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falkster



Member Since: 12 Nov 2023
Location: Sutton Coldfield
Posts: 19

United Kingdom 1988 Defender 110 V8 Petrol CSW Trident Green
Head unit fed from leisure battery
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
Post #1037062 11th Jun 2024 12:13am
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landy andy



Member Since: 15 Feb 2009
Location: Ware, Herts
Posts: 5454

2006 Defender 110 Td5 USW Zermatt Silver
You don’t have to go to ignition if it is required for memory as that is a permanent live, not a switch live. That way the radio would still come on/off with key but retain it’s memory
Post #1037074 11th Jun 2024 8:07am
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Mo Murphy



Member Since: 01 Jun 2008
Location: Letchworth Garden City, Herts
Posts: 2104

United Kingdom 1984 Defender 90 200 Tdi HT Pennine Grey
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.
Post #1037076 11th Jun 2024 8:38am
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TexasRover



Member Since: 24 Nov 2022
Location: Paris
Posts: 838

France 2002 Defender 110 Td5 DCPU Chawton White
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.
Post #1037079 11th Jun 2024 8:53am
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blackwolf



Member Since: 03 Nov 2009
Location: South West England
Posts: 16994

United Kingdom 2007 Defender 110 Puma 2.4 DCPU Stornoway Grey
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.
Post #1037159 11th Jun 2024 7:34pm
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landy andy



Member Since: 15 Feb 2009
Location: Ware, Herts
Posts: 5454

2006 Defender 110 Td5 USW Zermatt Silver
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.
Post #1037174 11th Jun 2024 8:44pm
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custom90



Member Since: 21 Jan 2010
Location: South West, England.
Posts: 19729

United Kingdom 
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. Diesel$ Live$ Matter. ⛽️🛢️👨‍🔧🧰⚙️ RED, WHITE & BOOST! 🇬🇧


Last edited by custom90 on 11th Jun 2024 11:32pm. Edited 1 time in total
Post #1037177 11th Jun 2024 9:10pm
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blackwolf



Member Since: 03 Nov 2009
Location: South West England
Posts: 16994

United Kingdom 2007 Defender 110 Puma 2.4 DCPU Stornoway Grey
landy andy wrote:
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.


Fair enough then, personally I wouldn't do it but if it hasn't fried your radio yet it must be OK. Thumbs Up
Post #1037182 11th Jun 2024 9:28pm
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falkster



Member Since: 12 Nov 2023
Location: Sutton Coldfield
Posts: 19

United Kingdom 1988 Defender 110 V8 Petrol CSW Trident Green
landy andy wrote:
You don’t have to go to ignition if it is required for memory as that is a permanent live, not a switch live. That way the radio would still come on/off with key but retain it’s memory


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...
Post #1037188 11th Jun 2024 10:43pm
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falkster



Member Since: 12 Nov 2023
Location: Sutton Coldfield
Posts: 19

United Kingdom 1988 Defender 110 V8 Petrol CSW Trident Green
Thanks everyone. al ot of food for thought as always. Thumbs Up
Post #1037189 11th Jun 2024 10:44pm
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