Nope, most of them don't even have the wattage to overcharge a single small battery. I have one that is called a "battery maintainer" and it says it only puts out 1.8 watts. I have yet to see more than half of that when I tested the wattage so I'm not worried. When you start getting up around 5+ watt chargers you want to look for ways to protect from overcharging. Many of them have have that built in but you always want to check.
I'm still testing because got mine a few weeks ago (whenever it actually snowed that 5 hours in Texas
) to help keep the battery cranking strong.