Battery seems to drain pretty rapidly when working on the car.

[Pyrenees]

I've drained the battery while working on the car maybe three times now, and each time I've been surprised at how fast it happens. I say this in relation to other vehicles I've had, where I might leave keys in the ignition/dome lights on/etc etc while doing some casual maintenance and after 45-60 mins things are fine, but then suddenly my 100 battery is dead (like down to 5 volts) when I do the same thing.

This is my daily driver. No issues starting, not even once. None of that "weak battery" slow feeling when starting even in the cold. Voltages all seem within spec. Voltmeter in the cluster is always around the 3/4 mark. 12.6V at the terminals today (turned off), 13.4V charging, at the terminals.

Yeah, I know I'm supposed to disconnect the battery every time I do any maintenance, but for really basic stuff where I simply have a door opened for a bit, it seems like I shouldn't have to worry.

Battery is an Exide Classic 27F, date 2/16. No bulging. I keep the terminals clean and greased. Rated CCA is 710 at 0F, 850 CA at 32F. I've only had a 100 for a few months.

Is this battery rating adequate?
Is that brand crap? (says 20-mo warranty on sticker, which seems short).
Is there a battery I could get that would hold charge longer?
If I did that, would I need an alternator upgrade?
Am I overthinking this?

 

[Spike555]

The only time you need to unhook the battery while working on the truck is when doing electrical work that cannot be unplugged, starter and alternator, that's it. Everything else...either unplugs or is fused and unplugs when you remove the fuse.
MAF...you unplug it and it no longer has power, stereo...you unplug it and it no longer has power...

Anyway, your battery is bad. Dome lights do not draw enough power to drain the battery, they will take days to do that.
Stereo on, still takes days. I am assuming if you leave the key in the ignition (like I do) you do not have the full dash lit up just the stereo on.
Leaving the key "on" with the dash active and live will drain the battery pretty quick, but it sounds to me like you have a droppe cell or two in your battery.
This will not show any signs of going dead or being weak, it just will not give y9ou as much reserve power because instead of having say 12 cells giving you power you only have 10 or 11.

Have your battery tested and go from there, but my money is on the battery being bad. I've had batteries go bad in less time than yours. It happens.

 

[morganism]

Diode in the alternator? If blown, you could be powering the windings at all times......

 

[ERMB]

Mine seems to be having similar issues. The other day I went to make a phone call and to keep the phone from picking up on Bluetooth I just shut the car off. Made my call, started it again, turned it off again to make another call and went to start it again and it wouldn't turn over. It was definitely strange. Turning the car on and off a couple times within a few minutes should not drain the battery! I replaced my alternator this summer so it must be the battery.

 

[Pyrenees]

I just noticed that my headlights/fog lights were selected to "on" pretty much at all times when the key is on 2nd position. Never really thought too hard about it until now since most newer cars I've had already have DRLs burning. So I guess we can add a couple hundred watts to the draw.

In this scenario would one expect to drain the battery within an hour? Stereo on (but not in use), dome lights on, all four door puddle lights on, headlights and foglights on. Am I just raggin' on my battery too hard and need to cut it out?

I'd be really interested in a battery that simply takes longer to die, even if my actions are the cause of the drain.

I suppose the alternator *could* be a problem but wouldn't it have a lower charging voltage? I've seen zero "alternator is dying" signs.

 

[uHu]

Your voltage is low, both resting and charging, so either alt or batt, or both, is not top notch.
Otoh, my radio takes 8 Amps! ! Couldn't believe it first time I did a service after fitting the Alpine, and draining the battery. Together with a few dome lights it will drain the battery in few hours. I can blank the 8" screen, but still it takes nearly as much, and there is no off button.

 

[Pyrenees]

Interesting. I'll have to check those voltages against the FSM to see what the appropriate range is. Alternator issues are usually the brushes on these, right? Or is it diodes/something else? Brushes are at least not too bad to replace.

 

[MuseChaser]

Another vote for a bad battery, especially if it's been down to 5v a couple times. That's REALLY low, and tough for even deep cycle batteries to bounce back from, much less regular starter batteries. Anything below 11.2 on a regular basis isn't good, and some would be more conservative than that.

As far as disconnecting the battery when working on the car, that's not to protect the battery, it's to protect the electrical components in the car and, more importantly, you. 12v isn't a lot of voltage, but there's a lot of current. In the admittedly unlikely event you short something while holding metal, you can get a bad burn really fast. That's why mechanics don't wear rings or jewelry of any kind.. or at least one of the reasons.

 

[Pyrenees]

Ok, I checked the FSM and it shows 12.5-12.9V for the normal range for the battery.

Alternator check "with engine between idle and 2000 rpm" 10A or less, and 13.2-14.8V.

I looked back on one of my previous posts, post-draining-the-battery, I was getting 14.14V running, 12.9V charged just recently.

Maybe when I checked yesterday the battery wasn't at 100% yet...

 

[Pyrenees]

12.26 V today. Seems like this one lasted 2.5 years before getting lousy (at least per the manufacturing date stamp). Never outright stranded me, but I'm not taking any chances with it since "winter is coming". Picking up a new 27F this afternoon.

 

[Pyrenees]

Alternator was at 13.45V today with the new battery, so within factory spec but toward the bottom end. I’ll check it every now and then.

Bosch 27F, $107 at Pep Boys. 36-month swap, 96-month prorated. Perfect fit in my 2001 LX tray. Greased the terminals and hooked it up. Hope that does it.

 

[uHu]

13.45 will never get your battery fully charged. You have to have over 14. At idle you might not get more, but if you increase the throttle to a hi idle, you should have well over 14 V on a fully charged battery.

 

[nukegoat]

13.45 will never get your battery fully charged. You have to have over 14. At idle you might not get more, but if you increase the throttle to a hi idle, you should have well over 14 V on a fully charged battery.

Thats not how electricity works

 

[Pyrenees]

13.45 will never get your battery fully charged. You have to have over 14. At idle you might not get more, but if you increase the throttle to a hi idle, you should have well over 14 V on a fully charged battery.

Honest question though, why? If it is (consistently) within the specified range in the factory service manual for this model year of this exact vehicle, why would that be problematic especially with a new battery? I can imagine it might not charge the battery as hard and fast as 14+ volts though. My FSM says 13.2V-14.8V.

 

[Davio6]

Honest question though, why? If it is (consistently) within the specified range in the factory service manual for this model year of this exact vehicle, why would that be problematic especially with a new battery? I can imagine it might not charge the battery as hard and fast as 14+ volts though. My FSM says 13.2V-14.8V.

I am going to guess that it's a long trip/short trip problem. Your car runs off the alternator, once the battery supplies the power to start the car. The battery gets replenished from its starting duty, by alternator voltage while you drive. If you don't put in enough miles to re-charge the battery, or if the charging voltage is too low, you will eventually run down the battery. For that purpose 14.4V from the alternator is better than 13.4V.
I think.
Good luck,
Dave

 

[Pyrenees]

I am going to guess that it's a long trip/short trip problem. Your car runs off the alternator, once the battery supplies the power to start the car. The battery gets replenished from its starting duty, by alternator voltage while you drive. If you don't put in enough miles to re-charge the battery, or if the charging voltage is too low, you will eventually run down the battery. For that purpose 14.4V from the alternator is better than 13.4V.
I think.
Good luck,
Dave

Interesting point. My daily commute to work is 7 miles and everything I need is within 5 miles of my house.

I guess I will keep an eye on the alternator output. I saw 80A and 100A in my FSM, are these easily interchangeable? Just thinking ahead before the time comes. Not sure what's in my 01 LX.

 

[Daddy Rabbit]

I had the same problem a year or so ago. I would pull in and watch my sons baseball practice for a little while and listen to the radio. If I left it on over 15 minutes or so I could barely start it or have to use my jump box. I had a cheap battery from Wally World at that time that wasn’t a year old. I finally bought an Interstate and the problem was solved for a while. This fall I started out to deer camp pulling a tractor and I noticed my lights were dimming when I was coasting. They would brighten back up when I was under power. Then my alternator light would come on intermittently. I turned off everything I could and when it got daylight turned my lights off. I made the 400 mile round trip with my butt cheeks clenched so hard together it took me an hour to get my shorts out. Ok too much information. Anyway when I got back I drove it a couple hundred miles and the light started staying on. I changed out the alternator and now everything is fine.

 

[Davio6]

Yep. The alternator controls its own output voltage and current. Sounds like both probably were just not quite enough.
Glad you got it fixed.
Good luck,
Dave

 

[Pyrenees]

Ugh, 13.32 V at idle today. Just barely in spec. Time to do some alternator research while I can. Are remans good on the 100s? I’ve had some horrible reman experiences with other vehicles.

 

[Pyrenees]

Do you guys think that worn brushes could cause the voltage to be lower, or would that just cause an absolute failure? It looks like Oreilly has reman Densos for $130 plus core, but a brush set is $17 and there's zero bearing noise.