Nearly every boat has a 12 volt boat battery and understanding how to determine it’s charge status is vital to keeping your boat’s electrical system safe and functional. Let’s take a look at your basic system.
Your 12 volt battery is the life of the entire electrical system on your boat. Many boats have a combo starting/deep cycle battery to save weight and space. Others have dedicated batteries for each function. Never use a plain starting battery for deep cycle service and never use a deep cycle battery for engine starting. A combo battery usually is a compromise between the two and one that I recommend. A boat’s battery and electrical system is very similar to the boat trailer wiring system in that many of the same components are used and the same wire is usually used along with both being a 12v system. You can learn about your boat trailer’s wiring system here.
Understanding your battery charge level is key to knowing the health and charge status of your battery. Most battery manufacturers agree that you should never run a battery down below it’s 50% charge level for optimum battery longevity and life. The best way to determine your battery’s charge level is to use a standard digital multimeter and measure the voltage directly from the battery terminals. Here is the one that I use and recommend.
INNOVA 3320 Auto-Ranging Digital Multimeter
When using a multimeter, touch your test leads directly to the appropriate battery terminals and take a reading. After you have taken note of the reading refer to this chart for the status of your battery charge;
This will give you a very accurate indication of the current health of your battery. There are various on-board voltmeters and fancy monitoring systems available, but the plain ole manual voltmeter test is quick and easy. That meter comes in handy for diagnosing other electrical issues around your boat and should be in your toolbox at all times.
Also check your battery water level if your battery design allows it and when adding water use only distilled water from a jug to avoid adding mineral deposits inside your battery. Gel batteries or AGM batteries do not have liquid electrolyte and are generally service free. I highly recommend this battery for the ultimate in long life and good starting power.Optima Batteries 8016-103-FFP D34M BlueTop Starting and Deep Cycle Marine Battery
I have used this battery in my boat for several years and it has been truly maintenance free. You can mount it in any position even on it’s side if necessary and sometimes that is a good thing if your boat is small.
I also recommend that you get a good automatic battery charger to keep your battery topped up. This is the charger that I use and it has always done the job well.Schumacher SSC-1500A-CA Ship ‘N’ Shore 15 Amp SpeedCharge Charger with Battery Clamps
By keeping tabs on your battery voltage and using a proper charger you can rest assured that you will maintain your battery for optimum service!