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Old 05-21-2010, 09:38 AM   #1
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Hi All.

We are finally living aboard on Camelot! What a wonderful feeling to wake up every morning on the water... and know that it is not just that we are away for the weekend!!!

We moved on last weekend after a mad fortnight of downsizing and packing away things that wouldn't fit into long term storage. Now we are in the process of coming to grips with juggling power usage, charging etc.

Of course there comes a downside... our alternator has not been charging the batteries effectively so we are running perilously low of juice far sooner than we anticipated. We need to replace the Xantrex 20A, 110V shorepower charger that came with her with something that can take the 240V power supply we use here in NZ.

Simple right? Well, the trouble now is that every electrician I talk to suggests we need a different size of charger. We have 760Ah in the house bank (2 x 6V in series, paralleled with the same for a 12V system) so the question is- how big a charger do we need? One sparky suggested we need something with at least 20% of the rated capacity, or a 150A charger...$$... ...... ??????

Any and all suggestions appreciated

Cheers

Dan
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Old 05-21-2010, 02:34 PM   #2
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It depends on how much you want to spend, and how long you want to wait to charge your batteries. I have 1800Ah of house batteries, 10x80W solar panels, a wind gen, a small 40A x 12V alternator on my engine (which is a 24V engine), and a 6KVA genset. I'm using a STUDER inverter charger which is rated at 2.5 KVA output. It charges at 70A from shore power or genset. The genset is 12V and its alternator adds another 30A or so.

That's the plus side. The minus side is 5A 30% duty cycle fridge and 4A 90% duty cycle freezer plus say 2A of other stuff at anchor or say 10A at sea. That's a draw of around say 15A/h or around 300Ah per day, about 20% my battery capacity.

On a bright sunny summer day, I make 50A/h for 6 hours = 300Ah just from the solar panels, do I don't need to run the genset at all. I like that because it sounds like a herd of elephants charging through the jungle.

In bad conditions, the genset puts out 100A/h so it would take 3 hours to fully charge the batteries. In practice the solar panels and wind gen produce something even on bad days, and my consumption is overstated: on my mooring on overcast days I'm using about 30 minutes of generator.

The charger/inverter cost around $A5000. The batteries consist of 6x200 Ah AGMs at $700 each, a bank of 6x100 Ah lead acid wet cells probably worth $200 each, plus the 2 calcium engine start batteries (in series to get 24v). I also have a small 8A x 24V charger for the engine batteries driven by the 240V system.

The point: it is quite simple to calculate how big a charger you need. If you have an alternator and with 20% the battery capacity per hour output clearly it takes 5 hours to fully charge the batteries. However, the question really is: how much are you actually using per day?

My system was designed so I could live and work on my boat with no inputs, hence a stack of solar panels, and a heap of 240V power. Enough to run a vaccuum or microwave a ready meal, and keep my computers running. Not really enough for cooking or hot water without using the genset though.
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Old 05-22-2010, 10:36 AM   #3
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Quote:
Originally Posted by canuckiwis' date='21 May 2010 - 04:38 PM View Post

Hi All.

Now we are in the process of coming to grips with juggling power usage, charging etc.

We need to replace the Xantrex 20A, 110V shorepower charger that came with her with something that can take the 240V power supply we use here in NZ.

Any and all suggestions appreciated

Cheers

Dan
Hi Dan,

Maybe I missed it in Camelot's specs, What charging equipment is functioning on board when away from a marina? - eg Solar panels (pilot house roof) Wind generator (away from other boats in anchorage? Small generator << 3KVA? Main engine alternators = amps ?)

Richard
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Old 05-22-2010, 03:23 PM   #4
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Just like you Dan I have a 760aHr service battery bank and a 120 aHr starter battery. I cruise extensively away from marinas and AC power. I have a 100 a alternator with a Balmar smart regulator, an AirMarine X wind generator, and a 40 a 220V AC TrueCharge charger. I am fairly pleased with this setup, although I wish I had room for a photovoltaic panel.<div>
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Old 05-23-2010, 08:29 PM   #5
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Camelot has a 100A alternator (which isn't 7@#!! working just now) with a Balmar smart regulator and 2x130W solar panels with a Blue Sky Solar Boost. We also just purchased a Duogen which is not yet wired in. And while we do continually find more bits and bobs from the last owners, I have yet to see a separate genset!!! (I think that one would be fairly easy to spot!!!" src="http://www.cruiserlog.com/forums/public/style_emoticons/default/happy.gif">).
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Old 05-25-2010, 05:12 PM   #6
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Hi Dan,

a battery charger should have at least a capacity of 10% of the over all battery capacity, if you just think of recharging the batteries while they are not in use. That means a charging capacity of 80Ah, just concidering your house bank. Isn't there a battery for the engine start too?*

As soon as you have users drawing energy while you are loading, it should have a bigger capacity, otherwise the bulk- and absorb- charging phases (at 14,4V) will take unnecessarily long. Or you decide to turn off all users until the float-phase is keeping the batteries fresh at 13,4V (or more or less, depending on temperature).*

And finally the use of solar panels and wind gens with Charge Controllers: as these Controllers cut in at a Voltage of 13,8V *(to avoid uncontrolled overloading *i.e. gasing of wet batteries and as Gel- and AGM-Batteries cannot gas they do not like any overcharging at all!!), they do not recharge your batteries as effective as modern regulating battery chargers with a bulk - absorb- and float charging cheme do.

So, we use our solar panels (2 x 60W) and the wind gen to keep the batteries (600Ah) fresh during the days we are not on the boat. And they provide the energy for navigational instruments and lights while under way but we try to charge the batteries with the battery charger at least once every 14 days (as the battery manuals advise).

Uwe

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Old 07-04-2010, 05:29 PM   #7
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Quote:
Originally Posted by Aquaria' date='25 May 2010 - 10:12 AM View Post

Hi Dan,

a battery charger should have at least a capacity of 10% of the over all battery capacity, if you just think of recharging the batteries while they are not in use. That means a charging capacity of 80Ah, just concidering your house bank. Isn't there a battery for the engine start too?

As soon as you have users drawing energy while you are loading, it should have a bigger capacity, otherwise the bulk- and absorb- charging phases (at 14,4V) will take unnecessarily long. Or you decide to turn off all users until the float-phase is keeping the batteries fresh at 13,4V (or more or less, depending on temperature).

And finally the use of solar panels and wind gens with Charge Controllers: as these Controllers cut in at a Voltage of 13,8V (to avoid uncontrolled overloading i.e. gasing of wet batteries and as Gel- and AGM-Batteries cannot gas they do not like any overcharging at all!!), they do not recharge your batteries as effective as modern regulating battery chargers with a bulk - absorb- and float charging cheme do.

So, we use our solar panels (2 x 60W) and the wind gen to keep the batteries (600Ah) fresh during the days we are not on the boat. And they provide the energy for navigational instruments and lights while under way but we try to charge the batteries with the battery charger at least once every 14 days (as the battery manuals advise).

Uwe

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You state that the batteries will be fully charged in 3 hours with an alternator of 100 amp size. In reality it takes much longer to "fully charge" them. As the batteries resistance increases the last 15% or so takes many hours. Many cruisers, if relying on engine alternator only, charge to 80% soc because of this. If solar or wind gen is on board the batteries will be fully charged but with engine alone this isn't practical.
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