Battery will not keep charge

1999 Lexus ES300 - 92K miles. I have had a reaccuring problem with the battery for the last three years. The battery will not hold a charge. The problem has become so bad that it is nolongerjust an annoyance. I have changed out batteries and alternators over the years. Less that thirty days ago I replaced both the alternator and the battery and had the belt examined - it was not replaced.Two days ago battery dies. I did not take it back to the shop that last did the work. The person who did look at it found that the positive connection was as tight as it could be but was still loose on the terminal. It was replaced.

The battery lost its charge again today and had to be jumped twice to get it home. As I was on the way home the turn signal stoped working so I turned off the a/c and cut all unneccesary power drains to get home.

I live in south Louisianna so the a/c is almost always on.

I have noticed over the last three year that when the moter is reved the lights dim.

Suggestions greatly appreciated

Have a parasitic load test performed to see if something is draining the battery, then have the alternator tested by someone who knows what they are doing and has the equipment to do it.

I totally agree with Caddyman’s good advice. Take it to a shop that can find the battery drain problem and check the charging system doing a load test.

Battery cable connections should be snug but not over tightened. Which I think is a pretty common mistake. By tightening the connections too much it stretches the clamp connector and damages it.

You’ve been paying for incompetence.

The battery should have been checked for a drain along time ago. You may not have needed the new alternators and batteries.

A parasitic drain does not explain this symptom:

I have noticed over the last three year that when the moter is reved the lights dim

Either the belt is slipping or you have some other weird problem. Too bad I can’t read the post with this reply box glued in front of it so I can see if you had the belt replaced and the pulleys etc inspected.

The part about the lights dimming when the motor is revved goes against all logic. If the motor is revved, the alternator had greater potential to produce current. The regulator reduces current to the rotator of the alternator to keep the voltage from going too high. The regulator would have to be over regulating to do this.

Most Toyota’s have the regulator built into the alternator so when you change it, you also change the regulator. It could be in the wiring to the alternator, possibly one of the wires where it is crimped to the connector has many broken strands or the wire to terminal part of the connector has gotten corroded or somehow the crimp got loose.

Also have them check the negative battery terminal at the chassis or engine terminal. Possibly this end is loose. Also check the engine to chassis ground straps.

***A parasitic drain does not explain this symptom:

I have noticed over the last three year that when the moter is reved the lights dim ***

I agree. If the problem is a parasitic drain, the battery should charge if the car can get started at all and symptoms of low voltage/battery should go away after driving a while, No?

Since the battery and alternator have been replaced, I’d have to go with some sort of wiring issue in the charging/battry system. My first three thoughts would be:

.Maybe a bad ground connection from the battery to the Engine,

.Or maybe a corroded positive battery cable (battery acid sometimes gets under the insulation and converts the wire to Copper Sulfate – which is pretty, but is a lousy conductor)

.Or maybe some sort of problem with the battery charge indicator? I’m not sure how this would work, but there’s a wire there that could maybe, somehow, cause the alternator to work poorly by somehow reducing the field current that the alternator needs in order to alternate.

… How about the belt? Is there anything else on the belt that could have bad bearings and could be causing the belt to slip a lot? It’d make a noise?

None of this seems very likely, but something must be causing the problem.

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.