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How to choose the right batter for your boat

Tips on How to Choose the Right Battery for Your Boat

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When you set out sailing, you conduct a thorough check on your vessel to ensure she is in the best condition. You don’t really want to be stranded in the water when you take her out for a spin. It’s why you ensure that you keep the boat serviced, well-maintained and get it detailed on a regular basis.

Current day boats are loaded with new and novel technology; while these provide more comfort and convenience, they are power guzzlers so to speak. This is what makes it quite difficult to choose the right battery for your boat. If you need to replace your existing battery, it’s important that you don’t be hasty and consider these points before making your final decision:


You may have heard of battery groups such as 8D, 6D, 34, 31, 27, 24 etc. These denote the physical size of the battery. All the manufactures follow this size grouping. While these are the basic group sizes, there is some leeway in the dimension specifications as there may be variation in post height, handles etc. It’s important that you ensure the group size displayed on the battery label matches the actual space available on your boat.


You will find that there are a number of types of batteries:

  • The ‘starting’ ones will deliver much shorter, higher bursts of amperage to get the starter spinning; these don’t react well to getting deeply discharged.
  • Then you have the’deep cycle’ batteries that are able to tolerate deep discharges (up to 50%) to the power accessories; these can also be discharged & recharged a number of times before you have to discard them as scrap.
  • The ‘dual purpose’ batteries give you the best of both worlds and these are also called the Hybrid batteries.


When it comes to determining the starting suitability, you have to check:

  • CCA which is an acronym for Cold Cranking Amps – This is the total number of deliverable amps at 0°F for 30 seconds
  • MCA, also called Marine Cranking Amps – This is typically the same as Cold Cranking Amps; however this is determined at 32°F
  • RC or the Reserve Capacity – This is the number of minutes that a fully-charged battery that’s at 80°F will discharge 25 amperes till it drops below the 10.5V point and dies out
  • Ah or Ampere-hour is the rating that you have to refer to for ‘house’ or deep cycle batteries. Typically, this is based on a draw of 20 hours on a fully-charged battery


  • If you are looking for a traditional standby battery, you can opt for the ‘flooded electrolyte’ variant; this one’s a reasonably steady performer at a very low cost. However it’s important to keep in view the fact that they also tend to self-discharge at a very fast rate. You will have to conduct regular maintenance and check and fill the electrolyte or acid at frequent intervals.
  • The AGM or Absorbed Glass Mat batteries soak the electrolyte using fibreglass coils in order that the acid doesn’t spill. These have a very slow self-discharge rate and offer a higher power; they occupy less space as they are more compact compared to the flooded electrolyte batteries. It goes without saying that all this comes with a higher price tag.

Date Codes

Regardless of the type of battery you decide to purchase for your boat, do not omit to check the battery labels. These will have the date of manufacture; the letters indicate the month while the digits indicate the year of manufacture. For example – if the battery label states “D2”- this indicates that the manufacture date is April 2012. Its best to buy the freshest one you can find.

If you want to know more about boat batteries or our custom made DC to DC converters and services, don’t hesitate to contact us at KaRaTec Power Supply Pty. You can give us a call at 612 9808 1127. You can also fill in this contact us form and we’ll reply as soon as possible.

Thanks for reading,
Karatec Power Supply Pty
612 9808 1127

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