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Old 07-01-2012, 09:06 AM   #21
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For the fastest charge of a batt set that has the ability to accept a huge charge , an alternator and smart regulator still makes the most sense.

A small charger can handle the tiny loads of the starts.

The alt setup should monitor the batt case temps during the charge.

FF
Thanks FF. I am looking into that. However sometimes we will anchor in one spot 3 or 4 nights. I am looking for a way to charge quickly without firing up a couple of 500 hp diesels. It seems in that case the generator and large charger is a better option. Just wondering how the 2 chargers would work together.
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Old 07-01-2012, 09:11 AM   #22
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First, multi-bank chargers which are programmable so that the charge profile for each bank can be seperately specified to suit different battery technologies, are readily available: Victron & MasterVolt have produced these for some years and most recently, Charles Industries has released a new "Intelligent Marine Charger" (IMC) series that does this. These were favourably reviewed in PassageMaker last month. It is really no big deal and since different battery technologies SHOULD be used for different on-board applications, they are a good idea. Second, it has been pointed out on another post that an alternative approach is to have a single charger focussed on the House bank and to charge start/genset/thruster/electronics batteries using programmable (for different battery technologies) charge-transfer devices off the House bank: products like Balmar's Digital Duo Charger or the Ample equivalent. Third, most competent installers of battery chargers will use the dip-switch or other control devices within the charger to de-rate the maximum output of the charger at least somewhat: for a 120A charger, it is not uncommon for an installer to de-rate these to 105-110A, for example....just so the charger is not operating right at its design limit. Further, the max rated output of a charger is achieved only at a specific ambient temperature, most often 20C; if you are in Florida in Summer...or if your charger is in a hot/poorly ventilated space, it will de-rate itself. (Good idea to install a brushless computer fan to cool the charger - or inverter - adjacent to help minimize this ambient temperature de-rating). Finally, if you only have a 440AH bank, that is not very big by today's standards and the C20 rule would suggest that for AGM or Flooded, the max charge should be only 88A anyway. C25, the absolute top end, would require 110A...not 120A...and I cannot imagine why you would go there. If your biggest concern is minimizing generator run time, then go for AGM's as they will accept the 88A charge for longer (ie they will stay in Bulk Charge mode longer) and so will re-charge faster overall....but you are reducing generator time at the expense of higher-cost, more charge-volt-sensitive battery technology. If you really want to impact genset run-time, get a quality, multi-stage external regulator that has BOTH battery and alternator temperature sensors so your alternator(s) are operated at maximum output consistent with not overheating either alternator or battery; and then to take it even further get a high-out alternator (120A+); and if you have twins, direct the charge from both alternators to the house bank. You will then find that even short cruises of 1-2 hours between anchorages put a lot back into the House bank such that genset operation for battery charging can be just something that happens in the background when you operate the genset for cooking, water heating, air-con or whatever.
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Old 07-01-2012, 09:17 AM   #23
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Problem with 2 independent chargers both connected to same battery/bank is that their voltage sensors will confuse each other: each will 'see' the charge voltage being applied by the other charger and not the real charge of the battery and so will step back their charge delivery, wrongly sensing a charged battery. You can gang together chargers of the same type often, but then you only connect one voltage sensing wire (and one battery temp wire) not two.
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Old 07-01-2012, 09:36 AM   #24
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Problem with 2 independent chargers both connected to same battery/bank is that their voltage sensors will confuse each other: each will 'see' the charge voltage being applied by the other charger and not the real charge of the battery and so will step back their charge delivery, wrongly sensing a charged battery. You can gang together chargers of the same type often, but then you only connect one voltage sensing wire (and one battery temp wire) not two.
Thanks, both posts are excellent info. I like your and FF's suggestion of a larger alternator and multistage regulator. I am looking into that. It looks like I will just have to put up with a little longer generator run time for the 60 amp charger. My house bank is AGM 510 amps.

My present set up is an 80 amp alternator on each engine. The port engine is dedicated to the house bank. That bank can be tied in with the others via a parallel switch which has never been used. I believe the larger alternator on the port engine will take care of it.

Thanks for the good info. All of you guys with the real technical skills are a huge asset to this forum.
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Old 07-01-2012, 11:06 AM   #25
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Don, with 510 amps AGM the total capacity of the charging system doesn't need to be bigger than 100 amps or so. I have 1300 amp AGM capacity and they will only absorb around 220 amps for 30 minutes before the absorbtion rate starts tapering off. This is from a 35% rate of discharge.

For future reference, Ample Power in Seattle makes a modular ac charger that goes up to 220 amps 12 or 24 Dc.
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Old 07-02-2012, 06:16 AM   #26
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The noisemaker would spin the alternator NOT the main engines.

Most noisemakers have a kit to install a pulley on the set as Hyd power , bilge pumping , deck wash, mechanical refrigeration or an alt. are common.

The noisemaker engine mfg will usually have a MAX for the power that can be front extracted.

This is usually just a side load limitation , so a dual pulley with another user on the other side may allow a really large alt.

The limit is frequently a Hyd problem , as some can eat BIG HP.

A second advantage for a cruiser is an alt can be rebuilt or carried as a spare.

Sending some majic box back to the Mfg may take lots longer.

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Old 07-02-2012, 09:05 PM   #27
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rvolkjr

Tim: I really appreciate the comments from all on the battery charger size issue. By the way I do have a 2011 brand new, in the unopened box, Xantrex 60 AMP three bank charger/inverter for sale. Drop me a note if you have any interest.
I have an 1981 IG36 which we restored completely and part of that included changing out the charging system. I have twin Ford Lehman 120s and a 5.0KW Onan genset. We carry three batteries: and 8D, and 2 4Ds. The vessel originally had a 30 AMP charger which we changed to a 60 AMP Mastervolt which seems to work just fine. We also have 2 inverters aboard (400 & 2000) which we run when we want quiet and not the gen set running. Over the past 5 years we have had this system it has worked well with flooded batteries, which we check every month. So far, so good! Bob
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