Hi there.

I've read several threads about the 380 throwing some weird codes when the battery is close to dead, and also reports that once a dud battery is replaced, the car seems to have a new lease on life.

With a mechanical and electrical background, this has somewhat intrigued me. But over time more and more people have said that a new battery seems to revitalise the car performance so I've been thinking it over in my spare time.

So, it seems illogical on first thought that an old, tired battery can cause this. But in my 380, my 4.5 year old factory battery is obviously on its last legs and I've noticed over the last 6 months a lot of poke seems to have disappeared. I've got less than 50k on the clock, so it's not a tired engine.

There's no way even a stuffed battery can could cause reduced performance through robbing power from the engine. Electrical loads once the car are started are furnished purely by the alternator. Even high electrical loads after first starting (to recharge the battery) are so minimal compared to the engine power it couldn't possibly be caused by this. Plus, once the battery is recharged (should take only 2-3 mins) the problem should disappear (which it doesn't).

So my long think about it has led me to only one conclusion. The only difference between a good battery and old one is in the starting output. I see this in the aircraft I fly when we start engines on battery power (very rarely). All batteries, new and old, show the same voltage before start. But during starter engagement, a poor battery will show a much larger voltage drop.

My theory is that the 380 engine does a lot of checking and calibration of sensors (such as knock sensor and air flow meter etc.) after the key is "ON". Perhaps if the key is inserted and turned to start immediately on a 380 with marginal battery, the ECU is initialised with low battery voltage which occurs during start and this causes problems with engine management. This might explain why the ECU throws weird codes such as crank angle sensor when the crank angle sensor is completely fine.

It is only a theory, but probably reasonably easy to test...

What if those with really old batteries who have noticed less poke turn their key to "ON", wait 5 seconds for the ECU to initialise on the full battery voltage, then kick it in the guts.

I've tried this for the last two days, and it certainly seems to have made a bit of difference to the butt-o-meter. Perhaps with a couple of weeks of this practice, the ECU will re-adapt and I'll get the extra performance back.

Anyone else with thoughts on this?
Can anyone else with an old battery/less poke than normal try this and get back to me with results?

Our 380 is 4 1/2 years old and the battery is also close to dead. Cold starts are getting harder, sometimes taking 5-10 seconds. Will let you know if anything feels different after replacement.

Sgeve

Well when your engine is running and you disconnect the battery then engine stops. I might misunderstand this but battery works as long as there are electrons are travelling between cathode and anode through a medium. Once there is no longer any potentinal difference then there is no voltage. Thus it basically breaks the circut or as it starts to die makes the electrical flow slower. Also the battery is charged by generator, not alternator afaik. Battery is DC isn;t it?

the battery is charged by generator, not alternator afaik. Battery is DC isn;t it?

Huh? What is the alternator for then? :S

Um, I think you're off the mark in several areas.
Disconnecting the battery after the engine is running has never caused any of my cars to stop running, and don't see why it would.
This is why you can jump start a car with a dead battery and then drive it around with the electrics running fine. As long as there is some voltage to initially excite the alternator, once it has started, no battery is required.
Cars use an alternator, not generator. The AC is rectified by a diode pack to DC.

Have you tried removing the battery after the engine is already running? I haven't myself, but I would imagine that there would be a difference between breaking the circuit and having a flat battery in series wouldn't there?

Nope, no difference whatsoever.

Thanks Steve, if you could get back to me that would be great.

I think the alternator needs power to generate power, the magnetism in it is provided by windings on the outside, not permanant magnets? If it stops producing power for a tiny bit it cant magnetise its own outside so with no magnetism generates no power?

Not a good idea to disconnect the battery while the engine is running . . . . I wouldn't do it, but its your car . . . . .

I think the alternator needs power to generate power, the magnetism in it is provided by windings on the outside, not permanant magnets? If it stops producing power for a tiny bit it cant magnetise its own outside so with no magnetism generates no power?

That doesn't make any grammatical sense whatsoever. An alternator only requires an inital excitation voltage. After it starts, it is self sustaining.

Anyway, can we can back to the original thread?

No, it is sustained by the running engine via the ancillary belt. It is not some perpetual energy device lol

To the OP, just change the battery if its showing its age. As long as the cold crank ampage is sufficient to start the engine, the DC current from the alternator takes over immediately and ensures a steady flow of power for all the electronics. It wont be playing any effect in your poor running engine so i suggest you look into other possibilities.

My 380 doesn't have a poorly running engine.

If the battery has nothing to do with it, why have multiple 380 owners on this forum reported the car feeling sluggish - and once the battery was replaced, it seemed to be back to its old self?

My 380 doesn't have a poorly running engine.



You said it yourself in your first post?!??! Power being 'robbed' from the engine?

. . . . why have multiple 380 owners on this forum reported the car feeling sluggish - and once the battery was replaced, it seemed to be back to its old self?

Purely psychological. lol

My 380 doesn't have a poorly running engine.

If the battery has nothing to do with it, why have multiple 380 owners on this forum reported the car feeling sluggish - and once the battery was replaced, it seemed to be back to its old self?

Placebo effect. They expect that it will bring performance back because other people said that doing the same thing brought their performance back. Because they expect it, they will see it - even if it's not there. The old seat of the pants dyno is not very accurate.

Aren't the 380's CANBUS managed, so if the voltage performance is poor, ie, the battery is demanding too much, I'm not surprised that they have a "new lease on life' once the battery is renewed, but I had the dreaded 380 poor starts and renewed the battery and it was fixed, the battery could still crank the engine, easily too, but the ECU wouldn't play the game till there was an abundance of current.

I can't justify it techically, but I wouldn't be surprised if it were true.

For the record, I had a boss with one of those Twin Turbo Fairlady Nissans, replaced the battery and a whole load of power came back. Like lots......

There could be a few things that come to mind.
A dieing battery could cause higher load on the alternator in an effort to recharge, or moreso the electrics that are relying on the alternator and not the battery, this could rob power that is normally used for spark etc.
The other could be that once the battery starts dieing it adds more resistance in the circuit?

I'm not an electrician, but generally if a system needs electricity to run and a part of that electrical setup is not running efficiently, this would cause those systems to be affected?

On the other hand it could just be worn terminals and the new battery + clean terminals makes better grounding in the system. When my terminals got dirty, i noticed more pickup in the car after cleaning them. That was without replacing the battery.

A dieing battery could cause higher load on the alternator in an effort to recharge

In the OP, I said that this isn't a reasonable explanation. Large current draws from an alternator are still miniscule when compared to the engine output. Also, the problem would disappear shortly after engine start once the battery is recharged (generally takes very little time).


this could rob power that is normally used for spark etc.

The battery/alternator system has absolutely nothing to do with providing spark to spark plugs, so it isn't that either.

I'm still adament that if in fact this is a real problem (rather than psychological), it is caused by the key going straight to the start position and the ECU starting up with the lower voltage which occurs during cranking.

In the OP, I said that this isn't a reasonable explanation. Large current draws from an alternator are still miniscule when compared to the engine output. Also, the problem would disappear shortly after engine start once the battery is recharged (generally takes very little time).
Yes but an alternator can only put out so much juice, if there is a big current drain on the alternator surely this would affect other systems. It's basic maths:
If the car needs 30A to run, and the alternator can produce 80A max, and there is a 65A draw elsewhere, this will cause issues. These figures are made up I have no idea what it actually is, or if this is even the issue, but it could be related.




The battery/alternator system has absolutely nothing to do with providing spark to spark plugs, so it isn't that either.
Where does the spark come from then?

Sorry, that should have read battery system has nothing to do with the spark to the spark plugs once started.

The alternator maximum output is much higher than that required to charge the battery and run all the electrical systems at once.
Cars with an under-powered/failing alternator which can't match the demand of recharging the battery and powering the car normally show this in the headlights - at night when the car is idling, the headlights might dim just a little bit. Once the car accelerates and the RPM goes up, the headlights will brighten a little.

Anyone have access to a dyno, a 380 and a good and bad battery so this could be tested scientifically?
Would be interesting if its true

Well, that would be the ultimate solution pretzil. Unfortunately I don't have access to a dyno.

Once my battery completely dies and I replace it, I guess I will be able to see for myself if the perfomance changes. For now, I'll stay with the delayed cranking (to allow the ECU to initialise itself on full voltage) and see if it makes any difference.

For whats its worth, my car is an 01/06 model on the original battery and I havent noticed any decrease in performance at all.

After doing a google (http://www.google.com.au/search?source=ig&hl=en&rlz=&q=low+battery+poor+engine+performance&oq=low+battery+poor+engine+performance&aq=f&aqi=&aql=&gs_sm=e&gs_upl=186l14639l0l15435l35l32l0l22l2l0l453l2366l2-5.2.1l8) search, we are not the only particular car owner that suffers from poor performance when a low/dying/dead battery is connected to electrical system.

Perhaps we can settle this more scientifically by have some memebers with bad batteries/performance reading the stored diagnostic codes before and after changing the battery?

Sh00t is correct - any car with a CANBUS management system throws low voltage codes when the battery is on its way out. The VE commodores are exactly the same with a whole bunch of nonsensical codes that logged DTCs and dash lights when the battery was low voltage.

Sh00t is correct - any car with a CANBUS management system throws low voltage codes when the battery is on its way out. The VE commodores are exactly the same with a whole bunch of nonsensical codes that logged DTCs and dash lights when the battery was low voltage.

But are these codes sufficient to cause some kind of limp home or restricted power mode of operation?

But are these codes sufficient to cause some kind of limp home or restricted power mode of operation?

Weak/dying battery shouldn't result in limp mode, if that's what you asked - but it can throw a CEL. Mine did for 2 days, but it cleared itself before I could check the code with a friend's obd2 port thing.

But are these codes sufficient to cause some kind of limp home or restricted power mode of operation?

To be honest, I wouldn't be suprised if it did in the 380s - its completely plausible for the system to perform a check, find the voltage insufficient to power up and then by default, put the car into failsafe mode because it thinks theres a problem.

To be honest, I wouldn't be suprised if it did in the 380s - its completely plausible for the system to perform a check, find the voltage insufficient to power up and then by default, put the car into failsafe mode because it thinks theres a problem.

So to my earlier post today - we need a bad battery memeber toi read the codes before battery swap and after

I disagree, if there are some people that believe that there car is underperforming with flat battery, why not believe them.

I disagree, if there are some people that believe that there car is underperforming with flat battery, why not believe them.

The OP himself wants it to be confirmed.

Can anyone else with an old battery/less poke than normal try this and get back to me with results?

OK, when my battery was dying, I tried, and I told my missus, to leave it in the on position for a about 5 secs before starting, and yes it started normally, before it wouldnt fire after cranking. It had just been plain difficult to start.
But I still got the CEL, so in with the new battery, and 100% fixed, as for performance, she drive's it like miss daisy anyways. But that was way back then.

Funnily enough, now she is complaining of robbed performance, poor acceleration, I might check out the battery again, It does mostly 20 mins city trips, she drives with the lights on, and we run an amp, I wouldn't be surprised if our battery didnt charge properly.

For my two cents worth, I've also experienced the performance drop and I agree with flyboy. It doesn't make sense but it is a real phenomenon.

I've also had the alternator fail completely, due welding on the car for crash repairs. This lead to draining the battery over two days, unbeknown to me (there was no alternator warning light) and the car failing because the fly-by-wire throttle stops working.

Classic arc welding problem - if you don't disconnect both sides of the battery you can punch through one of the many diodes in the alternator, making it conductive, when your engine is cold and hasn't been used for hours, but the alternator feels hot you know what has happened.

That could be the performance problem people have noted - the fly by wire gizmo gets lazy. Just a guess though . . . . .

There is an earth strap directly onto the fly by wire throttle & it is very important this is a good earth. I believe the 380 can benifit from additional earthing due to the full canbus electronic nature of the car.

Our 380 was taking a little longer to start recently and with an impending trip to Melbourne I changed the original battery out before we left, rather than possibly have to do it interstate. I put an Optima Yellow Top in, like I did with my Falcon last year.

The car ran fine before the change, was just not confidence inspiring starting in the cold weather. Car runs much the same now only cold starts are fine again. No other changes noted and the battery was disconnected for a while too.

Only improvement is knowing there is a good battery in the car which should be reliable and last a long time.