I kept the keys in my 355's ignition for about ten days with my battery tender connected as usual in the engine bay and now battery flat. When i disconnected and reconnected the tender there are a load of relay switch clicks happening, the hazard lights are trying to flash and the door locks keep trying to open and lock. What to do? I want the tender to charge up the battery but concerned about all the above happening!
Wow. My battery died a couple winters ago and it never acted like that on recharge. Maybe try an exorcism?
+1 great suggestion. Many electrical gremlins and adjustments can be solved by turning the "power" off switch on the car.
I would check the electrolyte level before continuing a charge. I know most batteries are maintenance free and no one thinks of that any more but they really aren't maintence free unless they are a dry cell.
If the battery is more than two years old, replace it with an AGM battery. Don't waste you time if the battery is more than two years old.
The battery is simply dead flat. This exact scenario has happened to me a few times when I've accidentally let the battery go dead. I have separate GPS/GSM tracker, alarm and immobiliser that have a relatively high quiescent drain between them, if I leave the car two weeks without driving or putting the tender on it will do exactly what you have described with all the clicking and flashing of lights etc. The best thing to do is simply charge the battery at least overnight with a proper full-size car battery charger. There will be no repurcussions, everything will work fine once the battery is fully charged. I have never successfully recovered the situation with the battery tender alone because on my car (due to the security accessories) the quiescent drain alone is like 50% of the tender's max output. I worked out once that it would take 5 months to fully charge the battery from empty to full on the tender alone.
Above post is correct. You can not revive a dead battery on a tender. (Most of the times) One good thing to check is if the cells are still "alive" meaning that they are flat and have no deformation on their surface. You can inspect it through the electrolyte slot on the top. But if the battery is maintenace free, this does not apply.
FYI. I killed mine by leaving the obd reader plugged in as well. I always drop the key on the floor so not sure if that causes a drain.
I agree w. others - AGM is the answer, but the question that I never even thought about is the key in the ignition causing battery drain.
I don't know about the 355, but my 348 has actually 4 positions for the key. 1: when you put in the key. Nothing happens. 2: When you turn the key about 5-10 mm, the ABS bulb lights up and then goes out. 3: All bulbs light up. 4: You crank the engine. In position 2, you will flat the battery as nothing indicates that you are sending power to the ABS unit. More power than a small charger will supply. Don't ask me how I know.... Bertil
Not surprising, battery tenders are not meant to be able to charge a dead battery. A "real" battery charger may have worked better.
