Answer
There could be two causes to this problem. One might be that your negative post is loose inside the battery and the second reason could be that your negative cable is loose. If the post is loose there is no way to tighten it. You will have to change your battery. It sounds to me as though either the negative battery connection is bad (take it off clean it & smear with petroleum jelly/vaseline before replacing)
Their pooping.
Recharging a car battery should normally only be done if the care has been sitting for a long time. If this a common issue, the battery or the alternator is probably defective. The best way to test this is at a local car parts shop. They can tell if the problem is the battery or the alternator. In order to jump start a vehicle, you will either need jumper cables or a jump start pack. Simply connect the positive (red) to the positive of both cars batteries. Then connect the negative(black) to the negative of the dead battery vehicle. Then connect the other black, negative end to the engine block hook of or negative battery location of the powered car. Start the dead vehicle and let run. If nothing happens, then shake the jumpers in order to insure a solid connection.
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Connect them in series. With the 2 batteries sitting side by side just connect the negative terminal (-) on battery # 1 to the positive terminal (+) of battery # 2. Now connect the red hot cable to the positive terminal of battery # 1. Then connect the negative black cable to battery #2. You will have 12 volts but the amperage of only 1 battery.
It does not matter what the battery is sitting on. Concrete, wood, brick, dirt, etc. Makes no difference at all. It is not true that sitting a battery on concrete will drain it. Where does the battery sit in your car? It sits on a steel surface that is grounded. So charge it anywhere you want. Just remember that battery chargers have been know to catch on fire, so place the charger in a location where if that happens no damage will be done.
It has a dead cell. I know it is only 2 years old but it happens especially if that battery was run completely down which shortens the life. I suggest you purchase a different brand as this brand was not very dependable. My answer is assuming nothing is on pulling power from the battery when the car is just sitting. Have the battery checked to make sure it is actually defective. Any auto parts store will check it for you. It has to be fully charged in order for it to be checked.
you are sitting .so sitting itself is doing something
No, -12 > -13. The further you go down the number line the more of nothing you have. If you have $0.00 in your bank account and buy something for $5.00, you are going to be sitting at $-5.00 in your account. Now If I deposit $5.00 which brings it back to 0.00, is more than $-5.00 I was sitting with earlier.
Nothing you have to do. It will be fine sitting for 1 month. If you plan on storing it for 3 or more months then put a trickle charger on it and leave it connected.
Yes you sure can. It is a myth that sitting a battery on concrete will drain the battery. It will not drain it at all.
Purchase a trickle charger and keep it connected to the battery.
Yes. It is a myth that a battery will run down sitting on concrete.