Hello all. I don't know if this is normal for our cars. But I don't think it is. For YEARS if I let my car sit untouched for around three weeks (garage kept) it cranks very slow. If I let it sit four weeks untouched it might crank once and that's it. Then it needs a charge or jump. I finally got around to doing a parasitic draw test. I believe my results were good. With the car off, doors shut, no under the hood light...etc I had a draw of 10 milliamps. From my research it seems the general consensus is anything under 50 milliamps is ok. I let it sit for 30 minutes and it never changed. Then I opened up my door so the dome light and footwell lighting would turn on. And the draw went up to 920 milliamps. My battery is on the older side for sure. But I've had this issue with a few batteries I've had over the years.

The stock harness is untouched and hasn't been modified or hacked up. When I put the new motor in years ago I cleaned all the grounds and contact points. I'm 100% certain all the grounds are hooked up and secure. When running the alternator is charging the battery fine.

Any suggestions would be appreciated!

 

Keep it at a high state of charge.

You are regularly deep discharging the battery as evidenced by the slow cranking. Flooded lead acid batteries hate that and will lose capacity and performance. Basically your habits are ruining the battery.

 

We have NOCO 2amp maintainers on all our non regular cars, works great.

 

I have my '84 T/a connected to a "Battery Tender" when garaged. Same scenario for my 2015 Chevy Colorado. It still has original battery.

 

Sound all too familiar and normal. Always have mine plugged into a C-Tek battery tender.

 

Hi IROCThe 5.7L

Please don't hate me for saying this, but I do believe, like you suspect, something ain't quite right. I don't say this to gloat or to brag about how great my third gen life is, but I can let my car sit a month and it cranks like it was just run yesterday. I'm left wondering things like, do you have only the factory stereo in it, is there an aftermarket alarm, or could any possible parasitic draw only be happening part time?* You say when it's running it's charging fine, could it be charging a bit too much and damaging your battery by overcharging? I do believe any car should be able to sit 3 weeks to a month and not have a battery so discharged as to not be able to properly crank the engine if all is truly OK with it.

* I once encountered a situation where a bad capacitor in a car's radio was temperature dependent. When cool, the cap's ESR was fine, but in the heat of the day when the sun warmed the car's interior to the kinds of heat we all know car's interiors can reach in bright sunlight, the cap's ESR would drop enough to present enough of a parasitic drain to significantly discharge the battery in a couple week's time. I'm not saying "Yes, this is for certain what ya got going on", merely presenting it as an outside possibility, having seen it once in person myself.

From an internet search of "How do changes in ambient temperature affect a capacitor's ESR"

"Ambient temperature affects capacitor ESR (Equivalent Series Resistance), especially in aluminum electrolytic capacitors. In general, higher temperatures can lead to a decrease in ESR in some cases, particularly in aluminum electrolytics, while lower temperatures can increase ESR. This is due to the changes in the electrolyte's conductivity and other factors related to capacitor material and construction."

(Decreased ESR means less resistance, as in at higher temperatures the cap's resistance LOWERS, effectively making it a better conductor, a very undesirable trait for any capacitor)

 

You know how it goes. Work, family, house...etc Not a ton of free time to drive it. I still feel a 10 milliamp draw should not deeply discharge a battery in three weeks.

While a tender is a great solution. And I'm sure is 99.9% safe. I had a buddy that had his battery on a tender all the time because he didn't drive the vehicle much. The tender randomly started on fire and almost burned his garage down. I understand this is an extremely rare occurrence. But I'm paranoid, haha.

I appreciate the reply! I have a pretty broad spectrum of vehicles here. The wife has a new fully loaded SUV with all the bells and whistles. This has sat for a month before and started just fine. I have a 2001 Saturn winter beater I refuse to get rid of because it drives fine. This has sat damn near close to 5 months before and started up fine. I'd have to agree with what you're saying. When I checked the battery voltage with the car running it was 14.2 or something close to that. So it appears to be charging correctly.

Unfortunately it has both an aftermarket radio and alarm. The radio is a junk Sony Xplode from like 2001-haha. The alarm hasn't been used or "armed" in well over 15 years. I sat outside the first few years I owned it so I had one installed by a reputable shop. That's not to say it's not the issue. What if I pulled the fuse for the radio and let it sit for 3-4 weeks. Then tried to start the car. Do you think this would be an effective way to see if the aftermarket radio is the issue?

 

Absolutely.

I think if it's not too much trouble to get to I'd start by unplugging the radio entirely, fully charge the battery, and then see how it starts 3 weeks later. If that don't locate it, unplug the alarm module next & repeat the test. One other consideration here is that, as mentioned by QwkTrip, repeatedly deep discharging batteries damages them, is there any possibility of trying these two tests with a fresh battery?

 

U have the right ideas. A step by step detective pursuit to resolve the battery discharging.
I had to do that to discover what was causing the parasitic draw on my battery. Turned out it was a button/switch in the radio that was in constant contact.

 

Your batteries have lasted years, yes?
If you want the batteries to last longer then you have to maintain them better on float charge.

If you look at a battery high-current discharge curve (starting scenario) you will see the voltage gradually declines over time as the battery is discharged, and then BOOM! it falls over a knee in the curve and battery suddenly goes dead. That knee keeps moving to the left (shorter amount of time) as the battery ages and degrades. All that's happened is you are now in the knee of the curve within 3 weeks of parking. If you want to preserve battery capacity and extend the life of the battery (keep the knee out to the right) then you've got to better maintain your battery.

 

Absolutely. This current battery is at the end of its life. I'll probably purchase one in a week or two. But this problem isn't anything new (same issue with other batteries) so I don't believe it's just an old battery issue. It's not very common I don't drive it for 3-4 weeks. So I really didn't take the time to do any troubleshooting over the years. But last year was a crazy year and I barely drove the car. So it bothered me enough to start digging into this issue. Do you think it would be quicker and just as effective to fully charge the battery. Take a voltage reading with my multimeter. Let it sit a week, then take another voltage reading. Then charge it back up to full, disconnect the radio, and take another voltage reading in a week?

I really don't feel it's a maintenance issue. I was fortunate enough to get my current Optima RedTop when they were made in the states. I also purchased Optima's charger meant for AGM batteries. My red top has lasted 14 years. It's now showing signs of needing to be replaced. I don't think I could have made it last any longer than that. This has been happening for years, even when the battery was healthy. It's not common I let the car sit 3-4 weeks. If this was new problem on a 14 year old battery. I'd assume it was the battery for sure.

I absolutely appreciate everyone's input! Thanks guys.

 

Hi IROCThe5.7L

Were this mine, I'd want to replicate the exact condition of failure. Meaning, I'd get a good battery in it, unplug the radio, and let it sit 3 weeks. Actually, on second thought and it might be detrimental to your new battery, the real test would be to put the new battery in, don't disconnect anything, and see if it has trouble after the three week sit. Very likely it will. Then fully charge the new battery, disconnect the radio, and see how it starts after the three week sit. I know, deliberately letting the battery run down is a crazy proposition since we know it's not good for it, but it's really the only way to properly replicate the failure for additional testing.

 

That sounds like a great plan! It’s going to be tough not driving it for 3 weeks. Weathers getting nice. Haha. I”ll have to do some homework. I’m reading a lot of poor reviews on the new Optima’s. I don’t think I’ll get close to 14 years out of the next one. The Odyssey batteries look nice. But very pricy.

I spoke with an Optima rep years ago. He was telling me people let them drain. Then try to charge it with a normal charger for an acid battery and they don’t recover. He said he lost count how many “dead” batteries he got back and was able to bring them back using the correct charger.