Battery / alternator electrical question

[Mazmatic]

Hey lads,
Quick electrical question for you... My wife's 09 Santa Fe wouldn't start for us 2times in the last 3 weeks.

1) started fine, drove 1 hr, visited with family for an hour, started back up, drove 45 min, visited more family for a bit. From there, Drove to a campsite down the road where my wife turned the ENGINE off, but kept ACC on ( the lights and radio on, but no more than 10min). When I went to start it up, it died.
Got a boost, drove to our lot 30seconds away, and parked for 4 days....it didn't start after that, nor did I expect it to, only drove for 30 seconds...

2) yesterday, I had driven about 20min on the highway, stopped for a coffee. Knowing what happened last time, I promptly turned the car off while my wife went inside. It was taking a while so I quickly turned the car to acc mode, lowered some windows, and turned it back off.....sure enough, I needed a boost.

I drove home the rest of the way, no issue.

Just tried it now started up no problem. Multimeter shows 12.69 when off, and 14.25 when running.

Is this indicative of a battery not being able to hold a charge? (My thinking is that any time there is a draw and the alt isn't running, it drains very quickly, and then there won't be enough power for the starter)

[shorod]

Is this the original battery? If so, you're overdue for a new battery. Yeah, it used to be common to get 5 years out of a battery. Lately I feel lucky if I get 3 years out of a battery in a modern car.

-Rod

[Mazmatic]

Yea, original battery.
I wasn't sure if that was the culprit simply because it seems to start normally outside of a small drain while in ACC.

[shorod]

What you can try is to put your meter on the battery and monitor what the voltage dips to when the starter motor is engaged. If your meter has a "Min" setting that would be more accurate, but positioning it to where you can see it from inside the car would work or having a helper either read the meter or start the engine would work as well. If the battery voltage drops to something less than 10.2 volts when the starter is spinning the engine, you either have a severe load on the starter or the battery is weak. Since the Hyundai generally starts up fine, the load is probably not the issue.

After a 20 min drive, turning on the ignition long enough to roll down windows should not have drained the battery.

-Rod

[Mazmatic]

Originally Posted by shorod

What you can try is to put your meter on the battery and monitor what the voltage dips to when the starter motor is engaged. If your meter has a "Min" setting that would be more accurate, but positioning it to where you can see it from inside the car would work or having a helper either read the meter or start the engine would work as well. If the battery voltage drops to something less than 10.2 volts when the starter is spinning the engine, you either have a severe load on the starter or the battery is weak. Since the Hyundai generally starts up fine, the load is probably not the issue.

After a 20 min drive, turning on the ignition long enough to roll down windows should not have drained the battery.

-Rod

Hi rod,
Thanks for the input. I'll try to run this test.
I also find it odd that I can start it up a few times in a row....my thinking is that I'm turning it over, which uses what juice is left in better, BUT it's not running for very long to allow the alternator to charge it; so then why can I crank it over again a minute later?

Anyways, Rod, on face value, do you think it's a poor battery?

[kcducttaper]

I would second the vote for a new battery. Batteries can do some goofy things when they're starting to die. If it's not the battery that's specifically causing it, you're due for one pretty dang quick anyways, so you might as well swap it out and see if it fixes it. Just my .02.

[Crvett69]

your local auto parts store can usually check the battery and charging system in the car. might be worth a trip to your locall one, they can put a load on the battery and alternator to see if one of them checks weak

[shorod]

Yeah, I do think it's a dead battery. One possible reason it might start easy after a very short run, but not after sitting longer, could be due to a lower load on the starter from having oil lubricating all surfaces (speculation, no data to back this up) from the very recent engine start.

I will caution about the "load" tests performed in the car by many of the chain parts stores. If they condemn the battery, that's pretty conclusive. However, on more than one occasion the test has shown "pass" even when the battery was junk. The testers don't seem to do a sufficient load test to support the loads provided by the electrical system in some of the modern cars. I prefer the multimeter voltage drop test under a start condition versus the automated tests often used by parts stores.

-Rod

[Mazmatic]

Originally Posted by shorod

What you can try is to put your meter on the battery and monitor what the voltage dips to when the starter motor is engaged. If your meter has a "Min" setting that would be more accurate, but positioning it to where you can see it from inside the car would work or having a helper either read the meter or start the engine would work as well. If the battery voltage drops to something less than 10.2 volts when the starter is spinning the engine, you either have a severe load on the starter or the battery is weak. Since the Hyundai generally starts up fine, the load is probably not the issue...

-Rod

Well, just to close the loop, I did the test as suggested above.
Battery reading from my multimeter prior to starting the engine was 12.8, 12.7,12.6.
Battery reading dipped to 9.8 as we started the engine.
I don't think anything significant was drawing power (headed seats, ect), so it's likely an old battery...

Guess my next stop is Canadian Tire or Costco.
When I was casually looking at batteries last week, there were a few that 'fit' my vehicle, but they had varying CCA (cold cranking amps).
Any suggestions on how many CCA I should look for?

[shorod]

General rule of thumb is as many CCAs as will fit in your vehicle and budget. There's no real down side to having more CCAs (except the batteries typically cost more). If you're in a cold environment, probably 650 CCAs would be absolute minimum.

-Rod

[kcducttaper]

Originally Posted by shorod

General rule of thumb is as many CCAs as will fit in your vehicle and budget. There's no real down side to having more CCAs (except the batteries typically cost more). If you're in a cold environment, probably 650 CCAs would be absolute minimum.

-Rod

The more CCAs the battery has, the more current it can shove out to the starter when it's cold, which means easier cold morning starts.