Use a multimeter or build a polarity checker to ensure the polarity of the connector on the replacement battery matches that of the original battery.

If the connectors on the new battery do not match, you may destroy your CoxBox electronics, so compare the new battery connections to the old battery connections carefully.

Do not trust the wire colors - use a multimeter or purpose-built polarity tester.

There should be a positive wire, a ground wire, and a thermistor wire.

In addition to checking the positive and negative lines, verify that the thermistor is wired correctly. On the CoxBoxes I've opened the thermistor is connected to the middle pin and the ground pin.

Your CoxBox may be different. Compare your new battery to the old battery you are replacing.