Direct Wire for GPS - Parasitic Current Draw?

[sign216]

I'm putting in a direct wire for my GPS. Goes from two raw leads at the battery, to a mini USB plug for the Garmin. Direct Wire Unit

 

I was surprised when I attached the leads, to see a small spark at the positive connection. Nothing's attached to the line yet, just the wire, so there should be no current draw, right? Multimeter says a current draw of 0.5 volt and 0.003 amp (3 m Amp).

 

Although the GPS isn't attached, is it possible that the voltage reduction circuit in the line is causing the parasitic drain? I think the black box in the line may reduce the voltage from 12 to approx 3 volt for the GPS.

 

Is the 0.5 volt 0.003 amp drain significant? Is it normal?

[mikie]

I always hardwire my Escort radar detector to my bikes, and instead of going directly out from the battery I use a not hot fuse. That way if the bike's turned off, so is the connection.

[sign216]

I always hardwire my Escort radar detector to my bikes, and instead of going directly out from the battery I use a not hot fuse. That way if the bike's turned off, so is the connection.

 

I did it via a small fuse block. I just slapped on the GPS line to go up to Laconia tomorrow, for a trip of a few days.

 

I also got a micro-relay + fittings for a better setup, but that will have to wait until I get back.

 

In the meantime, I'm curious about this drain, on what should be a dead line.

[v11cafe]

 

...I was surprised when I attached the leads, to see a small spark at the positive connection.

 

Maybe reason was the order of attaching the wires

I think it is first pos(+) then neg (-)

If you attach neg(-) first you might get sparks while attaching the pos(+)

 

If you did it right ignore my comment

[Kiwi_Roy]

My buddy connected his GPS direct to the battery, Even though he unplugged the cable from the unit the power supply in the cable ran his battery flat over a couple of weeks.

Connect your load to the headlight relay circuit or to one of the fuses that is switched by the ignition switch and you won't have to worry about flattening the battery.

The headlight relay is only energized when you turn the key on and there are lots of point in and around the dash where you can connect.

Most GPS units have a voltage regulator built into the plug, don't try to cut the cable and connect it directly to 12 Volts.

Don't ask me how I know.

 

Roy

[sign216]

V11, you're right, I think I connected the neg lead first, in error. Still, I'm surprised there's a current draw in the power line, even when the GPS is unconnected.

 

Kiwi, I would have connected the GPS directly to the 12v current too, but fortunately I checked some online forums first, and had previously disassembled a cigarette plug and seen the circuitry inside. Or I would have made that mistake too.

 

It's all powered off a small after-market fuse panel, that's nice because it fits so well in the tight space that cycles have.

 

Joe

[Mikuzzi]

I needed the GPS in a hurry so wired up a Garmin Zumo mount directly to the battery - the supplied cables have an in-line fuse. Obviously the mount is live all the time so the GPS comes on as soon as it's fitted to the mount. I'm convinced that there is a small drain on the battery from the mount itself - at least the battery has started losing more charge between rides than before.

Next job is to change the supply from the battery to a switched source.

[Kiwi_Roy]

I needed the GPS in a hurry so wired up a Garmin Zumo mount directly to the battery - the supplied cables have an in-line fuse. Obviously the mount is live all the time so the GPS comes on as soon as it's fitted to the mount. I'm convinced that there is a small drain on the battery from the mount itself - at least the battery has started losing more charge between rides than before.

Next job is to change the supply from the battery to a switched source.

I think the Voltage is stepped down to 5V, the adapters use a few mA even without the GPS plugged in but that's enough to drain the battery over 2 or 3 weeks, connect your multimeter in series you will see (provided that the meters fuse isn't blown of course, try it with the GPS installed to be sure)

[Dan M]

If the power line has circuitry to reduce voltage that is likely your draw.

I have an older Garmin Streetpilot that is hooked up directly and there is just B+/- right to the unit. No draw when switched off or disconnected.

 

3mA is pretty small. Would take quite a long time to run down a good battery.

[Mikuzzi]

I needed the GPS in a hurry so wired up a Garmin Zumo mount directly to the battery - the supplied cables have an in-line fuse. Obviously the mount is live all the time so the GPS comes on as soon as it's fitted to the mount. I'm convinced that there is a small drain on the battery from the mount itself - at least the battery has started losing more charge between rides than before.

Next job is to change the supply from the battery to a switched source.

I think the Voltage is stepped down to 5V, the adapters use a few mA even without the GPS plugged in but that's enough to drain the battery over 2 or 3 weeks, connect your multimeter in series you will see (provided that the meters fuse isn't blown of course, try it with the GPS installed to be sure)

 

I'm getting 0.3 Amps with the Zumo in the mount and working, and 3.3mA with just the mount by itself

(disclaimer - I'm using a multimeter that cost all of $9 so accuracy may not factor!)

[Kiwi_Roy]

I needed the GPS in a hurry so wired up a Garmin Zumo mount directly to the battery - the supplied cables have an in-line fuse. Obviously the mount is live all the time so the GPS comes on as soon as it's fitted to the mount. I'm convinced that there is a small drain on the battery from the mount itself - at least the battery has started losing more charge between rides than before.

Next job is to change the supply from the battery to a switched source.

I think the Voltage is stepped down to 5V, the adapters use a few mA even without the GPS plugged in but that's enough to drain the battery over 2 or 3 weeks, connect your multimeter in series you will see (provided that the meters fuse isn't blown of course, try it with the GPS installed to be sure)

 

I'm getting 0.3 Amps with the Zumo in the mount and working, and 3.3mA with just the mount by itself

(disclaimer - I'm using a multimeter that cost all of $9 so accuracy may not factor!)

Even a $9 meter would be better than +/- 10%

A 10 Amp hour battery would be at 1/2 charge 5/0.0033 = 1,500 hours (2 months)

[Mikuzzi]

I needed the GPS in a hurry so wired up a Garmin Zumo mount directly to the battery - the supplied cables have an in-line fuse. Obviously the mount is live all the time so the GPS comes on as soon as it's fitted to the mount. I'm convinced that there is a small drain on the battery from the mount itself - at least the battery has started losing more charge between rides than before.

Next job is to change the supply from the battery to a switched source.

I think the Voltage is stepped down to 5V, the adapters use a few mA even without the GPS plugged in but that's enough to drain the battery over 2 or 3 weeks, connect your multimeter in series you will see (provided that the meters fuse isn't blown of course, try it with the GPS installed to be sure)

 

I'm getting 0.3 Amps with the Zumo in the mount and working, and 3.3mA with just the mount by itself

(disclaimer - I'm using a multimeter that cost all of $9 so accuracy may not factor!)

Even a $9 meter would be better than +/- 10%

A 10 Amp hour battery would be at 1/2 charge 5/0.0033 = 1,500 hours (2 months)

So...my Ballabio has a 13 AH sealed battery. The GPS mount will take this down to 80% charge in approx 4 1/2 weeks. Add the normal self discharge for these type batteries of around 2.5% per week and I'll get around, what, 2 1/2 to 3 weeks from full charge to 80% - I've got to ride more!

[Kiwi_Roy]

 

So...my Ballabio has a 13 AH sealed battery. The GPS mount will take this down to 80% charge in approx 4 1/2 weeks. Add the normal self discharge for these type batteries of around 2.5% per week and I'll get around, what, 2 1/2 to 3 weeks from full charge to 80% - I've got to ride more!

EXACTLY, you can't risk a flat battery

[sign216]

 

So...my Ballabio has a 13 AH sealed battery. The GPS mount will take this down to 80% charge in approx 4 1/2 weeks. Add the normal self discharge for these type batteries of around 2.5% per week and I'll get around, what, 2 1/2 to 3 weeks from full charge to 80% - I've got to ride more!

EXACTLY, you can't risk a flat battery

 

I am amazed that the line will draw amps without even being connected to the GPS. The draw is small, but something to watch for. Thanks all.