Dead battery wont start the car? See how to care for your battery and perhaps restore a dead battery to be healthy again. Most batterys in a car or elsewhere never get charged up completely and end up losing their ability to have 100% capacity through sulfation. Sulfation occures when the battery produces electricity. To convert this layer of sulfation back into battery acid and restore the capacity of the battery to produce electricity the battery must be charged completely. The alternator will produce 13.5 to 14 volts to charge the battery back up but...can you drive for the 10 hours or so it would take to completely charge the battery? Only a separate charger plugged in at home can do a trickly charge for a long period and restore the capacity but, even then some sulfation can be left behind. Equalization is overcharging and occurs at about 16 volts on a 12 volt battery and is used by deep cycle solar battery bank owners to restore their batterys as Trojan Batterys youtube video will show. Having an old school transformer style battery charger capable of getting an 'overcharge' will help restore a battery that has lost capacity and is not up to the task of starting the car easily. Of course the downside is that overcharging can cause erosion of the plates and shorten the life of the battery, but...a battery that can't start your car HAS NO LIFE, so you have nothing to lose by overcharging it.
Other ways of elimating the sulfation that is stealting the acids ability to work on the plates and procuce enough capacity to start the car are : battery additives like ChargeIt, Battery Equalizer, Mx2 and others, and high frequency chargers like BatteryMinder, PulseTech's XC 100 extreme, Cteks mus 4.3, and others and then there are the so called "smart" chargers like Shumachers "Speed Charger" and other similiar items. My experience is that the $50 BatteryMinder worked well on a 5 month old Interstate that wouldn't register more than 12.6 volts after charging but did measure 12.8 volts after 12 hours of BatteryMinders charge. I also put ChargeIt in 3 days prior and so that may have had a good effect I dont know.
My advice is always clean, clean, and clean your battery terminals (posts) because I've seen many cars that WOULD start after cleaning the terminals that wouldn't start before. Cleaning also allows the alternator to put IN the electricity. Next the water level needs to be checked and I have seen batterys that would start after adding distilled or Reverse Osmosis water to the cells because the water had gone below the top of the plates.
Buy a set of jumpers as I have yet to see someone with their hood up and standing there with a set of jumpers that wasn't helped by a passerby, pretty quickly, we all want to help those stranded.