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Old 30-03-2011, 07:13   #61
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Re: Questions about replacing battery charger

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I was speaking with a sales person regarding the correct size of charger and they mentioned something that I found interesting.

Let's assume one has 300Ah in the house bank. Using the 20-25% sizing recommendation on the charger would dictate a 60-75AMP charger. However, as one would not discharge the bank below 50%, the actual capacity to charge is only 150Ah, which would require a charger of 30-40 AMPs which should charge a fully diminished bank in roughly 5 hours.

Which is the correct target? 40 or 75AMP?

Thanks,

Andrew
Andrew,

The 75A charger is better. You're not charging only half the battery; you're charging the battery to half its capacity!

By the way, in the real world you're not charging to 100% of capacity unless you're at dockside or have a large solar panel or wind generator capacity. It simply takes too long to get that last 15% or so into the battery. Most cruisers operate between 50 and 80% of capacity, or one-third of the battery's rating. So, with a 300AH battery capacity your effective availability while cruising is 100AH.

While it is correct that a fully discharged flooded battery will take an inordinate and possibly damaging amount of current, its ability to take high current is limited to the last 10-15% of its capacity. That is, once the battery reaches about 10% charge, it's ability to take high current reduces DRAMATICALLY, and remains low during the rest of the recharge cycle.

Since we're talking here about batteries which are only partially discharged -- say to 50% capacity -- there's no way in hell you can put too much amperage into them when recharging UNLESS the voltage is allowed to rise above about 14.4-14.6VDC for a 12V battery. Even if you connected a 500 amp alternator or battery charger!

BTW, emergency vehicles are living proof of this; they have HUGE alternators, but don't overcharge the batteries because they are voltage-limited.

I have a 100 amp Balmar alternator on my boat, with a Balmar MaxCharge programmable external regulator. This alternator charges my 675AH house battery bank (6 T-105s in series/parallel) and, via an EchoCharge, maintains my 100AH group 31 starting battery.

I have never seen more than 80amps or so charging current, but then I've never let my battery bank discharge below about 40% of capacity, usually only 50%. However, the 80 amp charge rate will hang in there for a very long time, until the batteries reach a reasonably high state of charge, whence it will dial back to lower numbers and, eventually, to about 10 amps or lower.

Same thing with my 120amp capacity Victron charger.

As I said, batteries are going to take what they're going to take, given adequate voltage regulation and provided they're not fully discharged to begin with.

Bill
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Old 30-03-2011, 07:28   #62
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Re: Questions about replacing battery charger

we worked it out before that the honda 2000i will not run the iota 75 (17 amps at full blast eu2000i is 13 amp nominal 16 peak) i would get a sterling pro ultra 60 charger not much price difference and will run at half the load on the genny (has pf of .97) ie the sterling will require 900kva for 60 amp to the batteries the iota 75 requires 2040KVA for 75 amp to the batteries, its a no brainer to me. It will save you in fuel and also on shore power if you have metered power. The small purchase difference between the 2 will be returned fairly quickly.
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Old 30-03-2011, 07:35   #63
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Re: Questions about replacing battery charger

and another point is the sterling will put a far greater charge into your batteries, the iota tops out at 13.6 v the sterling goes as high as 14.2 a huge difference in just how much of a charge of the batteries full capacity you will obtain.
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Old 30-03-2011, 07:41   #64
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Re: Questions about replacing battery charger

As stated earlier, the Honda EU2000i will run the Iota DLS-75/IQ4 just fine.

And, the Iota does not "top out" at 13.6V. That's the FLOAT VOLTAGE. With the IQ-4, Iota's use a 3-stage "smart" charging regime.

And, in my experience, they put out more power for longer than most other "marine" chargers.

Bill
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Old 30-03-2011, 07:43   #65
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Re: Questions about replacing battery charger

btrayfors one of the other reasons i neglected to look at the power factor is that over here in euro land anything over 75 watts must be power factor corrected, its the law and one law that i actually agree with for a change!
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Old 30-03-2011, 07:49   #66
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Re: Questions about replacing battery charger

ok im lost here the max amps of the iota 75 is 17 the max out of the honda is 16, sounds like a struggle to me, certainly it will run the 60 but the 75 is at the extremes of its abilities, the 75 specs show open circuit voltage of 13.6 full load voltage of 13.4 am i missing something?
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Old 30-03-2011, 08:21   #67
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Re: Questions about replacing battery charger

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ok im lost here the max amps of the iota 75 is 17 the max out of the honda is 16, sounds like a struggle to me, certainly it will run the 60 but the 75 is at the extremes of its abilities, the 75 specs show open circuit voltage of 13.6 full load voltage of 13.4 am i missing something?
Look a little deeper at the Iota web site. Specs for the IQ4 smart charger show max of 2.466VDC per cell for bulk charge phase. 6 cells in a 12V battery gives max voltage of 14.8VDC. 2.366V per cell for the absorption phase, 2.266V for float.
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Old 30-03-2011, 08:24   #68
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Re: Questions about replacing battery charger

Yes, you're missing the fact that the 17 amps is the MAXIMUM, not the maximum continuous. That's more like 13 amps.

Steven, I completely agree with you re: the importance of power factor (PF) compensation. AFAIK, the Iotas do NOT have any PF compensation, and their PF runs about 0.67 from measured reports. Not great; it means a bunch of "available" power from the generator isn't put to use in actually charging the batteries.

However....and there's always a however...there are other considerations. These include other characteristics of the charger (charging curves, RFI, ability to handle "dirty" power input, regulation, temperature and other protections, etc., etc.), reliability, availability, track record, manufacturer's support and, of course, price.

Here's where the Iota's shine, in my experience and opinion.

- low price and good availability
- good quality construction
- excellent support from manufacturer
- small, compact
- very reliable
- quiet
- excellent charging with the IQ-4 (14.76V
bulk, 14.16V absorption, 13.56V float)
- extremely low RFI (doesn't interfere with HF radio reception)
- a very excellent track record from virtually all users.

That certainly doesn't mean that these chargers are for everyone, or that there aren't other options. And, new products are coming on the market every day, some of them PF corrected and quite efficient. Here's one from China which many of the solar affectionados are trying and liking: http://www.powergatellc.com/pdfs/PB-1000.pdf

But, before making a decision as to which one to put on your boat, I believe it's important to take ALL the factors into consideration, not just the PF.

Bill
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Old 30-03-2011, 08:57   #69
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Re: Questions about replacing battery charger

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Andrew,

The 75A charger is better. You're not charging only half the battery; you're charging the battery to half its capacity!
Thanks Bill for your detailed explanation.
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Old 30-03-2011, 09:29   #70
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Re: Questions about replacing battery charger

This is getting stranger than a gun thread. Y'all are not well.
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Old 30-03-2011, 09:57   #71
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Re: Questions about replacing battery charger

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This is getting stranger than a gun thread. Y'all are not well.
You're right, Lorenzo! As Johnathan Winters used to say, "sometimes I get to believing my own stuff"!

How's the crawfish business?

Bill
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Old 30-03-2011, 11:04   #72
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Re: Questions about replacing battery charger

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and another point is the sterling will put a far greater charge into your batteries, the iota tops out at 13.6 v the sterling goes as high as 14.2 a huge difference in just how much of a charge of the batteries full capacity you will obtain.
Nope, a Digital Sterling charger will go higher than that. Since we have FLAs we charge at 14.8 volts, until the charger drops the voltage down for the float. Thump those amps in baby

Pete
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