2.5 LiFePO4 vs. Lithium-ion compared

From the outside you can not see the batteries, what was installed inside the battery. In the Torqeedo Travel 1103, for example, it is the cylindrical cells. Often these are the cells of brand manufacturers such as Panasonic, Samsung or Sony. 

The round cells have the highest energy density of all types. The outer shell is usually made of very thin nickel-plated steel. Advantage of the round cells are a high stiffness and robustness.

Due to the round shape, however, the cells can not be arranged efficiently within the housing and take up relatively much space. Another disadvantage is higher production costs, especially due to the material of the outer layer.

Inside most LiFePO4 are four prismatic cells. The advantage of only 4 single cells is a simpler interconnection inside the box. This saves time and money in manufacturing.

Because of the square shape, the space can be used much more efficiently than with a round cell. The shell of the cells is usually made of slightly cheaper aluminum. However, compared to the round cell, the prismatic cell takes up more space and the outer shell thus also weighs more. 

The ePropulsion Spirit 1.0 PLUS uses so-called pouch cells. The difference to the other forms is the highest energy density and the best use of space. If you look at the battery once cut open, it is noticeable that the actual cells make up only a small part of the battery.

The shell of the pouch cells is made of soft aluminum composite foil. This is the lightest and most compact compared to all other forms. The advantage of pouch cells are high energy density and low cost of packaging.

The pouch cells are not as robust and stable compared to the other cell types though, so should be well protected. Another advantage is the good cooling, heat can escape much easier with the pouch than with the prismatic cells.

Continue in the text with the lithium batteries and the different technologies. When we talk about lithium batteries, we usually mean lithium iron phosphate batteries, or the chemical name LiFePO4. 

In the housing of the battery are then usually these blue prismatic cells. In China, there are a few large manufacturers, for example CATL, Calb or EVE. To the advantages and disadvantages we come in a moment.

In addition, there are still lithium-ion batteries. Behind this term is a whole range of different cell chemistries. The most common is lithium nickel cobalt manganese oxide. You will often see the abbreviated form NMC, Li-NMC or NCM. But there are also other mixtures such as lithium nickel cobalt aluminum oxide or other variations. All have different advantages and disadvantages.

The lithium ion batteries are mostly integrated in the cylindrical cells or the pouch cells. For example, also in the battery from the ePropulsion Spirit 1.0 PLUS or the Torqeedo Travel 1103. You know these lithium-ion batteries of course also from e-cars or from e-bikes. These batteries are also integrated into every laptop or smartphone.

LiFePO4 weighs a little more. Here we usually have just under 10 kg per kWh. Li-NMC, on the other hand, sometimes only bring between 6 or 7 kg per kWh on the scales. 3 kg more per kWh sounds little, but are still 50% more weight.

That's why the lighter lithium-ion batteries are also used in e-cars or e-scooters. Here, every kilogram has a major impact on acceleration, consumption and range. The bottom line, then, is a clear advantage for the lithium-ion batteries.

What about the safety of lithium batteries? The LiFePO4 batteries have a very decisive advantage over the lithium ion batteries: lithium iron phosphate is not flammable or explosive. In the news circulates from time to time a burning Tesla with lithium-ion battery, which must then be extinguished with special fire extinguisher.

Even if batteries cause proportionally much less damage than burners, one should at least know that. With LiFePO4, however, really nothing can happen. This is especially good on the water, where the batteries can only be badly extinguished or the fire department can intervene only with difficulty. So with lithium iron phosphate, it can also not lead to further environmental damage.

The discharge cycles and thus the service life play a major role in weighing up whether lithium iron phosphate or lithium ions. Here there are partly very large differences. LiFePO4 usually has 3,000 charge cycles at 80% discharge, the latest LiFePO4 batteries have even more, i.e. 4,000 or 5,000 charge cycles. Lithium-ion batteries, on the other hand, only have around 800 to 1,000 cycles.

So you should think very carefully in advance about how often the battery is to be used. This has a significant influence on the selection of battery technology. If the battery on the boat is discharged and recharged perhaps 50 times a year, even the 1,000 charge cycles of a lithium-ion battery will easily last for the next 20 years.

If the boat is used in a boat rental on 200 days per drives, that is 400 used charge cycles per year. We would therefore definitely recommend a lithium iron phosphate battery.

Let's take a look at the current prices. The lithium battery from Ecowatt with display costs 499€. That's under 400€ per kWh. With renowned brands, it is sometimes significantly more: rather 600 to 800€ per kWh. The price depends on the range of functions. If a Bluetooth BMS is installed, the battery can be connected in series or the battery can handle more discharge power, the battery logically also costs more.

On the other hand, we have the lithium-ion battery from the Spirit 1.0 Plus and this has the same capacity as the Ecowatt battery and costs 1,150€. Per kWh, that's just under 900€.

Lithium-ion batteries are used when the battery should be as light as possible. Either when I have a light planing boat and want to get planing as early as possible. Or if I carry the battery around regularly, as with a dinghy or rowboat. For example, with a 1 kW motor with integrated battery like the Torqeedo Travel 1103 or the ePropulsion Spirit 1.0 PLUS.

For all other displacement boats, it is not dramatic whether I have 30 kg more weight in the boat or not with a 10 kWh now. For sailboats, houseboats and motorboats in displacement, the weight makes no difference. However, it makes an enormous difference if I spend 3.000 to 5.000€ more money for the 10 kWh. Therefore, we recommend for larger systems mainly the LiFePO4 battery.

Summarizing one can say: Alone due to the charge cycles and the higher security LiFePO4 batteries are almost always to be recommended, besides can be saved thus partly tidy money.

The from my view most important advantage of lithium iron phosphate is the cheaper price. LiFePO4 batteries are available from as little as 400€ per kWh from us. We recommend, for example, the batteries from Ultimatron and BatteryTechnology, which are really very affordable.

Lithium-ion batteries, on the other hand, start at 800€ and usually cost even closer to 1,000€ per kWh. For planing boats mostly lithium-ion batteries are better suited, simply because of the lower weight, which has a positive effect on consumption and speed.