demark1

My 2005 LS430 ultra got a new battery in January when the old one failed to start the car. I was told old battery was bad (was under two years old!).

Well, today, my 5 month old replacement battery died (failed to start car, motor had that wheezing clicking that i know all too well). I am thinking I should get a charger from auto store, but for now, I have AAA (got it 3 week ago actually) and they came by and told me battery was bad (22% of cranking capacity? He was going to email me the report but I never got it) and that alternator was good, but jump-started it in any case. (Not sure how alternator can be measured or where that 22% number came from.)

The voltage on the battery was 11 volts when tested. So I left car running around 20 minutes then drove around 8 miles over to Autozone to have them check/potentially swap it since I got it there. Well the gentleman at autozone tested it twice and said that it was charged up to 80% already and was fine, but alternator was bad and "drawing charge off battery".

FYI since I drive the car less frequently with lockdowns and all, I have turned OFF the smart key system (press the switch under the front dashboard) which I know is recommended when you leave the car more than normal. But I still drive the car once every week at least, probably for 10 miles or so, and the car started immediately without problem last time.

I am thinking of just letting it go one more time and see it car is fine for next few months, being sure to drive it more often (though I really don't think I should need to).

My question is this: If I go to a mechanic or dealer, can they determined via voltage drop test or other test whether (1) battery is bad or (2) alternator is bad or (3) there is some parasitic drain?

The autozone and AAA guy basically gave me opposite answers... Is this something a competent mechanic can tell definitively? Or my myself just by getting a voltmeter? (The autozone guy mentioned something about a diode, but not sure if he was speaking generally or specifically).

My car eats batteries every two years or so, but 5 months (and with the remote access turned off for last several weeks) is very frustrating. Even more, I am not sure if car is good to go now for foreseaable future or not, and I do not want to just to to a dealer and scream "get this guy to but an alternator!!"

Any advice on what to look for in a diagnosis is appreciated. I still love my care with around 145k miles on it... Had it going on 11 years in July and want to keep it, but need reliability. The car has never left me stranded on the road EVER, but it has more than once left me with a dead battery, sometimes right after a drive. Fortunately this time it was in my driveway.

Finally, if I were to actually need an alternator, any advice on if I need to go OEM (Lexus dealer) and some idea of price? I am going to guess at least $1000 as I am not DIY but just wondering...

Thanks!

Johnhav430

A couple of thoughts. A test does not lie. When they say 22%, that means that it can provide 22% of the CCA it was rated for. Now if the tech punched in a really high number that is wrong, like say he thought it was 950 CCA, and you cme back with 60%, that's more than my mom's Acura TSX brand new (now I forget but it has a teeny weeny battery with a low rating).

Secondly, over the past 15 years, I've gotten bad batteries pretty much from the go. One was a Die Hard, the other was a Bosch Premium. Both were replaced for free. Nowadays, I kinda see batteries like I do floor jacks. They are all about the same so they're only as good as their warranties. I would try a Costco 24F for about $85, and if 5 mos. later it's shot, a) you can get a free replacement b) ok something's not right. But this only cost you $85 more dollars and if the battery is ruined you'll get a new one and move on to the root cause.

That's not a bad idea either to get the alternator tested. But the bad battery has a high resistance, it'd be good to test the alternator with a known good battery. These are annoying things, I know, but they are "correctable" issues. Meaning it's not like my buddy's Audi that would simply die in public, get towed to the dealership, and be perfectly fine and then die again. He even had them keep it 3 weeks and put 700 miles on it and found nothing....our cars are fixable! Good luck.

demark1

Thanks for the reply. I finally got the report, and it does say 23%, but the battery was fully discharged at the time and the report says to retest once fully charged, that the CCAs cannot be determined from a near-dead battery (makes sense). Even with Costco, if the car has died I need to jump it to get it there to be checked, etc. Major hassle but perhaps getting myself a
Once things settle down from the virus (I am on Long Island in NY and things are pretty bad, trying to avoid unnecessary forays into public) I will check with Costco about what they charge for a battery and how they determine if it is bad. Otherwise it might be like with autozone where they just say nothing is wrong with it... I will talk to a mechanic too once things have calmed down.

smokey6010

I have a problem with what the person at Autozone stated. You said the battery was dead and had it jump started. You let the car run 20 min. and drove it to Autozone at that point it was tested and shown to be 80% charged. He stated your alternator was bad. If the alternator was bad, it would not have charged your battery to 80%.

BigBoomer

If you are not doing at least 25-30 miles in one run every week then you will have battery issues.
If that is the case you may want to consider a plug in battery maintainer or if parked outside, a solar battery maintainer.

Once a lead-acid battery is completely flattened, it will rarely recover 100%.
Every time you completely flatten it, it will lose more of it's maximum capacity.

Get a new battery and then go get your alternator tested.