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Old 12-08-2013, 13:29   #1
RDW
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Charging Alternatives

I have two 65 watt solar panels, two alternators on main engine ( I think one is 60 amp and one is 200 amp) and I have a Northern lights M673 8KW generator and a 75 amp 110 battery charger. I have 4 Rolls T250 12 volt house batteries and one engine start battery for the generator and one for the main engine. I will be doing the Caribbean 1500 which will be 8-10 days off shore.
I am not very experienced and not into electronics. I am assuming that my engine with 260 amp of alternators would be the best way to make significant charging. It is my thought that I would run my engine first thing in the morning when the batteries are most discharged and can take amps faster and then let the solar panels top off the batteries. My main engine uses a gallon of diesel per hour and the generator uses 1/2 gallon per hour. We do not make ice, run airconditioner, or make water.
Am I way off base? Any suggestions on energy management?
I did the Caribbean 1500 in 2011 with no problems but I am trying to learn.
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Old 12-08-2013, 13:41   #2
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Re: Charging Alternatives

I would suggest equalize the batteries so they are at their best before the race gets near. And if there is any doubt, load test them to make sure they're pulling their weight, so to speak.

The genset should be the most economical way to charge them, in terms of pounds of fuel versus power output. The solar panels might put some 50-60AH of energy per day into the system, so you probably should actually measure your energy budget, see what you are consuming, and then see if the solar panels can get you through it.

Depending on your budget, that might also mean replacing all the incandescent bulbs with LEDs, since just changing the demand from nav lights and cabin lights can quickly pay off in reducing the energy demands, allowing you to carry less fuel and race a bit faster.
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Old 12-08-2013, 13:42   #3
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Re: Charging Alternatives

The batteries are Rolls T12 250 which are 200 amp hour batteries.
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Old 12-08-2013, 13:49   #4
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Re: Charging Alternatives

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. I honestly do not know. Does the generator charge the 12 system other than by running the battery charger?
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Old 12-08-2013, 14:01   #5
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Re: Charging Alternatives

"Does the generator charge the 12 system other than by running the battery charger?"

Wait a minute, I'll flhy in and take a look at the boat. What's the combination for the lock?

No really, *you're* the guy who has to know that. If you don't know that, you're nowhere near ready for an ocean race.

Even with an inverter, the genset should be more efficient than using the engine and alternator. But again, you've got to know the fuel consumption on both, under load.

If the race requires 48 hours worth of fuel for the engine, do you burn two liters per hour? Or four? Into winds and seas? A difference of 96 liters of fuel could mean 200 pounds of dead weight, and that's going to cost you time.

Since racing is by most definitions "abuse" rather than normal use, you might consider abusing the batteries a bit by drawing them down to 25% capacity instead of the more normal 30-50% before recharging them. That would give you 150AH of power before you needed to run a motor to recharge them. So even if the solar doesn't put back everything you use every day, you can afford to run up an energy deficit before running the genset or engine.
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Old 13-08-2013, 01:41   #6
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Re: Charging Alternatives

99% chance you're not going to get any more then 75a from the genny


you also won't get 260a from the alts at idle. if you are just running it and sailing. you'd need to rev it up to get some amps.

do you have a battery monitor?...
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Old 13-08-2013, 03:26   #7
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Re: Charging Alternatives

I have found that with nav lights, autopilots, fridges, house lights and a reluctance to run engines at night because they are noisy and would mask the sound of other unlit boats, whales, surf on rocks etc the batteries tend to be lowest first thing in the morning. Since this is also the time when they will accept the highest charge rate I have found it to be the best time to do a bulk charge with an engine driven charger and when the charging amps fall back I shut this of and then allow the solar panels to do the slow, top up charging during the day.
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Old 13-08-2013, 14:32   #8
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Re: Charging Alternatives

one thing you want to be careful of with running the engine to charge the batteries is running it for hours under little to no load. Diesels like to be run at 80-85% max rpm under load or they start to foul up. I know you may not care about that during the race but it can cause you problems down the road
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Old 14-08-2013, 09:20   #9
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Re: Charging Alternatives

I did some leg work. The Northern Lights M673 mainly produces 110 AC. It does have an alternator, 35 amp which is mainly to charge it's own battery but it would produce extra juice. The main way I would charge house banks using the generator is to produce 110 AC which would run my battery charger (75 amp). So in a very simplified look I produce 260 amps (at max) with my main engine versus 75 to 100 amps with the generator for twice the fuel and also run refridge compressor and anything else I can add to load the engine.
One of the best comments was not running your engine in the dark that would interfere with hearing other boats or waves on rocks.
Thanks for all the comments. I am climbing a steep learning curve but this is my second Caribbean 1500. I made it there and back once so far.
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Old 14-08-2013, 09:34   #10
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Re: Charging Alternatives

jn-
That is a 6kW generator, which could potentially provide over 400 amps of "12" volt power. All you'd need is a fairly inexpensive ac-to-dc battery charger to make it useful to your batteries. That might be worth looking into as well.
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Old 14-08-2013, 10:36   #11
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Re: Charging Alternatives

hellosailor,
Tell me much more. Would this fairly inexpensive ac to dc battery charger be different than a normal battery charger that you would use with shore power? Would it be one with the potential to put out 200 to 300 amps? Please tell me more, specifics with brand and models.
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Old 14-08-2013, 10:43   #12
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pirate Re: Charging Alternatives

I'd run the gen-set 1hr in every 12 hrs... how long depending on the drain over the 12hrs... that'll let you know in the 1st 24/36hrs your efficiency... then run for longer if needed..
Dunno if that made sense.. but I know what I mean..
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Old 14-08-2013, 10:43   #13
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Re: Charging Alternatives

I think your plan sounds about right. Run the engine 1-1.5 hours per day. Start out at higher than idle, maybe 1200-1400 while the big amps are going in. Truckers idle their engines for many hours and those engines go multiple 100's of thousands of miles.... just make sure you also run the engine under load through it's life also.
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Old 14-08-2013, 11:06   #14
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Re: Charging Alternatives

rdw-
I'm not going shopping for one. But pretty much any conventional battery charger can be plugged into your AC genset the same way it would plug into an AC mains line. If the genset can put out 6kw continuously, then ignoring losses (which could easily be 10% in the real world) you should be able to put 6kW into the batteries, which would be 416 ampos at 14.4 volts, more amps at lower voltage. I'd expect a 300-350A 14.4vdc battery charger to be about the max for the real world.

How fancy, how expensive, your choice. If what you want it for is bulk charging, and it won't be left connected or turned on after that, you've got enough leeway so that even a cheap "dumb" charger would do the job. If you can find and afford better, great. If you use a 100A or 200A charger, again that's still going to work. There's whole world of options out there.
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Old 14-08-2013, 12:20   #15
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Re: Charging Alternatives

Hellosailor,
Why would that be better than running my engine and getting the added benefit of a engine run compressor for refridgeration? Just interested in your logic.
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