Is there anything that could draw down a battery in a day WHILE A BATTERY TENDER is on it?

 

...maybe the battery itself is defective? While I've never experienced it, I have heard of one defective BATTERY TENDER (by DELTRAN).
You might send a PM to member Bill Curlee, he's the site electrical guru. I suppose it might be possible to have some electrical gremlin that is pulling more power than a BATTERY TENDER (by DELTRAN) @ .75 amp or 1.25 amp can keep up with.
Do you actually have a BATTERY TENDER (by DELTRAN) or are you using that term generically? They have a great warranty if it turns out that is the problem.

 

I've been running a Battery Tender Plus. Battery still croaked while on it....Yellow Top bought in January.

 

I use only red top OPTIMA batteries and have never had one of those fail with the BATTERY TENDER PLUS on them for prolonged storage. I keep the car locked so the alarm and all electronics are being supported by the battery and the charger. It's certainly possible that your yellow top has failed.
You should have no problem with getting a replacement from the January purchase.

 

I had Autozone charge it and test it yesterday. They said it was fine. I popped it back in. The vette (still turned off) said it was at 11.8v. Popped the Battery Tender Plus back on....It was charging all night and was still charging this morning (red light on), which seems strange, because the green starts flashing when its at 80%. I will check again when I go home.

 

You might contact DELTRAN and get their input...

 

i don't understand why zone said it was fine with only 11.8 volts across the terminals. you should have at least 12v and probably more. as far as can it drain with a battery tender on it, absolutely. tenders usually have .5 to .75 amps to charge the battery. if your draw is more than that, the rest will come from the battery itself. i put a meter on mine, (disconnect neg terminal and connect black to the loose lead and red to the neg terminal of the battery - make sure your amp sitting is 10 amp initially) and the draw was 75 - 80 milliamps which is higher than the 35 milliamp norm but the difference was not enough to draw the battery down in a few days which was what was happening. i charged the battery to fully charged and let it set for a few days and the volts dropped from11.8 to 11.5 while disconnected and did not have enough juice to start the car. i went to zone for a new one and problem solved. i found out that red tops (what i had) do not survive discharges well. i had a battery tender on it but somehow it came unplugged from the a/c and the battery was powering the red light and drawing it down while i was gone for a couple of weeks. red top no good after that!
check your current draw (after the car goes to sleep - about 10-15 min) and it should be under 100 milliamps at least and closer to 35(i read bill curlee too!). you can go from there but it sure sounds like battery or battery connection to me at this point.

 

I am on my 3rd red top optima in the last 5 months! First two had bad cells. Not sure why. Had autozone test them and they replaced them both. Just had them give me another new one yesterday! Hopefully this one will be better! I heard optimas were supposed to be pretty good but im begging to think i got a bad batch! 2 bad so far!

 

I too have had issues recently. I have a 98 C5 automatic, 48,000 mile calif. car. When I bought the car- the gm battery was about 4 years old and it died. I replaced it w/Optima Red Top- and after a couple of days I have a very hard time starting the car.

Bought a Battery tender Jr- hooked it up, got the green light the car started right away- went on a week long business trip and w/out the battery tender on, the battery went low, while I was on the trip?

Charged it up again w/ the battery tender, the light was green, but this time the car was hard to crank over initially, then it starts. Drove it 5 miles to the store and came out about a half hour latter and the car was difficult to start again. Funny part- on my way TO the store, I reset the clock to 3:45 pm. When I went into the store and came out, the clock read 1:00 PM.?? Thus, I am thinking a loss of power somewhere? Battery Voltage was 14.2 after it started.

I am going to check the battery and replace as a first option. Then get the Alternator checked, the go through all of the electrical grounds and clean them up just in case.

Kind of afraid to take it on a long drive at the moment.

First Corvette owned!

Chris

 

Send a PM to member Bill Curlee...he is the site electrical guru. I'll bet he can narrow it down for you and save you time/trouble/money. It could be a grounding issue, which Corvettes are apparently notorious for...

 

Hi, Yes a draw higher than the tender is putting out will cause a battery to discharge over time. You may have a high draw somewhere, or the tender may not be working properly, or your yellow top may be defective. I'm tending to think the latter is the case, because a fully charged 12 volt battery should read at least 13 volts or more across the terminals. You are saying that it read 11.8, was that on the dic, because using an external volt meter usually reads higher than the dic. And also, the yellow top takes more amps to fully charge than a red top because of it's deep cycle nature, and there are some battery maintainers that will never charge a yellow top or any deep cycle battery past a 90% charge. One easy way to find out if it is the battery for sure is to put in another battery if you have one and if it stays charged, you know it is not the car or charger.
Good Luck