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Old 14-08-2013, 12:42   #16
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Re: Charging Alternatives

It might or might not compete with an engine run compressor for the icebox, you'd have to figure out the engine run times needed, etc. for that.

But for electrical loads, using the main engine should always wind up being less efficient, costing more fuel, and adding engine hours which means more expensive maintenance much sooner. A lightly loaded main engine is also going to build carbon in the cylinders, glaze the cylinder walls, and plug up the exhaust elbow (with carbon) much faster than a heavily loaded engine, or so all the reps seem to say, and their universal advice is not to use the main engine as a battery charger unless that's your only power source.
Of course if you're going to use the main engine for all of that, why not pull out the 6kw genset and sell it off? Get rid of deadweight, open up space, get some cash back all at the same time.
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Old 14-08-2013, 13:40   #17
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Re: Charging Alternatives

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Originally Posted by RDW View Post
My question about the genset using less fuel is that it is producing 110 volt which would run the battery charger which is only 75 amp charger. Would I not be better producing 260 amp from my alternators on my main engine.
Do you know what the battery manufacturer's maximum recommended charging current is? If the max charge current for the bank isn't over 75 amps, that may influence your decision.
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Old 14-08-2013, 14:37   #18
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Re: Charging Alternatives

1. The Caribbean 1500 is not a real "race". It's a 10-day rally to the BVI.

2. The two 65-watt solar panels are not big enough to do much real charging.

3. The two alternators on the main engine -- if correctly connected -- could certainly provide the bulk of the charging during the trip.

4. The 6kw genset could be set Up to provide more charging. For example, two 90-amp iota chargers could provide as much as 180 charging amps (two identical Iota's can work together in parallel to double output capacity).

5. Not sure if those Rolls batteries are flooded or not. If they are, they'll only take about 25% of CA charging current maximum....in this case about 150 amps. Any additional charging current would be superfluous since the batteries themselves wouldn't accept more.

FWIW,

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Old 15-08-2013, 10:38   #19
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Re: Charging Alternatives

Btrayfors
1. any two boats out there are racing
2. Solar panels are just a good way for me to top off batteries and more importantly keep them u while I am away.
4. not interested in adding more stuff I have to learn unless I really need.
5. Rolls batteries are flooded, 200 amp hours each for a total of 800 amp hours. What is 25% of CA charging current maximum. Mostly what is CA.
Thanks
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Old 15-08-2013, 12:36   #20
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Re: Charging Alternatives

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Btrayfors
1. any two boats out there are racing
2. Solar panels are just a good way for me to top off batteries and more importantly keep them u while I am away.
4. not interested in adding more stuff I have to learn unless I really need.
5. Rolls batteries are flooded, 200 amp hours each for a total of 800 amp hours. What is 25% of CA charging current maximum. Mostly what is CA.
Thanks
RDW
1. Yes, of course; however this is not a strict formal race where you have to worry about strict compliance with race rules;

2. Yes, again, they're fine for that but not a major charging source for when your house batteries are way down;

4. Fine.....then stick with what you've got!

5. "CA" means capacity, generally specified at the 20-hour discharge rate. Your Rolls flooded batteries have a CA of 200 amp-hours each X 4 batteries in parallel for a total CA of 800 AH. So, 25% of 800 = 200 or 200 amps as the maximum amount of amperage your battery bank will accept. Approximately. And, only at a significant state of discharge, and only with sufficient charging voltage (14.4 - 14.8) and only if the batteries are in good condition.

Any charging capacity over 200amps would be superfluous. And, that 25% acceptance rate will dial down quickly as the battery state-of-charge increases.

Aren't you glad you asked?

Bill
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Old 15-08-2013, 13:07   #21
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Re: Charging Alternatives

I'd heard a charge acceptance of 25% quoted mostly for AGM batteries, with 20% more typical for wet lead. Which would put rdw down to a maximum rate of 160A for charging, still pretty much the same as the 150A you're suggesting.

But 2x65W solar panels would give him 130W, possibly 7.6A at 17V, good for about six times that in amp hours in a sunny carrib settings, maybe 46AH per day. That should pretty much put back whatever the nav lights take, leaving some deficit for the VHF, instruments, cabin lights...and if he can allow a 250-300A deficit befoire he starts chagring, he'll only need to run the genset or engine twice to make it through the ten day rally. Once if he cycles a little more deeply. Way more often if he's got one a them pesky new cold food boxes onboard. <G> I think the iceless box pretty much is the elephant in the room.

No?
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Old 15-08-2013, 16:16   #22
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Re: Charging Alternatives

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Originally Posted by hellosailor View Post
I'd heard a charge acceptance of 25% quoted mostly for AGM batteries, with 20% more typical for wet lead. Which would put rdw down to a maximum rate of 160A for charging, still pretty much the same as the 150A"..........
AGMs will accept a LOT more current than that. For example, a 4DL Lifeline AGM battery which is just 50% discharged will accept over 120% of its AH rating. Deeper discharge states lead to higher acceptance rates, i.e., 5-6 times tha AH rating. And, there is evidence from the manufacturers that these higher charging rates are actually good for the batteries, and lead to longer life.

In general on boats, batteries suffer from undercharging much more than from overcharging.

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Old 15-08-2013, 16:36   #23
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Re: Charging Alternatives

I found this spec sheet on the batteries in question - http://www.rolls-battery.com/pdf/pdf_rolls/t12250m.pdf

I also found this information from the battery manufacturer - State of Charge & Charging - Flooded Lead Acid Batteries : Technical Support Desk

"We recommend a charge current of 10% of the 20 hr rate (max) for both Bulk & Absorption settings. [5% min]"

If I am reading things correctly, that means that the manufacturer is saying not to charge an individual battery of this type with more than 20 amps. If someone else reads that differently, please explain to me how you came to a different number.

Thanks,
Jim
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