12 Volt Car "Jump-Starter" or??

[peejman]

Seems pretty clear that something isn't working properly. I'd guess that police cars have heavy-duty batteries and charging systems given the loads they must support. The battery shouldn't drain down in 48 hrs. It sounds like either the battery has a bad cell and isn't holding a charge or you've got a light staying on and draining it (which will also ruin a battery).

I'd start with the suggestions of just disconnecting the battery when you know it'll sit for a day or two. Wrap a rag around the cable so it doesn't short. If the battery goes down while it's disconnected, clearly it's a bad battery.

I don't know if the car has a volt meter in the dash, but connect a good one across the battery terminals. Watch the voltage when you start the car. It shouldn't drop much. If the voltage drops to about 9V or less when you hit the starter, bad battery.

[hardknox00001]

An even easier (and less permanent) option is the battery disconnect knob that MCSCOTT suggested. I was looking at this one - BATTERY DISCONNECT SWITCHES - JCWhitney

It has a 15 amp bypass to allow the clock to keep settings, etc. For my issue, it seems like this would defeat the purpose. I reckon I could install the disconnect knob without the bypass. It's rated at 125 amps. I figured it all up and all the aftermarket doodads running at once should be about 75 amps at the most (yeah, there's a lot of crap on the car). That'd leave about 50 amps for the vehicle itself. What kind of amperage does the average car without aftermarket crap use?

EDIT: A deeper search into that product suggests that it is rated for 125A continuous, 500A peak. I think this would work. Any naysayers? Please feel free to jump in and keep me from screwing something up!

The big load that a car pulls normally (ie, not accessorized heavily) is when it starts. Once it starts, the alternator powers everything with the battery as a backup. This is proven that when somebody accidentally leaves the headlights on and drains the battery, a jump start gets the alternator going and as the person will drive around for a while, the battery will recover its charge.

As far as the disconnect goes that MSCOTT links to, that would work but only if you screwed that knob completely out. Remember you have a drain somewhere that runs you out of juice and leaving that 15 amp "memory" power source in line doesn't stop the rundown leak. To stop the leak, you must turn the source off completely.

As far as the amperage rating, without testing the load and seeing what everything is pulling, we can't really say. However, I am like you and would think just off my head that that would be big enough. Somebody with a DC amperage clamp meter should be able to test what your pulling very easily.

What is a clamp meter you say?????

This;

Edited August 3, 2010 by hardknox00001

[Guest db99wj]

You could just taze it in the mornings.

Nothing more to add, sounds like you have the Ford Electrical gremlin.

[MCSCOTT]

The disconnect that I was talking about can usually be found at any Advance or Autozone in the section where their battery cable ends are. You definately don't want to go with the one with the fused link, because this will just be defeating the purpose of disconnecting the battery. Other than the fused link, they pretty much look the same as that one.

Lynx/Quick connect top post battery terminal | Battery Terminal End and Adapter | AutoZone.com

Pop the hood, unscrew the knob, and you're good to go. The disconnect switch that hardknox posted is also a good idea, because you could mount this just about anywhere so that you wouldn't have to raise the hood. The drawback to that kind of thing is that you also have to buy a good bit of 00 wire and pretty much make a whole new battery cable that's long enough to go from the engine compartment to the switch, and then from the switch back to the engine compartment. With the knob style disconnect you simply cut the end off the stock battery cable, and clamp the new end in place. Stop by Advance or Autozone or somewhere and take a look at them.

It's still my opinion that this is only a temporary fix, and at some point you'll want to really spend some time tracking down every connection until you find the one that's draining the battery.

Edited August 3, 2010 by MCSCOTT

[Capbyrd]

Jon,

When is the next time you go to work? I am off Friday and can help you with this. I've found to never trust tests on batteries and alternators while they are in the car. The first thing I would recommend is taking the battery out and having it tested. Then go from there. But I am a hobbyist mechanic and can probably help you sort this out. Shoot me a text.

[kb4ns]

Thanks for the input guys. Chris, it'll be next week sometime, but I'll holler at you.

[Capbyrd]

Cool. Well I am off every Friday, Saturday and Sunday so just let me know.

[Guest Lester Weevils]

Just a dumb question about a battery master disconnect switch. Dunno about modern cars, but would routine use of a disconnect switch perhaps tend to wipe the memory of some of the onboard computers? Cause them to reset more often than expected. Weird "service engine" codes and such?

Mom had a Camry that if you disconnected the battery then reconnected it, the factory burglar alarm would go nuts, turn on, and you had to go thru a long elaborate reset routine to reset the alarm and get it to shut off.

[Capbyrd]

Yeah Chevy's and Toyotas have that problem. I haven't run into that problem with any of my Fords though.

[Guest jackdm3]

That's cause they're "Built Ford Tough!

[kimbercarry]

A quick way to locate the current drain is to disconnect the negative cable and connect a volt/ohm meter set to the amp setting connected between the battery neg post and the cable and observe how many amps are being pulled with everything shut off then began pulling the fuses one at a time until you locate the offending circuit.

[peejman]

Just a dumb question about a battery master disconnect switch. Dunno about modern cars, but would routine use of a disconnect switch perhaps tend to wipe the memory of some of the onboard computers? Cause them to reset more often than expected. Weird "service engine" codes and such?

Mom had a Camry that if you disconnected the battery then reconnected it, the factory burglar alarm would go nuts, turn on, and you had to go thru a long elaborate reset routine to reset the alarm and get it to shut off.

Not anymore. Early ECU's required a small amount of power to maintain their memory (ROM). Newer cars use either flash memory (just like a camera card) or EPROM cards. Some have a hard-drive like a PC. It's cheaper, more stable, and doesn't require power.

[hardknox00001]

A quick way to locate the current drain is to disconnect the negative cable and connect a volt/ohm meter set to the amp setting connected between the battery neg post and the cable and observe how many amps are being pulled with everything shut off then began pulling the fuses one at a time until you locate the offending circuit.

This is a good idea. This will defininately help narrow the search, point in right direction.

[Guest Lester Weevils]

Thanks all for the answers about disconnect switch and modern autos.

Kimbercarry's debug method, ammeter on ground and fusebox process of eliminations, sounds really good. Only thing it wouldn't catch would be something wired in aside from the fusebox. Dunno how likely that would be.

[titan14]

Why are 90% of you guys suggesting a "temporary" fix????????

I dont understand!

There is something OBVIOUSLY wrong with the electrical system.

And to Jack, I worked at the local Chevy dealership for a couple of years, and we had THP cruisers in EVERY week looking for "bugs" in the vehicle. I agree, they wont fix it under WARRANTY, but, someone that looks at these vehicles EVERY DAY, may see something that is "out of whack"(awry)...

To the OP...your cruiser should NOT be dead after 48 hours....hell....it shouldnt be dead after 6 months.....

Maybe the law enforcement agencies, around the country, should start looking at NISSANS for their vehicles....

[kb4ns]

Maybe the law enforcement agencies, around the country, should start looking at NISSANS for their vehicles....

Lol. Just bought the wifey an Altima. It's nice. Our admin (Chief down to Inspectors) all got new Altimas last year. Nissan just doesn't make anything competitive in the "patrol-ready" area. I wish they did, though.

[G27]

Lol. Just bought the wifey an Altima.

Tell her not to give the little one food in the back seat...

[Bubba0031]

FORD

Find On Road Dead

Fix Or Repair Daily

[Capbyrd]

First on Race Day!

[MCSCOTT]

Why are 90% of you guys suggesting a "temporary" fix????????

I dont understand!

There is something OBVIOUSLY wrong with the electrical system.

And to Jack, I worked at the local Chevy dealership for a couple of years, and we had THP cruisers in EVERY week looking for "bugs" in the vehicle. I agree, they wont fix it under WARRANTY, but, someone that looks at these vehicles EVERY DAY, may see something that is "out of whack"(awry)...

To the OP...your cruiser should NOT be dead after 48 hours....hell....it shouldnt be dead after 6 months.....

Maybe the law enforcement agencies, around the country, should start looking at NISSANS for their vehicles....

A temporary fix keeps the OP from having a dead battery until he can get the real issue fixed, but on each of my suggestions I did mention that these were only temporary and the problem shouldn't just be left alone. I was under the impression that the OP didn't have time to start tracking down all of the wires, because in a police cruiser that could take a full weekend or longer dedicated to nothing but tracking each wire. At least with a temporary fix in place, he can do away with the dead battery issue and track different wires in his spare time until he finds the culprit.

[Guest db99wj]

I still think you should taze it, might not fix it, might not work, but at least you get to taze something.

[kb4ns]

Tell her not to give the little one food in the back seat...

Yeah, um, that lasted about the first week...

A temporary fix keeps the OP from having a dead battery until he can get the real issue fixed, but on each of my suggestions I did mention that these were only temporary and the problem shouldn't just be left alone. I was under the impression that the OP didn't have time to start tracking down all of the wires, because in a police cruiser that could take a full weekend or longer dedicated to nothing but tracking each wire. At least with a temporary fix in place, he can do away with the dead battery issue and track different wires in his spare time until he finds the culprit.

I'm slated to get a new ride within the next year. A temporary fix might be just the ticket!

I still think you should taze it, might not fix it, might not work, but at least you get to taze something.

We have no tazers...

[Guest db99wj]

Yeah, um, that lasted about the first week...

I'm slated to get a new ride within the next year. A temporary fix might be just the ticket!

We have no tazers...

Booooo!

[titan14]

Lol. Just bought the wifey an Altima. It's nice. Our admin (Chief down to Inspectors) all got new Altimas last year. Nissan just doesn't make anything competitive in the "patrol-ready" area. I wish they did, though.

I think my wifes 370 is patrol ready....and I also think my titan is patrol ready....i even think my stedaughters 3.5 altima coupe is patrol ready....

These 3 are just 3 of the 8 we have owned....in a row...I like my Nissans!!!!!

[Varmint]

Speaking of temporary fixes, until you can get it looked at, why not just start the car for a few minutes on your day off to let the battery recharge?