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Author Topic: Solar  (Read 848 times)
luvrbus
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« on: March 19, 2014, 01:46:59 PM »

How does one stop the solar from charging when under way and the alternator is charging the house batteries ?   
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« Reply #1 on: March 19, 2014, 02:43:02 PM »

This is a really good question.  The solar panels I am aware of actually generate 17-26 volts.  I wasn't aware of this until I put a meter on a small panel I had.  The so-called controller regulates or mediates that as necessary so I would expect the controller to handle the situation -- but I don't really know.

e3
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Iceni John
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« Reply #2 on: March 19, 2014, 03:00:50 PM »

There's no reason one can't have a battery (or a bank of batteries) simultaneously charged from two sources.   The renewable-energy folk do this all the time when they have a battery bank or PV array larger than a single charge controller can handle  -  they'll have two charge controllers charging one battery bank, and each CC charges according to what parameters it was set up for.   In practice one would want both CCs to be set to the same voltages etc for Bulk, Absorb and Float, but it's not critical if they're slightly different.   Some folk are even running one PWM controller and one MPPT controller into one battery bank, with no reported adverse effects.

Is your solar system for the starting batteries, house batteries, or both?   Any PV system should have breakers to isolate the panels from the charge controller and to isolate the CC from the batteries, so you should be able to turn off the PV system anyway.

I'm now putting 2kW of solar on my roof for my house batteries, and I'll also have a separate small CC to keep the starting batteries always fully charged (the DDEC draws about 8mA, enough to drain an 8D after a few weeks).   I don't plan on switching off this small CC every time I drive the bus  -  its own diodes will prevent the alternator's power from back-feeding into it, just like any other CC has.

John      
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luvrbus
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« Reply #3 on: March 19, 2014, 03:27:20 PM »

I have a problem my daughters MH has a 170 amp alternator with built in VR with the solar on a bright day I get 14.8 volts charging rate disconnect the solar I get 13.2 volts these are the house batteries it has the Specialty Concept Mark V PV controller and monitor any ideas ?

good luck
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Iceni John
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« Reply #4 on: March 19, 2014, 04:06:32 PM »

The manual http://specialtyconcepts.com/SPECIALTY_CONCEPTS_PDF_FILES/MARK_20_INSTRUC_MANUAL.PDF   states:
"OTHER CHARGING SOURCES:  Systems with an additional source of charging (alternator, battery charger, etc.) can operate with a solar array and a MARK/(15,20,22).   All charging sources need to connect directly to the battery on independent lines and have their own form of over-charge protection."

So, this would suggest it's OK to have it setup as you described.   Are there "independent lines" connecting the alternator and CC?   14.8V is actually a good voltage for bulk-charging a FLA battery, provided it then switches to a lower Float voltage to prevent boiling out the electrolyte.   Bear in mind that this CC is a PWM design, without separate set-points for all four charging parameters.   Curiously, the specs say that the high-voltage disconnect is 14.4V (+/- 0.2V!), so 14.8V is slightly beyond its standard setting.

John
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1990 Crown 2R-40N-552:  6V92TAC, DDEC II, HT740, Jake.      Hecho en Chino.     
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« Reply #5 on: March 19, 2014, 04:24:04 PM »

I was reading the same stuff you were John but it sounds to me as though the controller is going to target 14.4 float voltage and not cut out until it reaches that point.  It appears there is a method to change that cut out to a lower number (they call it "set point" voltage).  It sounds like a pretty dumb controller to me but I think I'd turn it down to a lower "set point" if it was mine.  I think the right fix is a genuine 3-stage controller. 
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R.J.(Bob) Evans
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« Reply #6 on: April 05, 2014, 10:38:44 PM »

Hi, Cliff.

At least some controllers have a float voltage adjustment on the board. And some don't. Since both the VR and the controller merely limit the voltage at the power source, they shouldn't interfere with each other.

If the controller is a three stage MPPT unit, then it ought to have a setting it falls back to when it reaches full charge. A good example is one which defines full charge based on how long the unit has been at acceptance voltage.


I remember some of the old mechanical regulators liked to get upset if there was more than one charge source. That shouldn't be much of a problem anymore.

Good luck, Cliff and take care.

We hope to see you again on one of our trips.
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Tom Caffrey PD4106-2576
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« Reply #7 on: April 06, 2014, 03:48:28 AM »

Clifford,

Read this guys blog:

http://handybobsolar.wordpress.com/

He's pretty hard to take sometimes because he really doesn't care. He's old, He's living off grid every day, and he doesn't care if you believe him or not. (You know anybody like that???    Grin Grin Grin Grin   )

His site has the most complete info I have ever seen on  solar charging as a whole system and what I have tried is working so far.

The guy is a piece of work though.

TOM
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