Mains chargers allow the batteries to be charged while the boat is in the port. Also, when in use, these chargers power entire boat's electric grid - lights, electronics, refrigerators etc.
Since larger boats can operate in different areas and in various countries, it is important that these chargers accept various voltages (110V, 220V, 380V), phases (single-phase or three-phase electric power), various sockets etc.
Good charging controller is usually built as Maximum Power Point Tracking (MPPT) controller, which is electronic DC (Direct Current) to DC converter that optimizes the voltage between the wind generator (or solar panels, or power generator, or ...), and the battery/boat electric system and protect the battery from over charging. It is often the best solution to get a good charging controller which accepts all planed power sources (mains power, solar panel, wind turbine, etc.).
Also, good chargers monitor currents and voltages and send alarms (audio, visual, wireless, SMS etc.) if certain thresholds are met.
Mains Battery Chargers
The simplest battery charger is basically a transformer followed by Graetz bridge (diode rectifier) which uses battery itself as 'ballast'. Such crude charger will do its job, but with no control regarding charging current, overcharging the battery and similar.
Fortunately, these days good battery chargers are relatively cheep and has many, very useful features, like:
- battery charging and battery test,
- digital displays provide information about battery, charging status and battery condition,
- several charging modes like battery maintaining, slow charging, fast charging, etc.
- overcharge protection and float mode monitoring,
- reverse hook-up protection, etc.
Some models even feature battery type selection: standard, AGM or gel cell (due to small voltage differences in these battery types) providing real-time data on the actual battery charge percentage.
Intelligent battery charger can recognize the condition of the battery and charge it properly in three phases:
- Bulk Charge - current is sent to battery at the maximum safe rate, until the voltage rises to near full charge level.
- Absorption Charge - voltage remains constant and current gradually tapers off as internal resistance increases during charging.
- Float, Maintenance or Trickle Charge - it's main purpose is to keep an already charged battery from discharging, to reduce gassing and to prolong battery life. AGM batteries easily tolerate certain trickle charge, too, but don't overcharge your VRLA batteries.
Which battery charger to choose? Well, if your boat is equipped with small solar panel and/or wind turbine, your main battery will remain in good condition even for months during winter. However, once in awhile starting a boat's main engine and going for a short trip will help your battery and the boat to endure the winter.
Since deep cycle batteries are used in golf carts, RV and ATV vehicles, snowmobiles and similar applications where there are no onboard power source which can be used to charge the battery, it is recommended to buy intelligent charger which can charge the battery during the night and, if needed, in fast mode, in just few hours.
To prolong the battery life, don't discharge the lead-acid batteries below 20-25% charge and avoid regular 'fast' charging.
If your battery shows the sings of problems, some chargers have 'repair' modes, which can help with 'sulfation' (build-up of lead sulfate crystals) and similar problems - to avoid such problems, charge your batteries fully (to attain full saturation) with chargers which have overcharge protection.