dlearl476

Let’s me preface this by saying I’m 90% certain I have a bad battery. (<1yr old)

As long as I’ve owned my car, after it’s sat for a week or month or two, the ammeter would read ~14V when I first started it. For some period of time, eventually dropping down to 12.75-13V. In 2019 before I took it in for a front end service, it started to read lower, so prior to service I bought a new set of brushes and one of the upgraded Alt-Starter harnesses.

Back to how it ever was. Reading -13V after sitting a bit, but generally always reading 12.5V<. I put it up about a month ago and when I went to get it the other day, it needed my booster box to start. (Thank you Anti-Gravity for the great deal. I love it.)
Several times since, when it’s been hot enough for the fan to run 3-4 minutes after I shut it off, it’s required a boost. Took it on a long cruise Sunday, and it started fine 4 times Monday, then the fan ran and it needed a boost the 5th time. And for the first time ever, my ammeter was reading <12V.

So I pulled the battery and put it on my good charger overnight. I ran a charge cycle, a recover cycle, and another charge cycle. The recover cycle took about 6 hours to get to 75%, then another 14 to get to 100%. Which is way abnormal.

Put it back in today, Ammeter started off reading ~13V, slowly dropped down. As it was evening, I noticed it dropping a little with parking lights, a little more with fogs, a little more with headlights. It kind of seems like my ammeter is reading the battery voltage, not charging voltage.

Any insights? Like I said, I suspect the battery. And as soon as I can next week, I’m going to head up to the East Penn distributor and get a new Deka to replace the cheap POS battery the shop that redid my belts last year put in after they let my 1 year old Deka go flat, rather than put it on a charger. (I suspect it’s in one of the techs cars now) Well see how it behaves with a new battery.

931guru

Sounds like a bad battery. (Sams club sells Duracell, which are made by Deka, and have a 3 year warranty. I have one installed in my Audi that is six years old and going strong.)

Paul Waterloo

I had a new Audi battery in my Q5, after about three months the car would barely start. It ended up having shorted cells. Here is a video of it in action. If you turn the headlights on with the engine off and watch battery voltage with a voltmeter for five minutes, if it drops like a rock, it's a bad battery. You would not believe the hoops I had to jump through to get Audi to replace my battery. Was very, very, painful.

Yogii

Could you have a parasitic draw down? If either the glove box light or the underhood light switch is broken, you would never know and your battery would be flat overnight.
Ask me how I know??
I have disconnected both!

-Yogii
AKA 968 Novice

PS my cars fan runs for about 3-4 minutes after I stop ALL the time.

quick968

i kinda like having a light in the glovebox and under the hood. Why not just replace those cheap and easily accessed switches and fix the problems? Just a thought…..

Mikey

quick968

A couple things. First off , it’s a voltmeter not an ammeter. Ammeters measure amps, voltmeters measure volts. The scale on the gauge is in volts. It shows the system voltage while the alternator is in operation. Low voltage is a sign of either a dead battery the alternator can’t keep up with or rarely, a dying alternator. Secondly, our cars have parasitic draws, the clock and a few other items. If they are to be stored more than a few days to a week, they MUST be kept on a trickle charger, even the Porsche manual states this. More than 2 weeks you will have a dead battery. I just replaced mine after 8 YEARS when it finally gave up. But I religiously kept it on a battery tender. Lastly a dead/dying battery causes all sorts of other issues on the cars. Dead batteries cause the alternator to work way too hard all the time to try and charge the battery, causing the wiring to overheat, making the insulation brittle which why so many of them have that wiring loom section falling apart.

Keep you cars on a tender when not driving them. Your entire electrical system will thank you. The Deltron Battery Tender Jr works swell.

cheers
Mikey

dlearl476

Yeah, so does Batteries+. But the East Penn distributor is about 30 miles north, the batteries are $15-$20 cheaper, and they have a “no questions asked” warranty policy. Like Batt+ used to. I’m going to have to check Walmart to see if they carry those Duracell-branded batteries. My brother was telling me last night those guys are a “no questions asked” place, too.

Ive heard Interstate batteries are equal in quality, but I have no FHE with them.

I love Deka (EastPenn) batteries. I’ve used them in my cars and bikes since mid-2000 when I first discovered them. I’ve had them start my car after 4-5 months in winter storage. But I take them out now. I’ve soured on Battery tenders since I had one go bad and cook a battery. I put them on a charger in my storage unit/shop for a day or two every 3-4 weeks now.

dlearl476

My deal is I always hit the friggin dome light when I put the top up, and if it’s daylight it’s not bright enough to notice. But thanks for reminding me. I’ll check both the glove box and the under hood light today.

My fan doesn’t always come on, only if I’ve been doing a lot of stop/go driving or when I get home. (I live at the top of three steep hills) If yours is always staying on, you might have the lower temp switch. The OEM switch comes on at 210° and turns off at 192° and there are aftermarket replacements that are listed as “80°C” which is 172°F.

dlearl476

While we’re on the subject of electrics, David Cunningham is back up and running with his upgraded alt-starter harnesses If you haven’t checked yours, you should. The insulation on the factory unit gets brittle and cracks and, worst case scenario, can short out and activate your starter. If your car is in gear in your garage, look out. This is what mine looked like when I replaced it in 2021.

dlearl476

So today following a charge, recover cycle, charge with my fancy battery charger. All was normal. ~13.5V for about two minutes after I started it, eventually settled down to 12.25V at idle to 12.5-12.75V underway. I don’t have time to deal with replacing the battery so I put it away and unhooked the battery. We’ll see what state of charge it’s in next week when I get it back out.

Being a cheapo battery, I suspect I damaged it by letting it go flat. Generally, my good charger will fully charge a discharged battery (9-10V) in 8 hours. The recover cycle I did took 20-22 hours. It also dawned on me today that this battery is an inch or two shorter than the Deka batteries I’ve been using. I forgot to look at the CCA and cold start specs. I suspect the shop put a 911 battery in my car.

I also forgot to check my glove box and engine compartment lights. I checked the glove box after I started it up but I couldn’t tell if it was coming on or not in the sunlight, and when I got to the darkness of my storage unit, my pup was getting too hot so I rushed putting it away and forgot to check. One thing I did notice was that the switch felt sticky, but it’s not inop or broken so the glove box door isn’t activating it. Next week I’ll check all that stuff out and R&R both switches and verify their operation. If the battery is below 12.5V after sitting disconnected for a week I’ll go ahead and replace it.

Yogii

Mikey,
Because then it become a 5 year service item.
I have powerful flashlights in my door pockets, easily replaced.

-Yogii
AKA 968 Novice