Benefits of switching to lithium batteries on-board a boat. 

When you first learn about switching to lithium batteries aboard their boat, often the cost of the batteries puts people off immediately. In this article we discuss the true cost benefit analysis of changing over to lithium batteries, to see if it makes both financial and useful sense for the end user.

When considering a battery type, we must consider various characteristics of different batteries to understand the full story. Let’s go through them now.

1. Cost of Lithium Batteries

On the face of things, lithium batteries seem expensive. However, they may be run up and down many more times than a typical lead acid battery. A lead acid or AGM battery typically has 300-500 cycles, after which, it can store less and less energy, by comparing this to a lithium battery like the Aceleron Essential LiFePO4 at Pro Marine Store, we can see that the battery is warrantied to 3000 full cycles, and has an expected useful life of up to 5000 full cycles. 

Thus the lithium battery lasts 10 times as long. But is it 10 times the price? For a good AGM battery, like the Victron 110Ah Deep Cycle AGM battery, the price is £343.20. Therefore for 10 times the life, the Aceleron Essential 115Ah battery is under 4 times the price. And this isn’t even taking into consideration the fact that Aceleron lithium batteries are serviceable at a fraction of the price of buying a new battery - but we will talk about this later...

2. Charging Speed of Lithium Batteries

On a blue water sailing boat that is typically powered via solar panels on deck or on a solar arch, getting in as much power to the batteries whilst the sun in optimally shining is critical to recharging the battery bank for the day's use.

Lithium batteries can accept considerably more power to recharge than lead acid or AGM batteries, thus they recharge quicker. If you were to run a generator to recharge the batteries, this means that the generator is run for less time each day. This also means that you may install a larger solar array to recharge your lithium batteries as quickly as possible.

3. Discharge characteristics

Let’s take a look at a typical discharge graph of lead acid verses lithium. Here we can see that the lithium batteries remain at a high voltage output before quickly tailing off to a zero charge point. In contrast, lead acid batteries have more of a continuously reducing output voltage over their discharge cycle. 

Why is this important? For this we have to look at Power. Every item on your boat has a particular power requirement. Power is a function of voltage multiplied by current. Let’s have a look at the windlass. A typical windlass might have a 1000W motor - the motor will demand this power, no matter what. This power is made up of voltage multiplied by current. On a 12v system, a full battery float voltage might be 13.5v. Thus the current draw to this 1000W motor will be 1000/13.5 = 74.1A. If you were to use a lithium battery bank to run this windlass, the current draw through the wires would stay the same for the majority of the discharge life of the battery, thus the current flowing through the windings of the windlass motor stays the same. 

Now let's look at an AGM battery at around 50% where the discharge voltage will be around 11.95v. Now the current draw will be 1000/11.95 = 83.7A. This is a considerably more current passing through the cables feeding the windlass and especially important - the motor windings of the windlass motor. More current over many cycles will weaken and wear out the motor of the windlass much quicker than when operating at a higher system voltage of a lithium battery bank. 

Therefore, to preserve the life of the windlass motor, it is best to run at the highest possible system voltage, to reduce the current flow and so preserve the life of the motor.

4. Battery Capacity

AGM and lead acid batteries can only be discharged to around 50-60%% of their capacity without damaging the internal battery plates. In contrast, a lithium battery can be discharged to around 10-20% charge. Thus a lead acid battery of 100Ah will give you 40-50Ah useable, whereas a lithium equivalent will give you 80-90Ah. Therefore, for the same house bank useable capacity, you need to add more lead acid batteries that lithium’s. 

5. Battery Serviceability

We accept that batteries are consumable items on a boat - over time they degrade, fail to hold their charge properly and become unsatisfactory. Up until now this meant buying new batteries and dumping the old ones in landfill. This has clear environmental consequences, but what choice do we have right? We need good healthy batteries on our boat. 

Enter the Aceleron Essential battery. This battery is made using the best cells available today, but critically, it is designed to be serviced when needed. Indeed all parts can be serviced when needed. After all, when your car needs its clutch replacing, you don't throw away the whole car, you just replace the parts you need to - at a fraction of the cost of the whole car. 

The same principle is true of the Aceleron battery. The core of the battery is replaceable at one of our approved service centres. The core is the part that that will degrade on all batteries and with a lithium battery this will happen around 3000-5000 cycles. Once the health of the battery reduces, the core can be replaced at a fraction of the cost of a complete new battery. 

Additionally, as this servicing will only be done after years of use, the battery capacity of the new core will be more than the original battery, so you get a bigger battery at a fraction of the cost of a new one - a no-brainer.

Now, if we consider the cost of running a lithium battery bank with one swap-out of the battery core for around £300 per battery, we see that the cost of running a lithium battery back for around 10000 cycles, we see that each battery including servicing costs around £1600, compared to 20 x £343 = £6860 for the same in AGM.

5. Battery Monitoring 

Battery capacity goes hand in hand with 'range anxiety' - we hear about this all the time with electric cars. On boats, we can simply use a battery monitor to keep track of the state of charge, but what if we could take this to the next level and have Aceleron themselves monitor the state of the battery, not just as a state of charge, but as a state of health. 

This is now possible with the new Aceleron Essential batteries, that feature a CAN Bus data connection, and options for remote monitoring of battery health down to small groups of cells. In this way, if the battery ever shows signs that even one group of cells has a problem, the user can be notified and a swap out can be arranged, therefore keeping your batteries in their best state of health. Again, this is only possible with modern intelligent batteries with Battery Monitoring Systems, and from companies dedicated to the best in battery technology

Conclusion

We have now seen that if you are careful in learning about lithium batteries, we see that they are cheaper in the long run, give you greater useable capacity, charge quicker, have better discharge voltage characteristics, and can be serviced, and are even lighter than their equivalent AGM battery. The more we look at using lithium batteries on a boat, the more we realise that the only reason we don't already use them is that we've always used lead acid and didn't realise just how good they are. 

At Pro Marine Store, we are passionate about educating people about the best equipment available for their boat, helping them choose the right equipment for them, and giving them the tools and advice to educate them about using and installing this great kit. We believe that through education and careful consultancy, we can find the right setup for your needs. 

We are proud to be the UK's only marine supplier of Aceleron lithium batteries, a company with a philosophy of making the best batteries on the market, with serviceable parts meaning environmental waste is kept to a minimum, and the cost of the battery to the end user becomes cheaper over time through replacement of the core when needed at a fraction of the cost of a complete new battery. After all, if 90% of the battery is perfectly healthy, why are we throwing it all away?