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Old 10-27-2011, 02:08 PM   #1
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How big of a charger do I need?

How big of a charger do I need?

Simple enough question I suppose, but I doubt a simple answer. The big winter project is overhauling electrics and charging. How do I determain how large of a charger I nedd? Or is it how much I want?

I'm looking at two brands: Iota (non marine but lots of boater use it) and Charles. I want separate charger and inverter (inverter size question is pretty easy to figure).

Thanks.

Tom-
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Old 10-27-2011, 07:42 PM   #2
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RE: How big of a charger do I need?

Usually answered by type of batteries and size of bank

IOTA makes good stuff.
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Old 10-27-2011, 08:25 PM   #3
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How big of a charger do I need?

Tom,

I have a large house bank 1100AH and went with a Magnum 3100watt 160amp inverter/charger and I love it. You can even run an AC off the thing. You can never have too much of a charger when your on the hook and trying to limit genset time


-- Edited by Daddyo on Friday 28th of October 2011 07:19:58 AM
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Old 10-27-2011, 08:27 PM   #4
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RE: How big of a charger do I need?

I sure like the pricing of the Iota too. Which inverter do you have in mind?
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Old 10-28-2011, 03:52 AM   #5
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RE: How big of a charger do I need?

An inverter WITH a charger is usually the lowest cost and easiest to install.

Dockside a tiny unit that will simply keep up with DC loads is fine 20A ?

If you wish to charge from the noisemaker a belted 130A truck alt and 3 stage smart V reg will cut the noisemaker time in half or less .

Depends on what you are willing to pay for the "sounds of silence" on the hook.
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Old 10-28-2011, 04:22 AM   #6
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RE: How big of a charger do I need?

i have iota chargers love them
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Old 10-28-2011, 05:54 AM   #7
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How big of a charger do I need?

I currently have four golf cart batteries as a house bank and one Group 27 to start up Dr. Perky. I am planning on replacing the house bank during this project and MAY go up to six GC batteries. I'm also thinking of adding a dedicated "booster" battery to the windlass circuit, but I haven't worked that out yet.

So is the amperage amount more of a function of how fast you want to charge the batteries back up and not a function of what load it will carry (ie... number and size of cells)? I was thinking of a 50A Iota because I wasn't sure I wanted a three bank charger. I was going to use a Balmar Duo Charger to charge the starter battery, but haven't worked out the windlass battery when I do that. That's where Charles came into the picture. Well, that and the price. I can get two or three Iota's for the price of one Charles.

Time to crack open Calder's book again ;-)

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-- Edited by GonzoF1 on Friday 28th of October 2011 05:56:19 AM
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Old 10-28-2011, 04:30 PM   #8
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RE: How big of a charger do I need?

my house bank consists of 12ea AGM 6v 'golf cart' 250AH ea in series parallel for a bank size of 1500ah (theoritcally).
Start battery is one grp 31 AGM for a single Cummins 6bt.

Windlass is powered from the house bank, as well as everything else on the boat except the start battery. (big wire was cheaper than a remote battery and associated charging/maint. hassle).

Charging is accomplished underway by a large frame 200A alternator, regulated by a Balmar ARS-5, with temp control for battery bank and alternator.

Charging dockside is by an IOTA 70A with Iota's regulator.
(normally for wet cells 25% of AH capacity is used to size the charger - higher is possible for AGM's and some gels)
In my case, when I return to a dock, the bank is normally mostly if not completely charged, so the load on the IOTA is usually finishing float cycle.

Another nice feature of the IOTA is they are rated as a powersupply as well and at dockside the IOTA takes care of all 12v loads.
- I leave the house bank isolated when dockside to avoid inadvertant overcharging from continued float voltage
- AGM"S take many months to lose voltage, so I manualy float them for 5 hours once or twice during the winter months.

Start battery is recharged via Balmar Digital duo(echo charge concept)

I sized the house bank on the following criteria:

- typical cruising use of 130AH in a 24 hour period
- desire to be able to remain at anchor up to 6 days without having to initiate a recharge cycle (without using more than 50% of the bank capacity).


After talking with the battery mfg engineers, I was able to identify the ideal voltages for these AGM's. I found the 'pre-set' charging voltages that Charles and others had, were not necessarily the same.

The IOTA has a way to set these voltages(via potentiometer) for the charging cyles.

Of course, the Balmar regulators can also be programmed to the voltages you want.


I am guessing Gonzo1 is planning to replace the house bank with flooded wet cells, so the charging voltage issue is less critical and factory pre-sets should work adequately.



I have a schematic in powerpoint of my system which does not post on this site, but if you want a copy, send me a email offline
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Old 10-28-2011, 06:09 PM   #9
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RE: How big of a charger do I need?

Thanks Shan... I only have about 440Ah total. 25% of that is over 100A... You sure that's the right formula?

So you disconnect the charge from the house bank at dock? Do you just use a switch? What about if you are gone for a week or two?

Yes... Wet cells will replace these. But I may go up to six for 660AH.

My issue about a separate battery for the windlass is that with this small of a house bank, a couple of failed attempts to get anchored might kill my house bank just before I need it to be strong. (ie: sitting at anchor)
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Old 10-28-2011, 11:14 PM   #10
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RE: How big of a charger do I need?

Don't quote me on the ratio of the shore charger - this is what I have been told.

I suspect with enough time even a charger rated at 5% of the house capacity could charge it, but there seems to be a point where it just doesnt make sense - on either side of the scale.

A 350A charger would be one heck of a piece of equipment for your boat and bank - plus the bank would probably be unable to accept the amps at that rate for very long - unless they were AGM's, but would fall off drastically when the bulk phase was done -- of course you would have to have one HEFTY shore cable to make that work.

On the other hand a 5A charger would probably take a miserably long time to recharge the bank if you had depleted it to 50%. And there is the matter of sulphating when you can't pump it up some.

So I think the 20-25% ratio is a ballpark.

My house bank is 1500AH. In my case my engine charger at 200A is well below the 25% mark, but does a very adequate job.
The shore charger at 70A would be way too small according to the theory, but again it rarely has to pump out many amps as it typically comes into use when the house bank is mostly recharged, although I think it would do an ok job of bringing the bank back up even from a 50% discharge if necessary.

I have yet to read or hear of any 'negative' talk about the IOTA's, instead the units will put out the full rated amperage for quite a long time period(bulk phase).




And yes, I isolate the bank via a rotary switch and leave it 'uncharged' for months at a time - Remember these are AGM's which do not self discharge like wet cells do.

The IOTA remains on 24/7 when dockside to provide incidental 12v to any parasitic loads or bilge pumps in an emergency, or when we are aboard in the off season.
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Old 10-28-2011, 11:16 PM   #11
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RE: How big of a charger do I need?

Incidentally, IOTA's can be paralled for more amps - I understand they are one of the few chargers that can operate like this without conflict.
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Old 10-29-2011, 08:20 AM   #12
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RE: How big of a charger do I need?

One side note: I think that if I did go with a booster battery for the windlass, I would consider a much smaller and separate charger for it. Maybe one that is local to the battery location.

So a 60 or 70 amp would be adequate? I was originally looking at a 40 or 50 amp.
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Old 10-30-2011, 09:18 PM   #13
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How big of a charger do I need?

Gonzo,

My 660AH GC bank gets topped off at the slip by a ProTech 30A charger. When I return to the slip after an hour or so run, the batts are nearly topped off at 90% or more. The shore charger just puts the finishing touches on the charge with the float charge. I have recently added Water Miser battery caps to limit the off venting of the battery electrolyte during periods of extended charging. If I were buying a charger today, I would consider a 3 bank 60-80A charger if money was not an issue.

One engine will have a Balmar 120A alternator (regulated to 100A due to 1/2" belt size limits) with the Balmar MC-612 smart regulator when I finally get around to installing it.

I've heard the rule of 25% bank capacity in a charger, but have thought it was more appropriate for alternator sizing which is limited to big engine running time. And even at that, it's a goal for battery utopia more than real world practices. Not many folks have shore chargers that will provide 25% of the charge for their bank.

My 100A Balmar will provide a 15% smart charge to the house bank which will be a considerable improvement from my current alternators. And even with my current alts, I don't notice any problems charging.

Have you considered upping the size of your start battery to something like a group 31 and connecting your windlass to that battery? The engines are already operating when the windlass is in operation and there should be plenty of juice there to provide the 5 mins or so of windlass operation. If you decide you want a separate windlass battery, consider the advantages of a combiner to provide the charge once your start battery gets up to voltage (~13.2V). It saves you from buying and installing a separate charger.


-- Edited by FlyWright on Sunday 30th of October 2011 09:20:45 PM
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Old 10-30-2011, 11:33 PM   #14
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RE: How big of a charger do I need?

Not exactly sure what this means, but both 110 shore power*(8KW toroidal isolation transformer) as well as 2000 watt interface and charger, charges*my three*24-volt batteries fully.
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Old 10-31-2011, 05:37 AM   #15
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RE: How big of a charger do I need?

Thanks Al... I have now seen the 25% rule in Calder's book, still, I don't see it being realistic.I think I am going to go with a 50 or 60 amp charger and be done with it. Probably the Iota as the price is right, it can be a power supply and has a good battery maintenance ability.

As for the windlass... that's a good option that I will consider. It's a tough nut to crack. I don't want, have the money, or have the space for a big house bank, but just minutes before I need my batteries to be on a full charge, I put the single largest load I have on the entire boat onto it. I suppose that part of this project will be a Link battery gauge. At least THAT way, I'll know where I stand during the process.
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Old 10-31-2011, 05:58 AM   #16
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RE: How big of a charger do I need?

Have you done a lot of research and face to face talk on the Link monitor???* I have heard from REAL people that they aren't satisfied and would never rely on one...even though most magazine aticles rave about such gizmos (go figure).

Not positive myself as there are mixed reviews and I know these types of instruments take a lot to get right and understand (lots of peole don't)...if you are satisfied then great...just throwing up the red flag as I'm waiting till I have some more experience with them.
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Old 10-31-2011, 07:41 AM   #17
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RE: How big of a charger do I need?

Are there any options to this particular unit? TBH, I'd be happy with just a meter that tells me what my aH usage is at a glance.
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Old 10-31-2011, 08:56 AM   #18
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RE: How big of a charger do I need?

I think a battery monitor of some type that tracks amps(or power) used is a very valuable tool - at least to initially determine your normal power consumption.

Agreed it has to be set properly, as there are some variables that come into play as you use juice.

Also make sure that the bank being measured has no 'hidden' loads that are not being tracked through the shunt.

I have a Link 10 and it comes with a 40+ page manual that runs through some of the theory behind the algorithms the unit uses. And the 'actual' readings the monitor gives are directly related to how you set the unit up.

On the cruisers forum website(http://www.cruisersforum.com), there is a gent named Rick located in Bremerton WA, who was one of the original designers of this monitor. Check the archives and if you post a question about the Link 10 you can usually get him to advise/respond.

Rick advises to begin by changing the readings from 'amps used' to 'KWH used'. You have to adjust the way you think about your house bank a bit, but it is not too hard to do.

Also, getting the Puekert effect setting right is important. I spoke to the battery Mfg engineers and got Rick's take on this as well. To date, it appears I have it about right - although as the bank begins to age, this setting can require some tweaking.


Now that mine is set properly, I find it to be reliable enough to indicate a realistic state of charge.
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Old 11-01-2011, 06:55 AM   #19
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RE: How big of a charger do I need?

Something the guys at Iota pointed out to me was to be careful not to get a charger that the output of the genset can't cover with the other loads you might need while it's running. That said, I may back down to the 55 Amp instead of the 75 Amp.
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Old 11-01-2011, 08:22 AM   #20
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RE: How big of a charger do I need?

Quote:
GonzoF1 wrote:
Something the guys at Iota pointed out to me was to be careful not to get a charger that the output of the genset can't cover with the other loads you might need while it's running. That said, I may back down to the 55 Amp instead of the 75 Amp.
If your daily amp hour usage at anchor is ~150 amps that 55 amp charger and generator will have to run*more than 3.5 hours and it still won't cover your daily usage.** If you have the 75 amp the run time will be 2 plus hours.* The typical marine hot water heater of 6 gallons draws about* 12.5 amps AC and recovers in about 45-60 minutes.* The Iota charger needs 18.5 amps at full load.* Since you'll be running the charger probably all the time the generator is on but not the hot-water heater what other loads are you concerned about?***How big is your generator?* I would get the biggest charger that fits the system so you aren't running the generator anymore than you have to.
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