Battery issue?

BHAMDOC1973

MEMBER
2011 AUDI A3
4 CYL
TURBO
2WD
AUTOMATIC
142,000 MILES

Bought a car that needs jumping to work and once running its fine, so before buying another I said let me try to tickle charge it. Tried 2 different types one that would just blink while charging, but it didn't, other one says wrong connection, meaning positive and negative are flipped, but they are not. Weird that neither one is trying to charge it. Even if it's totally bad my charger would say that after charging for few. You ever had that issue before? The voltmeter shows 0.010 which is strange, how can the car run when jumped with a jumper box after its removed with this much low voltage in it.

1 Reply

CARADIODOC

MECHANIC
33,752 POSTS

You're describing a battery that has either a broken connection inside, or a really poor connection between one of the posts and the cable clamp. When you measure its voltage, put the probes right on the posts and see what you find, not on the cable clamps. If you find significantly higher voltage there, we can figure out which clamp has the connection that must be cleaned. If you still find 0 volts, the battery must be replaced.

It takes some really good jumper cables to get an engine started when the battery is not helping. Once the engine is running, you can remove the jumper cables because it's the generator's job to recharge the battery and to supply all of the current for the entire electrical system. Driving the car that way is asking for a really high repair bill. The voltage regulator's job is to maintain system voltage between 13.75 and14.75 volts. It can only do that when the entire system is working properly. The battery is one of the most important parts of the charging system. Without it in the circuit, either due to it being defective or due to a bad cable connection, it is real easy for system voltage to go well over 30 volts, especially when there's little load on it, meaning no high-current things are turned on, like the head lights, heater fan, and wipers.

There's dozens of computer modules on your car. Those are very intolerant of high or fluctuating voltage.

First measure the battery's voltage right on the posts. If it looks like that might be okay, clean and tighten the cable clamps. If you aren't sure, remove the battery and have it tested. That can be done at any auto parts store or battery store

It sounds like there is no need at this time to have the charging system tested. To explain how that is done, take a look at this article:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

This is where you're looking for 13.75 to 14.75 volts with the engine running. It can remain within those limits, but more commonly without the battery in the system, you'll find the voltage is too high. I would recommend not driving the car to the battery store that way. Safer to buy the battery and install it at home.

If this test passes, that only means it is okay to perform the rest of the tests, but those require a professional load tester. You'll need to visit your mechanic for that. Those additional tests include full-load output current and "ripple" voltage tests. Those are indicators of whether one of the three sections, or phases, is dead in the generator. With one dead phase, the most the generator will be able to develop is exactly one third of its design value. That is usually not enough to meet the demands of the entire electrical system under all conditions. It can be enough to keep the engine running, but only until you start turning on a lot of other stuff.

Let me know what you find up to this point.