Truck Battery Issue

[Donald]

Originally Posted By: 1 FMF
the "false charge" is known as a "surface charge".

A fully charged car battery (valve regulated lead-acid VRLA) is 12.65 volts at 70F or 80F ambient temperature. If it's colder then 100% state of charge will be slightly lower like around 12.62 or 12.60 volts. When you're down around 12.50 to 12.40 volts the battery is near 50% state of charge.
If possible charge the battery overnight or for 6-8 hours at 2amp setting but not higher than 2amp. Then let the battery sit not connected to anything for 8-12 hours to get rid of the surface charge. What you can do is put the battery on charge in the evening then take it off first thing in the morning before leaving the house, then measure the voltage on it that evening which should be > 10 hours later. You are measuring "open-circuit voltage" on the battery, which means voltage across the positive + and negative - terminals with them not connected to anything. You should see around 12.65 volts on a digital multimeter. All batteries self discharge over time, so to know whether you have a bad battery is you have to let it sit a day or two then remeasure open circuit voltage and see how much it dropped. Over a week it should not drop more than around 0.02 volts, as long as the ambient temperature did not change much, you should still be over 12.60 volts. if open circuit voltage dropped significantly then that's a good indication the battery is bad.


I was thinking that it was not really called a "false charge" but something close. I guess I was close enough as you knew what I was talking about.

 

[wolfehunter]

I'm still not convinced that I do not have a parasitic drain on this truck. The new battery had 12.60 volts and I redid the test for parasitic drain as described by 1FMF above. I only had a 12 gauge wire but it arced as he described and I noticed the dome light came on so I know the truck was "powered up". I had my wife assisting and she said the digital clock came on also. I waited 10 seconds and the dome light turned off. I then touched the probes of the ammeter where needed....one to the cable and the other to the post on the battery. I then removed the 12 gauge wire so the power was going through the ammeter. It read 2.22 mA however my wife said when I removed the 12 gauge wire the digital clock went out. Doesn't that mean that not enough power was traveling through the ammeter to power the clock up? How can this be an accurate test? Just asking is all.

This is bothering me too. I hooked the battery up and it read 12.60 volts. When running the truck it reads 14.14 volts. I drove it yesterday for about 1 1/2 hours and it sat overnight. I checked it this morning before starting it and it was at 12.27 volts. Drove it for 90 minutes and it is at 12.75 after shutting it off (probably the false or surface charge described earlier). Something is still draining it down since it was only at 12.27 this morning. I have an old Chevelle in the garage I haven't started for over 5 weeks and that NAPA Legend battery is holding at 12.40 Maybe I worry too much!! Is it possible this battery might normally just hold a charge of around 12.27 volts? Time will tell. I'm going to let it sit in the truck a few days and check the voltage. It can't be another bad battery if it drains it down.....gotta be something in the truck. Just needed to vent some frustration I guess. I'm afraid that one day I'll jump in it to go somewhere and it is not going to start is all.

 

[brianl703]

Are you sure that it wasn't reading 2.22A?

What's the reading you get with the dome light turned on?

Also your digital clock shouldn't be lit up with the key off.

 

[Donald]

The battery does not get a "surface charge" when the alternator charges it. Only when an AC charger does.

Your battery (if everything is working 100%) will have the same voltage every other battery has, assuming you are using the same DVM and not the dash gauge of each vehicle.

The best and the cheapest battery will always have the same voltage. Its physics or maybe chemistry.

I'd see if I can obtain a clamp-on DC ammeter. Its much easier than what you are doing.

 

[1 FMF]

what type of meter are you using, and what type of charger are you using?

with the battery disconnected from the truck, when you first make the connection you will get that small arc as you touch the battery post and complete the circuit. you should immediately hear a bunch of clicks, that's all the relays powering and switching.
When you connect your ammeter as shown below, it's connected in series, you have to make sure it's a solid connection that doesn't break easily, otherwise the whole system powers off and will mess up your reading. that's why i recommended alligator clips, but you don't need them provided you understand you have to be careful that the electrical connection is good.
I also show the test using the + side of battery, which is dangerous if you short that to any metal, you can also do the test in series on the negative side of the battery if you wish, does not matter. What you might want to try is start with meter on 10A or equivalent setting which is NOT fused, but you won't have resolution below 1 amp. Start this way and when you disconnect your jumper wire and run soley through the ammeter, you should not break the circuit and NOTHING should turn off inside the truck. Fact that you said inside clock turned off means you broke connection somehow, possibly the fuse in the meter on the milliamp scale, so open the meter and check/replace fuse before using the milliamp scale. But with ammeter on 10 amp scale, it is not fused so you will not break the circuit and it should read basically 0 but everything inside truck should have power, turn on dome light and parking lights and you should see a few amps on the meter. Now with all that working, proceed to phase 2: disconnect everything and set meter on next lowest setting which is like up to 40 mA but fused (with a good fuse) and connect the lead to the correct hole in meter case. Set up and power up, then wait 30 seconds before disconnecting jumper, now running on mA scale monitor draw with everything off in truck but making sure clock is still on from outside of truck, don't open door because interior light will pull more than fused meter can handle and will blow fuse. Monitor milliamp scale and maybe leave connected overnight, it may take an hour or better for something like the body control module to go faulty and pull excessive current which then would blow fuse in meter and show you had an excessive current draw. the craftsman meter in the pic you can get for around $30. hope that helps.



No, the battery should not hold 12.27 volts as normal. at 100% state of charge for all lead-acid batteries, it's 12.65 volts or better at 80F temperature, 12.63 volts at 60F, 12.60 volts at 40F.

http://www.batteryfaq.org/

your 12.40 volt battery in your chevelle is around 50% discharged, do it a favor and charge it before it sulfates and loses capacity (read batteryfaq)

a lead-acid battery will get a surface charge any time it is charged. It is DC current that charges a battery.
If you have an "AC" charger, as in one that plugs into a 120 volt AC home wall outlet, that is not an "AC charger". It converts AC current into DC, and regulates DC current into the battery.

a clamp on meter will only measure AC current, at least the one you would most likely buy. you would not want to buy a clamp on meter that measures DC current nor do I think they have resolution down below 100 milliamps.

 

[wolfehunter]

I've got the same Craftsman ammeter you have pictured. The charger is a Schumacher 2/10/50 amp starter/charger that uses the 120 volt home wall outlet as you described. It converts AC into DC. I just checked the voltage in the battery again and since I made the above post around 3:00 pm until now (7 hours) it reads 12.57 volts.

My brother has a clamp on style ammeter and I'm going to ask him if I can borrow it. I'm going to check the voltage first thing in the morning again. I'm guessing it will be down again which will tell me I've probably got the drain thing going on. But I'm still going to get my brother's ammeter to see what the draw is in mA Then the fun will start trying to determine what it is that seems to be drawing it down.

Gotta get that charger hooked up to the Chevelle!! I'm on my way. Thanks for your patience and great information.

 

[wolfehunter]

12.45 this morning. Something has got to be sucking the life out of it. Should be easier to figure it out with a clamp on style ammeter. From what has been posted I'll need to pull fuses first and then find the individual component.

 

[Pop_Rivit]

Just as a comparison I have a 1999 Dodge pickup that often sits for a month or two at a time. It always starts right up after sitting, I assume any normal drain wouldn't be too different between the trucks.

 

[wolfehunter]

Thanks Pop Rivet. I've got an issue but I may be on to it. I pulled the Radio(battery) fuse this morning which is a 15 amp and of course the digital clock went out and I'm assuming all my presets on the radio. I just checked the volts again and it is now up to 12.54 volts.

I'm wondering if the digital clock is not supposed to be on all the time as mentioned earlier. Someone also had thought a digital clock shouldn't draw enough current to make a problem. I've had the truck for almost 8 years and can't remember if it has always stayed on after turning the ignition off!! Anyone have a 98 Silverado that they could tell me? I asked this same question a few weeks ago on a Chevy Truck Forum but nobody answered me. Only response I had received on there was that the clock wouldn't draw enough current to cause a problem as was thought here too.

I remember when the 7 year old battery died that all my gauges and door chime and lights were flickering, making noise and carrying on. I wonder if something happened at that time to the clock in the radio at that time to now be causing it to stay on all the time or at least causing me some problem with drain?

 

[NYEngineer]

With the battery connected normally in the truck, place the meter leads across pos and neg so the meter displays the battery's voltage. Put the meter where you can see it and crank the truck. Watch what the voltage drops to during cranking. This will truly show the battery's condition.

 

[wolfehunter]

NYEngineer,

With my 8 year old starting the truck it drew the volts down to 11.????? each time. There was one occasion it was 10.???? but the numbers flash by pretty quickly I couldn't get the tens or hundreds digits. It is a new battery so I'm guessing that is within normal operating volts?

 

[brianl703]

Originally Posted By: wolfehunter

I'm wondering if the digital clock is not supposed to be on all the time as mentioned earlier. Someone also had thought a digital clock shouldn't draw enough current to make a problem.


If the clock is an LCD type of display it probably wouldn't consume enough power to cause a problem unless the backlight isn't turning off.

However, I don't believe that GM uses that type of display on your truck. GM with very few exceptions uses vacuum-fluorescent displays (VFD) which are much brighter (they need no backlighting) and consume a lot more current than LCD displays. (Wikipedia says .2 watts, which is about 180mA at 12V--enough to drain a car battery fairly quickly)

If your truck has a clock display that stays lit up when the key is out of the ignition--well, there's your problem.

This is what a VFD (from a VCR, but a car radio clock will look similar) looks like:

If it helps, I have NEVER seen ANY GM vehicle where the clock stayed on after the key was removed from the ignition (and the driver's door opened for the ones with retained accessory power). There are some where you can push the button the radio to display the time with the key off, but they only display for a few seconds and then turn off.

Does yours have the clock display on the right side of the radio with the words "THEFTLOCK" on top and "Delco Electronics" on the bottom?

If so, that clock display will definitely drain the battery if it stays on. (I searched Ebay for 98 Silverado radios so I know what they look like).

 

[wolfehunter]

Brian,
I think you nailed it! My radio has Delco Electronics to the left of the digital display(which is on the right) but doesn't have "theftlock" anywhere on it. It is just a standard AM/FM cassette with treble and base knobs. No equalizer or anything too fancy. The fade and balance controls are on the outside of the Volume and Tuning knobs.

That VFD picture of the VCR in your post is what my display looks like. If you look real close you can see other words that are not lit up in the background like AM P.SCAN FM1 SET FM2 ST. These are to the right of the clock display.

Since I pulled the Radio(battery) fuse and the clock is no longer on the volts on the battery are holding at 12.55 all day. I was on the right track but you just confirmed my suspicion. Thank you so much!! It was a learning experience.....thanks to all.

I suppose there is no way to fix this problem except to get another radio?

Scott

 

[jim302]

Originally Posted By: wolfehunter

I suppose there is no way to fix this problem except to get another radio?

Scott


Before replacing the radio, try checking the wiring harness that goes to it to make sure wire that is controlled by the ignition switch (or BCM) is not constantly powered. Also, check your other accessories such as the power windows... if those also work, you definitely have an electrical problem.

There should be at least two wires with 12V... one is constant, which lets you keep your presets and time. The other has 12V only when the ignition switch is on the ACC or RUN position, which is how the radio knows when it can be turned on and when it should automatically turn off.

Some GM cars (and possibly others) have a feature that lets the radio stay on, along with a few other accessories for 10 minutes or until a door is opened, so make sure to account for this in testing

You should be able to find a guide to the wiring harness online. If nobody here has one, some car audio sites should have the info.

If your switched/ignition wire to the radio is always powered, a number of things could be wrong, possibly even a body control module issue (hopefully it is NOT that). This kind of thing could be a pain without a wiring diagram.

 

[Jimmy9190]

Wiring for a 1998 GM radio should be:

Orange: constant 12 volts +
Yellow: accessory 12 volts +
Black: Chassis ground
Gray: Illumination/dash lights 12 volts +
Brown: Dimmer lead 12 volts +
Pink: Electric antenna 12 volts + output only when radio is on, this wire is probably not present in a truck wiring harnesss

Tan: Left front speaker +
Gray: Left front speaker -

Light green: Right front speaker +
Dark green: Right front speaker -

Brown: Left rear speaker +
Yellow: Left rear speaker-

Dark blue: Right rear speaker +
Light blue: Right rear speaker-

The yellow accessory power and orange constant power wires will be up in one side of the radio connector plug, along with the ground and illumination wires. The orange constant power wire is supposed to have 12 volts all the time to retain the radio presets and clock setting. If your yellow accessory power wire has voltage present even with the ignition off, then either there is a problem in the body control module or the wiring for the accessory wire to the radio. Be sure to have the driver's door open when checking the accessory power wire, so the retained accessory power function does not keep voltage on that wire and fool you. If the accessory circuit checks out OK, the radio might be defective. A good car audio shop could bench test and check the radio for you. You can save some money by removing and reinstalling the radio yourself. You don't even need any tools for the job, the dash trim panel snaps out, it is held in place with metal retaining clips on the back side of the panel. Then just press down on the plastic retainers on either side of the radio and slide it out of the dash. If it is a bad radio, it might be cheaper to replace with a good aftermarket cd/mp3/ipod player. Nowadays you can buy a good quality aftermarket unit and the parts needed for installation for around $150.00, maybe less depending on where you shop. There is an installation kit made for the dash of your truck to install the new unit, and you wil need an antenna connector adapter, GM uses a miniature antenna connector, the adapter changes the antenna connector to fit the standard antenna jack found on all aftermarket units. There is also a matching wire harness connector that takes all the guess work out of wiring the new radio and it makes the installation a lot easier. Best Buy will sometimes run free installation deals, and any good independent car audio store can also install it for you if you decide to go that route.

 

[wolfehunter]

Thanks for the detailed information fellows. I was able to get the radio out with no difficulty. The orange wire had over 12 volts and with the driver's door open as instructed the yellow wire had 13.5 mV Is that enough voltage to indicate a problem with the body control module?

None of the other accessories work with the ignition off including the wipers, power windows, blower fan or the radio. It's just that the clock stays on in the radio. I guess that is something a radio shop probably can't fix so I might be looking at getting another radio....maybe even from a junk yard pretty cheap. I do like the thought of the aftermarket though with all the goodies.

Thanks a million for the assistance.

Scott

 

[jim302]

Originally Posted By: wolfehunter
Thanks for the detailed information fellows. I was able to get the radio out with no difficulty. The orange wire had over 12 volts and with the driver's door open as instructed the yellow wire had 13.5 mV Is that enough voltage to indicate a problem with the body control module?

None of the other accessories work with the ignition off including the wipers, power windows, blower fan or the radio. It's just that the clock stays on in the radio. I guess that is something a radio shop probably can't fix so I might be looking at getting another radio....maybe even from a junk yard pretty cheap. I do like the thought of the aftermarket though with all the goodies.

Thanks a million for the assistance.

Scott


The small reading on the accessory wire should not be enough to cause a problem. It sounds like an internal problem with the radio (if it was a BCM or wiring issue, the actual radio function would probably work too, not just the clock).

A good shop might be able to fix it, but it will probably cost as much as a decent aftermarket unit. Thankfully, some aftermarket units look decent now and blend in relatively well with everything else in your dash.

If you go aftermarket, you may want to check out Crutchfield since they will include the mounting kit and wiring harness adapter (though you must still connect the aftermarket harness to the adapter, so keep that in mind). They aren't the cheapest, but if this is your first install, they have everything you need in one place with good documentation and support.

 

[Jimmy9190]

The clock is not supposed to stay lit up all the time. On a Delco radio you can press the volume knob in and the radio will display the clock for a few seconds, then it goes off again. GM calls this the Recall function. If you had the 13.5 millivolts on the yellow accessory wire with the radio still connected to the power/speaker harness in the dash, that could indicate an internal problem with the radio.

What does your meter say when you check the yellow wire for Amperage? When you unplug the radio, the yellow wire should have no voltage at all with the ignition off. If it does, there may be a problem with the accessory power circuit to the radio or a BCM problem. I am no expert with GM body control modules but I think that is the next test to do.

If you do buy a new radio, Crutchfield is very good. They have good prices, IIRC they include the dash mounting kit and wire harness connector for free if you spend over $125.00 or $150.00 on the new radio, they also provide free detailed installation instructions and their installation/technical support after the sale is said to be excellent. It is super easy to install a new radio in a 98 GM truck.

 

[1 FMF]

Originally Posted By: wolfehunter
NYEngineer,

With my 8 year old starting the truck it drew the volts down to 11.????? each time. There was one occasion it was 10.???? but the numbers flash by pretty quickly I couldn't get the tens or hundreds digits. It is a new battery so I'm guessing that is within normal operating volts?


yes, it is normal for battery voltage to drop significantly when a significant load is placed on it such as starting an engine.

and because of that, there is what's called a capacity load test which can generally be performed at any auto part store except those monkeys only know how to push a button and don't know exactly whats happening: on a fully charged battery it should be able to output half of it's CCA rating for 15 seconds and the battery voltage should stay above 9.7 volts at 80F (section 4.5 of batteryfaq.org)

 

[Donald]

HV has a 20amp or 30 amp auto circuit tester for pretty cheap where the "probes" are the size and shape of one of car fuses. So you pull out the fuse, push in this tester and it will tell you how many amps going through the fuse. You could get test leads and use it as a normal ammeter also I assume. Given that its 30 amp (there are two I saw) it would handle most everything in your car expect the starter.

I think the price was $10 and $15??