battery replaced 10 times in 4 years; but no parasitic drain reading

[jspeagle]

I have replaced the battery in my 1999 540i every 3 to 6 months for the last 5 years. The towing and batteries must be a multiple of the value of my car by now. This seems to be a classic parasitic drain issue. But the amps are small. The spec is for 50mA max, which is supposed to be low enough that the battery lasts for 30 days. My readings: 0.019 A (on the 10A scale - 19 mA), 0.19mA on the mA scale (this should be 19mA?)

I wonder if I could be measuring the current incorrectly? The think car was asleep. It sat for 1 hour with the door and trunk locks "rolled." I have a brand new, charged battery, and a new $20 Innova multimeter. I attached the positive lead of the multimeter to the negative battery post, and the other lead to the negative end of the battery cable.

I installed aftermarket headlights about 2 years ago. I have an aftermarket stereo with an amplifier in the trunk, installed by a sound shop. I wonder if I should remove the stereo? Nothing else aftermarket.

I was driving it less than daily for some of the 5 year period. Could that be enough?

[jspeagle]

Very short daily commute (5-10 minutes.)
https://www.theglobeandmail.com/glob...rticle4490484/
Leroux recommends installing a smart charger.
Unlike a traditional charger, which can eventually overcharge a battery, a smart charger only delivers as much power as your battery needs – once the battery is fully charged, it will turn off the current.
They can stay in the vehicle all year round – you end up with a plug hanging out of the front of your vehicle, just like with a block heater.
"You plug the car in and forget about it," Brown-Harrison says. "For the average driver, plugging it in once a week overnight is enough."



It can stay plugged in all the time, but if you don't have regular access to an outlet, even just a three to four hour charge once or twice a month should do the trick, says Sergio Marsili, product specialist with Canadian Tire.
"For only $30 to $40, it can save you from dealing with a car that won't start and a lot of money in replacement batteries," he says.

- - - Updated - - -

I have had a smart charger, but I used it not that regularly. Less as time passes. Maybe once every 1 to 2 months. I suspect that all I need to do is put use the charger overnight once a week, with regularity.

[seagreen323i]

A few dumb questions. Is the battery the correct cca and size? Does your amplifier have remote turn off? Could the parasitic draw be an intermittent problem?

Sent from my SM-G973U using Tapatalk

[f355spider]

Are you absolutely sure your FSU (final stage resistor) for the HVAC is good? You have to let the car go to sleep and be sitting for a good 15 minutes or more before the FSU can do the classic failure mode of cycling the blower motor on and off, and run the battery down.

If you elect to start using the smart charger the easiest way to run it, is by using a cigarette lighter adapter. Your cigarette lighter is always "on" or powered. It makes for super convenient attachment, and you can easily close the door on the cord, as the thick door seals will collapse around it, no problem. Also, you will never drive away with it connected, as it is so obvious.

This method is much mover convenient than opening and connecting through the trunk or engine compartment.

[ChrisMelnyk]

As an aside, have you thought about getting an AGM battery?

Those are supposed to allow for a near total drain many more times without going bad compared to a conventional battery.

Maybe that coupled with putting it on a decent trickle charger overnight every month or so would be more convenient than really making sure your conventional battery doesn't get too low by putting it on a trickle charger everyday.

*Note - this is my suggestion assuming your problem is short commutes and not something actually wrong with the car

[TiesTorN]

alternator may be bad... have u ever measured the voltage while the car is running?

btw it doesn't mean the battery is dead when it gets totally depleted. just charge it with an external charger.

[ross1]

All good advice above.
TEN batteries before addressing the issue?

[philly98540]

Yeah, life gets busy and troubleshooting a drain issue is a PIA, but 10 batteries...

Anyway, check your cars voltage while running to ensure proper charging. Should be in the range of 13.7 - 14.4 volts. Turn on headlights, hvac blower, and defrosters to stress the system. Voltage can drop below the range at low idle, but should come up with some light revs.

The final stage resistor and that aftermarket stereo look like first places to look for parasitic drains. Search around as there are some good threads on how to find the drains.

[Chedley]

And I thought I am an outlier using 5 batteries over 20 years....?!

Pass on the AGM battery. Stick to standard flooded battery for your 1999 540.
And definitely, use a battery trickle charger/maintainer to keep it well charged. Hook it up at least once a month, more often in cold weather, or whenever you do not use the car for long periods of several days.

[JimLev]

All good advice above.
TEN batteries before addressing the issue?

I should have bought stock in his brand of batteries.

[BimmrMeUpSnotty]

Im thinking his amp is always staying on, he said something about an amp earlier, I'm thinking the remote wire may be loose, or not hooked up, switch turned to on.....

Ten batteries??? You must love living in misery.

[adm750]

^^^^ yeah...that's tough man.... The original battery in our 97 528 lasted till 2012. sold the car 12/2019 with the 2nd one still in place and in good shape (kept on a batt maintainer while not being driven...).

jspeagle - everyone has posted great advice about charging issues, battery styles, and connecting a battery maintainer when the car sees little use... again...all good stuff to look for and rule out.

Like F355 and philly noted...that FSU is a tricky bugger to trap and almost a guaranteed failure point. If it has never been replaced, (or you don't know the history..) then source one up and replace that b**ch anyways just because we all know it fails and leaves you stuck. May not be your issue now, but one day it will be.

I would get the car opened up so you have all of the fuse locations accessible (so you can probe the exposed side of the fuses...including any non-OEM ones in place for that sound system...) - then get the car to go to sleep.

Set your voltmeter to read millivolts then do a voltage drop on each fuse by probing across the back of each fuse. The goal is to read the voltage being consumed on that circuit with the car asleep. This site can give you a table to convert that voltage reading to milliamps being drawn for the style of fuse you are probing. Now...I have never used conversion charts like these because the draws I've found were so blatantly high that I didn't need a chart to know there was an issue....lol...but I thought I would add it as a tool to use.

https://www.powerprobe.com/fuse-voltage-drop-charts

This way you can find the circuit that may be causing the drain if you don't have a charging or battery issue like the guys have mentioned in this thread. That will help narrow down your search so you can start to dial in on what components that circuit feeds that is draining the battery.

anyways...it's a pretty quick and easy way (like less than or equal to a 1-beer effort...) to get yourself in the ballpark so you can stop funding the battery and tow truck barons of the world.

Hope this helps....
Good luck boss !!

tony

[DrCharles]

I ran my H8 battery down flat recently (left the key in the car for a couple weeks). It won't hold a charge and start the car for more than a couple of days any more No parasitic draw either.
Time for another $150+ battery. I just replaced it a couple years ago, too.
Maybe an AGM will be worth the investment if they're resistant to discharge fatality...

[edjack]

jspeagle, You may need a 'scope to capture the intermittent current drain.

[Chedley]

....
Maybe an AGM will be worth the investment if they're resistant to discharge fatality...

No, they are not more resistant to discharge.
In my experience, AGM batteries were the worst for these old car.. Though I still keep one as a backup
Also, a severely discharged battery could be revived and recharged if it is not too old . But if it is more than 3 years old, it is best to replace it..

[rlordjr]

What makes the AGM batteries not the best for the E39 and cars of a certain age?

Sent from my SM-G970U using Tapatalk