Crank Wet battery dead flat after a month of inactivity

[Bru9]

I recently replaced my crank battery with a Century wet maintenance free 85ah.

Right before I added this battery it was fully charged up outside of vehicle from my AC multi stage charger. After about a month of my Paj sitting in the drive way the battery was reading ~9volts at the terminal. I have the standard red acr sbi12 isolator dual batt setup.

Does this sound right going this flat in almost a month without a charge? Could there be a drain?

Sorry for my in depth lack of knowledge but I thought the crank battery gets isolated & cut off after at certain voltage level. So i don't see how a drain could do it? Maybe the isolator itself drains the batt + the natural self discharge?

Only use on power was keyless opening doors a couple of times.

[andy_q]

Does not sound right. You must have a drain fault of some kind.


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[nj swb]

No, that's not right. A new, fully charged battery shouldn't drop that far that fast in a stock vehicle.

So something non-stock is creating a drain (and depending how the accessory is wired, it's quite possible that any cut-out in the system would save the battery). What are the accessories wired to you main battery?

I have a car with an after-market blue-tooth kit, installed using a commercial "ISO adaptor" so that it was plug & play - no cutting of factory wires. The instructions with the harness stated that even the "ISO" standard isn't implemented standard by all manufacturers - so the permanent power and accessories power may need to be swapped.

All was fine until the blue-tooth kit was removed for a software update. Afterwards, the battery would go flat in about a month. Pulled it apart, swapped permanent and accessories power, and it's now good as gold - goes many months and still starts.

So, check your accessories, and how they're wired. Even "standard" wiring can sometimes lead you astray.

[BruceandBobbi]

Certainly not right. We left the Pajero garaged, didn't disconnect the battery for 4 weeks. Started first hit.

[Bru9]

No, that's not right. A new, fully charged battery shouldn't drop that far that fast in a stock vehicle.

So something non-stock is creating a drain (and depending how the accessory is wired, it's quite possible that any cut-out in the system would save the battery). What are the accessories wired to you main battery?

I have a car with an after-market blue-tooth kit, installed using a commercial "ISO adaptor" so that it was plug & play - no cutting of factory wires. The instructions with the harness stated that even the "ISO" standard isn't implemented standard by all manufacturers - so the permanent power and accessories power may need to be swapped.

All was fine until the blue-tooth kit was removed for a software update. Afterwards, the battery would go flat in about a month. Pulled it apart, swapped permanent and accessories power, and it's now good as gold - goes many months and still starts.

So, check your accessories, and how they're wired. Even "standard" wiring can sometimes lead you astray.

Hi. My Paj is pretty bare & nothing directly attached to the crank battery as far as I can tell. Sounds like I have to take it to the auto electrician.


thanks all.

[Drewan]

Back to basics park for the day, pull the + off check voltage with a multi meter 1 hour later , come back next morning check voltage again. Battery " could" have crapped out and be not holding charge. Its not common but it happens

[2bad4u]

I'll put my flame suit on first........

I disagree, this is normal for a lot of modern cars or maybe just Mitsubishi Both my current NW & previous NS would go flat if I left them for more than 2 weeks. My daughters Lancer (with no after market accessories) will also go flat if left for more than 2 weeks. I gave up trying to chase possible causes on my NW and now just leave it on a trickle charger when ever I go away.

Search on the forum and I think you will find that I am not alone here.

[erad]

My NW Manual transmission gets started and used once a month at times if it is lucky. It always starts first time (after I installed a N70ZZ battery). That is until this week.... We went to Canberra and I came home via the back road - minor corrugations, nothing to worry about. 3 days later and I had to go downtown and the shopping jeep (my wife's outlander) was out, so I tried to start the beast. NOTHING... Not even dashboard lights. Jump starter comes out and got it going OK.

I later disconnected the battery and put a trickle charger on it. 24 Hrs later and it was fairly well charged - certainly enough to kick the engine over at -6 Deg C. I looked for something draining the battery, and found it - the under-bonnet LED light strip. I have a normal type car door switch, and I had to cut the probe down a bit to make it operate correctly. It seems as if the end of the probe has somehow disappeared, and the light was on all the time. Strip the switch and repair it - all good (for now) but I will keep an eye on it in the future.

[Bru9]

Back to basics park for the day, pull the + off check voltage with a multi meter 1 hour later , come back next morning check voltage again. Battery " could" have crapped out and be not holding charge. Its not common but it happens

Will try that, but now that I recallk my previous batt went flat pretty quickly & behaved similar to this.




Could the readarc isolator be sucking the power? Or defective perhaps?

Are there any things that still run directly off the crank battery like door & interior lights, central locking even when the isolator kicks in isolating the crank?

This might explain perhaps as I frequently opene the doors each week keeping them open for some time to clean etc when ever modifying anything storage wise in the back cargo bay.

[chrisall]

9v is pretty much flat.

Firstly charge the battery, then pull the +ve terminal off and with your multimeter on Amps setting measure between the battery post and the terminal. That will tell you how much current is being drawn.

If you have even a 0.25A drain then your 85Ah battery will be flat in a couple of weeks.

Then start pulling fuses one at a time until the current reading drops.

[starjunk]

I had something similar a few weeks back, during an extremely cold night. battery went flat... I mean dead flat... Over a weekend of non-use. Charged it up and it's been fine ever since. Charge was ok the previous time it was driven, the battery has a colour change indicator that I check regularly.
Sometimes the cold weather can affect wet cell batteries. Thankfully it came good with a recharge.

[Bru9]

9v is pretty much flat.

Firstly charge the battery, then pull the +ve terminal off and with your multimeter on Amps setting measure between the battery post and the terminal. That will tell you how much current is being drawn.

If you have even a 0.25A drain then your 85Ah battery will be flat in a couple of weeks.

Then start pulling fuses one at a time until the current reading drops.

Thanks, I will try that.

[Bru9]

Well this is beyond me

After I got my multimetre the first reading was around 0.7A when everything was off & Paj locked. Straight after i pulled the first 10A fuse (think it was car horn or lights) the draw went down to 0.1A, and pulled the next few & draw went down a bit less. Put fuses back in & the draw didn't go back up.
Connected + lead back to batt terminal & unlocked doors with remote and opened door then re-locked with remote.

Straight after that I pulled + cable off batt terminal again & measured the draw was back up to around 0.7A, when I tried puling same fuses no drop in draw but alarm was triggered a few times during following repeats (the lights flashed but no sound as I had annoying speaker/horn removed)

These lights flash on/off for about 5secs sometimes when ever I close bonnet or sometimes in hot heat when using key remote to unlock-or if Batt voltage is very low.


Next few days another quick check showed around 0.1+A drain, this was one week after charging up with ac charger & the start batt is 12.5v, the drain must vary.

But always the starter batt is unable to start after 2+weeks of inactivity and dead flat within a month.

[peter54smith]

The pajero will in fact have a very small drain on the battery , the clock, the radio memory and possibly an alarm system if fitted can equate to 30 milliamp not a vast amount but if left over a few weeks will drain down a lead acid battery I use a small solar charger with an output of approx 150 milliamps in full sunlight to counter the drain solar may be the best way to go as your down under. But get the vehicle checked for a possible major short the alternators on pajero are well known to have this problem, also if your running a duel battery set up standard factory, one of the batteries may be defective draining the good battery. Regards and good luck getting this sorted.

[Bru9]

The pajero will in fact have a very small drain on the battery , the clock, the radio memory and possibly an alarm system if fitted can equate to 30 milliamp not a vast amount but if left over a few weeks will drain down a lead acid battery I use a small solar charger with an output of approx 150 milliamps in full sunlight to counter the drain solar may be the best way to go as your down under. But get the vehicle checked for a possible major short the alternators on pajero are well known to have this problem, also if your running a duel battery set up standard factory, one of the batteries may be defective draining the good battery. Regards and good luck getting this sorted.

I didn't bother getting it fixed, saw no point in the fuss, just hooked up a solar panel to maintain, which is a necessary thing to do regardless.