flypigs
Outside the beltway
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Hi All,
My first post here. We have our first RV, and things are going great so far. One nagging issue I have is that the Jenson radio doesn't have unswitched power supplied to it (even though it has a wire that can accept it) so every time I turned the 12v master off I loose all the presets.
1. Other than the tiny trickle of energy it takes to maintain memory, is there a downside to running a "home run" from the battery prior to the master switch?
2. Would I need to add a fuse and a switch in-line?
3. Is there any other reasonable way of maintaining presets? (I wonder how long a 9v battery would last for that application?)
Thanks,
Pete
2012 Fun Finder XT-245
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LAdams
Northern Illinois
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Pete,
12 volts unswitched power is available at many locations in your trailer... If you have access to any light fixture wiring in the ceiling or walls, the 12 volts that supplies it is not switched...
Is your 12 volt cigarette lighter plug power receptacle near your TV antenna amp switch close??? I don't believe that the 12 volt power plug is switched either - a simple voltage check with a meter or 12 volt trouble light will tell you if it is... Just remove the panel from the wall or ceiling and check it's power with a meter or trouble light...
Yes, you could run a home run from the battery (I would suggest fusing it if you did) but I think finding a 12 volt unswitched source will be a lot easier than that 
Les
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Old Hammer Boy
Utah
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If you have a 12v disconnect, yes, you will have to "home run" a line to somewhere before the switch to the radio's positive lead. And, yes, fuse it as close to it's origin as possible. A 9 volt battery would probably hold memory for several months, but it should be taken out of line when the trailer voltage is applied, or you could experience a blown-up battery, even a rechargeable type could over heat from over charging.
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You can't take the Fisherman out of this Camper
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If you already have 12V available at the radio then add a switch to the main line into the radio and connect the existing (available) wire so that the presets etc. are always connected. That's what I have on my 12V radio and it's never been a problem. If you add an 'in-line fuse' that you can pull when the trailer is in storage you're all set!
When my trailer is in storage (beside the house) I have it connected to shore power through a timer (1 hour per day) and even after 7-8 months of storage my batteries are both fine!
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1960's: Tents.. 1970's: Soft top & Hard top P/U.. 1980's: 17' RV.. 1990's: 24' RV.. 2000's: 2002 Cougar 276EFS; 2005 Laredo 29GS; 2002 GMC 2500HD Ext Cab 4x4;(Nfld/Labrador-Yukon/NWT/Alaska-Gaspe', Que./Florida!!)
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RoyB
King George, VA
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I just added a nice SPST Illuminated Rocker Switch from Radio Shack and separated the two 12VDC hot lines going to the radio. One is wired to be on all the time to keep the presets going and the "Ignition KEY" hot wire goes to the 12VDC switch I got from radio shack. works good here.
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LAdams
Northern Illinois
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Ah, my mistake - I reread the post and see your turning off the 12 volts via a "master" battery cutoff switch or similar device 
If in fact your killing all power from the battery with a "master cutoff" then abot your only choice is to run a home run from the battery on the "live" side of the cutoff or use an independent battery to keep the radio memory alive...
I guess another option would be a small solar array on the roof to keep a small battery charged for radio memory... I would think the radio memory would only draw a few milliamps if that...
Les
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flypigs
Outside the beltway
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Thanks all for the quick replies. A few more thoughts: I think that on my trailer, there is no unswitched power. When I enter the trailer there is a switch labeled "12v main" on the bank of switches that controls some of the other 12v devices and circuits (water pump, porch light, etc). When that 12v main switch is off, I don't think anything else has 12v power.
I will need to investigate further to see if that "12v main" switch by the entry door actually caries all the 12v current, or if it just controls a relay that is in the circuit breaker box where the 12v fuses are.
The circuit breaker box is fairly close to the radio, so if there is unswitched power there, I will just try to run a wire with a switch and a fuse in it.
I guess sooner or later, you have to find out what is behind the wall covering, right?
Thanks again
Pete
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Chuck_S
Broadview Hts, OH, USA
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The "tiny" parasitic electrical draw of the my Roo's radio memory is only about 0.10 amp but that adds up to 17 amp hours per week. I can't measure the exact draw as my LP detector and radio are permanently wired to the 12v system. Total draw of both devices is 0.15 amp or about 25 amp hours a week.
Considering the Group 24 "80m amp hour" battery on your trailer tongue really only has about 55 useful amp hours the radio consumes 30% of your useful power just sitting in the driveway or yard every week between camping trips. Pretty big draw for what's the convenience of maintaining presets. (This draw and others like keyless entry is also what causes your car and truck batteries to go dead over a fairly short period of non-driving time.)
17 amp hours won't be made up by your truck's charging system unless you're on an all day drive.
Bigger battery won't solve the discharge but will keep more power in the battery. I'd think a small solar panel should make up the wastage without a lot of exotic wiring. But even small solar cells can be expensive.
-- Chuck
'06 Roo 23SS behind '07 Expedition out of Cleveland
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redwake
Visalia, CA
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flypigs wrote:
1. Other than the tiny trickle of energy it takes to maintain memory, is there a downside to running a "home run" from the battery prior to the master switch? you should be able to put a 12v source inline and put some kind of a diode type device to prevent it from powering every thing on the circuit.
flypigs wrote:
2. Would I need to add a fuse and a switch in-line? no
flypigs wrote:
3. Is there any other reasonable way of maintaining presets? (I wonder how long a 9v battery would last for that application?)
yea just not maintaining them... unless you stay close to home all the time when you camp i'm not sure why you would even use the presets i dont, we have the ipod hook up and the famous camping CD i made when we first bought the trailer and has still never left the deck.
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flypigs
Outside the beltway
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Redwake,
The reason the presets matter is because of how awful the channel controls are on the Jensen I have, it only has a "skip to next channel that has signal" button, or a "skip to a lower channel that has signal button". Even if you press and hold one of those buttons, it doesn't move more than one channel per "click".
I can't see myself going through the effort of doing a solar panel for this, but a single wire w/ a switch and a fuse might be reasonable. That will limit me to 1 channel setting per trip.
Again,
Thanks to everybody who responded.
Pete
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