[Putershark]

No such thing as a dumb question and much better to ask than get blown up, which could happen if you are not careful... If this is your standard 12VDC charger then I recommend you disconnect "all" the battery leads and yes, you have to charge them 1 at at time... Now when you get sick and tired of going though all that headache all the time, you can do 2 things to help save on all that time and hassle...

1. Buy and install a on-board charger that is rated for 24VDC systems that is always connected so all you have to do at the end of the day is just plug in the system OR in the mean time (Lower budget way)...
2. Add 2 extra gator clips and 2 extra leads to your present charger and you can find them at most auto parts stores. Just remember, if you elect to do #2 you STILL have disconnect the leads so that you are not trying to charge a 24VDC system. Just make sure you remember "where" you removed the battery leads though or you could go up just like the Hindenburg and always install the ground /negative (black) leads first to help keep the sparks from flying