Power Drain question on car battery


I have a Garmin C340 and like to leave it plugged into the cig lighter in the car and just turn off the power with the power button. This way I can let the internal battery charge with the key OFF since my cig lighter stays live with the ignition off.

My question is does the unit continue to draw power from the vehichle batter AFTER the unit battery is fully charged, which would eventually run down the vehichle battery, or does it go into some kind of hybernation mode, with a minimal, or no, power draw? I am not talking about an extended period of time. Usually just overnight.

Drain is low

The power drain is pretty low after the unit is fully charged. I have left mine in the car overnight in the same way, plugged in and powered - but turned off - with no ill effects. I usually pull the charger out just enough to get the light to go out before I leave the car, though.

One thing for you to check though is if the power LED on the cig charger is still lit when you get in the car the following morning. As a battery protection method, my car automatically shuts off most of the power after 30 minutes with the ignition off. For example, if I manually turn on the interior light, it will go off after 30 minutes if the ignition is off. I don't know if this applies to the cig lighter socket, though.

I would say no

I often times leave my Motorola vehicle radio on over night (it has a constant power drain - I usually forget to turn it off after a FD call) and as long as I don't let the vehicle sit for days on end without driving it, the vehicle starts right up with no problems. So with a GPS that powers off when fully charged I would have to say you would be safe.

But usually, 15-20 minutes of driving (not just idling) will help recharge your battery as long as 1) your alternator isn't going bad 2) your water level in the cells is good or 3) your battery isn't near the 5 year mark or 4) the battery terminals are kept clean, etc.


johnc wrote:

I don't know if this applies to the cig lighter socket, though.

My BMW x3 cigarette lighter socket is always "hot" but my wife's Grand Cherokee goes off when the ignition is off. Each car / company seems to have their own approach.



I have two, one is switched and the other isn't.

Garmin Etrex Vista, Streetpilot 2610, GPSMap 60Csx, Nüvi 750, Colorado 400t, Nüvi 3790t

Battery drain

Either way - switched or not - I don't think you'd have to worry about a GPS draining your car battery even if you left it turned on overnight. The capacity of a car battery (which I have read is typically between 50 and 60 amp hours, at 12 volts) is roughly 65 times that of the C340's internal battery (3.7 volts, 2.4 amp hours - at least, that's what the replacement ones for sale on Ebay are rated).

"Recalculating... drive 0.2 miles, then abandon vehicle." ------------- [ETrex Venture CX; Nüvi 40; Drive 52]

Both of my vehicles have switched recepticles

Both of my vehicles have switched recepticles, so the nüvi and Sirius both turn on and off automatically. An unswitched main recepticle would be a real bummer, though having a spare that stays on would be nice for charging phones and such.

><> Glenn <>< Garmin nüvi 2598


Some vehicles (GM, I think) you can easily make them unswitched or switched. Our 2-way radio guy told me that, he checked my Nissan Altima, but said they didn't have that feature and it would take a re-wire job. All mine go off with the ignition. He said that with the computer chips in cars nowadays, it can be a pain to re-wire some vehicles.

John - with a Garmin 650 and a 750

Simple solution

install a separate 12 recepticle and wire it to a fuse that turns of with the ignition.

Charley - Nuvi 350 - Bel STI Driver - Cobra 29 w/ wilson 1000 - AIM: asianfire -