Reviewers who think this charger won't work on the recondition mode on a really dead battery, take note. For this charger to activate a charging sequence, whether a normal charge or a recondition, it needs to sense a minimum voltage level. If the voltage is too low, it won't fire up. This is most likely in recondition mode when you have a really deeply discharged battery. The trick to get it to fire up is to connect a known good battery in parallel, connect the charger, (I connected the charger clips to the clamps on the jumper cables) and start a normal 2 amp charge sequence. The charger will see enough voltage from the good battery to start charging; and it will charge both batteries. Leave it like this for a few hours until the dead battery has built up some charge. Now disconnect the jumpered good battery and attach the charger clips to the dead battery, and initiate a recondition charge. The charger should see enough voltage to function. If not, repeat the jumpered charge for a few more hours, and try again. Not all dead batteries can be recovered, you just try. Old school chargers did not have this type of voltage sensor, you connected them and they put out current. If you have an old charger, you can use it to charge the dead battery for a while, get some voltage built up (IF it will take a charge) and then try the recondition charge on this charger. I unfortunately needed this charger three times in the first two weeks of having it. A friend discharged his car battery and I was able to restore it as described above. My own battery discharged when I left a door open. Hurrying off to work, the car would not start! I used the start assist function, started the car and got to work. I installed a new battery in a car and noticed it wasn't fully charged off the shelf from the car parts store. I got it fully charged overnight. I got my moneys worth and then some in two weeks!!