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Radio "off" current killing battery

Old 05-27-2008, 04:45 PM
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Default Radio "off" current killing battery

Found battery dead, nothing left "on", charged battery and then went hunting. Found the VHF radios when OFF were still pulling a half-watt or so each. Confirmed by pulling an accessible fuse on one of them, dropped the battery drain by half.

This boat was wired without any switch between the radios and the battery ostensibly because of some CG or other requirement to have radios always able to be used....obviously it is creating an unintended problem.

Anyone else see this? Do most people just put in a big switch or other way to be certain their batteries don't get killed?

For now, I'm just going to pull the fuse going to the radio stack when I leave the boat, but I want to do something brighter for the long run, like maybe an ON OFF switch by the radios or else a big switch at the battery.

Your suggestions would be appreciated.

thanks
gordon
Old 05-27-2008, 04:53 PM
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Default Re: Radio "off" current killing battery

Pulling a half watt or a half amp? ;?

Why not just wire them into a power source that shuts off when you turn the key off, and rig an override switch to power them up if/when you don't have the keys?

I've never heard of any CG or any other regulation that requires the radios to always be operable.
Old 05-27-2008, 09:59 PM
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Default Re: Radio "off" current killing battery

If you dont want to install a battery switch (best option) then just splice a toggle switch in line
Old 05-27-2008, 10:11 PM
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Default Re: Radio "off" current killing battery

IMHO, the radio should be installed forward of your battery switch, the bilge pump should be installed with a three way Auto-Off-On switch with a circuit to the battery.
Old 05-27-2008, 11:26 PM
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Default Re: Radio "off" current killing battery

Thanks guys. Much appreciated!
Roughly 100 mA total (0.1A) = approx 1 watt total; 1/2 watt each radio.

I did a brief search via google. The ABYC books are $60; the CFR does not list any such requirement to have radios continually able to turn ON.

So I'll add some sort of switch. I don't want to have to turn the ignition ON in order to use a radio. so I think I'll just add some sort of inline toggle or some other kind of switch.

thanks again for the ideas and info!
gordon
Old 05-28-2008, 02:01 PM
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Default Re: Radio "off" current killing battery

Diagnosed a similar problem for my brother's VHF - except it was worse - over an amp draw when off. Many (if not all) VHFs do not remove ALL power from the circuitry. The RF power amplifier stage can draw significant current when transmitting, but due to the design *should* draw no current when in receive or "off". Because of this trait, the manufacturers do not usually run the supply voltage for the pwr amp through the on/off switch. A bad (leaky) power transistor in the P.A. changes all this and can result in a constant current draw. The VHF I looked at was so bad that the heat sink was a bit warmer than ambient temperature!

Woody - KZ4AK
Noran, Albe24 Express
Old 05-28-2008, 04:55 PM
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Default Re: Radio "off" current killing battery

1. You can put any switch you want between the VHF and the battery. There is no requirement to wire it directly to the battery, nor is this a good idea.

2. A VHF that draws current when switched off is likely defective. It has no memory circuit and no need to be continually powered.
Old 05-28-2008, 04:57 PM
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Default Re: Radio "off" current killing battery

ggibby - 5/28/2008 2:26 AM

So I'll add some sort of switch. I don't want to have to turn the ignition ON in order to use a radio. so I think I'll just add some sort of inline toggle or some other kind of switch.
Connect it to the "load" side of your battery switch. You can probably do this at the helm because the power available there is most likely switched by the battery switch.

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