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Old 07-18-2011, 02:36 PM   #1
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battery charging with solar and shore

i have a dumb question. being self taught, there are gaps in my knowledge.


solar panel>mppt charge controller>batt bank.

shore power>inverter charger>batt bank.

solar amps around 7-10 depending on conditions and mppt effect
inverter/charger rated as 10amp charger

do they both charge the batt bank at the same time? do they conflict in any way? does the charge controller sense that the batts are receiving higher amp from inverter/charger and stop? or do both devices sense when the bank is at the right voltage for fully charged and stop? is the charge additive from both sources?

so a sunny day charges via pv and i have the inverter/charger plugged in as well.

cant figure that out. i dont see any mention of this. i see that folks have two (or three if you count vehicle alt) methods of charging but not how to manage between them.

thanks for the nudge in advance
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Old 07-18-2011, 05:04 PM   #2
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Re: battery charging with solar and shore

Here's how I understand it:

The amps aren't relevant as far as conflicts. It's voltage that you're interested in. The voltage of a battery relates to its state of charge; a charger senses this voltage and decides to charge based on its reading.

In theory, if you're on both solar and shore, you might end up just float charging the battery, regardless of its state of charge. This is because the solar charger will be charging at, say, 14V. You hook up shore power, it sees the high voltage, thinks the battery is charged, so sets itself to float. The solar charger then senses this float voltage, stops charging, and also settles into float mode. Because they're both providing float voltage, neither can sense the battery's true voltage, so can't provide the correct charge.

I've heard that some shore chargers are smart enough to sense a charge from another source, and will shut themselves down. Can anyone confirm?

You could also set your shore charger to avoid float mode, if that's an option with your charger; in this way, it would simply stop charging, and your solar panel would continue to charge.

If you want to use shore charging (because of higher amperage) during the day, you probably need to hook up a disconnect to the solar system. This could be some sort of relay that opens when 120V is sensed and disconnects the solar, or just a simple on/off switch.

Hope this helps!
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Old 07-18-2011, 05:36 PM   #3
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Re: battery charging with solar and shore

thats what i was getting at. i dont think my inverter/charger can respond to other charging sources (although it does have an automatic transfer switch but i dont think that is relevant here. seems more related to uninterrupted power which im not concerned with.)

a few weeks ago, the engineer who will be helping me with the install, did mention a disconnect between either the pv panels and controller or controller and batt bank (hes on vaca so i cant pick his brain) i think it depends on the controller as some need power from batt bank and others take power from pv panel.

disconnecting pv source to charge from shore and vice versa works for me if i need to do it that way.

but i have to say, if im doing that, its probably night, cloudy or i need to charge the bank a little faster. in that case, im thinking that a separate inverter and charger would be better since i could pick up a 55 amp charger or even a 90 amp charger and get it done quicker in those situations. ive seen models that can do the proper 3 stage charging for agm batts. the 10 amp charger that the inverter i was looking at will take a long time to charge the bank i plan on installing (600ah).

thanks for he info..have to read up some more.
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Old 07-18-2011, 05:55 PM   #4
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Re: battery charging with solar and shore

i will be acquiring a solar world 245 watt pv panel for free (barter for my time) and plan on putting it to good use.

i looked at most of the other mppt controllers and ruled out some brands that had a bad rep (2 come to mind but i wont name them here).

i found this one by accident and it seems to be a great choice and value.

http://www.roguepowertech.com/products/mpt3024.htm

some of the brands that i would consider using for the mppt controller seem to rule out using this panel due to one or several stats like Voc being out of range. not to mention cost. the rogue model also has a digital display included.

on the inverter side, i was considering an AIMS pure sine inverter/charger in 1500w or 3000w. im reconsidering this. their pure sine inverter only plus adding one of their stand alone chargers (iota) seems like a better choice.

anyone have any experience with AIMS or the mppt controller i linked?
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Old 07-18-2011, 07:42 PM   #5
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Re: battery charging with solar and shore

Quote:
Originally Posted by cygvan
thats what i was getting at. i dont think my inverter/charger can respond to other charging sources.
I might be wrong but it should not pose a problem unless it's a very basic charger and flat out overcharges or is not regulated (never tapers off). Having a shore charger on with sun on the panels is the same as driving down the road on a sunny day. The alternator isn't much different than most taper chargers.

I can't comment on solar controllers...some might have a problem with the charger or alternator charge. I'd ask the company that sells the controller and tell them its going in a RV.
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Old 07-19-2011, 10:49 AM   #6
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Re: battery charging with solar and shore

What kind of charge would my house battery get if I just ran a portable solar panel into my DC cigarrette outlet that runs off my house battery? No shore power just using solar. How many amps can be sent from the DC outlet, through the electrical panel, and back to the battery?

Trying to avoid having to create a direct wire to the house battery from the solar panel as this means having to come up with some sort of new wiring scheme and my battery is buried on the underside of my van. Being able to charge my house battery off of the existing DC outlet wiring would be ideal.
I have seen chargers for a cars main battery utilizing the DC outlet and am wondering if I could do the same for the house battery. My issue is amps as I ideally would like to be able to send 5 amps per hour to the house battery.

thanks, L.
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Old 07-19-2011, 11:13 AM   #7
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Re: battery charging with solar and shore

If it comes with a cigarette plug, why not?

Quote:
Originally Posted by Google
A charge controller is not needed for the two smaller panels however, in most cases, the 7 Amp Charge Controller should be used with the Solar Battery Charger to prevent overcharging.
I'd say that supports 5amp.
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Old 07-19-2011, 09:34 PM   #8
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Re: battery charging with solar and shore

Quote:
Originally Posted by louie
What kind of charge would my house battery get if I just ran a portable solar panel into my DC cigarrette outlet that runs off my house battery? thanks, L.
Yep, I also agree with Jage, why not. Most light solar window type chargers have little effect on batteries other than to keep them topped off. But if you have any load that is larger than the solar can output can handle, you'll never keep the batteries up to par.
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