The batteries are wired in SERIES, which means they are added together to increase the voltage,,,,,like my battery right there is rated at 18 volts,,,,,there are different voltage tools but they all are wired the same,,,,,you got 2 wires going to the batterys,,,,,probably a RED positive wire and a BLACK negative one,,,,the red wire goes to the positive side of a battery,,,,,then you need to connect all the other batterys to it,,,,so you connect the negative side of the 1st battery to the POSITIVE side of battery #2,,,,,neg of #2 to pos of #3,,,,,,,,,,,,,,,make a train of batteries,,,,until you come to the end and that battery will finally hook up to the black negative wire going out to the terminal,,,,,the batteries have connector tabs,,,,or use a small piece of wire,,,,so you can easily hook it up to the next battery,,,,,you heat up a spot on each end of a battery,,,,melt a little solder on it,,,,put the tab in that solder,,,heat it up,,,,hold the tab down in the solder with a screwdriver until the solder melts again,,,,then keep holding the tab down until the solder cools and you are done..... look at your batterys,,,,,you will see a pattern,,,,,each NEGATIVE goes to the next POSITIVE,,,only the 1st and last battery are hooked a little different....
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