Hey Fellas, I haven't been around for a while (family issues)
I have a problem:
I haven't been driving my car much this year so I've been keeping it on a battery tender jr. I've been doing this for years, mostly in the winder. When I'm ready to drive I disconnect the tender and the car starts right up.
Today I disconnected the tender and the car was completely dead, would not turn over at all.
The Tender indicated a full charge.
Any thoughts?

 

How old is the battery? I'm wondering if the capacity just isn't there anymore on the battery, so it'll show as charged, but just not have enough cold cranking amps to turn over the starter.

If it is going to sit for a while, I take the battery out of the car and keep it indoors on the tender. Batteries seem to do better without temperature fluctuations.

On my old Nissan Frontier, I had a parasitic drain somewhere that couldn't be located. I'd go through a new battery every year or two. However, it was always replaced under warranty, so I wasn't too concerned about figuring out what was causing it. I wonder if you might have a drain somewhere?

 

How is the tender connected? 12V port or hardwired to the battery? If hardwired, doublecheck the connection to ground but I agree with Schizo that it sounds as though the battery is unable to hold charge.

I recently purchased a CTEK MXS 5.0 that I've hardwired to one of my cars.

 

I'm going to start with the battery.
What threw me was the tender indicated full charge but the car was completely dead....radio, dash lights....everything. The tender is connected directly to the battery.
Now, what's concerning - I reconnected the tender, let it charge for a while. I then tried to start it again. I got the dash lights and some clicking when trying to start it. Then I heard a pop noise. Can't be good.

 

keep it in the day
battery tender indicates full charge but won't turn over - S2KI Honda S2000 Forums

 

The advice Crazy and Mark is spot on in my opinion. I'm using both BT and CTEK. CTEK is my preferred.
As a rule my batteries are replaced after 7 years. Kind of like buying insurance.
Good luck with your situation.

 

The battery in Aashish's car was 11 years old (2013). Although on a tender all last winter, I was unable to start the car in the spring. But the car was still reading about 12 volts by voltmeter. Electrolytes in the battery had gone close to dry. Filled with H2O and the battery did charge up. Drove all summer, but battery seemed weak. Then a week ago, left the door open for 10 minutes and the car wouldn't start. 12.4 volts. Then tried to start again, Got dash lights and some clicking. 11.6 volts. Bought a new battery and it fires up nicely. It seems like a fresh battery reads about 13.4 volts.

 

quick update:
New battery from West Herr Honda (Lockport, NY). $132 after 15% discount.
Started right up, no issues.
I guess what through me for a loop was my battery tender indicated "full charge" and the car was completely dead (no dash lights, no radio.....)
Anyway. Thanks for the help guys!

 

12v just off the battery charger is another term for dead battery.

-- Chuck