12   #12
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The honda EU2000i has a 8 amp 12 volt output, but will run my 55 amp ITOA charger.
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Old 13-08-2013, 15:56   #13
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Re: Size of Battery Charger

Quote:
Originally Posted by zboss View Post
I currently have a 30 amp charger that has failed and I want to take this opportunity to increase my battery bank size and charger. However, I am reluctant to invest in a 100 AMP charger if a 30 AMP charger will suffice for 500 or more amps of AGM battery power when hooked up to shore power for a day or two.

The electrician gave me the impression that even if I were to be hooked up to shore power long enough for the 30 AMP charger to fill the batteries, that I would somehow be degrading the batteries by not hitting them with enough juice.

How may 12 volt amps does one get out of a Honda 2000 generator?
IIRC correctly Lifeline recommends, in their technical manual, a charger capable of a min of 20% of Ah capacity for the longest life. This is the min recommendation. Just be glad you don't have Odyssey batteries as they want to see a min of 40% of Ah capacity...
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Old 13-08-2013, 16:40   #14
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Re: Size of Battery Charger

Get an iota DLS-55/IQ4 charger. Low cost, very good smart charging, and about the largest charger the Honda EU2000i will handle.

If you want to go fancier, get a Sterling Ultra 50A or 60A model. Great charger with all the bells and whistles, including worldwide input voltage capability and power factor correction.

Bill
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Old 13-08-2013, 17:35   #15
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Re: Size of Battery Charger

I have the Sterling Pro 60 Amp charger and a 500Ah Battery bank. I run this off a Honda Genny just fine. If I run the Batteries down to 12.2 to 12.3 Amps the charger shows 60amps going in for a bout an hour then will drop pretty quickly to about 30 amps. I generally run it for 2-3 hrs and it tops the batteries off to probably 90%. If I run them down to 12 - 12.1 which is not often then it will take 60 amps for an hour then slowly drop back. Like Bill said they are not cheap though and will run you around $700 I think when I bought mine.
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