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Old 13-04-2010, 11:39   #1
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Multi-Input Charging

Hey folks,

Working on my electrical system redesign/rebuild over here.

Say I have 400aH or so of AGM golf cart batteries. I'm currently thinking that the Xantrex Freedom SW 2000 is the right answer for a three-stage charger and inverter, especially with several computers onboard.

However, I will *rarely* if ever be connected to shore power - I have a Honda EU2000i generator, and I intend to add wind and solar in a few months.

My question is - I can't seem to understand how a multi-stage charger and, say, a wind generator fit together. Does the wind generator just bypass the charger altogether and help provide the float charge? How about if I have 240w or so of solar, providing input at the same time? Nothing in the manual for the Freedom SW 2000 mentions any other input besides AC shore power...

Am I maybe looking in the wrong direction altogether?

"Analogies are dangerous, Amanda, because life is like a sandcastle."
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Old 13-04-2010, 11:51   #2
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Essentially when you combine charging systems they work "in parallel" -- whichever has the highest voltage output in its configuration for a given "stage" puts the most power on the bus. With wind its a little tricky because you have to burn the power off or the unit can overspeed. With solar its not that much of a big deal - disconnected or free-floating solar panels are safe.

So the way that most people wire things up is as follows:

Solar -> MPPT charge tracking converter/charger -> Positive and Negative charging posts on the batteries
Xantrex/AC charter -> directly to the same posts.
Wind -> controller with diversion load -> charging posts
Alternator -> Some multi-stage charge controller -> charging posts

Then you try to configure them as close as possible to the same config and let 'em sort it out. Yes, its safe as none will really "backfeed" the other - they all sense the voltage at the charge point, and if its above their set threshold for the state of charge (bulk, acceptance, float) they are in, they throttle themselves back and don't contribute because contributing would require them to force additional current through the system, and that would by definition raise the voltage further. (V = IR, after all, in a typical mostly-resistive, mostly-linear, mostly-DC system).

Now, the trick is matching the wind and solar up, as many wind units don't have multi-stage charge controllers. Blue Sky has a charge controller with MPPT AND a diversion load, which can manage the wind input simultaneously with the solar input, and doesn't care if the solar or wind are set up for 24V and the battery output is 12V (or v-v, I think). Its the 3024iL and there is a diversion option for it. This is the controller I've decided to buy for myself (no affiliation whatsoever with the company, I'm just doing the same research as you right now). This would then combine the wind and solar charge points into a single unit and has the advantage of being able to dump current to something such as a water heater element in good wind/sun days to give you some (probably tepid) hot water. Alternatively you can wire the HW heater to AC, and just dump the excess energy through a dump resistor or find some other creative use for it.

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Old 12-09-2011, 13:03   #3
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Re: Multi-Input Charging

Anyone here currently using the Blue Sky Energy 3024iL DUO? Please share experience(s), especially re: using wind generator and any RFI with HF.

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Old 12-09-2011, 15:49   #4
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Re: Multi-Input Charging

Maybe this one could help...

Sterling ProSplit R Alternator Distribution Systems

But i have no experience with the wind "overload" yet.
It could be nice with "one box solution" and at least 3 battery banks.
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