Tender Junior charges at .75A and the larger one I think charges at twice that. I got the junior version yesterday and put it on my Stingray and it's been charging for 24 hours now, non-stop. It never has given the green signal to indicate a full charge.

On the Sears trickle charger that I just replaced (it only lasted two yrs), it was a 2A charge but would easily top the battery off overnight. Now, I know that there is a big diff. between 3/4 of an amp and a 2A charge ... but I'm thinking that 24 hours should be enough to top off an Optima battery that was new this Summer.

Three days ago, I fired the engine & ran at a high idle until it reached normal operating temp (Still raining so it has not been driven in a month). But my garage has been dropping down to the thirties at night so I wanted the Battery Tender to keep the battery up for another couple of weeks until clear sky came along.

Shouldn't it have achieved full charge after 24 hours on this device? The vehicle has no battery drain or parasites other than the alarm system which is off, when in my garage. But the red LED is lit to show the alarm status.

Could that alarm system be consuming the .75A that this charger is putting out? Do I need to get a more powerful charger?

 

I literally just ordered a battery tender plus on line right before I saw your post and thought to myself-oh no! I went with the plus for my 2010 Z06 since I figured that there is more drain on the C6 than the C3's with no computer. I hope that I made the right decision.

As for the 78 and my 94 Mustang GT I use a quick disconnect on the negative terminal of the batteries (real cheap) and always just turn the green **** after I have driven the cars to prevent any battery drain. I have been doing this for many years and both batteries are Kirkland batteries (Costco batteries installed in 1998!!!!) and both batteries are still in great shape-started all 3 cars yesterday. The 78 and the 94 always seem to crank stronger than the Z06! If I was you, I would get a battery disconnect and call it a day. All of my cars sit most of the time and I am much more concerned about the Z06 than the other 2 with the battery disconnects which have never not started the cars in 12 years! I live in New England where it gets very cold!

 

I just checked my BT Jr. I put it on last night about 7 PM and I had not run the car in 3 weeks. The battery I have is not the best and it would lose some charge in 3 weeks for sure. I just checked and it is flashing a green light after 12 hour of being charged. So it is not full but at 80% or better.

Steady green now.100% charged

 

I believe there is a way to check the tender by plugging it in, and with the ends not connected to a battery the light should be green. I have a tender that checks itself this way, but it isn't the battery tender brand. Maybe the unit is bad. Cheers.

TommyJ

 

CHeck the specs of your charger & make sure it's good for AGM batteries.
Optimas will take everything your charger will throw at them. I had a BT brand charger hooked to a NAPA AGM battery for +4 months. I never got a green light. Battery tested fine when I returned the car to the customer

 

sd, paul put an ammeter in series with your disconnected battery cable and determine just what your parasitic draw is.i had the sears 2 amp charger connected to my car and removed it because it would never indicate a full charge was achieved.i now use my old 6 amp sears charger with current indicating meter.it will charge my 6 year old interstate battery to full charge in less than a half hour.the meter will drop to below 1 amp charge rate.with this i know my battery is fully charged while with the trickle charger i never knew.i found that my draw was from the msd ignition box but that it was less than 1/2 an amp.good luck.

 

Paul, My car sits in a cold garage in Buffalo with a 3 yr. old interstate battery, and it starts in winter after sitting in my garage without charging after a month! Your new Optima should last at least that long in San D.
By the way, us hardy Buffalo guys call 32 degrees summer!!

 

Thanks everyone for the replies. Tommy, re: your above post - no, the way this tells you it's not connected is by blinking the red light. When you connect to a battery, the light goes solid red. After 80% charge, it will blink green then go eventually to full green.

This is on a tender junior, that looks like a wall wart with long wires.

 

Actually it has done that many times. But it won't last a month when the garage is that cold.

 

I have two Battery Tender Jrs. one for each of my Corvettes. I now keep them hooked up 24/7 on both cars. Before that, if I hooked one up to the ZO6 that had been sitting for about 14 days, it would take up to 48 hours to reach the fully charged state. (C6s are known to have a relatively high current drain when parked.)

I had a similar situation with the '69; if I left it off for a month or so, it would take days to reach full charge. When I hook either of them after a drive, the green light comes on in a very short time.

The maintainers are meant to be on all the time. With a charge rate of only .75 amp, a badly discharged battery will take a long time to reach full charge with a Tender Jr., so while yours might be bad, it may not be.


Pete

 

Thanks Pete eventually the three batteries did indeed come up. It makes me think that Sears 2A unit that I just tossed was not charging them well for a long time. Two of the 12V batteries I need to keep recharging run camera equipment and dew control for my telescope gear (I am an avid Astro Photographer when not working on the C3).

Those are small Gel Batteries that can fit in the palm of your hand. I am surprised they too, took 36 hours to charge just like the one in the Corvette. But they all did eventually come to show green on the charger ... so I am going to take the leap of faith and keep the Tender Junior.

Heck, if worse comes to worse and I need those smaller batteries charged faster than this little unit is capeable of, I can always just buy the larger unit. I'll only be out 35 bux and I guess that's tolerable. I could keep this one on the old hot rod, and the bigger one with my Astro Gear if I have to.