Hey Guys
My battery is still going dead in my 85 with a battery tender hooked up. Its a brand new battery and fully charged. After a long ride I hooked up the tender and after two weeks it went dead. Tha same thing would happen to the old battery. That's why I bought a new one and new tender. If there was a parasitic draw, wouldn't the tender compensate for that. Thank you for any help or suggestions

 

A person would think the Tender would more than compensate for "most" parasitic draws BUT I don't understand attempting to use it long term to compensate. Why not just address the real issue and be done with it? Perhaps you've maybe a basic "charging" problem and regardless of what you do with the tender the system isn't going to last long when relying on only the alternator.

I'd start with a complete evaluation of the "charging" system.

 

I would trace your pos battery cable some have reported wear where it goes by the steering column. I would disconnect the battery till I found it would be afaid of a fire.

 

I ended up going with a battery disconnect switch on mine on the negative post. If your drain is as bad as the one I had at over 2 amps then a 1 amp battery tender isn't going to handle that. Most tender chargers don't put out much power since anything over an amp or so would roast a battery charging all the time.

The battery disconnect was $10 or something from amazon. I just turn the **** on it when I'm not going to drive the car for awhile. Ended up putting them on several of my vehicles.

 

You should test for a parasitic drain. I'll bet that there is something "on" that is causing the battery drain. My '87 can sit for over a month and will start right up.

Have you checked for any interior lights that may be staying on? The two lights in the rear view mirror? Maybe a light in the glovebox or console? Maybe the underhood lights? It's also possible that some relay may be sticking and causing a drain.

You can do a Google search for something like "parasitic battery drain check" This video is somewhat long, but it does have some good details on how to find a voltage draw.

 

I appreciate all the responses.
Ordered a switch and in the nean time will look for the draw. Good video
Yhanks again

 

Many parasitic drains are caused by motors that should shut off but don't. Obvious candidates are: Electric seat, antenna and headlights.

 

Or lights that done turn off like interior, glove box, underhood etc.

 

2 amps is a ton. Enough to cause a fire depending on what and where the problem is.

 

I do not know if this is your problem but I recently left my key in the ignition with the car was parked in the garage. The car was not started for a few weeks. It was dead as a door nail. I have a '94 which has a chip on the key. It was the parasitic drain on my fairly new battery.

 

What is normal? Mine is doing the same thing (draining overnite). I think it's the crappy aftermarket stereo. 1.4 AMPS as is. 0.2 if I pull the stereo fuse (#40). If I pull the stereo fuse is starts just fine every morning. Time for a new stereo I guess.

So is 0.2 the correct draw?

 

Yep that's about normal around .2 and a tad over sometimes. 1.4 will kill a battery in a few days for sure.

 

50 Milliamps is normal but on the high side for any car. This is .050 on your voltmeter (that your using to measure amps).
250 Milliamp draw is .250 and will stop a starter from cranking over in a typical car in something less than 3 days. Radar detectors and phone chargers fall into this category.
Anything over the 250ish milliamp draw can basically leave you stranded overnight depending on battery condition.
I didn't watch the video but hopefully the guy covered the important things, one of which is you must parallel the battery cable that you disconnect with your meter leads before you disconnect it. You cannot just disconnect the battery, then reconnect your meter leads in between. The meter has to be connected in place before the battery is disconnected. Current cannot be interrupted. There are tools made for this exact task. In the event proper tools are not available, then disconnect the battery, connect a jumper wire between the cable and battery terminal. Then connect your test leads. Then remove the jumper wire. I realize this sounds silly. Its not. None of the various systems in the car can be counted on to "time out" properly when this is done wrong. Instead you find systems like the keyless entry constantly has a huge draw. The older cars don't suffer from this issue like the newer ones but even digital hvac controllers and any ac programmer will all draw too much current for too long of a time. Not less than five minutes is how long it takes for everything to time out and totally shut off. You have to wait that long unless your meter drops down into an acceptable range in less time, which it probably will.
Next is you can easily damage your meter by accidently doing any number of things. Turning the key on is pretty much a sure thing. At the minimum your going to blow the fuse in your meter. Opening a door to access a fuse panel or something might do it depending on the power locks. This is a hard mistake to stop repeating, and it sucks when your last meter fuse has popped.

Really high amp draws are usually stuck window switches, power seat switches and motors. Once in awhile the alternator can fail internally and draw. Most of the time its not that easy. Any aftermarket equipment is always suspect, especially aftermarket alarms. Anything that turns on automatically such as the glove box light, underhood lights, lights in the sun visor are all good places to look.

 

At 2 amps my car will sit for 2 days and still crank so a 1/4 of an amp isn't going to kill a battery that fast.

 

Geez, where on earth is all that current going ?? It seems like the blower motor or a cooling fan is stuck on. One things for sure, that's not just a courtesy light somewhere, and a 2 amp draw is not normal.

 

Was a 2.56 amp draw actually and no its not normal and will kill the battery. But it takes a bit.

Mine seemed to be several different things causing the problem and I haven't bothered to see if I actually ever found all of them. One was the power antenna. I removed the relay for that one. I don't remember what the other things were I found. There is a thread on here from back in January where I was hunting the cause.

 

Been thru this with two cars, one my Vette, with two different solutions.

A cutoff switch is one solution after three very good batteries were fried by a battery tender. I reason, the normal drain in that ML430 was enough to constantly trigger the tender, which cooked them.

For a solution, peace of mind and the ability to actually enjoy the Vette, I followed both videos in the thread "don't usually ask for help, but"; one of which is above. The 'big picture' inf o is current draw through a battery cable, while specific circuit drain issues are tested with the ammeter replacing each pulled fuse; doesn't take all that long.

BTW, my large aftermarket amp draws ZERO when off, but it is wired properly.

Further, Roy's fairly stock '84 draws 10 milliamps when asleep; mine draws 48, which is a tad high. The two Interstate batteries that failed (unsure of their quality anymore) are replaced by an AGM, which is more tolerant of 'sleep'. We'll see how it lasts, but the Bosch has a 5 year replacement and, like any AGM, has different charging requirements than a lead-acid type. The built-in NAPA maintainer maxes out around 14vdc; has been working fine, shutting down while keeping the AGM at 13.2vdc.

Battery disconnects are a bit inconvenient, with loss of radio presets. etc. and reset of the ECM.

I also urge you to take 45 minutes to find the drain.

 

This is a very important point for our complex C4'S! This was completely ignored in the video, which wasted way too much time destroying his starter ring gear !!(??)

There are "time out" features that will drive you crazy if you don't follow Amotoxracers procedure!

I have a nice aftermarket Panasonic stereo, and an aftermarket remote key fob entry system in my '84, but the rest of the electrical system is original. My courtesy lights even work properly! I was surprised to learn my residual battery drain is only 0.010A. (10 milliamps).

 

Its actually GMs procedure, and they only recommend using the proper tool, but I have been able to use a jumper wire with great success, whenever the proper tool is not available .