Technical Battery Tender- Correct Operation

About a month ago, I started a thread about Battery Maintainers. A lot of guys recommended the Battery Tender Plus, so about $50 later I had one hooked up to a battery courtesy of Amazon. They get good reviews. Having never had a battery maintainer of any kind before, I am not sure what is going on. It is supposed to flash green when the battery is 80% charged and go green at full charge. I guess that is the maintainer mode. I have read the manual end to end, well, the English side anyway. The battery reads 12.7 volts before attaching the tender. I have a battery on the tender right now. The red light is lit solid. It's been on there several hours. I'm not very electrically inclined, but I would think that 12.7 volts is more than 80% charged and the red light should at least be flashing, if not solid green. The troubleshooting section of the manual says if the red light stays on, the battery is defective or has an excessive draw and to remove it from the vehicle for charging. I'm sure neither one is applicable in this situation. I have tried it on 2 fully charged batteries in 2 different cars with the same result. Just doesn't seem right to me, and I sure as hell don't want to burn up a $$$ battery by leaving it on with that red light lit.
So, am I the lucky one that gets the defective Battery Tender Plus, or is this kinda normal with how they work or not? If it is screwed up I can return it to amazon. It's just a PIA.
What do you BTP owners think?
Thanks

 

Mine usually takes a couple of days to go to solid green.

 

mine does not have a light at all. I don't have a "battery tender" if that is a brand name. it is not overcharging the battery and has been on my car for a few months now.

 

Mine take a while to go from red to flashing green then to solid green.

 

I don't use battery tenders and AGM batteries but I use on my OT 442 with a conventional battery. Red typically indicates an error. Flashing green is charging, steady green is monitoring, it will start flashing green again when the battery is charging.

You started 2 threads on the subject, it sounds like you have a battery issue. Maybe it is time to check it out.
Or you have a draw (load). Which may be why you started the threads and bought that tender.

 

i have one of those,sometimes the red light comes on,i usually unplug it and try it again,i always have it hooked to the battery before i plug it in? mine has 3 lights a red green and a yellow ,it goes yellow when i put it on,when its charged it goes to green.It is slow to charge,i only have it because it will do a 6 volt battery,my car is positive ground,i unhook the battery and hook it up as normal,seems to be working. Harvey

 

I'm beginning to think the issue may be inherent with some of the full electronic chargers/tenders.
I've got a 15 amp HF charger that works great if you have somewhat of a charge in the battery but flashes the "defective battery" sign if there isn't enough charge in the battery to properly trigger the sensors in the charger from what I figure.

 

I use one on the 25yr old battery in my riding lawn mower. Without it, battery's dead and I don't mow. It stays red all the time. On the battery, off the battery, it's always red. Leave it hooked up 24/7/365. Only time it's unhooked is when I'm mowing. Think I paid 6 bucks for it about ten years ago at Harbor Freight.

 

I have a half dozen Battery Tenders (the trade name one). They have been functioning without issues for at least 15 years. They all show "red" immediately upon hooking up, but turn to flashing green , within an hour or so.....for a short time. Then turn solid green for the duration. Have one on my hot rods, "high end" Mercedes SL, and my tractor......never an issue.

 

Just leave it on, it'll eventually swap over to green, I have 2, one for car battery and one for the motorcycle, they both stay red for awhile before going green.

 

Yeah , it could be showing solid green and if you unplug it and plug it right back in , it will be red for a while.

 

YES...could be a bad charger.
Had one myself, years ago.

Use a multimeter to check the actual battery voltage. Connect and leave the charger on for about three hours. Check the voltage with the tender in place at the beginning of the charge. Check again, before disconnecting the charger. Remove the charger, check the voltage. SOMETHING...should have happened after three hours..!

If nothing, return the charger.

Mike

 

Same here, had lots of them at work maintaining 4 battery truck systems. They worked great.

 

They are excellent for maintaining a serviceable battery, though they aren't a good choice for re-charging a deeply discharged battery.

12.7 is a good number, assuming this is a true OCV and not a surface charge measurement. It does sound a bit like you've a dud charger on your hands. On a well charged battery the BT Plus I have will switch over from solid red to blinking green in about 30 seconds.

I had one fail, can't remember what happened, I think it "got dropped". Anyway, their return policy as I recall was not the best ("really shitty") and seemed a wash after paying shipping both directions and I pitched it. Its replacement has done fine. If you can get a replacement without any drama on your part that's a good deal.

 

Have one on my dads car, he only gets out every few weeks. Starts out red for a while then flashing green and then solid green after a few hours. 5 yrs no problems, or me having to go there and jump it.

Is the battery still connected to the vehicle? I would suspect a wonky battery if it's not connected to a vehicle. The 12.7 could be a surface charge. Try leaving the headlights on for a few minutes and then connect the charger, OOPS I mean maintainer.

 

I have two of them, a 12v and a 6v. Battery Tender Junior brand. The 12 volt works exactly as we are led to believe they should. On the 6v one, sometimes I might come back the next day and light is still red when I would expect it to be green. I've learned to disconnect it momentarily, reconnect and it quickly goes to blinking green and then solid green. I don't leave these hooked up, just use as needed and have been happy with them for several years. Don't know what that one is doing while light stays red, but everything seems okay.

 

Neighbor left his connected to his Harley while trying to start it. That didn't work out quite the way he had hoped it would and it killed the tender. Sounds like it just needs some time. I have put them on a battery and come back a day or two later and they were green.