Timers & Battery Draw Protection


What does a timer do in a law enforcement vehicle? What equipment does it control?


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The ones we install run the radios. With a 15 min shut off. The new Motorola APX radios have a parasitic drain that will kill the battery.

I know some are used for MTDs

We've always used the Ram safe-t charge. But I've had 2 malfunction in the passed week. So maybe something new is in order.


Site Regular
We put all aftermarket (installed) electrical equipment on our's.  They sense voltage and shut off when the battery/batteries get to 11.5 VDC


Registered Member
We have Chargeguards which is now, or maybe always has been, a Havis product? They have been put in the vehicles since the 90's i want to say. They are set for one hour. Never had one fail and absolutely agree about the APX radios drain.

They used to have them in the passenger compartments but people would keep hitting the emergency override...for hours at a time...and kill their batteries anyway. With them in the backs of the cars it's easier to get juice by starting the vehicle. 

Not sure about others, but they have a delay power output and over volt protection which is handy. They are only attached to the radios and computers. The newest vehicles are also having the warning lights wired in due to low current LED's on most everything now. 


Senior Member
We have used charge gard and copeland tophat timers for radio, cameras, lightbar controllers and inverters.


We use Charge Guard.  Havis bought them a couple years ago.  Have tried the ones from Ram, but they had a bad failure rate.  Back in the day I used some from EVModules too, those were great!


With the APX radios, at least the remote head style, You have to keep the small red batt wire that is on the HEAD hooked to hot all the time, and the yellow to IGN. If you shut down both the red and the yellow from the back of the head with the key, the base unit will stay on and drain a battery in 3 days or less.  We have tested both conditions and found a high drain when wired with the red to IGN and no drain when wired as intended. It may be possible that something else in programming causes your parasitic drain but I do not do any radio programming so it is just an assumption.

We use copeland "Top hatt" timers and have been shutting off pretty much everything after 30 min. it also senses low/high voltage conditions and can run 200 amps through it. Kinda pricey, but we like what it does for our purpose.


Senior Member
We used Power Patrol. All of the electronics are wired to this unit. Timer can be set to 10, 15, 30 minutes or an hour. They are very good for fleet cars. http://www.patrol-power.com/
now those units are pricy and the origional person who came up with them now has a different company that makes the same unit.

I was looking thru a police magazine and saw a new timer from copeland that controles 6 circuts with 6 different timers and 6 fuses, nice looking unit.
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I do a lot of Cantrol based installs and started using the Cantrol it's self as the "charge guard/ shutdown timer" I can pick my shut down time, it will also monitor voltage and shut down at whatever voltage I tell it too.


Registered Member
In my installs, all radios and devices with parasitic drain are wired to an ignition sense rail. This has a timer that cuts off the load when the car isn't running for more than 5-30 minutes.

If you need to keep the radios on for longer (or the warning lights are activated) a switch on the dash overrides the auto shutoff and enables a Havis IdleRight, which starts the car is the voltage drops below a threshold (12-11.75 depending on vehicle)

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