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Old 21-12-2010, 07:26   #1
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More Battery Questions !

Thanks to all for your help on the prior thread.

Situation: We are trying to understand our short term options relative to a most likely undersize battery charger situation. The facts:
Catamaran with dual Yanmar 27hp engines equipped with OEM 55amp alternators.
Batteries - House bank is 3ea 205ah AGM, Starting batteries are 100ah AGM,s, one each on both port and starboard engines.
Battery Charger - Xantrax TruCharge2 40amp (Xantrax tech rep said it is adequate for our battery bank. Maybe so given enough hours?) After talking to the tech rep, we put our regulated power setting back to 100%. We had been running it at 20% setting for AGM batteries as directed in their Operater Manual. He said that was only for small battery banks 100amps or less, but the manual never addressed that.
Generator - Norpro 7kw
Demand - We have all the normal stuff the one has on a 38' cruising catamaran, including a WAECO AC 2.4cubic foot cockpit refrig/freezer, plus the 12v OEM fridge, TV, computer recharge, vacuflush toilets, etc.
I am guessing that our daily demand is 150-200amps, but it is only a guess.

Question - The boat is in the Bahamas where we have limited availability to parts and service. For the short term, until we can upgrade the battery charger, or upgrade the alternator(s), or both, will we be able to shorten our recharge time by running both the engines and the generator? The alternators should run current directly to the batteries while the generator is running current to the battery charger - does this make any sense? Is there any downside to it?

I really appreciate any help from the forum because we just don't have a good feel for the competency of the mechanics down here.

Thanks in advance,

Tom
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Old 21-12-2010, 08:06   #2
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You may be able to do that effectively for the initial charge in the morning, and then drop off a motor or two as the batteries get up to about 80 % charged. A larger battery charger would be better. Keep in mind that you will probably have to upgrade your wiring from the new battery charger to the batteries. You might want to think about solar panels.

Running 3 diesel motors to charge your batteries is certainly not very efficient and of course will be noisy.

You really need to think of your electrical system as a "system" and design it so it is balanced.
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Old 21-12-2010, 08:43   #3
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Tom,

I'd bring along a new Iota battery charger, 75A or 90A, with the IQ-4 smart charge option (either external or internal). You can power this charger off your generator.

The Iota's put out more average power than most chargers, work fine with AGMs, and are very cost effective. A good supplier is Northern Arizona Wind and Sun. http://www.windsun.com/

Two identical Iotas can be run at the same time, doubling the available amperage. E.g., two 75A Iotas slaved together would give you 150A charging capacity. A big step up from your 40A charger! Even a single 75A or 90A Iota would be a major upgrade, and would cut your charging time way down.

Running three diesel engines at the same time really doesn't make sense, as noted above.

Bill
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Old 21-12-2010, 09:53   #4
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Quote:
Originally Posted by thomaswaier View Post
Thanks to all for your help on the prior thread.

Situation: We are trying to understand our short term options relative to a most likely undersize battery charger situation. The facts:
Catamaran with dual Yanmar 27hp engines equipped with OEM 55amp alternators.
Batteries - House bank is 3ea 205ah AGM, Starting batteries are 100ah AGM,s, one each on both port and starboard engines.
Battery Charger - Xantrax TruCharge2 40amp (Xantrax tech rep said it is adequate for our battery bank. Maybe so given enough hours?) After talking to the tech rep, we put our regulated power setting back to 100%. We had been running it at 20% setting for AGM batteries as directed in their Operater Manual. He said that was only for small battery banks 100amps or less, but the manual never addressed that.
Generator - Norpro 7kw
Demand - We have all the normal stuff the one has on a 38' cruising catamaran, including a WAECO AC 2.4cubic foot cockpit refrig/freezer, plus the 12v OEM fridge, TV, computer recharge, vacuflush toilets, etc.
I am guessing that our daily demand is 150-200amps, but it is only a guess.

Question - The boat is in the Bahamas where we have limited availability to parts and service. For the short term, until we can upgrade the battery charger, or upgrade the alternator(s), or both, will we be able to shorten our recharge time by running both the engines and the generator? The alternators should run current directly to the batteries while the generator is running current to the battery charger - does this make any sense? Is there any downside to it?
With a house bank of 615AH, you'd have roughly 185AH of usable power (615 * .3, if you charge from 50% discharge back up to 20% discharge). As a rule of thumb the batteries should accept up to 25% of their capacity in a bulk charge - that would be 120amps/hour max current going into the house bank. AGM's will have slightly a broader discharge/recharge range and will charge at a slightly lower voltage than wet lead acid batteries.

Theoretically you shouldn't break anything if you run all three chargers at once - though I have not tried to run an engine hi-output alternator at the same time as operating a 110vAC battery charger. There may be some arguing between them as to what the battery voltage is, and that can hurt efficiency. As mentioned, this will also be noisy, and you're not doing any favors for the engines by operating them at low-load for long periods of time.

I would be concerned about the ability of the OEM 55amp alternators to put out significant amounts of charge current for long, as they will heat up and many OEM alternators aren't hot-rated and as a result can cook themselves (the alternator's internal regulator should prevent that, but then you don't get much current out, either - sounds like you may have an external regulator you can control). See if you can find out whether or not the alternators are hot-rated; if they are you're in luck and can push 55AH eaches all day long, if not then be a little careful of them.

Have fun in the Bahamas!

- rob/beetle
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Old 21-12-2010, 10:08   #5
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Your Yanmar's Hitachi 55 amp alternators with internal regulators are set for about 13.5 V output. When the Truecharge gets up to that voltage, then the Hitachi will do nothing. In any case you won't get more than 10 amps out of a Hitachi a few minutes after starting as the voltage will quickly rise to about 13.

Running your Yanmars for charging is not good for them, particularly with no alternator load.

As the other posters have recommended, bring in one or more IOTA chargers as I recommended on your original thread.

And this is a good lesson for anyone planning to go to the Bahamas for an extended period. First spend a few weeks on the hook (or even at the dock unplugged) where you have good access to parts and mechanics to get all your systems sorted out first. Fixing them in paradise isn't always easy.

David
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Old 21-12-2010, 17:28   #6
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"Two identical Iotas can be run at the same time,"
Bill, do they slave/synch their voltage regulators together? Or do anything special so that they don't argue about what voltage to sense and set?

Tom, I would think the 100A AGMs are way larger than needed for just starting batteries, but the 55A alternators are quite adequate to maintain them. Assuming you let those "sets" take care of themselves, and use a genset/charger to charge the house bank as needed...then the only real question is the genset/charger. With over 600A of AGM house bank, they could easily absorb power at a 150AH rate from a genset. (More, depending on charge state and who's numbers you go by.) Assuming you intentionally cycled them only to a 30% or 50% discharge point...you could put that back in an hour or two, if your genset/charger was able to supply over 150A of DC power. Fuel consumption, equipment prices...no matter what you choose, you can do way better than letting a 40A charger run and run for hours trying to do that job.
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Old 21-12-2010, 18:26   #7
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Originally Posted by djmarchand View Post
Your Yanmar's Hitachi 55 amp alternators with internal regulators are set for about 13.5 V output.
If this is a 3GM or similar those factory alts should be regulating to somewhere around 14.3 +/- 0.3V @ 68F if the older style or the newer style which is set to regulate to 14.5 +/- 0.3V @ 68F. Hitachi made a change from 14.3 to 14.5 but I can't recall exactly when.

Even the very old SM/YSM alts were regulated to 14.3 +/- 0.3V. Some of the older Motorola/Prestolite alts came through at 13.6v & 13.8v but most Yanmar alts I've worked on were regulated above 14 volts..

Even the 60A Hitachi LR-160-741's on the newer 3YM30's are set for 14.4V +/- 0.3V @ 68F.
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Old 21-12-2010, 20:39   #8
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G'day, Tom, You said you have a 7kw generator, does it have an alternator on it? If so, and it's in the 50 to 80 amp range, shouldn't have to use the motors until you can upgrade the battery charger. Cheers.
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Old 21-12-2010, 20:42   #9
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I second the iotas I have 2 55ampers with the duel smart regulator Great price and work great I had nothing trouble with the true charger
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Old 21-12-2010, 21:12   #10
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Quote:
Originally Posted by thomaswaier View Post
Thanks to all for your help on the prior thread.

Situation: We are trying to understand our short term options relative to a most likely undersize battery charger situation. The facts:
Catamaran with dual Yanmar 27hp engines equipped with OEM 55amp alternators.
Batteries - House bank is 3ea 205ah AGM, Starting batteries are 100ah AGM,s, one each on both port and starboard engines.
Battery Charger - Xantrax TruCharge2 40amp (Xantrax tech rep said it is adequate for our battery bank. Maybe so given enough hours?) After talking to the tech rep, we put our regulated power setting back to 100%. We had been running it at 20% setting for AGM batteries as directed in their Operater Manual. He said that was only for small battery banks 100amps or less, but the manual never addressed that.
Generator - Norpro 7kw
Demand - We have all the normal stuff the one has on a 38' cruising catamaran, including a WAECO AC 2.4cubic foot cockpit refrig/freezer, plus the 12v OEM fridge, TV, computer recharge, vacuflush toilets, etc.
I am guessing that our daily demand is 150-200amps, but it is only a guess.

Question - The boat is in the Bahamas where we have limited availability to parts and service. For the short term, until we can upgrade the battery charger, or upgrade the alternator(s), or both, will we be able to shorten our recharge time by running both the engines and the generator? The alternators should run current directly to the batteries while the generator is running current to the battery charger - does this make any sense? Is there any downside to it?

I really appreciate any help from the forum because we just don't have a good feel for the competency of the mechanics down here.

Thanks in advance,

Tom
Tom
One thing I see that is being missed in all of this information is: A 40amp charger is really small... Remember that the charger must be able to handle the house load and then what is left will charge the battery set. So if you have a 20amp load, you will only have 20 amps left to charge the battery.
In chargers bigger is better and make sure it is a multi-stage smart charger. a 615 amp hour battery plant with a average load of 30 amps we use 90 to 120 amp chargers.

Gary
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