Best Batteries for a Narrowboat? [ULTIMATE GUIDE]

Canal Boat UK is supported by its readers. If you buy something with our links, we may earn a commission.

Welcome back to Canal Boat UK. We have been covering a lot of narrowboating hot topics recently, and here comes another one 🙂 What are the best batteries for a narrowboat? Narrowboats have been around for a long time. Has battery technology moved on? What’s the best option? It’s time to find out!!


Batteries CAN be dangerous if not properly fitted and maintained. THIS ARTICLE IS NOT A TUTORIAL! we always recommend using a professional for this if you don’t have experience with batteries!!

How do Batteries Work?

In order to select a good batter for our boat, it’s a good idea to educate ourselves first about batteries and how they work.

Electricity is a flow of electrons through a circuit. This circuit is often made from wire. Batteries are hooked up to this circuit to power it.

Batteries have a Cathode (denoted with a plus sign) and an Anode side (denoted by a minus sign).

The Anode side of a battery will contain metal (often Zinc) that will oxidize. This means that it will lose electrons and pass them through whatever circuit they are connected to and over to the Cathode side. When they arrive, the electrons are gained into the water solution (known as an electrolyte) there.

When all the metal is oxidized, and all electrons passed into the water solution, your battery is flat (known as one cycle).

Rechargeable batteries have made it possible for this process to be reversed. When you add an electrical source, it pushes the electrons from the water solution back over to the Anode side of the battery, and the metal contained there.

As rechargeable batteries complete cycles they will start loosing their capacity to store electrons due to the metal starting to degrade.

Battery technology has been improved mainly due to replacing the water solution with a gel paste instead.

What Batteries are Available for Narrowboats?

A narrowboat usually has two different batteries on board. A more basic starter battery (to start the engine) and leisure batteries used to give you power for all the creature comforts you want on the boat. If you want to extend the range of your onboard power, you need to improve the quality of your leisure batteries.

Are all batteries made equal? These are the different types of batteries available for use in a narrowboat?

Lead-Acid Batteries

Before we get into the types of lead-acid batteries, I wan’t to note that these batteries shouldn’t be regularly discharged below fifty percent of their capacity. This could lead to degradation and a lower life. If you don’t like the sound of this, you should look for “deep cycle’ batteries that are specifically designed to counter this problem (at a slight premium).

Wet Cell Variety

These wet cell lead-acid batteries are the very basic form as described above. A liquid electrolyte is used, so you must be careful that spillage doesn’t occur and turn into fumes. This is why these types of batteries must always be housed in something that can vent.

As these are the most simplest batteries they are also the cheapest. Most narrowboats come with these as standard. They need to be maintained, and the electrolytes topped up from time to time.

Gel Cell Batteries

This type of battery replaces the liquid electrolyte with a gel one, meaning that the risk of spillage is gone. Also, this battery type can charge much faster than the traditional wet cells.

These batteries are sealed, making them maintenance free. Just make sure you are charging them in line with the specifications. If not, the gases inside the sealed battery could be building up too much pressure. The chargers required are different from wet cells, so be careful.

The downside is that, as electrolyte can’t be manually added, when they lose a lot of their charging life there is nothing you can do to rectify the situation.

These batteries are more expensive than the more basic wet cell variety.

Absorbant Glass Mat (AGM) Batteries

These are again a step up from Gel batteries, using a woven glass mat to store the electrolyte. These are great because they are also spill proof as well as being much more resistant to vibrations and bangs. Also, the charging specifications are the same as wet cells, so it is much easier to find compatible chargers.

As they are also sealed, care needs to be taken to charge them at the correct rate so as not to cause too much pressure from the gases being released. As with gel cells, once they are worn out there is not much you can do!

Carbon Enhanced

The final type of lead-acid batteries are the carbon enhanced versions, a fairly recent innovation!

The most expensive lead-acid batteries, but also ones with the most charge and longer life. So before you decide on very expensive lithium ion below, consider these!

Lithium-Ion batteries

These are the new kids on the block, having a completely different chemical makeup to the other batteries described above. They are widely used in modern power hungry devices such as smartphones, so offer the best longevity of any battery on the market.

Lithium Ion batteries are the most expensive narrow boat batteries, but they would offer up to five to six times the usable power of a standard battery. They are smaller and lighter and faster charging!

Lithium Ion batteries can be discharged almost fully without any noticeable degradation of their charge. They also perform better whilst under heavy load (using power hungry hair dryers or washing machines, for example).

They are expensive, but they are by far the most powerful and flexible batteries you could buy. Lithium-ion also output a much more stable voltage as they discharge, whereas lead acid start to tail off the more they discharge.

Just make sure to keep them within their operating temperature and voltage requirements, especially when charging. You will brick these batteries if not managed properly.

Note, only LiFePO4 rated Lithium Ion batteries are used on a boat, as they are the most stable type.

These are the battery types you can choose with lithium-ion:

Home Brew

It is possible to buy your own cells and arrange them into a battery pack arrangement to suit your power needs yourself. Although I wouldn’t recommend this unless you have a good knowledge of batteries. One mistake and you could break a whole set of very expensive cells. Also, this is not a popular method in the United Kingdom, so the parts you need are hard to come by.

Drop In

Drop in lithium ion batteries are designed to drop into a pre-existing battery setup/rack designed for traditional lead-acid batteries. This makes them very simple to convert a narrowboat over to. The downside is that, although they do usually have internal battery management systems, there is no way for you to monitor battery condition and performance yourself.

Smart Batteries

These are a halfway house between the two. You can buy these in a variety of sizes and arrange them as you need. With lithium ion, it is OK for you to add to the battery arrangement at a later date. This means you have the flexibility to build a battery system that can be incrementally upgraded over time. Also, these smart batteries will give you a way to monitor your batteries externally, giving you peace of mind.

Which option is the best for me?

I will start by saying that if you like your power hungry appliances (such as washing machines) and want to run them for any length of time outside of a marina, Lithium Ion are your best and probably only option!

Other than that, if you are a narrowboater that is permeant in a marina or cruises very little, you will always be close to shore power at a marina and don’t need to worry about paying top dollar for the best and most efficient battery systems. A decent lead acid battery would be fine.

If you are someone that cruises year round but parks up in a marina over winter, you should also be fine with a pretty basic battery setup. Especially if you have solar panels helping to top up your batteries too. Couple this with the frequent running of your engine to cruise, and your batteries should be fine even if they are not top-notch. A higher grade lead acid battery, such as the AGM, would be fine here.

The people that really need to invest in the best battery systems are those that cruise all year round and rarely stay in marinas (even in winter). It will be tough to get through winter (even with solar panels) in this situation. Lithium Ion would ease a lot of your power storage woes, although at a pretty heavy cost.

What size Ampere battery should I buy? How long will they last?

There are ways to calculate and estimate what batteries you will need to match your usage, but they will just provide a rough estimate. The best thing to do is to talk to other narrowboaters (either face to face or in an online forum) to get an idea from real world experience.

Century batteries have an excellent tool you can use to simplify the whole process. Simply enter the wattage of all of your electrical appliances into their tool, along with how long it is used each day. This will calculate an ampere hours (Ah) figure that you can match to the rating of your batteries.

This will give you a full day of use followed by a new cycle/charge. This will be extended if you use your engine or solar panels to recharge. Or you can double the result if you want an idea what is needed to last two days.

All of this is pure estimation! This is why talking to actual boaters is the best way to get a real world estimate.

Anything else to consider?

I have talked above about different batteries needing different methods of charging. It’s vital that you know what the correct voltages are needed to charge your battery through its different stages (main and float charge). Whatever is being used to charge these batteries (outside charger or solar panels) needs to be set up correctly to match these voltages (especially with lead-acid batteries) to prevent overcharging and the gases building up too much pressure in them. If you are not sure what these voltages are, contact the manufacturer of whatever batteries you are using.

Leisure batteries (when arranged together) produce 12 volt power for use in your narrowboat. You can buy fridges and TV’s etc. that can run directly from this power. If you want to use normal household appliances, you will need an invertor to change the current to a normal household one. But this conversion involves some wastage, so be aware that using an invertor with a lot of appliances attached could drain your batteries faster.

Finally, batteries don’t like heat or extreme cold. Venting your battery compartment is not only good for vented batteries where gases escape. Even if you have sealed batteries that are close to the engine, venting the compartment will help cool the heat coming from the engine. On the flip side, if your batteries are away from the engine somewhere cold, make sure your batteries can operate in these cold temperatures. Check with your battery manufacturer if you are not sure!

Are you confused yet?

Yes, this whole battery thing is confusing. Don’t just read this article, take some time to learn the ins and outs of batteries and boats. Especially if you are a live on boater and use batteries heavily!

And, as stated above, if in any doubt please consult an expert! Batteries can be dangerous things when not done properly!

Hopefully, this article at least gave you some ideas to start with 🙂 If you have any of your own experiences with batteries on narrowboats (that you would like to share), we would love to hear all about them in the comments section below 🙂

Leave a Comment