Overcharging is the number one cause of battery failure so it is important to buy a good battery charger, you get what you pay for, and trying to save money in short run will often cost in the long. With a single stage charger over time you can literally cook your batteries .
We recommend a high frequency 3 stage charger for most applications. This means that the system goes through 3 stages, bulk charge, top off, and maintains your batteries no matter the battery composition. The industry calls this a bulk, float, absorption charge or 3 stage charger.
The Battery Tender works well, but we also really like the Xantrex and C-Tek models.
When your boat is going to be in storage for an extended period, say winter storage, a smallcharger that works steadily will be more efficient on cost and power consumption. The C-Tek .8 amp charger is available online. It can be to tender hundreds of amp hours of batteries. It can take weeks to fully charge a battery. For a bigger marine battery trickle charger the Xantrex 40 amp charger will charge batteries up quickly.
A two stage charger is necessary to charge while using the battery. The Xantrex multiple stage, multiple battery bank charger is excellent for this purpose. For high amp loads a charger with a transformer is required.
Many battery trickle chargers can charge 6 volt and 12 volt batteries. It’s important to make sure you have selected the correct charge setting. Battery trickle
chargers can be left connected to the battery all the time. Periodically check on the battery, when checking the battery, feel if the battery is unusually warm, this is a sign of a damaged or shorted battery. If this happens, immediately disconnect the charger and get the battery tested by a battery expert.
Take care not to make any sparks around a charging battery. A charging battery creates hydrogen gas which is highly explosive and in combination with the acid that is present in the battery can be a deadly combination.