I left my Audiovox XC9 receiver plugged into the front cigarette lighter overnight. This morning, I went to work and my HHR started up fine, but I was wondering if I really should remove it from the power outlet each evening.

 

If it draws over 35 milliamps while the vehicle is off, I would unplug it. Here is a milliamp draw chart. These numbers are optimal conditions, so each battery would vary on how long before the draw would drain it to a no start condition. But continually having more then 25 milliamps will eventually take out the battery, probably on the first cold day you tried to start it.

Current Drain/ Days

25 mA/30.5

50 mA/16.5

75 mA/11

100 mA/8.25

250 mA/3.3

500 mA/1.65

750 mA/1

1 A/0.8

2 A/0.4

 

Therefore, remember to pull the plug! LOL



Thanks.

 

In my wifes Jeep I installed a second lighter outlet hidden under the dash and tied it in to a switched circuit. It not only goes off with the key but the ugly plug is routed under the dash and out of sight for a clean look.

 

These numbers do not look right. For example, if you have a 400 amp hour battery that is fully charged, then the battery would provide 1 amp of power for 400 hours or 16.7 days.

Parasitic loss in a battery is greater than 35mA.

 

I'm not sure where your numbers come from, but the battery run down time will vary depending on cold cranking amperage (CCA) and reserve capacity (RC). If the CCA and RC are higher, then the battery run down time would be longer. If the CCA and RC are lower, then the battery run down time would be shorter. The graph I posted indicates roughly how many days a 690 CCA battery with at 110 minutes RC (60.5 AH) starting at 80 percent state of charge will last with a constant current draw until it reaches 50 percent state of charge. Differences in battery rating and temperature will affect the results.

 

With the additional information you supplied, the table makes sense. Because parameters of the table were not listed along with the run down numbers, I could only assume the chart was referring to a drain down time, in days, from fully charged to a low voltage condition (< 8 volts).

My numbers are nothing more than the standard method used to indicate a batteries storage capacity regardless if it is an automotive battery or the AA in your electronic device. A battery’s ability to deliver power is rated as amp hours, the amount of amps the battery can deliver for a specified time. It is used as a comparison only because different chemistries force delivery thresholds.

A battery with a storage rating of 400 amp hours can deliver 1 amp for 400 hours, or 2 amps for 200 hours, etc., it is linear. This does not take in to consideration line loss or parasitic losses. This does not imply that a battery can deliver its rate amp hour in one hour though.

I am assuming the chart you referred too is from a manufacture, what I find interesting is that they consider 50% to be at the run down level. Why is that? I know the design purpose of an automotive batter is to start the engine, or, deliver a lot of amps in a short time period and not designed to power the radio, for example.

 

Yes straight from a manual. Sorry I should have posted more info.

 

I installed an outlet similar to dbfruth. I put it under the console area and wired it to the retained acc power going to the power windows. When I turn on the car, my XM turns on, and stays on with the radio when I turn the key off till the acc. power shuts off. Works great.

 

I think both of you have the right idea!