If your battery charger produces a charge rate greater than 12 volts it may damage your batteries. The negative terminal is labeled.
How To Connect Your Batteries To Make Up A 24v Or 48v System
How to charge batteries in parallel. Attach the battery chargers cable clamps to the terminals of one of the batteries connected in parallel. Instead of connecting the pos of the second battery to the charger you would connect it to the neg of the third battery. Connect the negative black wire from your battery charger to the negative terminal of one of the 12 volt batteries wired in parallel. To achieve the criteria for balanced charging you simply need to start one of the charging leads from the opposite direction. The correct method to charge batteries in parallel balanced charging. Its important the clamps are attached to the two terminals on the same battery.
In this example each battery will draw current through exactly three interconnecting leads. You would continue this positive to negative pattern until you reach your last battery. Twelve volt batteries wired in parallel must be charged at 12 volts. If you need to connect more than two batteries in series you would make the following adjustment. Once you connect wire from the positive terminal of battery 2 to the negative terminal of battery 1 the concentration of electrons shift toward the negative terminal and join forces in battery 1 as they flow forward. The red handled clamp attaches to the pos or terminal and the black handled clamp attaches to the neg or terminal.