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02-22-2017, 11:46 PM
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#1
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Junior Member
Join Date: Feb 2017
Posts: 18
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How do I hook up a solar panel to my coach batteries?
I have two deep cycle 12 volt batteries for the coach & want to hook up a 40 watt panel. Just to keep the batteries charged up when the motor-home is stored with no source of outside power. Do I attached to (+) red on one battery then (-) black on the second battery so both batteries are being charged equally? Thanks for your help......Len
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02-23-2017, 12:34 AM
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#2
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Senior Member
Join Date: Oct 2014
Posts: 119
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If your panel doesn't have a built in charge controller, you'll need to buy one so you don't send too much voltage and so it can shut off when the batteries are charged. You can get one on amazon for $10-$20 that would be sufficient for a 40w panel.
__________________
'03 Newmar KSDP 3703 • Magnum MSH-3012 • Magnum PT-100 • GS 160w x 6 • 655 AH
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02-23-2017, 03:40 AM
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#3
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Senior Member
Tiffin Owners Club Appalachian Campers Mid Atlantic Campers Coastal Campers Freightliner Owners Club
Join Date: Jan 2015
Posts: 1,622
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To answer your question on the battery connections, I'd suggest making the connection on the buss bar, to avoid having multiple wires at the battery connections. Then by default, the connection is spread correctly on the batteries (not that it matters much with little charge current).
If you have to go with attaching at the batteries, it's not a lot of current so really isn't going to matter that the + is on one battery, and the - is on the other battery. Do it where you can get good clean connections and the wires won't rub/fray.
__________________
DaveB, Raleigh, NC
2015 Tiffin RED 33AA, w/Honda CRV
VMSpc, Magnum BMK/ARC50
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02-23-2017, 06:32 AM
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#4
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Senior Member
Join Date: Mar 2009
Location: Apollo Beach & Key West , FL
Posts: 3,803
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Quote:
Originally Posted by Mike Bartelt
If your panel doesn't have a built in charge controller, you'll need to buy one so you don't send too much voltage and so it can shut off when the batteries are charged. You can get one on amazon for $10-$20 that would be sufficient for a 40w panel.
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That's what I did --- I put a 40w on the roof of the storage building and ran the wires to the controller then into the chassis batteries.
__________________
2013 DS 4338
2015 F-150 toad with kayaks,bicycles and a Harley in the back
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02-23-2017, 07:11 AM
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#5
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Senior Member
Monaco Owners Club
Join Date: Jan 2008
Location: Olympia, Wa
Posts: 2,772
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At 40 watts you don't need a controller. At most you will get 2-3 amps to the batteries. You, if the batteries are off(disconnected) will at most maintain not charge. At 100 watts I would add a controller. Red on one battery and black on the other would balance both batteries.
LEN
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2004 Clss C 31' Winnebgo
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02-23-2017, 09:11 AM
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#6
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Senior Member
Tiffin Owners Club
Join Date: Jul 2014
Posts: 487
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Quote:
Originally Posted by OLYLEN
At 40 watts you don't need a controller. At most you will get 2-3 amps to the batteries. You, if the batteries are off(disconnected) will at most maintain not charge. At 100 watts I would add a controller. Red on one battery and black on the other would balance both batteries.
LEN
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Len has it right. And to go one step further, the panel will act like a drain when connected to the batteries directly without the sun. This is one of the reasons for the charge controller. If you want to do it right, get two panels about 235 watts a piece and hook them up in parallel to a charge controller and relax. I looked on my local Craigslist and found panels for $90. Otherwise, when you hook them up to the batteries, without the charge controller, you might do as much harm as good.
The most absurd work of a solar panel-discharging a battery |
__________________
Bill & Mary USN 69-73 ASW Technician, MBA.
2006 Tiffin Allegro Bus QDP 1060 watts solar
2012 Jeep Grand Cherokee '16 Polaris Razor 4
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02-23-2017, 09:20 AM
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#7
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Senior Member
Join Date: Jul 2014
Posts: 35,317
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Quote:
Originally Posted by billdreamlv
Len has it right. And to go one step further, the panel will act like a drain when connected to the batteries directly without the sun. This is one of the reasons for the charge controller. If you want to do it right, get two panels about 235 watts a piece and hook them up in parallel to a charge controller and relax. I looked on my local Craigslist and found panels for $90. Otherwise, when you hook them up to the batteries, without the charge controller, you might do as much harm as good.
The most absurd work of a solar panel-discharging a battery |
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From your article,
Most of the solar panels produced today have a series diode to block the discharge of the battery.*
You would probably have look hard to find one that doesn't.
This is a non issue.
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02-23-2017, 09:55 AM
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#8
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Senior Member
Tiffin Owners Club
Join Date: Jul 2014
Posts: 487
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Quote:
Originally Posted by twinboat
From your article,
Most of the solar panels produced today have a series diode to block the discharge of the battery.*
You would probably have look hard to find one that doesn't.
This is a non issue.
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"This is a non issue" because you know for a fact that the 40 watt inexpensive panels have diodes built into them? And your electronic credentials are? Sometimes reading information from people who don't have a clue about electronics can really be damaging to your coach.
__________________
Bill & Mary USN 69-73 ASW Technician, MBA.
2006 Tiffin Allegro Bus QDP 1060 watts solar
2012 Jeep Grand Cherokee '16 Polaris Razor 4
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02-23-2017, 10:12 AM
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#9
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Senior Member
Join Date: Jul 2014
Posts: 35,317
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Don't know for a fact. Yes It is a non issue.
BLOCKING AND BYPASS DIODES
Many older books and articles recommend using blocking diodes to prevent reverse current flow back through the panel at night ("dark current"). Many others do not (including us, mostly). It actually depends on the situation, but as a general rule in 12 volt systems, you will lose more power from diode losses than you will from leakage back into the panel at night. The situation gets much worse at higher temperatures with crystalline panels. All regulators (charge controls) have built-in blocking circuits. About the only case where a blocking diode might be needed is with small thin-film panels, such as the Unisolar US-5 or Siemens ST5, where the panel is connected directly to the battery. Diode losses are much less in higher voltage systems, such as 48 volts.
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02-23-2017, 01:39 PM
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#10
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Senior Member
Tiffin Owners Club
Join Date: Jul 2014
Posts: 487
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Quote:
Originally Posted by twinboat
Don't know for a fact. Yes It is a non issue.
BLOCKING AND BYPASS DIODES
Many older books and articles recommend using blocking diodes to prevent reverse current flow back through the panel at night ("dark current"). Many others do not (including us, mostly). It actually depends on the situation, but as a general rule in 12 volt systems, you will lose more power from diode losses than you will from leakage back into the panel at night. The situation gets much worse at higher temperatures with crystalline panels. All regulators (charge controls) have built-in blocking circuits. About the only case where a blocking diode might be needed is with small thin-film panels, such as the Unisolar US-5 or Siemens ST5, where the panel is connected directly to the battery. Diode losses are much less in higher voltage systems, such as 48 volts.
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When you plagiarize someone else's work you should at least give them credit. I believe you copied this website for your insight.
https://www.solar-electric.com/solar...cal-tips.html/
" About the only case where a blocking diode might be needed is with small thin-film panels, such as the Unisolar US-5 or Siemens ST5, where the panel is connected directly to the battery."
From your own quote.
__________________
Bill & Mary USN 69-73 ASW Technician, MBA.
2006 Tiffin Allegro Bus QDP 1060 watts solar
2012 Jeep Grand Cherokee '16 Polaris Razor 4
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