Battery keeps draining every few days ugh

I checked on mine today: 12.15 after charging yesteday. Sounds low but it was 15-20F today. Started it up and... 14.8V. ??? Drove around a bit and checked again, while idling, after 30 minutes of slow speed driving. 14.5V. So wild guess here: I'm overcharging. Might explain why it's not holding a charge ('cuz the battery is on its way out).

Wonder what an ELD does, someone on here me told me to replace mine, so I bought one but haven't installed it yet. I wonder if it's time... [I know it's part of the charging circuit, presumably it measures battery charge/discharge, so it could be this--but I'd think it'd have a voltage measurement circuit too!]
 
supton said:
I'm planning on Wallyworld's finest. Just need FM, Bluetooth and aux input.
Click to expand...

Sure, if you know what you’re doing. I like that Crutchfield provides everything needed, including instructions AND over-the-phone help if you need some.
 
supton said:
I checked on mine today: 12.15 after charging yesteday. Sounds low but it was 15-20F today. Started it up and... 14.8V. ??? Drove around a bit and checked again, while idling, after 30 minutes of slow speed driving. 14.5V. So wild guess here: I'm overcharging. Might explain why it's not holding a charge ('cuz the battery is on its way out).

Wonder what an ELD does, someone on here me told me to replace mine, so I bought one but haven't installed it yet. I wonder if it's time... [I know it's part of the charging circuit, presumably it measures battery charge/discharge, so it could be this--but I'd think it'd have a voltage measurement circuit too!]
Click to expand...

12.15VDC is low no matter the temp.

Your alternator outputs listed look fine. Mine outputs the same with a full battery. I haven’t monitored it over LONG distances, but it and my Legacy stick with around 14.3-14.4VDC almost all the time.

I wouldn’t mess with the Electronic Load Detector unless it was bad.

I had a TSB performed on my Legacy due to too low of output voltage, resulting in dead/undercharged batteries. I don’t recall what the voltage was before the TSB, but it sticks to 13.3-14.4 now.
 
I have not messed with equalizers and whatnot, but usually radio swaps are pretty easy--the radios have only a handful of wires, so as long as I buy the matching connector that has a pinout info with it, I'm golden, no wire cutting involved.

Yes, I'm not sure what is up with the battery, I think it charged up too fast and it certainly is discharging too fast also. 14.8V sounded too high to me, as does 14.5V--that is measured at the battery, on the posts, at idle.

Just ordered some battery parts so I can swap in a larger battery.
 
My 2007 Ram was loosing power to the battery at just over 200ma. Pulled all the fuses in the power block and it was still the same. Hit the power module with the handle of my screwdriver and the short was gone. Normal draw was 30 ma on it. Put it all back together and has been good ever since. I have worked in electronics my whole life and have seen bugs get fried by voltages and turn into resistors. Mice do it too. I just have to assume that it was something like that.
 
Spent ten minutes this time.
Max: 129mA blip

Ave: 38mA

I thought I read somewhere that leaving the headlights set to AUTO might draw more. Nope! Exactly the same draw as in OFF.

supton said:
I have not messed with equalizers and whatnot, but usually radio swaps are pretty easy--the radios have only a handful of wires, so as long as I buy the matching connector that has a pinout info with it, I'm golden, no wire cutting involved.

Yes, I'm not sure what is up with the battery, I think it charged up too fast and it certainly is discharging too fast also. 14.8V sounded too high to me, as does 14.5V--that is measured at the battery, on the posts, at idle.

Just ordered some battery parts so I can swap in a larger battery.
Click to expand...

Sounds like you’re good to go. I prefer to buy an adapter harness so I don’t have to hardwire or splice the new head unit to the factory wiring.

Like I said, 14.8 at cold start and 14.4 at idle sounds perfectly fine to me. In fact, go to batteryuniversity.com and you’ll see that 14.4VDC is right in the middle for expected bulk-charging voltages per six cells.

/

@SubLGT:

I can’t find my IR gun right now. Everything feels cold to the touch in the fuse box.

Im going to purchase some alligator-ended leads for my DMM and hang out in the garage one afternoon and listen for the min-max beep to alert me to a potential large rise in draw. Like I said, no luck upon several checks now.

I’ll also be able to mess with things like the lift gate and doors.

In the end I’ll just have to do what the article you posted mentions: wait until it dies again and then see if I can check draw without disconnecting the battery.
 
supton said:
I checked on mine today: 12.15 after charging yesteday. Sounds low but it was 15-20F today. Started it up and... 14.8V. ??? Drove around a bit and checked again, while idling, after 30 minutes of slow speed driving. 14.5V. So wild guess here: I'm overcharging.
Click to expand...
14.8V at a battery temperature of 20degF is OK, but slightly low for 20degF. 15.0V would be closer to optimal. Temperature compensation is working as it should. Definitely not overcharging.
 
Hmm, interesting. I did not take into account temperature.

I plan to monitor (not that I have much else to do!) and see how the situation goes. Might just be a bad battery. Although it was replaced under warranty in 2019. So maybe not... probably parasitic draw. Gonna wait on that one, it's been a bit chilly lately and I have other vehicles.
 
Divide and conquer. It is slow, but methodical. And it gives you the correct answer.

I use to repair industrial electronics and industrial computers. Divide and conquer was a good fall back method of trouble shooting that worked in some situations when other approaches were not getting results. I remember there were D to A boards that you had to cut traces on in order to use the divide and conquer troubleshooting technique, but that always let you find out where the problem was.

With an intermittent problem, divide and conquer may be one of the best ways to find the problem.
 
supton said:
Hmm, interesting. I did not take into account temperature.
Click to expand...
Different battery and charger manufacturers suggest different charging temperature coefficients, ranging from 12-16mV from what I have seen.

With a temperature coefficient of 13.3mv/degF, a battery that has a suggested charging voltage of 14.4V at 77degF (common for many AGM batteries) will require around 15.7V at -20F and 13.9V at 110F.
 
I had a problem similar to this a few years ago and it was failed diodes in the rectifier. Two easy ways to test for that:

a) go to an LAP and have them put a loop clamp over the alternator output and analyze the wave forms.
b) with the car running, look for AC voltage across your battery terminals. If present, then one or more bad rectifier diodes.
 
Oro_O said:
I had a problem similar to this a few years ago and it was failed diodes in the rectifier. Two easy ways to test for that:

a) go to an LAP and have them put a loop clamp over the alternator output and analyze the wave forms.
b) with the car running, look for AC voltage across your battery terminals. If present, then one or more bad rectifier diodes.
Click to expand...

LAP? local area professional?

I’ll check for AC current tonight.

My DC clamp-on ammeter just came in. For $243, I’m not sure I want to keep it.
 
BISCUT said:
Hi! I am currently going through the same situation with my 17 Subaru Outback. If it sits for 3 days the battery is dead. I've never jumpstarted any other vehicle with the car. I'm using a battery pack to start it when needed. Battery is good. I replaced the horrible and underpowered battery within the first 20k miles of ownership IIRC. I went up a size and used Interstate.

I'm thinking mine is tied to the rear liftgate somehow. No evidence, just a theory.
Click to expand...
Outback is well known for random battery discharge. Sometimes sits 3 weeks. Sometimes won't sit overnight. The capacity of the OE battery is irrelevant because the problem is excessive draw not insufficient capacity to feed the draw.

As others have observed, Startlink is listening 24/7 for commands from the mothership. Subaru's keyless entry system is known to draw extra power if the key fob is kept in range of the parked car.

There is an EPA mandated pressure test of the fuel tank 5 hours after last operation. All gasoline vehicles have had this for at least 15 years. If you install one of the several Bluetooth battery monitor/loggers ($35 or less) you will see this event.
 
GrumpyCat said:
Outback is well known for random battery discharge. Sometimes sits 3 weeks. Sometimes won't sit overnight. The capacity of the OE battery is irrelevant because the problem is excessive draw not insufficient capacity to feed the draw.

As others have observed, Startlink is listening 24/7 for commands from the mothership. Subaru's keyless entry system is known to draw extra power if the key fob is kept in range of the parked car.

There is an EPA mandated pressure test of the fuel tank 5 hours after last operation. All gasoline vehicles have had this for at least 15 years. If you install one of the several Bluetooth battery monitor/loggers ($35 or less) you will see this event.
Click to expand...

I agree. I never had a problem with the OEM battery. I just replaced it in my 14 Forester last April @ 78k miles. It lasted that long even after accidentally being drained a couple of times.

Im really hoping to get lucky and catch something easy while troubleshooting. I CANNOT have my wife’s vehicle randomly drain the battery.

At least she has the large NOCO jump pack. Speaking of which, I’ll have to make sure it’s still charged fully. It’s been a few months since I last checked.
 
Oro_O said:
I had a problem similar to this a few years ago and it was failed diodes in the rectifier. Two easy ways to test for that:

a) go to an LAP and have them put a loop clamp over the alternator output and analyze the wave forms.
b) with the car running, look for AC voltage across your battery terminals. If present, then one or more bad rectifier diodes.
Click to expand...

Because if any one of the power diodes in the output 3 phase bridge rectifier of the alternator goes leaky, the first step in my detailed first write-up of how to divide and conquer ( post # 18 of this thread ) was removing all the fuses and letting it sit. Because with the output of the alternator still connected, if one of those diodes is leaky, it will still be connected and drain the battery. Though usually this type of a problem shows up as a constant small drain, and that should be easier to find. Also note that the starter is still connected.

BTW, it is quite posable for the AC ripple output of the alternator to still be proper ( a good alternator will have a small AC ripple from the 6 diodes in the 3 phase bridge output, a bad one MAY have one or 2 of those 6 pulses missing ).

Even with a bad leaky ( reverse polarity leakage ) of the diode, the 6 output pulses may all be there because when in the forward conduction mode it may still conduct properly. So a test of the AC ripple may not show a leaky output diode.

-------------------------------------------------------------------------------------------------

As I have posted before, Divide and conquer is slow, but it does yield the correct answer.

-------------------------------------------------------------------------------------------------

I like the idea of a battery logger. I did not know those were made.
 
Last edited:
JimPghPA said:
Because if any one of the power diodes in the output 3 phase bridge rectifier of the alternator goes leaky, the first step in my detailed first write-up of how to divide and conquer ( post # 18 of this thread ) was removing all the fuses and letting it sit. Because with the output of the alternator still connected, if one of those diodes is leaky, it will still be connected and drain the battery. Though usually this type of a problem shows up as a constant small drain, and that should be easier to find.
Click to expand...
That was the problem with my old BMW, even with every fuse out of the holders it still drew over 4 amps from the battery. It turned out to be dead insects in the housing, that vehicle had an air-cooled alternator with a duct to under the bumper. Many things had crawled in there over the years.
 
You must log in or register to reply here.

Similar threads

Bailes1992
Disconnecting Negative Battery Sensor
Replies
12
Views
650
Craig in Canada
Donald
Old Century battery charger
2
Replies
25
Views
2K
Volvohead
B
Electrical Mystery-Battery or Parasitic Draw or ?
Replies
11
Views
1K
Sequoiasoon
Cujet
DC arc welder restores sulfated golf cart batteries.
Replies
8
Views
1K
Cujet
S
Need a Battery Charger for Top Up - Optimate 6 or Ctek 4.3?
2
Replies
20
Views
2K
Majsmith
Back
Top