How Does 'battery Run-down Protection' Work?

[n8wrl]

I'm not a EE - I'm a software guy (which means we are happy to assume there are 0's and 1's and go from there) so I'm hoping someone can explain the workings of this cool feature to me. I see mention of it in the manual, and I've noticed that when I turn on something with the engine off I hear a relay click somewhere in the dash. After about 20 minutes or so the relay clicks again and whatever I turned on is turned off!

This is pretty cool since I have an old (very old) Passport radar detector that takes 9V. It came with a small DC-DC 12V-9V converter which I installed in the overhead unit where the front-seat map lamps are. A small wire comes into the cubby up there where the Passport neatly fits - no more suction cups on the window or wires dangling down to the 12V outlet on the dash! I was worried about leaving it on but when I turn on the Passport I hear the familar 'click' of the relay and assume battery run-down protection is engaged. Neat!

Thanks!

-n8wrl

 

[ygmn]

Works like you said...after 20 mins the the brains of the truck turnthings off that it is allowed to turn off if juice is being sucked from it,,,,,,

 

[n8wrl]

Thanks for the reply! What I was actually looking for is, electrically, how does it work?

 

[wyrickre]

More specifically, I'd be curious to know how to wire a new source to the battery AND have this battery run-down protection. The way I currently have my new aux power line run is straight to the battery (fused, of course). What circuit would I need to add a relay to in order to have the new aux power line automatically shut off after 20 min, too?

I'm asking about the '03, too.

 

[rod]

mine is an 02, dont know if 03 is different. the control is done by the body control module(BCM). it is simular to a PLC. it controls the rundown protection relay. i dont know for sure but i would assume the BCM talks the CAN network. it talks to the radio, engine control module, mirrors and seats. on an 03 even each door has a door control module..... all talk to the BCM serially. wish i could find an affordable CAN chip.

rod

 

[ShapeShifter]

Thanks for the reply! What I was actually looking for is, electrically, how does it work?

Just about everything is computer controlled these days. There is a computer that controls the engine and transmission called the PCM (Powertrain Control Module) and another one that controls just about everything else called the BCM (Body Control Module.)

Most of the various power controls and switches go through the BCM, so it can monitor what is going on and properly control all of the equipment on the truck. It also controls a relay called the inadvertant power relay. Turn on something, like the dome lamps, and this relay lets it have power. The BCM also starts a timer, and if it is left on for too long when the truck is off, it trips the inadvertant power relay to turn things off. It's called the inadvertant powre relay, because it protects the batter if something is inadvertantly left on.

Hit another switch, like the map lights, and the BCM senses this and turns on the inadvertant power relay again for another 20 minutes.

When you get right down to it, it's relatively simple, but still pretty slick.

I've left the dome light switch on all night in the past, but it doesn't matter, 'cause the computer turns it off in 20 minutes. It's already saved my butt a couple of times.

-- SS

Update: I guess others snuck in with some answers, and a few new questions, while I was typing the above. It shouldn't be hard to tap into power after this relay, the trick is getting the BCM to realize that you have something there and turn on the relay when needed. Also, you want to make sure that whatever you add doesn't overload the relay. This will take some investigation...

 

[entree18]

I just purchased my first AV and now am busy installing mods, etc. I researched radar detector on forum and found your message from earlier this year. Does the Escort work in the cubby under the map light - read through the plastic? I have an older battery powered Escort and that would be an easy location choice if it worked there without having to mount behind glass.
Tom Albers

 

[n8wrl]

Our passport works great thru the plastic in the cubby by the map lights. Mine sits in the cubby with the front on the 'lip' so the back points down slightly, and if you look from the side you can sort-of visualize a 'line of sight' slightly down thru the windshield. It seems to work fine and is very convenient.

I'm still not sure if the battery run-down protection is working tho - I tapped into the power at the map lights up there. I know when I turn on one of those lights I hear a little 'click' which I assume to be the battery run-down relay. After 20 minutes the map light does go out. I have forgotten to turn off the radar detector and come back hours later to still find it on. It does not draw much so I guess it isn't a problem but I thought I'd get run-down protection there.

Anyway, go for it - the cubby is a good spot for the detector and it keeps the suction-cup-grubbies off the windshield, and wires off the dash!

-Brian n8wrl

 

[ygmn]

I feel the plastic will lower the effective range a bit...and I want as much range as possible..,....IMO

HTH

 

[MagicMtnDan]

I just purchased my first AV and now am busy installing mods, etc. I researched radar detector on forum and found your message from earlier this year. Does the Escort work in the cubby under the map light - read through the plastic? I have an older battery powered Escort and that would be an easy location choice if it worked there without having to mount behind glass.
Tom Albers

Welcome to the forums Tom.

Radar detectors must "see" outside and have an unobstructed "view" forward (and rear if it has rear-facing sensors) to work effectively. If it can't see the radar it can't help you. Put it up on the windshield where it can do the best job for you.

If you want the very best radar/laser detector get yourself a Valentine One. In my opinion, nothing else comes close (no matter what the magazines & Web sites say this one's the best for performance AND usability).