Q45 Battery Drain Mystery

Post by **MinnyQ** » Mon Dec 01, 2003 6:12 am

Ok gang, here's one that has the dealership stumped. My '95 Q (184k) has burned out four batteries in two years. BUT the dealership detects no abnormalities with the alternator, parasitic drains, no loose belts, etc. The latest battery -- the heaviest duty I could buy -- is only two months old and already struggling. Symptoms are these: The longer the car sits the harder it is to start. I drove it from Minnesota to Denver for Thanksgiving with relatively normal starts after fueling, eating, etc. But overnight it was a near dead start, then, after holding the key down, the starter would begin spinning and it would kick over. Leaving the lights on for even a couple minutes, like while pumping gas, will cause the same near-dead, aggravated start. As I say, the dealership checked it out the day before I left, found the battery badly undercharged, (after being parked in their lot overnight), but couldn't detect anything else. Ten pounds of Minnesota road salt to whoever correctly diagnoses this one. Thanks in advance.

Post by **DAEDALUS** » Mon Dec 01, 2003 6:12 am

Hook up a current meter between the battery and the cable, and then begin removing fuses one at a time until the current drain goes away. I'm guessing a bad relay somewhere.

Post by **Q45Viper** » Mon Dec 01, 2003 6:12 am

Also try a different dealer if the above does not work, you've probably got the same tech and service manager looking at it over and over and not coming up with any new ideas. Or a real good independent mechanic should be able to trouble shoot an electrical drain methodically. Until then you might want to consider a battery tender from pep boys, they have permanently mounted pigtails on the battery that you can run out somewhere for quick hookup without even opening the hood, you've got a grill so you could hide the ends in the grill, real quick hookup at night, this would keep you with a high charge if you put it on every night until you solve the problem. Can't overcharge either, it shuts off and on as needed.

Post by **sachmo12345** » Mon Dec 01, 2003 6:12 am

electrical drain on our two 1994 q 45s after one week away.

one shows normal battery drain signs as in rapid tick tick tick when we try to start.the other one started on the first try than was driven 5 miles and parked therafter it would not start and was totally dead-we tried to jump startit and the car went bizerk--lights flashing ,horn tooting all the dash lit up--when we took off the jumper cables after failing to start the car continued to make noise until toatlly drained--did we mess up the ju8mping ? i checked the book and we did it right

both cars have not had starting probles --by the way the temperature went down 35 degrees whilwe were gone.

any ideas ??

Post by **sijoko** » Mon Dec 01, 2003 6:12 am

My Q has gone through 3 batteries in the last 2 years. But the car did sit unused for extended periods.

There will always be a drain on the battery. Once the charge level has gone below a certain point, the battery is pretty much on its way out.

Also, I believe that the battery is subject to extreme heat in its stock location. With the engine running, the fan is throwing hot air directly onto the battery. Some kind of battery blanket or shield would definitely add to battery life.

-sijoko

Post by **fxjackso** » Mon Dec 01, 2003 6:12 am

An obvious question, but do the cars in question have any, repeat any, aftermarket accessories that may have been installed by someone who was not knowledgable of the Q's wiring? I had a hard to trace drain that was associated with an aftermarket remote unlock. Cured only by removal.

Post by **MinnyQ** » Mon Dec 01, 2003 6:12 am

The dealership will give this problem another try Friday. But in response to all above, I'm still favoring the parasitic drain theory, either that or a uniquely damaged alternator. There are no aftermarket devices (that I know of). The remote lock is an Infiniti-brand device (purchased from Scottsdale) which, coincidentally. I did acquire more or less about the time this problem began. Other notable symptoms, all related to low battery power I assume, are: The CD deck resetting itself to disc 1, track 1 after the overnight drain, and the "Low Fuel" indicator popping on and staying for several minutes after start even though the needle indicates a nearly full tank. If the Infiniti kids can't figure this out this time through I'll try the fresh eyes/independent mechanic route.

Post by **Q451990** » Mon Dec 01, 2003 6:12 am

Have you tried disconnecting the remote lock device? I thought these were standard by 1995.

Heath

Post by **MinnyQ** » Mon Dec 01, 2003 6:12 am

Are we talking the same thing here? What I'm using is just a programmable key fob device. I'm not aware there is anything "connected" to it.

Post by **maxnix** » Mon Dec 01, 2003 6:12 am

My 1995 stock Q45 will be fine for a least two weeks with no starts.

Post by **szh** » Mon Dec 01, 2003 6:12 am

maxnix wrote:My 1995 stock Q45 will be fine for a least two weeks with no starts.

Similar results here on my 1995 Q that I sold recently. Even left it for six weeks in an airport long-term parking once. No problems whatsoever starting when I returned.

I only had to replace batteries every four years or so. This is normal.

Z

Post by **MinnyQ** » Mon Dec 01, 2003 6:12 am

Quite right. The beast used to sit for a week or more with no problem. Hence my conviction that something is whacko and belief it is a parasitic drain problem. But where? And why can't the pros detect it?

Post by **hal90000** » Mon Dec 01, 2003 6:12 am

Were you able to resolve this issue? I have a similar problem with my 96 Q.

Post by **azskygod** » Mon Dec 01, 2003 6:12 am

Seems I remember a thread on the old Yahoo board about parasitic battery drain. I think it was linked to a stuck ABS relay... Just a thought.

AZSKYGOD

Post by **hal90000** » Mon Dec 01, 2003 6:12 am

Thanks for the reply. I did find that thread, but I don't think that is what is happening. That thread indicates some sort of whine from the ABS relays and I don't have any unusual noises. If I let the car sit for more than 2 or 3 days the (new) battery is too low to start it. But if driven every day it seems to do fine. It has been cold though. Snowy too, that is why it is not being driven.

Post by **driverdriver** » Mon Dec 01, 2003 6:12 am

I don't know if this helps, but I remember hearing a similiar problem with a J30 up here one summer at 300ZX/J30 club meet and greet. It was eventually diagnosed to be the alternator. Apparently the J30 (I don't if this is true on the Q45) has got an one and off switch or wire somewhere inside it. For whatever reason the alternator was always on "on" mode and it would drain the battery. I had a similiar problem with my car. A good test is to disconnect the battery cables from both terminals and try reconnecting (works best with a fully charged new battery). If one or both of the cables arcs or sparks during reconnection its your alternator and that "on" problem I mentioned.

Post by **hal90000** » Mon Dec 01, 2003 6:12 am

Seems like every car I ever had sparked a little bit when re-connecting.

I read somewhere else today that you can use a voltage meter between one of the battery cables and the battery to measure the voltage drain while the car is in the key off condition. If the drain is greater than 100 milliamps or so you can start pulling fuses until you find out where the excess drainage is coming from. Anyone have any ideas what the normal drain should be?

Post by **driverdriver** » Mon Dec 01, 2003 6:12 am

One time I was at my dealer piicking up my car, and a mid '90's Q45 was towed in. The owner had forcefully connected his battery even though the cable(s) arced/sparked when connecting to the terminals. He started his car up and blew away his ECU and a bunch of other modules and sensors. He was looking at a hefty repair bill.

Post by **Highlander322** » Mon Dec 01, 2003 6:12 am

Did you ever get this figured out? It is happening to me as well. Any help would be appreciated

Post by **hal90000** » Mon Dec 01, 2003 6:12 am

Not really figured out but it is solved for me. I replaced the battery and it has been fine since then. Can't really explain it as the old battery tested fine. So did the alternator. At least it is working.

Post by **Q45tech** » Mon Dec 01, 2003 6:12 am

Not sure very many techs know how to test batteries and alternators to exacting precision world class standards.

Lift the ground terminal and measure the current flowing from battery to ground terminal [make sure battery is 100% charged should be around 80 milliamperes key out, door closed only alarm light blinking [you will need to have someone hold down the hood alarm switch.

55 amp hours 55/0.08= 687.5 hours /24= 28 days if 100% charged at least 14 days to crank depending on ambient temperature.

The amount of parasitic drain can be fitted to formula.

Bad alternator regulator and blown phase diode with be just under an ampere ~~ 2 days.

Post by **Highlander322** » Mon Dec 01, 2003 6:12 am

Thanks Q45tech.

I tested the battery drain, it is almost 3/4 of an ampere. That gives me the usual 2 days of charge. I tried to reach the alternator but as you are aware, it is almost possible to get to and check. Any easy way to do that. Also, is the phase diode a part of the alternator or is it somewhere else?

Thanks, Rick

Post by **Q45tech** » Mon Dec 01, 2003 6:12 am

Inside the alternator -----regulator assembly.............you have to disconnect the alternator fuse [120 amp fuse] [where the alt output meets the battery bus and measure there to prove the parasitic load is inside the alternator.

Usually fails from bad [dead bat recharge] battery overtaxing the alternator. When you don't replace batteries every 3-4 years.

Always install a new QUALITY battery whenever you replace alternator [and only use oem replacement alternator..........the aftermarket rebuild are real SERIOUS junk.......they don't replace the diodes or regulator chips just change brushes and maybe a bearing clean them up and say the are remanned!

Post by **Highlander322** » Mon Dec 01, 2003 6:12 am

Thanks Q45Tech,

I took the 120 amp fuse out. Or I should say pulled it out. I had to do it with the pliers and the thing broke into pieces. IS/Was there a simpler way to get that out? I then checked the drain by puttina a lead on the battery cable and the wire under the fuse and it read virtually nothing. Does that tell me it is the alternator, or did I read at the wrong point? Was I suppose to disconnect the lead, or pull the fuse actually out?

Rick

Post by **Q45tech** » Mon Dec 01, 2003 6:12 am

Disconnect the leads, those big fuses don't pull out.

You just have to diagnose which of the main bus fuses the drain is comming thru then work your way to the appropriate fuse panel, then try each fuse till it goes away.Leave the terminal on the battery so you are not confused.

I unscrew the wires and aligator clip on it and on the screw terminal.

Post by **Q451990** » Mon Mar 07, 2022 5:45 pm

Q45tech wrote: ↑
Mon Dec 01, 2003 6:12 am
Not sure very many techs know how to test batteries and alternators to exacting precision world class standards.

Lift the ground terminal and measure the current flowing from battery to ground terminal [make sure battery is 100% charged should be around 80 milliamperes key out, door closed only alarm light blinking [you will need to have someone hold down the hood alarm switch.

55 amp hours 55/0.08= 687.5 hours /24= 28 days if 100% charged at least 14 days to crank depending on ambient temperature.

The amount of parasitic drain can be fitted to formula.

Bad alternator regulator and blown phase diode with be just under an ampere ~~ 2 days.

I'm resurrecting this zombie thread more to leave a note for myself. With everything off, doors closed, and hood switch down - I'm reading about 28mA. With the hood open, and the security light flashing, it pulses between about 70mA and 168mA. So long story short, leaving the hood open in the garage drains the battery faster. The security system does not appear to ever go to sleep with the hood open.