As per my other post, I had to replace my alternator earlier this week.

I read that one of the reasons for alternator failures is weak battery. An alternator have to work more if the battery is weak.

My battery is 4-5 years old. Is there any way to tell if it is still good? After sitting in the garage overnight, the voltage of the battery (in dyno mode) before starting the car was 12.4-12.5V. I am hoping that I can keep the battery for another 1-2 years.

Another possible reason for my alternator to fail is it was simply too old. It was almost 10 years old.

 

Have the battery properly load tested by a competent battery shop.

 

I was hoping thhere is a way to check based in the voltage values as reported in dyno mode.

I would have to pay to check the battery. I paid only $100 for this battery when I changed it 4-5 years ago.

 

A proper load test is the best way, and also, a specific gravity test of each cell using a hygrometer. But, for a quick check, voltage should be 12.6v or better at rest, no less than 11.5v when cranking, at at least 14v when at idle. It's best to use an analog voltmeter so you can actually see the needle fluctuate in real-time. TO check the alternator, if you aren't getting 14v at idle, then, with the engine running, disconnect the negative terminal from the battery. If the voltage goes up, then the battery is bad and drawing down the alternator. If not, then the alternator (or voltage regulator module on the alternator) is bad.

 

I just went to my car to check the voltages.

After the car is parked in the garage overnight (-5c last night), the battery voltage was 12.3v before I started the car. When I cranked the car, the voltage dropped to 10.7v. After the car was started dating and at idle in my garage, the voltage was 14.4v.

I do not have any voltmeter or ampmeter to measure the voltage. All these voltages were read from dyno mode.

 

Let me add mine I seem to be having the same issues dead rest over night Car reads 12.16. Start car voltage reads 14 + disconnect the negative terminal from the battery I get 13.3.


A few times the last 3 months car did not want to start but did after 2 times of cranking it did, with that said 2 months ago coming home from the casino after a 3 mile. drive I stop at a stop sign the car will not accelerate. Shut the car off restarted everything is fine.


Last night same thing left work hit a stop light car does the same thing. Pulled it over shut it off all ok. 3 hours later start and car take a drive car seems to be stuck in 2 3rd gear RPMS are high. Shut car off go home. Reset TCU all ok today. No Codes on the Scanner


If I leave the radio and the car door open while working car not running in the garage car has a hard time starting.

 

@mis3: That sounds a bit low to me. I would get to an auto parts store or mechanic and get a proper test.

@louie: The acceleration and limp mode is likely a problem in the transmission, specifically a bad speed sensor. Your OBDII scanner won't pull codes from the TCU, so you need to get the dealer or an indy with the proper equipment to pull TCU codes.

 

Rudeney:. Thanks for your advice. When I cranked the car, the voltage was 10.7v. This is well below 11.5v, the threshold you suggested.
Since I will have to pay to test the battery, I may as well buy a new one. I will buy a new one when any symptoms show up (like hard to start).

LouisD:. I had similar shifting issues back in June. I ended up changing the conductor plate.

 

mis3 ~ Make sure that you buy a premium 100Ah battery. I like using genuine Benz AGM batteries made for them by a few companies. They are expensive but will usually last at least 8 years. The one in my old C240 is now 10 years old & still passes a load test.

Obviously SA does not have your cold conditions to contend with.

 

I have been monitoring my battery voltage, via dyno mode, in the last few days.

Besides the low voltage when cranking, all seems okay with this battery. Starting of the car after a few hours sitting outside (-5c) has been great evey time.

I am wondering if I should hook up my battery charger overnight to reconditioned the battery. Don't want to damage the battery with overcharging.

I bought a new battery charger a few months (after the battery drained after I left the key in the ignition overnight) which has the following features:
- Optimal charge mode automatically selects the ideal charge rate for your battery to protect against damage and reduced battery life caused by overheating
- Automatically switches from full charge to maintenance mode to maintain batteries during prolonged periods of storage without overcharging or damaging the battery
- Battery reconditioning feature reverses sulphate build-up on battery plates and helps restore battery capacity.

 

Just have the battery properly load tested. It will immediately tell you of you have a battery issue.

 

OK. I will be going to my indie in Jan-Feb to replace my spark plugs. I will ask him to load test the battery.

Before he changed the alternator last week, he hooked up his big battery charger (?) to test the voltage of my battery. Hope he has the proper tool to do the load test.

 

Just an update.

I went to a battery shop and they tested the battery using a hygrometer. The tech said the battery is working fine. Of course, he would sell me a new battery if I insist!!!