Car Battery Information

When you buy a new car battery you probably expect that is fully charged, but it probably isn't. Most new batteries that come into my shop for install test about 90% charge. Yes, I always test new batteries before installing. It's rare but you can sometimes get a new battery that is already BAD. It is better to know that before you install it. Now a 90% charge should be fully capable of starting your car. So yes, you can put that new battery on and go. The thing to know is that your charging system wasn't designed to fully charge batteries. It was designed to maintain system voltage. You will shorten the life of both the battery and the alternator by not fully charging the new battery. Or let's look at it another way, you can increase the life of your battery and alternator by fully charging the new battery.  

I keep a few of the most common batteries on hand and I keep them tested and charged. The best way to charge a battery is slowly. The trouble with slowly is that if I'm testing an electrical system on a car and that car battery is discharged I don't want to have to slow charge it for hours before I can test the system. I can pull a good fully charged battery off the shelf if need be and get started sooner on system testing, while the original battery gets charged in the background. Every couple weeks the shelf batteries get an inductance test, a low amp full charge, a load test followed by another inductance test. If I do find the original car battery bad, I'm sometimes lucky enough to have a good replacement among these stock units. So while I do occasionally sell batteries, I'm not a parts store. I do full car repair and I have tested the full electrical system for current draw, charging and integrity of circuits. That isn't the same thing as selling a battery over the counter or even just installing one with no system testing. 

A few chargers to meet my needs:

 

This battery just arrived so I was doing the state of charge check and test. Happily surprised to see a full charge! 

 I also have a wireless version tester. Nice with it is you can hook the box up to the battery and be inside the car for more involved testing that requires starting or accelerating. Or you could just carry the control screen all over the shop and get some exercise while testing the battery. 

This one was my go to tester for many years. It got too expensive to keep it working. It won't shut off and will run the internal batteries down. I had that "repaired" twice. Finally just started taking the batteries out until I needed it as it still worked fine. Next was the selector wheel stopped working so I couldn't scroll menu items. Sigh... I retired it. 

Finally there are the load testers. 

But beyond me taking pictures of my testers, I really just wanted to point out that a new battery doesn't mean a fully charged battery and that a fully charged battery is what you need either to make the system stay trouble free longer or even to test and find out why it isn't trouble free right now. 

Kenny@ggauto.repair