Vehicle is a 2012 Grand Caravan 111K miles, 1 year old Advanced Auto Platinum battery, 2 year old reman Autozone alternator. I bought this battery because the prior battery was drained due to the TIPM's fuel pump relay being stuck on + maybe more, & a new TIPM was installed about a year ago. I don't hear the pump running.

DROP TEST RAEDINGS:
ALTERNATOR POSITIVE TO BATTERY POSITIVE, 55.5 volts.
ALTERNATOR CASE TO BATTERY NEGATIVE, 26.00 volts.

I did this test because my van failed to turn the starter thursday (battery read 11.5 volts), so I jumped the battery and the vehicle started. Charging reads 14.6 volts. With both test leads at positive & negative, then cranking the engine, the volts will drop to 9.3. I then took the van to Advanced Auto for a battery Warranty but they did a test and told me I had a drain (I'm suspecting they didn't want to warranty a battery due to some comments he made while doing the test) At first, when he had the parasitic draw clamp on, he got all excited about the readings because my aftermarket blend door that causes the van to run a short calibration test was throwing 1.8 amps for 7-10 seconds, then things settled to what Advanced Auto's printout calls ".57A PASS". That looks like 570 milliamps (or, realistically 57 milliamps if the printout says I pass?) which wouldn't be a pass, but when he was measuring my van, he told me, "Usually people's cars are two's or three's, your's is right there at just about too much." So, I guess I'm a 5, or almost a six, but this van gets driven every day, and the battery is only a year old. I'm picky with the electricity and educate family who drive the van.
WOULD A BAD BATTERY, OR LOW BATTERY CAUSE THE DROP TEST READINGS I RECEIVED? I verified the results with a second multimeter.

 

To answer your question directly, no, a bad battery will not cause voltage drops on any part of the electrical system except for the battery itself.

That said, your results are confusing because I don’t see how a 12 volt system can drop 26 or 55 volts - at peak usage (engine running with AC and every single accessory and light on), the alternator might put out 18 volts, but even that would only be temporary.

Voltage drop on the alternator to battery positive cable shouldn’t exceed 0.3 volts.
The alternator case to battery negative is better checked with continuity (ohms) rather than volts.

What type of meter (analog or digital) did you use and what setting(s)?

 

GumbyRT,
That's a great point about the 26 & 55 volt reading in a 12 volt system, and one which should be pretty obvious to me as I took the readings, but I don't know much about electricity and am fumbling through this with YT videos and this message board. I have a brand new battery that I will put in and repeat the test and report back. I used an analog meter, $40 Inova from AZ, set to 12V.
Last night I checked and found power at fuses, while the vehicle should be sleeping, and recorded the volts. I will try to see what the current draw is equal too somehow.
But, these were the findings:
J2 3.7V Power lift gate mod
J3 7.2V RR door mod, diesel pcm/T-tow
J4 6.6V Driver's door node
J5 6.5V Pass door node
J11 ?V Thatcham lock sawy bar/psdm T-case mod
J18 .90V PC Trans range
J19 6.0V Radiator fan
I had the TIPM replaced last year on this 2012 GC SXT w/ 111K miles. I'm wondering if I need a new TIPM again, or if wiring is bad somewhere.
I've heard of people trying a hard reset where they connect the pos & neg batt cables & disconnect the TIPM for a while, then reconnect everything and some have had success. I'm not sure what to do next.

 

Here’s a couple of diagrams that should help you with the testing set up. I’ll try to explain this briefly but completely.




Think of electricity like water running through a pipe - voltage is the water pressure, current is the amount of water moving through the pipe, and resistance is anything that restricts the flow of the water, such as reducing the size of the pipe or a clog.

To keep it easy let’s say the battery voltage is 12 volts, and I’m only explaining series circuit diagnosis - if we have to get into parallel circuit diagnosis later we can.

Voltage drop is a measurement of how much power is used by a load/circuit. IN THEORY, the wiring and connections shouldn’t be using anything, but since every part of a circuit has resistance, it takes at least some voltage to overcome it. Ideally, 12 volts leaves the battery and all but a couple tenths of it is used by the load.

The load can be anything - a headlight, a fan, a module, etc - anything that requires voltage to operate; but the process for checking voltage drop is the same no matter what the load is, so you can check voltage drop on a wire the same as you can a load. What’s important is making sure the meter is set correctly and the leads are in the right place - as shown in the diagram, it should be set to read 12v DC with the red lead on the positive side of the circuit and the black lead on the negative side of the circuit.

As for checking current/parasitic draw, that needs to be done with the amperage setting - many meters will have an amp and also a miilli-amp setting as well as a separate plug on the meter for the positive lead when measuring amps. Make sure to use the regular amp setting and that the meter is connected in series with the negative battery cable. I didn’t draw the diagram this way, but it’s easiest to just disconnect the negative battery cable and connect the meter between the cable and battery.

Once the meter is connected, turn the ignition to on/run but don’t start it, then shut it off. Allow a minimum of 45 minutes for the modules to power down before checking for parasitic drain - generally speaking, anything less than 25 milliamps is considered normal. If you see more than 25 mA after 45 minutes, give it another hour and check again. 45 minutes is usually enough time but some vehicles take longer than that so you want to make sure you actually have a drain by giving it the extra hour.

If a drain is present, remove fuses from the TIPM that have power to them with the key off. If a fuse does not affect the drain, leave it out until you’re done pulling fuses or it could cause a spike current flow and you’ll have to wait for it to power down again.

There’s a lot to cover on this topic but hopefully this gives you a good starting point.

Good luck.

 

With a new, fresh battery in the van the voltage drop test now reads 20.0v on the positive side, and 10.0v on the negative side, and 12.6v from battery positive to alternator ground. Battery voltage was 12.62v.
The 20.0v reading is taken from battery positive to alternator b post.
Two different multimeters were used to verify results.

 

Are you able to post a picture of your meter with at least one of these readings on it? Try to capture the graph and settings if you can.

I’m really curious to see this.

 

Here it is with the new battery installed, and the parasitic draw findings were .5Amps for 9 minutes, then .220Amps for two minutes, then .008 amps continually. This van sees at least ten one mile, or less trips per day, sometimes more. The one year old battery reads 12.5 volts, but won't start the van, but the new one reading 12.6 volts will easily. I assume the one year old battery has almost no amps left?
New battery drop tests showed 12.59V from batt + to alternator ground, and battery read 12.6V. Batt + to alternator + = 19.99V. This is better than the 50+V earlier! Batt neg to alternator ground = 10.0V
Drop test from battery post to battery cables just a few inches away (w/ engine running) showed about 10.0V on both sides, pos & neg. I don't know if this portion was done correctly. You can see the ends of the copper strands of the wire bundle that doesn't make it's way under the shrink tubing, so it was gently probed while contacting either's same side corresponding post to get a reading, and those were about ten volts. Could my wiring be fried already? My rad fan doesn't seem to kick on nearly as much as it used to, it still does though from time to time. Could my alternator be damaged? TIPM is a dealer installed rebuilt unit from a year ago.

Here it is in new packaging.

 

With that much stop and go, you can easily go through a battery in a year. I recommend leaving it running as much as possible, and if you have to shut it off, let it idle for at least 15 minutes to give the alternator a chance to recharge the battery.

0.008 = 8 milliamps which is nothing to worry about.

I’m having a lot of difficulty figuring out how you’re getting the readings that you are with the voltage drops. Either the meter you have isn’t designed for the tests you’re doing or you’re not setting up the meter and test correctly. So, here’s a couple of other ways to test the alternator to B+ cable.

1) With the engine off, ground the black lead to battery negative and confirm a good connection by checking the battery voltage - make a note of your reading (you said 12.6 in your post so let’s say that’s what it is). Then check voltage at the alternator - it should be the same but let’s say you get 12.2 volts. If that’s the case, then 12.6 - 12.2 = 0.4 volts dropped on the alternator to battery cable.

Perform the same test with the engine running, only this time check voltage at the alternator first.

2) Remove the cable ends from the battery and alternator (you don’t need to remove the cable itself - just unhook the ends). Set your meter to ohms and touch the leads to each end. What do you get? Shouldn’t exceed 0.3 ohms.

 

I'm embarrassed to say this, but I was showing an acquaintance my multimeter and he noticed even when it's set on 12V, it will read mV with the decimal to the right and display the tiny "mV" symbol in the upper right corner. I think it was reading millivolts regarding the 55V & 20+V mentioned earlier. Frustrating. Dropped the van off at the dealership today where it belongs.
GumbyRT, your responses are very helpful and I highly appreciate your time in helping to answer any questions and resolve any issues.
I'll keep the thread posted about the results from the dealership.

 

Don’t feel too bad about it - we all make mistakes, and at least you figured out what was going on.

I took a closer look at the pic of your meter (again) and I didn’t catch it the first time, but I think the setting just to the right of the off position is what you need to be using. Experiment with it when you get your van back and see what happens.