Skip to Content
Anchor Travel is reader-supported. When you buy through links on our site, we may earn an affiliate commission. Read more.

Cranking Battery Charger 101: The Complete Guide

Cranking Battery Charger 101: The Complete Guide

Are you interested in charging cranking batteries? Since these batteries are different from some of the other batteries that someone might use on a boat, it’s important to learn about them so they can be charged correctly.

No matter what your questions are about charging a cranking battery, we will answer them in this article.

Here’s everything you need to know about charging a cranking battery.

What is a Cranking Battery?

Optima Batteries OPT8022-091 8022-091 75/25 RedTop Starting Battery

Click for more info

A cranking battery is one of two types of marine batteries that you can buy for a boat. Another name for a cranking battery is a “starting battery”. It is designed to start your boat.

These batteries are made to give one large expenditure of energy. This is exactly what it takes to get your boat’s engine going.

A cranking battery can also run things like your sonar or GPS. However, these devices require a steady, small amount of energy over a relatively long period. This is the opposite of what a cranking battery was designed to do.

If you regularly use a cranking battery to run devices like these, your battery life will be significantly shorter. However, some anglers prefer to use a cranking battery for these purposes because then they do not have to carry two batteries on their boat.

What Drains a Cranking Battery?

The cranking battery expends a significant amount of energy in a very short amount of time when it starts your boat.

If you have your cranking battery connected to other devices, like a GPS or your fish finder, these will also drain the battery.

ProNav Angler for Minn Kota PowerDrive Trolling Motors

Click image for more info

While the cranking battery can power anything that you need it to power, asking it for small amounts of energy over a long period will shorten the battery’s life.

Will My Motor Recharge a Cranking Battery?

Most motors will recharge cranking batteries. As long as the motor has been built in the last 20 years, it should have either an alternator or a starter.

Both of these will work to slowly recharge your cranking battery after it starts the engine.

This includes the majority of outboard motors. As long as they were built within the last 20 years, they will most likely automatically recharge your cranking battery as your boat is running.

Depending on the power of your motor, it may take several hours to recharge your cranking battery. This time will be extended even more if the battery is also powering other things, like the fish finder or GPS.

Best Fish Finders for Trolling Motors

If you only take a short fishing trip, your cranking battery may not get fully recharged before you get back to shore. You may need to have a separate charger if you do this regularly.

Similarly, if you regularly turn off your motor while you are fishing and then restart it, your cranking battery may not be able to get a full charge before you need it again. While it should be able to start the engine for you, you will want to do whatever it takes to get it fully charged.

If you have an outboard motor that is not set up to charge your cranking battery, you can convert it so that it will do the job. All you need is to install a regulator/rectifier and a lightning cable.

Be sure you buy parts that are compatible with your brand of outboard motor, then follow the instructions below. It won’t be long before the outboard motor will charge your cranking battery every time it runs.

Charging a battery from an outboard

Can You Recharge a Cranking Battery?

You can recharge a cranking battery. You may want to hook your cranking battery up to a charger after every use. If batteries are left in a discharged or semi-discharged state, they can suffer damage.

You have a few choices when it comes to how you want to charge your cranking battery.

First, you need to decide if you want an onboard cranking battery charger or a portable one.

Onboard Cranking Battery Chargers

NOCO GENIUS GENM2, 2-Bank, 8-Amp (4-Amp Per Bank) Fully-Automatic Smart Marine Charger, 12V Onboard...
  • An 8 amp (4 amp per bank) on-board battery charger for charging and maintaining two 12-volt batteries independently.
  • Safely charge all types of lead-Acid batteries from 20-120ah, including wet, gel, AGM, and deep-cycle batteries.

Onboard chargers are wired into the boat itself. This means that you can charge your battery in the same place you use it, which is efficient and practical.

However, installing an onboard charger in a small boat can be overkill. These chargers can also take up valuable space that you need for gear storage and more.

Some onboard chargers can charge the battery while the boat is running, in addition to charging it when the boat is turned off. Others can charge more than one battery – or kind of battery – at once.

Portable Cranking Battery Chargers

NOCO GENIUS10, 10A Automatic Smart Charger, 6V and 12V Portable Automotive Car Battery Charger,...
  • Meet the GENIUS10 - Similar to our G7200, just better. It's 17% smaller and delivers over 115% more power. It's the all-in-one universal charging solution - battery charger, battery maintainer,...
  • Do more with Genius - Designed for 6-volt and 12-volt sealed lead-acid automotive, marine, RV, powersport, and deep-cycle batteries, including flooded, gel, AGM, SLA, VRLA and maintenance-free, plus...

Your other option is a portable charger. These must be plugged in, then attached to your battery. They can be useful if you have several batteries that you like to change out or rotate or if you prefer to store your batteries separately from your boat.

Portable chargers tend to be smaller than onboard chargers. Some of them come with the option to charge different kinds of batteries.

Solar Cranking Battery Chargers

Upgraded 7.5W-Solar-Battery-Trickle-Charger-Maintainer-12V Portable Waterproof Solar Panel Trickle...
  • ✅【Efficient conversion】Quality solar silicon material ensures high conversion and stable output, which is 20%-30% higher than average solar panels, and it even can charge your battery on cloudy...
  • ✅【Comprehensive Battery Protection】 Solar car battery trickle charger fully protects the battery. The built-in blocking diode structure ensures no reverse discharge, overcharge, overvoltage, or...

You may choose a solar-powered cranking battery charger. These come in both onboard and portable versions.

Solar power can be a slow way to charge your boat’s battery unless you have access to a large array of panels. However, it is a great way to save money and use resources wisely.

Can You Use a Trickle Charger with Your Cranking Battery?

NOCO GENIUS1, 1-Amp Fully-Automatic Smart Charger, 6V and 12V Battery Charger, Battery Maintainer, Trickle Charger, and Battery Desulfator with Temperature Compensation

Click image for more info

A trickle charger is a battery charger that is designed to be left on the battery for a long time. It adds charge to the battery slowly and prevents the slow drain on the battery charge that often takes place.

You can use a trickle charger on your cranking battery. These chargers are particularly useful when you are storing your boat during the off-season or not using it for a while.

If you don’t want to return to a dead battery the next time you want to use your boat, try a trickle charger. Make sure that your charger is designed to stop charging when the battery achieves a full charge.

Otherwise, you could end up with an overcharged battery. This can cause the acid inside the battery to boil and the casing to crack. If this happens, you will need to purchase a brand new battery.

Interstate Batteries 12V 110 AH SLA/AGM Deep Cycle Battery for Solar, Wind, and RV Applications -...
  • Interstate Batteries Deep-Cycle mobility product, our DCM0100 Replacement battery fits many top wheelchair and electric scooter brands and more. This product is not a replacement for golf cart...
  • Rechargeable, 12v 110ah AGM battery, Maintenance-free and spill proof because of the AGM & VRLA (valve regulated) technology that eliminates spills and overpressure

Do I Need to Disconnect My Cranking Battery to Charge It?

Different anglers have different answers to this question.

Most of the time, you will not need to disconnect your battery to charge it. Find out more here.

What is the Best Way to Recharge a Cranking Battery?

The best way to recharge a cranking battery is the one that works for you.

If your motor seems to successfully recharge your cranking battery, you may not need another charging solution at all.

If your motor is not successfully recharging your cranking battery or you want to take especially good care of your battery, recharge it after each use using an onboard charger or a portable one.

If you go long periods without using your cranking battery, connect it to a trickle charger. This will ensure the functionality you need whenever you need it.

What Cranking Battery Charger Should I Buy?

The NOCO Genius10 is one of the best chargers for cranking batteries. It can charge all types of marine batteries.

NOCO GENIUS10, 10A Automatic Smart Charger, 6V and 12V Portable Automotive Car Battery Charger,...
  • Meet the GENIUS10 - Similar to our G7200, just better. It's 17% smaller and delivers over 115% more power. It's the all-in-one universal charging solution - battery charger, battery maintainer,...
  • Do more with Genius - Designed for 6-volt and 12-volt sealed lead-acid automotive, marine, RV, powersport, and deep-cycle batteries, including flooded, gel, AGM, SLA, VRLA and maintenance-free, plus...

It can do everything that you might want a battery charger to do, including:

  • Maintain your battery
  • Function as a trickle charger
  • Act as a battery desulfator
  • And more

It is also temperature sensitive, meaning that it takes outdoor or ambient temperatures into account when it charges your battery. This ensures that the battery is not over-or undercharged and helps you get as much life as possible from your cranking battery.

Besides, you can use this charger for other batteries, too. It will work on batteries for your car, truck, motorcycle, and more. If you need a one-stop-shop for all of your battery charging needs, this is the option for you.

The BMK 12V 5A Smart Battery Charger is a great budget option when it comes to cranking battery chargers. This portable charger includes technology that will detect a defective battery before any attempts at charging occur.

BMK 12V 5A Smart Battery Charger Portable Battery Maintainer with Detachable Alligator Rings Clips...
  • 【UPGRADED DEFECTIVE BATTERY DETECT/FAST CHARGING CAR BATTERY BOOSTER】Updated with battery condition diagnose to detect the defective battery before charge. Input 100-240V AC, With 5A DC output...
  • 【UPGRADED 72-HOUR SAFETY FEATURES/MULTI SAFETY PROTECTIONS - BATTERY RESCUE & RECOVER】Updated with 72 hours safety feature to commence anytime the charger is onto protect marginal batteries from...

It uses a 4-stage charging process to make sure that the battery gets fully charged but is not under-or overcharged. The charger also automatically stops charging when the battery reaches a full charge.

You can use this charger on other batteries, too, like car batteries. It is a great option for people who only need to use their battery charger occasionally or who like to keep one on hand but rarely pull it out.


Now that you know all about charging and recharging cranking batteries, you should be ready to go.

Whether you charge a cranking battery regularly or you just want to know how to do it, you should now have the knowledge you need to proceed. Enjoy your time out on the water!