You need to know what the operating voltage of the system is. Four 6 volt in series provides 24 volts. If your system is 24 volt then the 12 volt will not not work no matter how high the amp hour capacity is. If it is a 24 volt system, you need to add a second 12 volt battery and connect it to the first one in series. Negative of one to the positive of the second. Check across the battery pack to verify that you have the correct voltage.
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