4 Batteries in 24 months

I own a 2006 Lexus IS250, equipped with navigation, back up camera, bluetooth. I have replaced the battery 3-4 times since I have owned the car. The car is now being serviced at the Lexus dealership but as of now they are not able to find the problem. They are doing a complete electrical review.

I do mostly city driving and then only use this car for about 500 miles a month. Is it possible my driving habits are not keeping an adequate charge in the battery, given all the electronics on the car? Any help would be appreciated, as I am stumped, and so apparently is Lexus.


How long is your average trip?

If the batteries were truely bad and needed to be replaced then there is only a couple of things that I can think of that would cause that to happen. One is the regulator of the alternator is putting out more than 15 volts DC and over charging the battery. I’m sure the shop would have seen that if that was the case. The other less checked cause is doing a voltage check for AC voltage. If some diodes have gone bad in the alternator AC can be sent to the battery when charging it. This will kill a battery pretty quickly. Have the shop make sure the AC voltage getting to the battery while the engine is running is less than 0.1 volts. If those two things are ok then I would say something is draining the battery while the car is parked. Normal drain should be around 30 milliamps. If there is over 80 milliamps of current draw there is a problem that needs to be tracked down.

There was a post last week or so about a similar problem. It was the basic consensus there were just not enough miles being driven to get and keep the battery charged without a battery tender.

Perhaps, in order to provide an instant start-up, all these electronic toys are kept in the standby mode even though the ignition switch is turned off. If so, the 24/7 drain on the battery is just too much for your limited driving to recharge the battery. A simple parasitic load test will identify this problem and a small battery charger / maintainer will cure it…Replacing the battery is NOT the solution.

The battery probably isn’t charging when the engine is idling. The engine speed needs to be held higher if large amperage load things are on, such as the blower motor, electric this and electric that.
When idling for an extended period of time, turn some stuff off (including high beams), and raise engine rpm.
Too bad your dash doesn’t have a battery charge gauge, so you could monitor the load, and control the charge with the engine rpm. You could have an after-market battery charge gauge installed and save your battery.

If the batteries are truly bad, or going bad, then it has to boil down to one of these:
Charging system overcharging and cooking the battery. (Check should be part of the inspection)
Charging system undercharging. (Ditto above)
Battery is being run down to a completely dead state repeatedly. This can do a battery in.
Battery is being drained by a voltage draw (trunk light staying on, etc.) in the system. Checking for this should be part of an electrical system check.

What are the circumstances behind the battery failures? Dead battery, won’t start, towed in, etc. etc.?
Have the batteries actually been put on a slow charge and then load tested? If not, this smacks of wild guessing on your dime.

Car is generally driven twice a day for 10 miles each…so 20 miles total a day. But city driving, with average speed of 45 miles per hour.

I have had the same battery problems with my previous 1997 SC 400 and in my current 1999 SC 400. The problem is most likely not with your battery or the alternator.

I have found by replacing the factory cable connectors to the battery with Marine type LEAD connectors that are painted, except for the areas in contact with the battery post and cables will correct the problem!

I discovered after numerous dead battery situations in both cars that the alternator was putting out the required 14.2 V (the nominal value), but the battery was not charging. Therefore the only problem could be that the charge was not getting to the battery. I replaced the connectors with new factory connectors that were flimsy aluminum. This did not solve the problem.

I finally got a good conduction current into the battery after replacing the battery connectors with plain old lead type connectors that can be purchased at any pep boys for less than five bucks.

I have since utilized the Marine connectors in my 1999 SC 400, because they are painted on any surface other than connection to the cables and the battery terminal to prevent shorts.

Hopefully this will help correct your problem as well.

PS: my brother who is a certified mechanic actually uses spray paint or grease on the battery post after tightening the connection in order to prevent oxidation of the connection.