FM radio standby drain

N

NickNap

Well-Known Member
Joined
3 Apr 2005
Messages
140
Visit site
I want to install an fm car radio but am concerned about the drain on the battery between trips (or having to retune each time).
I'm guessing that one of you guys out there might have a dodge to overcome this? Or isn't the current enough to be a problem?
 
The current drain is minimal, so no worries about it flattening your battery. You'll need to arrange a permanent live feed from the battery - but be sure to fuse it as close to the battery as possible.
 
Dunno how typical they are but these are the figures I measured on mine.

With the red wire 'off' around 10mA is drawn from the permanent, yellow wire. I assume this is little more than the self discharge on a leisure battery. The red wire is the one that is controlled by the ignition key when fitted to a car.

Interestingly, when the red wire is at 12v the unit draws 250mA, even though it is off. This current is again drawn via the yellow permanent connection.

In fact contrary to (mine at least) expectation, in use, all the current is drawn from the permanent yellow wire. Initially I connected this to the fine cable used for the battery meters which are fused at 1 amp at the battery. My daughter soon blew that! Typical draw when playing a CD is a little over 1 amp.
 
[ QUOTE ]
Depends on how long is 'between trips', a week or two should be no problem. A couple of months and you could kill a battery. My wifes sony car radio will drain her cars battery in about 2 weeks. It's a real pain!

[/ QUOTE ]It's not the radio, it's probably the other drains on the battery, such as the anti-theft system. The memory supply on a radio is just a few milliamps - it won't flatten a healthy battery in 2 weeks!
 
My electrical system is minimal being a 5w solar panel and about 10AH wet NiCad battery. I found that the keep alive current for the memory did flatten the battery faster than the solar could recharge.
Solar now works quite satisfactorily without the radio connected.

I found an old manually tuned AM/FM radio which sounds fine. You might finnd one in a car wreckers yard. olewill
 
[ QUOTE ]
My electrical system is minimal being a 5w solar panel and about 10AH wet NiCad battery.

[/ QUOTE ]I think "minimal" is a bit of an understatement!
 
With the number of blown out weekends we've had I find it does drain the battery sufficiently to notice, so I disconnect it. But the radio remembers the station tunings perfectly. What I do need to reset is to cancel the DAB auto setting each time.
 
That sony drains 100ma. I have measured it. The anti theft drains less than 10ma. This with a Fluke multimeter.

Its the radio believe me. I think it has an internal fault but since it works fine otherwise its staying where it is.
 
[ QUOTE ]
That sony drains 100ma...... I think it has an internal fault ....

[/ QUOTE ]Sounds like it! /forums/images/graemlins/shocked.gif

Does it retain its settings, and does it switch off when the ignition is turned off?
 
Hi PVB yes minimal but very adequate. The Nicad can be discharged for all of the 10AH so it is probably worth 25AH of lead acid. The 10 is actual tested I think it was rated at 14AH.
I run AM /FM radio seldom used, VHF T/R and a 27megT/R (Oz peculiarity) and GPS Etrex. Plus nav lights and cabin light. After a night race about 2hr of nav lights on there is still lots of life in the battery.
The solar recharges over about 2 weeks (lots of sun) so it is very practical. Perhaps not so good for those using plotters lap tops etc .
Good luck olewill
 
Go to Maplins and buy a 12v battery of the type used in burglar alarms (or cadge one off an alarm engineer. they often fit a new one when they service a system) or motor bikes. dont spend too much. Buy also a schmitt key diode. (50p). With a little logical thought you can charge the alarm battery from the ships battery via the diode. and support your radio memory from the alarm battery. I fitted this years ago and it works well. I also have a red flashing LED in the window also powered by the alarm battery to deter miscreants
 
You must log in or register to reply here.

Share this page

Top