Marine Electronics – Charging your Batteries

You might remember that a couple of years ago I wrote some posts about a marine electronics course I was doing with Chris from Tweeds Marine, and I’ve just realised that I didn’t finish putting them all up.

Here are the ones from last year:

So you may recall where we left off in making a power budget we talked about adding up all the things that use power on your boat and then sizing your battery bank accordingly.

The next thing to consider is how you are going to keep those batteries charged up.


A regulator ensures that the batteries are charged up correctly and not overcharged. You can get different types of regulators. A multi stage regulator has three different stages – delivering different charging rates depending on how much charge is in the battery.

You can also get a battery monitor. This will measure the voltage of your batteries, the current coming out and flowing in.

240 Volt Chargers

If you are in a marina and plugged in to shore power, you can plug in a battery charger on your batteries to charge them up. Chris from Tweeds Marine recommends that you always use a smart charger – this ensures that you don’t overcharge your batteries.


This is what we currently use on Wildwood, and what most cars use to charge their batteries up too. We simply start the motor up and run it for a while and hope for the best!

Alternators can deliver lots of energy in a short time. Every engine has got one and you can upgrade them if you want more power. They are cheap and reliable.

But – they require fuel to run them, Diesel engines don’t like being run for long periods under a light load, there is wear and tear on your engine belts and having the motor running is noisy.

Solar Panels

Solar panel technology is becoming much better and more affordable. They produce clean energy, have a long life, don’t make any noise and are reliable.

Each cell generates about 0.45-0.5 volts, so you need 32 cells to charge a 12 volt battery. There are different kinds – mono crystalline which are the most expensive and last the longest, polycrystalline and thin film – which are cheap but flexible – meaning you have some more options for where they can be mounted.

But to get the best out of them they need to be in full sunlight – even a small shadow can reduce the output considerably. You also need to have lots of sunlight, and the panels need a lot of space.

Learn all about solar power here. 

Wind Generators

Small generators range from 100W to 400W and output is dependent on wind speed.

Great in windy areas, and can provide power 24/7.

But if you always sail downwind and anchor in sheltered bays then they may not be as effective as you’d hoped. They are also noisy and cause vibrations. They require maintenance and shouldn’t be left unattended. They are heavy and need to be mounted high and they can be a bit ugly.

Learn all about wind power here

Hydro Generators

These are water powered generators which are either mounted like a little outboard or towed along behind the boat.

They can provide a lot of power.

But if you are at anchor then they won’t work (unless there is heaps of current), the propellors can be fragile and susceptible to getting damaged, they cause some drag.

Check out Watt and Sea.

What battery charging systems do you have on your boat and what do you think works best? Please comment below. 




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