Car enthusiasts/technically knowledgeable people I have a question!

JayandMeeka

So I had to get my car jumped tonight because it wouldn't start. The roadside assistance dude told me that my battery for my 2013 hyundai elantra should be around "12" and it was just below "7". Firstly, what does that mean?

Also - often times after work before I head home I'll plug my iPhone/iPad in and watch a video in my car. So I turn the key once so the car doesn't turn on but there is still power to the iPad/iPhone so it doesn't die on me. I asked the roadside dude if that damaged my battery and I didn't really understand his answer.

So does it?

And what happens now? Once he jumped my car it runs fine. And when I got home I started it again fine. Do I have to get my battery replaced? Once the battery drains is that it? Is there any "recharging" a battery?

So many questions! Hopefully someone can help me out!

TheDismalSimmer

Alternator (the thing that actually recharges the battery) issue, probably. The 12 and 7 are referring to the battery's voltage.

From what you describe, if your car runs fine but has trouble starting, combined with the low voltage issue, the alternator might be dying. Do you also hear a grinding or whirring noise as you drive?

You can often get your alternator tested for free at a lot of auto parts stores. The parts will cost range from 200 - 300 dollars, and sometimes mechanics will let you supply the car parts and only charge you for labor costs (but ask before you buy the parts though!!!!). So overall it should cost around 400 - 600 dollars.

Luckily, it's one of the easier things to change out in a car and if you can get a good quality refurbished alternator (those may range anywhere from 100 - 200, and they're pretty easy to find in the larger auto stores) you can replace it yourself and save a lot of money. But first...

PLEASE DISCONNECT THE BATTERY BEFORE DOING ANY WORK ON THE CAR.
PLEASE DISCONNECT THE BATTERY BEFORE DOING ANY WORK ON THE CAR.
PLEASE DISCONNECT THE BATTERY BEFORE DOING ANY WORK ON THE CAR.

(To disconnect, it goes: negative terminal first, then positive. To reconnect, it goes: positive terminal first, then negative. Yes, it's reversed.)

This video walks you through the process of replacing the alternator for the 2013 Hyundai Elantra

But there are lots of other videos out there too, just in case you want to see it from a different camera angle.

Another possibility is that you could have just drained the battery by using it too much without giving it a change to recharge by driving enough. This can be a common issue if you predominantly make short trips your car at night at relatively low speeds. Or if you left your lights on. Watching your iPad while it's connected to your car without turning it on also might be part of the problem. That in itself shouldn't damage your battery though.

But seriously, get your alternator checked. Driving with a bad alternator WILL damage your battery eventually.

JayandMeeka

@The_Dismal_Scientist wow thank you so much! That's very helpful. So, the battery can recharge? Because I'm 99% sure that I just drained it with my iPad. Do I need to get it looked at? The alternator has this rust proof cap on it that the roadside assistance guy couldn't look at with the tools he had.
But the car is only 3 years old, so it can't be the alternator already? That's what happened with my previous car.

TheDismalSimmer

Well, it depends on how much you drive your car, but it's probably more accurate to think of your car's age in terms of mileage and not time. Alternators generally last about 80k - 150k miles (give or take a few thousand), but it's possible for one to break much sooner. Of course, I was just speculating given the information, but the low voltage is a bit concerning. It's probably good to go get it checked just to be safe (most of the large auto parts shops will do it for free and it takes about 30 seconds).

Car batteries are rechargeable, as long as they aren't damaged (you can get that checked too at auto shops). Basically, think of your alternator as the battery's charger, and time spent driving your car as the amount of time the battery is plugged into the charger. As long as the charger works properly (in this case the alternator) and you give it enough time, the battery will recharge.

Making frequent short trips (especially at night) can drain the battery since it can't recharge enough to replace the electricity it used starting the car (it actually takes very little electricity to keep the car running, just to start it up). It also could very well be that you didn't drive the car enough after plugging your iPad into it.