LTC4150 SparkFun Coulomb Counter Breakout is here to be your odometer for current. If you are wondering: a coulomb is defind as, to put it simply, one amp for one second. This breakout is capable of constantly monitoring the current your sensor is using, is able to add it up, and will give you a pulse each time a given amount of amp-hours have been used. When used effectively and if you start with a full battery, you’ll always know exactly how much of it is left.