The QuadLink takes a single-output battery charger and can use it to charge and maintain up to four batteries at once. It works with both 6V and 12V batteries and comes with four battery cables and permanent harnesses for four different batteries. The QuadLink in no way diminishes the charging output and instead of trying to share the same charge power between four batteries, it switches from battery to battery (sequentially) every 10 minutes. If one of the outputs of the QuadLink is not hooked up, it senses this and automatically skips that output. A green LED light at the head of each output indicates which one of the four batteries is being tended to.