Solution to the battery failure issue

[SPL Tech]

With all these people having dead batteries, why doesent someone install a digital shunt inline with the ground cable on the 12v battery? You can get one on eBay for like $20. That way you can always know exactly if the 12v battery is being charged or depleted, and to what extent. No more guessing, you know exactly how much current is flowing in and out of the battery. Seems like a pretty basic troubleshooting step.

[SPL Tech]

Easy day:

http://www.ebay.com/itm/100V-100A-DC-Digital-Voltmeter-Ammeter-LED-Amp-Volt-Meter-w-Shunt-F-12v-24v-Car-/221273641721

[homestead]

With all these people having dead batteries, why doesent someone install a digital shunt inline with the ground cable on the 12v battery? You can get one on eBay for like $20. That way you can always know exactly if the 12v battery is being charged or depleted, and to what extent. No more guessing, you know exactly how much current is flowing in and out of the battery. Seems like a pretty basic troubleshooting step.

You can look at the battery voltage and tell if its charging,  what you really need is to know which branch is drawing excessive current.  That is very difficult especially if it is intermittant.

Edited December 24, 2014 by homestead

[SPL Tech]

You can look at the battery voltage and tell if its charging,  what you really need is to know which branch is drawing excessive current.  That is very difficult especially if it is intermittant.

Sure, but the advantage to an ammeter is you can detect if the intermittent problem is occurring or not by looking at the gauge. The voltmeter wont tell you that. So if you turn your car off and the gauge normally shows, say, 250mA draw, and one night it shows 2,000mA draw, you know the interment problem is occurring, and you can start pulling fuses to isolate the location of the draw.

[homestead]

Sure, but the advantage to an ammeter is you can detect if the intermittent problem is occurring or not by looking at the gauge. The voltmeter wont tell you that. So if you turn your car off and the gauge normally shows, say, 250mA draw, and one night it shows 2,000mA draw, you know the interment problem is occurring, and you can start pulling fuses to isolate the location of the draw.

Doesn't opening the car door wake up the car which will start some circuits drawing which will change your main circuit reading.

[SPL Tech]

Doesn't opening the car door wake up the car which will start some circuits drawing which will change your main circuit reading.

Sure, but those circuits typically go to sleep as soon as you press the lock and arm button on the key, or within a minute or so of doing so. In any case, it's not hard, just watch the readings until they drop to under 100mA and you will know the idle current draw. Most vehicles draw under 50mA when turned off. From what I am reading, people often experience a dead battery after driving home at night and trying to start the car in the morning. So we are talking fully charged to completely depleted in under 12 hours. The current draw would need to be at least 3000mA for that to happen, and more likely around 4000mA+. That is 80x what the car should draw when turned off.

Edited December 26, 2014 by SPL Tech

[drdiesel1]

Sure, but those circuits typically go to sleep as soon as you press the lock and arm button on the key, or within a minute or so of doing so. In any case, it's not hard, just watch the readings until they drop to under 100mA and you will know the idle current draw. Most vehicles draw under 50mA when turned off. From what I am reading, people often experience a dead battery after driving home at night and trying to start the car in the morning. So we are talking fully charged to completely depleted in under 12 hours. The current draw would need to be at least 3000mA for that to happen, and more likely around 4000mA+. That is 80x what the car should draw when turned off.

You are correct, but the car will not drop to sleep mode within that short period of time. Some vehicles can take up to 40 min.

Opening the door while the meter is setup could pop the internal fuse. I've seen this happen on more than one

occasion in the shop. If you want access to the car, flip the door latches to the closed position. This will act the

same as having the doors closed. Just don't pull on or touch the door handle because it will active the BCM.

 

I would also caution not to bring the key within range of the vehicle, as it will most likely active the BCM as soon

as it detects it's presents. You can not just unhook the battery and install the meter. You need a switch to open

the circuit off the ground cable and allow the meter to carry the load. If you open the circuit without the switch

and reconnect the meter, you're wasting your time. All the modules will sleep as soon as the cable is unhooked

and only a few modules will reactive when the meter is hooked up.

 

The switch keeps everything powered as normal and the meter maintains the circuit for memory feed when

with ground cable is disconnected from the system through the switch. It's not like the old days when you could just hook

up a test light after disconnecting the battery cable. The circuit must be maintained for proper test results when using

the parasitic amperage draw test on a computer controlled vehicle. You can use either positive or negative terminals.

It's exactly the same on either side. I made this drawing using the positive side. Just be very careful when working

on the positive side. It's best to use the negative side, but sometimes access is a problem.

 

Install the switch and close it. Run the vehicle around the block. Take the key out of the car and remove it from the area.

Flip the door latches and leave the doors open. Install the meter between the switch and set it up for amperage testing.

Open the switch and wait for it to time out and see what your reading is. It should be around 35M/A's or less.

Some vehicles will go as high as 50 M/A's.

 

Here's a drawing of the setup to put the meter inline without opening the circuit.

Click on it to enlarge the image.

Edited December 26, 2014 by drdiesel1

[SPL Tech]

Well, I was talking about installing a permanent shunt with a permanent reading in the cabin. The battery problem is intermittent, as it would be silly to connect a multimeter to your car every night to check up on it.

 

 

 

As far as the car not going to sleep if in close proximity to the key, what is close? I have the traditional key CMAX, not the push start. I was always under the understanding that the NFC communication in the key typically only has a range of about 1" or so, so it has to be in the keycylinder for the vehicle to recognize the key chip.

 

I ask because I sleep in my car on camping trips one and awhile, and I keep the key in the car with me. I just press lock on the doors inside and call it a day.

[drdiesel1]

As far as the car not going to sleep if in close proximity to the key, what is close? I have the traditional key CMAX, not the push start. I was always under the understanding that the NFC communication in the key typically only has a range of about 1" or so, so it has to be in the keycylinder for the vehicle to recognize the key chip.

 

I ask because I sleep in my car on camping trips one and awhile, and I keep the key in the car with me. I just press lock on the doors inside and call it a day.

If you don't have the electronic keyless system, there shouldn't be a problem with having the key near the car.

Just don't leave it in the ignition.