Does the word “onboard” indicate a battery charger “on a boat or a ship”, or does it refer to a battery charger that is “on a circuit board inside a device that contains a battery”?
In both cases, the answer is nearly the same.
1.) First, you need to determine the charging voltage and the charging current that the battery (or bank of batteries) requires.
2.) Secondly, you need to determine the maximum “footprint”, maximum height, and ventilation requirements for the space where you will install the battery charger.
On a boat or a ship, consider things such as close proximity to the batteries being charged, wiring, connectors, resettable circuit breakers, and remote wiring to the operator console, cabin, or bridge. Consider adding either an MPPT or a PMW controller, that can be programmed to allow multiple charging inputs, such as an engine alternator, solar panel, or wind generator, and allow you to select the charging voltage to match the quantities of batteries in your battery bank. Also ensure the onboard battery charger and controller are either a marine-grade, or at least protected from water splashes caused by the boat heeling from sails, high speed turns, or rough seas. If the boat is a commercial vessel, or if it carries any explosive fuels or heavier-than-air gasses, such as propane, any devices mounted below deck are required to be explosion-proof, so that your ship does not blow itself to smitherines when the charger relay engages or disengages. (I HATE it when THAT happens!) Sea-going vessels should also carry an identical complete spare battery charger and controller, in the event the charging system fails outside of the ship’s home port.
Considerations for a small device on-board battery charger include the items mentioned in bullets 1 and 2, but also include the circuit board connections, and mounting requirements that will prevent a sudden jarring of the device from damaging the circuit board or electronic components. Electronic component makers have already designed, tested, and built small components that can be mounted onboard your project circuit board. They typically charge one or more lithium batteries from an input voltage of 12volts DC. Some chargers are designed to have an input of 110 - 240 volts AC, but these will require a transformer and rectifier circuit that will add size, weight, and other aspects to consider when designing your system.
Good luck in designing and building your project. Don’t fear failure, because when you fail, you gain knowledge and experience and you can try again. Of course, if you are on your boat when it gets blown to smitherines, you might not get a chance to try again!
10 Best Marine Battery Chargers
Based on dozens of customer reviews and ratings, the followings are the top 10 best-selling Marine Battery Chargers: