Unfortunately this is another parasitic drain post, however mine is very odd.

First some specs 87 convertible L98, new battery, new 140amp alternator.

Now the interesting stuff. After having my old alternator ruin my old battery, I had both replaced a week apart from one another for the items listed above. Since then I’ve also bought a battery charger/maintainer since the vehicle is driving about 1-2x a week depending. For the longest time I thought had a parasitic drain because when hooking the battery to the maintainer after driving it 2-3 hours then letting it sit for anywhere between 2-12 hours before hooking it up, the maintainer always said I had between 67-87% charge on the battery. I brought it to my locally trusted mechanic who is the only one outside of me I let under the hood, and even advanced auto for ***** and giggles to do a battery and alternator test, both passed at both locations with flying colors. I even disconnected the underhood lights, and did my own multimeter test of both battery and alternator and everything is good, did a parasitic drain test with multimeter and it read 0 across the board (so no drain). Yet I drove the car last night for 2 hours, let it sit for 14 hours, re did the multimeter test again all 0, battery read 12.4volts, hook it up to the maintainer and it said I’m at 70% battery. How is this possible? At this point I’m going nuts chasing a drain that according to the multimeter doesn’t exist yet the battery charger claims there has to be.

Sorry for the the essay but I’m hoping someone might be able to shed some light on this or just tell me I’m crazy.

 

zero drain? can't be zero. how are you measuring that? maybe the wrong range on the multimeter rounds to zero...

 

To test for drain I’m disconnecting the negative battery terminal, clamping the red wire of the multimeter to the negative battery wire and connecting the black lead of the multimeter to the negative post of the battery itself, then turning the multimeter to 200mA, and I know it should read at least something, but mine shows 0.00, no key inserted, doors closed all lights off

 

sounds like a blown fuse in the meter. Can you try some other low amperage circuit, like a watch battery and a led?

 

sometimes the meter probes need to be plugged into a different port, depends on the meter .

 

Unfortunately, doing it that way will blow the internal fuse in your multimeter, so it will read "zero", and your interior lights will NOT come on. Are you using a digital meter?

When you first connect your battery, there are several things that require a "time-out", before you can measure your true residual current drain. To allow these devices to "time out", follow this procedure:
1. Doors closed, under hood lights disconnected, ignition off, all fuses in place.
2. Disconnect a battery cable (either one).
3. Install a jumper wire between the battery post and the battery cable. Your interior lights should come on.
4. Without disturbing the jumper wire, connect your (repaired) multimeter to the battery post and to the battery cable. Multimeter set to 200 mA (unless you have an auto-ranging meter).
5. Wait for about a minute for the electronics to "time out" (go to sleep). Your interior lights should go off.
6. Without disturbing the meter leads, remove the jumper wire.
7. Your residual current drain should be less than 0.050 A (50 mA). If your current drain is more than 200 mA, reconnect the jumper wire before you move the meter selector to a higher range.

Please report back.

 

Hot rod Roy, I’ll try what you say when I can tonight or tomorrow when I get home, as for quick answers, it is a digital multimeter, and if the fuse in the multimeter was blown why can it still read the 12.4v for my battery when set to the “battery” setting? (I don’t know much about multimeters) but to me if the fuse in the multimeter was blown then it shouldn’t read anything on any of the selections, but as I said I still get an accurate read on the battery itself, just not when set to 200mA

 

The circuitry in your meter is different for amps and volts. Take a look inside your meter. Do you have the instructions for your meter?

Since you have a DMM (digital multi meter), it doesn't matter whether you connect the red lead to the battery post or to the cable during this test. The meter doesn't care. It will read either + or - current.

 

Was able to check multimeter on an led light, was able to get a reading, no blown fuse inside the meter as well, tried your method hot rod, and still read 0 across the board

 

what was the reading on the LED light? Volts or Amps?

Measuring amps means you put the meter in series, as part of the circuit. That is putting the meter at risk of damage if the current is too high.

If you put the meter across a car battery (from + terminal to - terminal, and try to measure amps, you blow the fuse,
If the meters doesn't have fuse protection for that feature, that meter function will be destroyed.

if you then switch to volts, it will still give your the voltage of the battery.

If you have a big current drain in your system, it's possible you killed the ammeter function the first time you tried to measure the current drain..

 

Please post a picture of your DMM set to 200 mA with the leads installed in the positions you used for your tests.

 

Alright hot rod as requested, here’s how I’m doing it, I also noticed for the first time today that my negative terminal screw has a little rust around the edges and some of threading. I included a close up for the multimeter as well, you’ll see it’s -00.0 the - flashes from time to time but always 00.0

The black lead when I was doing it in hopes of getting a reading to start pulling fuses, was set up just like this but with a small wood shim to hold it in place

 

If I'm following this right you have 0.0 mA drain but your battery tender says otherwise. It's hard to believe that you have no drain at all.

Whose to say whether the tender is working properly.

 

It appears that you have your meter hooked up correctly! The Meter I have has two fuses in it, the only way to test them is to move the leads and turn on specific settings. I can test them without opening the meter or damaging anything. The voltage measuring capability is still there even with a blown current measuring fuse/s. You need to read up on your meter to be sure that you are not dealing with blown fuses.

I would like to add a couple points on this post. No battery charger or tender or floating device can accurately tell you the battery's State Of Charge (SOC). Most of them take an open circuit voltage and "guess" from that. It would vary from battery to battery based on the technology used in the making of the battery.

If you had it tested twice and it came out okay both times then I would be happy with that. Do not expect the battery tender to be accurate.

If you indeed had a real self discharge issue with your Corvette it would be fairly obvious when using a meter in the amp mode like you did. Use a battery charger that is big enough amperage wise to make the electrolyte bubble (gassing) and charge the battery completely on one of these units while the battery is disconnected from your Corvette. Check the electrolyte before and after the charging. I have a four stage charger that uses constant current and constant voltage and it will completely charge an automotive battery in a matter of hours.

Since your testing did not reveal any discharging lets try another test. After the battery is topped off record the open circuit voltage and then connect battery back to the Corvette. Every day at the same time try to record the open circuit voltage and graph how it drops. I do the test without a car load but that is just measuring a batteries Self discharge rate.

Now the big question is what kind of battery are you using now? Is it a standard flooded lead acid battery or something special like Absorbed Glass Mat? The different technologies used in Batteries makes them all act differently. If you use an AGM battery you will get less self discharge than from a FLA battery. A big majority of automotive batteries use antimony in them and the more they use the more water it will drink. Selenium is a better material for batteries but is more costly and therefore not used as much. Your standard old Antimony based FLA battery will self discharge at up to 1.5 % (of the capacity) per month. This can get worse when it is hotter outdoors and as it ages.

To monitor your battery for power going in and power going out you would need a current shunt to do it accurately. Harbor Freight has a device that plugs into a fuse spot and will tell you if there is any current flowing either way. It is about $15 and worth its weight in gold when you are tracking down a power loss. Here is the link to Harbor Freight: https://www.harborfreight.com/30-amp...ter-67724.html

What made your last alternator kill the battery? What happened?

Also whenever working on a live battery in a car disconnect the ground cable first. When you have a live cable laying around accidents can happen. I keep a fire extinguisher near me when I am working on one of my Corvettes. I am also a nut about maintaining my batteries. I remove them at the end of the season clean them up and top off the electrolyte with distilled water and then I charge it completely. Before re-installation I clean the terminals and the clamps so I have a good solid connection and again charge the battery and after verifying the electrolyte level I will re-install the battery. Batteries suffer from cracks or damage to their cases and you need to watch for Plate growth that can crack the case all by itself.

If you need anything specific regarding batteries please feel free to contact me. I spent many years studying, testing and learning about batteries. The only thing I will not have is a battery powered car..... especially with 10,000 little cells in the frame. In my ISO 9000 training I was taught that the higher the parts count, the less reliable the product will be.

I hope that you are satisfied with your Corvette and it's charging systems. May the battery you just bought last longer than the previous one! Whenever you buy a new battery for your Corvette be sure to charge it completely before installing it for the first time. One never knows how long that battery was sitting on the shelf. To get a longer life from your battery you want to keep it as full as possible all the time, If using a battery tender or charger be sure that it shuts off the current at a specified point or it will boil your new battery dry. I have my batteries on a rack where I charge them once a week during the winter months. The charger I use is big enough to make the electrolyte start to gas, I want to see bubbling action to De-stratify the electrolyte. Little 1 amp and less chargers have a bad habit of stratifying the electrolyte as it doesn't get mixed during the charging process.

Best regards,
Chris

 

Chris and hot rod and everyone else that commented and helped, thank you all very much, it is a standard Lead acid battery from advanced, their gold one. My dad has been helping me as well over the phone and he came to the same conclusion that it must just be a weird read from the battery tender, with that being said I’m just going to say it’s a perfectly fine battery with no abnormal drain and be happy til it leaves me needing a jump (hopefully no time soon) again thank you all and safe/happy driving

 

To solve this mystery, let's try a simple test. Using any 12 v. light bulb you have, what is the current thru the light bulb when connected to your battery and your DMM? If the bulb lights up when you connect it to the battery, but doesn't light up when you connect your DMM in series with the bulb, you have a problem with your DMM. (Do not use an LED for this test.)

 

I think that might be measuring AC current... almost looks like rms in the range indication switch , but too fuzzy to tell.