Marine Electronics - charging boat batteries
Batteries aren’t a limitless source of power
Batteries are storage devices, and you shouldn’t even use more than half what they store if you want them to keep working for more than a few cycles.
There are three ways you can refill (i.e. recharge) them:
- by plugging into the electrical system supplied in a marina berth
- by using a motor-driven alternator on the boat
- by using renewable sources such as wind turbines or solar panels (which are generally only adequate for topping up what you use for essentials such as lighting and instruments)
Charging from the marina supply
If you have a simple electrical installation and you dock in a marina every night, this may be the only charging system you need - but in that case, you should ensure that you have a backup battery for nav and cabin lights, because one day something will go wrong and you’ll be forced to return home after dark.
Charging from your own generator
On a small boat, this could mean using an alternator driven by the boat’s only motor. If you can’t start the motor by hand cranking it, then don’t use the starting battery for anything else except in an emergency.
On larger boats, it’s more economical and less noisy to use a separate small motor to run the alternator.
Charging from renewable power sources
Solar panels or a small wind turbine can be an effective way of replacing energy used for the boat’s electronic equipment, and even for nav and cabin lights. Except on very large yachts, the only safe place to mount a wind turbine is right on the back of the boat, and many cruising yachts put solar panels in the same place, perhaps integrated with davits for the dinghy. Racing yachts and larger cruisers may place solar panels on the coachroof.
Charging circuits
There are several decisions to be made, and safety rules to abide by, when designing a system to control the charging of your boat’s batteries by one or more of the means outlined above. I’ll talk about them in a future article.
