Why do I get a constant notice of 'battery discharge'? | Car Doctor

John Paul
·3 min read

Q: I own a 2012 BMW 750 with 84,000 miles on it. The issue is a constant notice when I start the car that says “battery discharge” and certain electrical features stop working, such as door lights. Even when the battery notice shows up, the car always starts just fine.

The BMW dealer advised me to get a trickle charger, which I did, but even after using it, the car only behaves normally for a few days and then it's back to the same notice at start-up time. Is this a common problem with such an expensive car?

A: All cars today have lots of demands on the electrical system — luxury vehicles even more so. Your BMW uses an absorbed glass mat (AGM) battery as opposed to a more conventional flooded lead acid (FLA) battery.

BMW was the subject of a class action lawsuit that had to do with battery failure. As part of this lawsuit, BMW upgraded the battery to a 105-ampere hour battery from the standard 90-ampere hour battery.

At this point, test and fully recharge the battery and check the current battery in the vehicle for the proper installation. The trickle charger is also a good idea for cars that don’t get driven often, but make sure the charger is a “float” style charger compatible with AGM batteries.

Q: I took my car in for wheel bearing and brake rotors because of a noise. Now, six months later, the noise is back. Could it be inferior parts (not factory) or poor installation? What should I do?

A: The best thing to do would be to return to the shop that performed the repairs and have them road test the car. Ideally, it would be best if you can go on the road test and demonstrate the noise and explain that this is why you originally took the car in for service.

Regarding replacement parts, quality aftermarket parts can be as good as and — in cases — can even exceed the quality of some factory parts.

Q: I am a retired person with knee trouble and occasional hip trouble. I currently own a 2002 Toyota Echo. Very soon, it will need to be replaced.

I had my heart set on a new Toyota Corolla until I realized that Toyota has made this car lower to the ground. I am not interested in an electric car or a hybrid. Do you have any suggestions as to what cars I might view as possible replacements?

Drivers who prefer a taller vehicle for easier entry and exit should consider subcompact and compact SUVs such as the Hyundai Kona, which sits higher and has the additional benefit of better visibility.
Drivers who prefer a taller vehicle for easier entry and exit should consider subcompact and compact SUVs such as the Hyundai Kona, which sits higher and has the additional benefit of better visibility.

A: You should take a look at subcompact and compact SUVs. These vehicles sit slightly higher, allowing for easier entry and exit, and they have the additional benefit of a little better visibility.

Some vehicles to look at are the Hyundai Kona, Kia Seltos and Mazda CX-30. These are not SUVs in the traditional sense with four-wheel drive, but are more of a tall wagon.

Q: I own a 1997 Jaguar in near perfect condition, with 47,600 original miles. I checked the manual and found that Jaguar recommends a transmission fluid change at 50,000 miles. I’ve consulted a few transmission places, as well as a Jaguar mechanic, for advice. All three seem to be in line with the following: do not flush or replace the fluid, as in their opinion that may cause unwanted problems.

I feel that, after such a long time, the fluid will break down to some degree and should be replaced. It has been suggested to me to replace the fluid but do not flush the transmission. What would you suggest?

A: If the fluid looks good — and smells like oil and not varnish — I would be tempted to leave well enough alone.

Over time, there can be some varnish that forms in the transmission and the new fluid or power-flushing can wash away that varnish and clog passageways in the transmission.

If the fluid is discolored, then I would perform a simple drain, refill and filter change.

It sounds like you have a good relationship with your Jaguar mechanic, and I would follow their advice.

AAA's Car Doctor, John Paul
AAA's Car Doctor, John Paul

John Paul is the AAA Northeast Car Doctor. He has more than 40 years of experience in the automobile industry and is an ASE-Certified Master Technician. Write to John Paul, The Car Doctor, at 110 Royal Little Drive, Providence, RI 02904. Or email jpaul@aaanortheast.com and put “Car Doctor” in the subject field. Follow him on Twitter @johnfpaul or on Facebook.

This article originally appeared on The Providence Journal: Why does BMW 750 keep giving 'battery discharge' notice? | Car Doctor