How to find a battery drain

[Rene T]

I have a 2011 Silverado 2500 Duramax. I put 2 new batteries in it last summer. Now just sitting in my garage while I’m in FL, the batteries will drain down to nothing after about 8 weeks. How would someone go about trouble shooting trying to find what’s causing it to drain. I think the clock in my radio and maybe the computer may have something to do with it. What else would do it. How can I locate any other draw.
I tried to find electrical cutout switches that I could put on one post of each battery, but because of the tight spaces, I couldn’t find anything that would work. I may have to keep looking

 

[Lou Schneider]

8 weeks? It's most likely the engine computer, clock, etc. that's causing the phantom draw and is completely normal, A 0.2 amp draw will drain a pair of 100 a/h batteries over that time and your starting batteries are likely smaller than that.

I have 3 AirXcel power vent fans in my Arctic Fox trailer. The receivers for their wireless remote controls are 12 volt phantom draws and will drain the house batteries after a couple of weeks in storage,

I'd get one of the $25 plug-in battery maintainers and connect it to one of the batteries while you're gone. Or a small battery maintainer solar panel if you have access to sunlight. Doesn't matter which battery you connect it to, they're both in parallel.

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[Rene T]

So let’s say both my batteries are dead from the draw, it would be bad to hook up battery #1 to a standard battery charger and put jumper cables from another vehicle on battery #2 all at the same time. Right?

I think I could charge both batteries at the same time quicker providing I disconnect one battery cable and put the alligator clip of the jumper cable or battery charger on that battery post. Is that right?

 

[Mr Lars]

For batteries that are completely dead, or darn near, it is preferable to bring them back up slowly. Use a 2-4 amp charge level for 2 or 3 days. The theory(I would imagine this has been tested) is, this procedure helps with longevity of the battery.

 

[jlhog]

I have been fighting a draw in my F150 for over a year. Had it to a couple different shops and nothing found out of normal. I can lose 20% overnight. I always run it every other day just to keep it charged good. Fourth battery in 2 years so it is not a bad battery,. I bought an AGM battery two weeks ago and it does seem a little better, but still not right, Good luck finding the draw..

 

[Kirk]

So let’s say both my batteries are dead from the draw, it would be bad to hook up battery #1 to a standard battery charger and put jumper cables from another vehicle on battery #2 all at the same time. Right?

You are over thinking this. Why are you in such a rush to charge the batteries so fast? Do you own a battery charger? If you drive the truck for an hour or two the batteries should be pretty well charged. The more you fool with things the more likely you are to create a new problem. Go back and read post #2 again. If you don't have a Harbor Freight or don't like them, Amazon has a wide range of them with quite a range of prices. I would get one that can supply at least 2A, but you really won't need much.

 

[bigbAZ]

 

[Gary RV_Wizard]

So let’s say both my batteries are dead from the draw, it would be bad to hook up battery #1 to a standard battery charger and put jumper cables from another vehicle on battery #2 all at the same time. Right?

Your batteries are in parallel, so you can hook the charger leads to any easily accessible positive and negative posts. The picture in post #7 is the ideal hook-up, but when using a smallish charger, say 6A or less, it really makes no difference. Give it a couple days.

If you are in a hurry, jump start the truck and drive it for an hour or so and that will quickly get it up to around 80%. However, the smaller charger over a couple days is a better choice for a longer battery life.

 

[Rene T]

You are over thinking this. Why are you in such a rush to charge the batteries so fast? Do you own a battery charger? If you drive the truck for an hour or two the batteries should be pretty well charged. The more you fool with things the more likely you are to create a new problem. Go back and read post #2 again. If you don't have a Harbor Freight or don't like them, Amazon has a wide range of them with quite a range of prices. I would get one that can supply at least 2A, but you really won't need much.

One of my grandsons jad to take my truck and my bobcat trailer to northern NH to pick up his brothers truck that had broken down . His tie rod rod broke im someone’s yard. That was 3 hours each way. He didn’t leave till after 2 so he’s he was in a hurry. My charger was on all night and it still wouldn’t turn over. He put jumper cables on the other battery and rotated the knob on my charger to the 100 amp quick start position. After a few minutes, it started

 

[bigbAZ]

If those batteries were allowed to go completely dead there is likely some permanent damage.

 

[Mark_K5LXP]

If a lead acid battery is dead-dead, zero volts and been there a while, it can take hours or sometimes days for a conventional ("dumbe") charger to wake it up. It's accurate to say charging slow is better but it can take a kick in the form of elevated voltage to get things started. From there, the charge cycle will complete by the numbers.

"Modern" cars draw current from the battery all the time. So it's not a matter of if the battery will go flat it's when. A typical spec is 100mA. So if you figure a nominal car battery is 60Ah, that battery is flat in under a month. So 8 weeks might be about it for a dual battery if it's near the max typical.

But, wonder and guess or measure and know. It is a nominal effort to spend some quality time with a basic meter and see if the draw is nominal or there's something else involved. I had an issue with my truck going flat after a week or so and discovered the glove box light wasn't turning off. So at least answer the question if there's actually a problem or not.

Even if parasitic draws are normal, 8 weeks is a long time to be idle. So either lift a cable or put a tender on it. I keep a tender on my wife's car even though it only sits a few days at a time. Removing even that little stress helps it last well beyond typical lifespan.

Mark B.
Albuquerque, NM

 

[RayIN]

FWIW, if you have a Tekonsha brake controller, they are always powered. This is not noticed in a vehicle that is driven daily or every other day, but 2 weeks or longer not being ran and the battery suffers.
I keep my Tekonsha brake controller unplugged on the rear until needed.

 

[Lou Schneider]

Even if parasitic draws are normal, 8 weeks is a long time to be idle. So either lift a cable or put a tender on it. I keep a tender on my wife's car even though it only sits a few days at a time. Removing even that little stress helps it last well beyond typical lifespan.

The problem with lifting a cable (disconnecting the battery) is the car's computer forgets it's history and reverts to default mode until it re-learns everything. This may take a while, for example CA won't allow a car to be smog tested if the battery has been disconnected within the last 125 miles.

 

[bigbAZ]

The problem with lifting a cable (disconnecting the battery) is the car's computer forgets it's history and reverts to default mode until it re-learns everything. This may take a while, for example CA won't allow a car to be smog tested if the battery has been disconnected within the last 125 miles.

It can be a lot more than 125 miles depending on the vehicle. There are stories of certain diesels taking close to 1,000 miles for all emissions monitors to come back online after a disconnect. I have read that on the very newest ones the ECM memory is now kept in a way that a disconnect won't affect it though.
I have a new Ford Ranger and after 600 miles it still had emissions readiness monitors showing "not ready". I now have 900 and will check it again now that you reminded me.

 

[klook]

View attachment 2398055

And that brand or a NOCO

 

[woof-n]

My experience with completely discharged batteries, is you have a 50/50 chance of bringing them back from the dead and a 90% probability they won't. If one battery has a shorted cell it will kill the other battery. I would charge both batteries full and do a separate load test to confirm they are good. If it is good I would invest in a budget line data logger. Such as a Hobo from onset. For a base price of about $200, you can data log almost anything. Check out the Onset web site. The software is really easy to use.

Years ago, I was at a generator repair shop. I was trying to have an insightful conversation with the old shop owner about the selection process for a quality long life battery. He cut me short and said son, Batteries are a lot like people. Some of them live a long time, and well, some of them don't. We shared the laugh. Hardly the answer I was hoping for. Over the last 50+ years I have found his answer is closer to the truth than any sales brochure.

Good luck let us know what you find.

 

[woof-n]

One additional thought is to lift the negative terminal off the battery so the battery cannot discharge while you're gone for an extended time. That's what I do with my wife's car

 

[DonTom]

This may take a while, for example CA won't allow a car to be smog tested if the battery has been disconnected within the last 125 miles.

If "ready," why not?

It's the same in Nevada--EXCEPT for motorhomes.

Cars that are not ready will show as "not ready" on their test equipment. The time it takes to get a car "ready" has MANY variables. It can take anything for a few miles to NEVER. Newer cars are more difficult, and the "never" is from not driving in the way a sensor needs to be reset.

For example, I can drive my 1999 Dodge Ram Truck for thousands of miles without it being ready if I do not decelerate from a long distance to near a stop, starting from a certain speed. Number 7 on the list below:

Best to check the web for your year and model:

With a motohome, you can get a smog test (Reno area) with the check engine light on and still pass. They only connect to the OBD2 port to read the RPMs. NV (at least Washoe County) ONLY checks motorhomes from the tailpipe.

None of the sensors needs to be ready in NV in a motorhome. Most if not all need to be ready in a car. Depends on the year and model.

With cars, they do NOT check the tailpipe, only the OBD2 memory; most sensors must be "ready" with no errors. There are a few exceptions for a few makes where one or two sensors can still NOT be ready and still pass.

I own a Ready or Not. I know if my Dodge Ram is ready and if it will pass BEFORE I have the smog test. I have no way to know in advance with my motorhomes.

I have no idea how CA does it these days. But to base it on miles for when "ready" makes little sense.

All my ICE vehicles have NV plates. My Tesla has a CA plate.

-Don- Kingsburg, CA

 

[DonTom]

My experience with completely discharged batteries, is you have a 50/50 chance of bringing them back from the dead and a 90% probability they won't.

What I discovered is that newer batteries are a lot more forgiving when totally discharged. When it happens to an older battery, expect it to be fine after a charge for around two weeks or so. Best to junk the older battery right after it happens, even though it will seem to be okay. That will not last.

That has been my experience over the years.

These days, all of my ICE vehicles are on a battery maintainer, except the Class A I am in right now, which charges every battery in it via the roof solar, and it is left where it gets enough sun.

In my Y2K Class C, I keep the engine battery disconnected until I am ready to use it (and I don't need to worry about it being "ready" for smog since that is not tested with motorhomes in Reno).

-Don- Kingsburg, CA

 

[bigbAZ]

I own a Ready or Not. I know if my Dodge Ram is ready and if it will pass BEFORE I have the smog test. I have no way to know in advance with my motorhomes.

I have no idea how CA does it these days. But to base it on miles for when "ready" makes little sense.

All my ICE vehicles have NV plates. My Tesla has a CA plate.

-Don- Kingsburg, CA

You can check with many different phone apps on that Smartphone you wish was never invented I use Torque Pro and a ELM 327 Bluetooth adapter. Check monitors, read and clear codes, get freeze frame data, stream live data. I paid $5 for the pro version about 10 years ago.