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Old 03-07-2008, 10:55   #1
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Charger for AGM?

I replaced my gel batteries with AGM this week and have a small fortune to protect. The Sentury charger has maintained the gells for 14 years, but all good things must end. I called sentury and the charger was built for Beneteau and they gave me the specs on the charger. It should start at 12.8V and shut down at 14.25V .I Have a multimeter checking the voltage and it has yet to exceed 13.2V . I am going to see what the max voltage will be from the altinator.
I have a wind charger and a solar pannel to install later. Any advice would be welcome.
Thanks, Tom

You can't drown a man thats destined to hang!!!
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Old 03-07-2008, 13:10   #2

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Tom, make two phone calls. One back to Sentury to ask what the three charging voltages are, for bulk-absorption-float voltages, and what is the max current at each stage. And if those are adjustable.

Then call the battery maker, each is a little different. Give them that information about the voltages and amperages, and find out if it is suitable for your batteries.

A wind generator requires a "dump regulator" usually, they don't really regulate the power except by dumping excess. That would conflict with a solar controller, which is incredibly more efficient with an "MPPT" controller than converts excess voltage into more amperage, and dumps nothing in normal use. But, each one will be mislead if the other is connected, and so far it seems best to use one or the other, or connect them to separate batteries, to keep them from confusing each other.

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Old 07-07-2008, 17:28   #3
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HS....wouldn't a simple shunt (dump) regulator make more sense for the wind/solar combo? Let's say you have a 200 watt solar panel array. You might expect 50ah's a day with a shunt regulator and perhaps 70 with an MPPT. On the other hand...a wind genny with big blades might average around 60ah's a day in a 10knot average wind speed over time. Switching systems or running two separate banks has disadvantages in convenience and complexity and I would be inclined to save my $$, shunt any excess to heat water and "waste" 20 ah's a day. Thoughts?

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Old 07-07-2008, 17:34   #4
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I don't see how a dump regulator will be confussed by an MPPT regulator or visa versa. I just installed a dump regulator for my Wind Generator and I set it to dump at 14.4 volts and float at 13.4 (If I ever get full while cruising.) When I hook up the solar it will convert the try to maybe set the voltage higher but since the batteries will take it then the value in the system will be overall lower and the dump regulator will not kick in.

Now just to set the record straight, I'm no electrical engineer and I'm installing now for our cruise set to begin this September. Thus.... if someone can set me straight in language a mere mortal can understand I'd be happy to listen and hopefully learn.

Fair Winds
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Old 07-07-2008, 19:54   #5

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"I don't see how a dump regulator will be confussed by an MPPT regulator or visa versa. " OK, consider this. Your wind regulator is putting out a merry 14.3 volts and your battery is merrily eating it all up. Now, what does your MPPT controller see when it looks at your battery? 14.3 volts, so it shuts down the solar panel. Unless your battery bank is so hungry, that it is pulling down the "wind voltage" to a lower level. But even then--it is reading that level, and not putting out as much power as it could or should put out.
In some situations I could see that would work, possibly not efficiently, possibly very well if the batteries were eating every watt they could find. In others...I just don't know, I have to suspect one system or the other would be running less than optimally, because it was not reading BATTERY voltage, but reading the other device's output.
Could it work? Sure. Would it be working optimally? I wouldn't bet on it. In the real world, would it still work well enough to keep you charged? Maybe. And 'maybe' isn't a good word for charging systems, is it?


Dunno. In the limited case that the batteries are fully charged, or there's so much power being generated that you can afford to bathe in it, dump regulators make sense, sure.

But how often does that happen, versus the 40-to-95% discharge area, where you want every erg coming out of every device to go INTO the batteries, before the sun sets and the wind dies? Or, the storm comes, and you have to stow the panels and feather the wind blades?

I think (and I admit to being underqualified on that front<G>) that the only way to do "one regulator to rule them all" would be to integrate multiple regulators with one mastermind, which would disconnect them ALL very briefly, perhaps once every couple of seconds, and in that instant take a look at the battery and see what it needed. Then, re-regulate and reconnect them all as appropriate.

This is what the internal regulator in some systems already does, except here we'd be asking it to sense multiple sources and rule them all in harmony. Shouldn't be hard, but it would require aequate capacity in each section, or a modular design, so that V & A were sensed from each device, and a common disconnect/sense/connect mechanism used to hook them all up to the battery banks. Probably would mean one "brain box" that had the battery connections on it, and maybe a choice of "high" vs "low" power modules for each device, i.e. so folks with lots of toys or just a few toys could buy the appropriate capacity in the modules. Wouldn't make sense to rate everything for 500 watts.

Or maybe there's a smarter way to do it with nifty digital bits these days, wire up everything to an MPPT-type "transformer" that eats all power, allows it to average itself out as magnetic flux, and then feed it back out again in an orderly manner.

Unlike the scene where the man foolishly shuts down the containment unit in Ghostbusters.<G>

It's the need for dump regulators on wind generators that complicates things most, I think. Maybe they need to be shunted to trolling motors instead?<G>
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