 | Home > In Car Electronics > Head unit fed from leisure battery |
 
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| falkster Member Since: 12 Nov 2023 Location: Sutton Coldfield Posts: 64   
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Hi All,
As I have a battery cut off switch, I am considering to connect the radio in the car to the leisre battery, so that I don't lose the time display and stored radio stations every morning... Is it as simple as connecting the cable that would go to the ignition and connect it to my leisure battery instead? Thanks, Falk |
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10th Jun 2024 11:13pm |
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| Mo Murphy Member Since: 01 Jun 2008 Location: Letchworth Garden City, Herts Posts: 2244  
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You could bridge the cut out contacts with a small piece of wire and a fuse big enough to supply the radio but will blow if there is any further electrical draw.
Mo The Land Rover 90 - Many are called, few are chosen. 50 Shades of Pennine Grey |
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11th Jun 2024 7:38am |
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| TexasRover Member Since: 24 Nov 2022 Location: Paris Posts: 1084  
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Normally a radio has a permanent live for the power consumption (amplifier) and to maintain any memory and a switched live just so that it knows if it should switch off when you switch off your engine etc. The switched live normally does not use a lot of power.
So if you wanted to keep the radio going at all times unless you physically switch it off you combine the two wires onto a permanent feed. If you want to have a regular radio setup but power it from from the leisure battery to avoid drawing down the main battery you probably best off connecting the permanent live wire to the leisure battery, but leave the switch live to the contact, but then you have to leave your keys in the contact to listen so maybe you should also change over the switched wire to the leisure battery. It's all common ground so it should work just fine. Modern radio's use very little power though so I am not sure you are gaining much. |
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11th Jun 2024 7:53am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17442 
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Power it completely either from one battery or the other, do not use both. If you use both you run a significant risk of destroying the radio if you attempt to start the vehicle or switch anything high current on while the isolator is off.
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11th Jun 2024 6:34pm |
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| landy andy Member Since: 15 Feb 2009 Location: Ware, Herts Posts: 5724 
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My head unit in my motorhome and many others is powered by their leisure batteries and switch live via the ignition. No problem for the ten years I’ve had that, and not read any issues from others. Some are wired like that a standard as they are used for tv sound as well.
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11th Jun 2024 7:44pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20441
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You’d need to ensure both supplies have common ground along with the head unit.
The ignition is the red switch and the yellow is battery power. If you put both together you’ll flatten the battery rapidly if you forgot to turn it off. The yellow will draw approx 5mA - 40mA on standby and whilst saving its memory. (Which is normal). somewhere between 6 to 14A when in use. The ignition probably only up to 200mA when on, none when off. If you put this on constant live it will still flatten the battery, just a bit slower than with the unit on. Standby current on yellow is up-to about 40mA is normal. Red should be off, unless the ignition is on and the Alt is providing charging voltage and current. $W33T $0U7H3RN $UG4R 🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 Last edited by custom90 on 11th Jun 2024 10:32pm. Edited 1 time in total |
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11th Jun 2024 8:10pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17442
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Fair enough then, personally I wouldn't do it but if it hasn't fried your radio yet it must be OK.  |
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11th Jun 2024 8:28pm |
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| falkster Member Since: 12 Nov 2023 Location: Sutton Coldfield Posts: 64
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The memory is usually the yellow wire out the head unit, right? So i could potentially bypass the cut-off switch with just that cable and keep everything radio related to the starter battery? This would actually be my preference as the leisure battery is further to the back of the vehicle... |
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11th Jun 2024 9:43pm |
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| falkster Member Since: 12 Nov 2023 Location: Sutton Coldfield Posts: 64
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Thanks everyone. al ot of food for thought as always.
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11th Jun 2024 9:44pm |
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| falkster Member Since: 12 Nov 2023 Location: Sutton Coldfield Posts: 64
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Need to bring this up again...
I now realised that my battery cut-off is on earth... That completely throws me as I simply don't know how I could get the memory in the radio to work. Basically the radio shows midnight every time I turn the cut-off switch. do I need to run a wire from my battery (starter or leisure?) earth to the radio's earth, basically bridging the cut-off switch? But by doing so, would I not create the earth connection for the whole electrical system that the cut-off switch cuts off?? I am seriously confused. |
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24th Jun 2024 9:17am |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8050  
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just do what Mo Suggests and easy simple fix to your problem. Cheers
James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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24th Jun 2024 9:41am |
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| Mo Murphy Member Since: 01 Jun 2008 Location: Letchworth Garden City, Herts Posts: 2244
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4" of wire, fuse and fuse holder, just like I said 2 weeks ago 🤔, doesn't matter that it's on the earth.
Mo The Land Rover 90 - Many are called, few are chosen. 50 Shades of Pennine Grey |
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24th Jun 2024 10:04am |
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| falkster Member Since: 12 Nov 2023 Location: Sutton Coldfield Posts: 64
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empty as originally quoted on wrong response...
Looks like I can't delete a post(?). Last edited by falkster on 24th Jun 2024 10:41am. Edited 1 time in total |
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24th Jun 2024 10:38am |
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| falkster Member Since: 12 Nov 2023 Location: Sutton Coldfield Posts: 64
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sorry not great with electrics. Wasn't aware that this works with earth as well... It wasn't my intention to make it look as if I dismissed your input. how much would you think is big enough a fuse? |
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24th Jun 2024 10:40am |
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