LFP batteries are gaining popularity. We understand the advantages and disadvantages of this type of battery and why you should switch to them!
What can not be installed
Before moving on to the discussion of lithium batteries, let's talk about what you definitely shouldn't install on your boat. Automotive lithium-ion batteries are something that absolutely cannot be installed. This is especially true for batteries with nickel, cobalt and manganese cells. Due to the nature of their operation, they are more prone to failure due to elevated temperatures and wear when used on a boat.
This moment almost completely eliminates the use of old batteries from electric cars. In the conditions of use at sea, it is not possible to provide the proper level of protection for them. After all, it is unlikely that they were originally developed even to work on a compact Dufour 37.
If you have an electric yacht, then you probably know that it has a higher voltage system than an electric car. Such a system requires a well-designed and well-functioning control system. Often on such yachts you can find systems under 48, 72 or even 96 V.
Lithium-ion batteries with a higher energy density are much more attractive for powering a boat. Among these are lithium-cobalt (LiCoO2). The disadvantage of such a battery will be the overall high cost and complexity of installation. And by expensive, we mean REALLY a lot of money. On the other hand, this option is more durable.
For those who didn't know, energy density is a scalar physical quantity, the amount of energy per unit volume.
Or maybe you should choose LFP batteries?
LFP battery is a lithium iron phosphate battery, a type of electric battery, which is a kind of lithium-ion battery that uses LiFePO4 as a cathode. The main advantage of such a battery is that they support fast charging, as well as recharging using high frequency currents.
Thanks to this, they can be discharged to almost zero, but there is no need for regular recharging. Lead-acid (LA) batteries, for example, have the above-described need for regular recharging, especially when not in use.
High-frequency currents are alternating current, for which such phenomena as the radiation of electromagnetic waves and the skin effect become significant.
Most of the time, LFP batteries perform best in the 20% to 80% range. At the same time, discharging “to zero” will not cause them much harm. Modern battery management systems all shut down batteries at 12V. This is the equivalent of 10% of an LFP battery charge. A similar process occurs when charging. The control system will normally automatically cut off the power supply at around 14.2V to prevent overcharging the battery.
LFPs have many more recharge cycles than their equivalent LAs. Plus - LFP is also much lighter than LA (of any type). So a lithium iron phosphate battery is much better suited for modern yachts.
Are we bulk switching LFP batteries?
The question is good. For such a transition, it is worth remembering that any associated wiring on your boat, as well as the protection of the entire circuit, must be adapted to the lithium iron phosphate battery.
Any subtype of LFP requires attention and care, as well as a comprehensive battery management system (BMS). It should provide protection against reverse polarity, help in balancing individual cells and limit the voltage for charging, control control and emergency shutdown. An equally important aspect of such a system is the detection of battery temperature, limitation and management during discharge, as well as visual and / or audible alarms.
One of the important points is that many LFP battery models are already equipped with a built-in BMS. But, alas, such batteries cannot always be connected in series or in parallel in an amount of more than two pieces. If you need more capacity and power, then the best option is to buy the required number of 3.2 V LFP batteries without a control system. Then connect one control system for all batteries.
LFP batteries are also not recommended for engine starting, windlass or thruster operation. These devices are generally unlikely to operate due to the fact that the instantaneous discharge of high frequency current can exceed the threshold for the operation of the control system.
Lithium iron phosphate battery, like anything else on board, is up to personal preference. With the peculiarities of working with it, this battery still has many fans.
Extended element life
LFP batteries have very low resistance compared to lead acid (LA) batteries. This allows you to charge and discharge them at a much faster rate.
Again, if the LiFePO4 battery is not fully discharged, it is not necessary to charge it after each use. Sulfation, which reduces the capacity of a partially charged lead-acid battery, does not occur with lithium iron phosphate batteries. However, if the control system disconnects the battery from the load due to low voltage, it is best to charge it immediately.
Sulfation is the process of gradually coating charged electrodes with lead sulfate, which is in the form of large crystals.
LiFePO4 batteries are charged at temperatures from 0 to 40 C. Some, but not all, are safe to charge at temperatures below 0 C. At negative temperatures, the charging current is reduced to 0.05-0.1 C (5-10% from battery capacity).
The control system protects the battery from overheating. But the temperature can also be controlled by a charger that has a temperature sensor. Such a charger reduces the voltage if the battery heats up over 20 C and turns off when its temperature reaches 55 C.
The charger duplicates the functions of the BMS and creates an additional layer of protection that will be the first to work in the event of an emergency.
Unlike LA batteries, the charge on an LFP cannot be determined from the battery voltage alone. The problem is that the voltage can reach its peak when the LFP is only half charged. That is, a voltmeter will not give an accurate idea of the condition of the battery. To determine its charge, it is better to use an ampere-hour meter or a battery monitor.
Moreover, a fully charged 12.8V LFP battery has a resting voltage in the range of 13.4-13.6V, which is much higher than the 12.7V of a conventional lead-acid battery. With 20% charged, it will still read 13V while the LA battery will show 11.8V.
The easiest and most popular way to charge LFPs is with DC-DC chargers (picture above). However, the charge delivered to the battery may be limited by the maximum power of the DC-DC charger. But even this can be overcome! It is enough to install several DC-DC chargers in parallel. This should be done if more total charge current is required.
Don't forget the belts!
One of the most important aspects, besides those described above, is the physical wear of the belts. I'm talking about drive belts. LFPs use a faster charge rate, which will put more strain on your generator. Therefore, it is worth (highly recommended) to make sure that the drive belt can withstand the load.
The belt must be of the correct type, look normal (no signs of heavy wear). Immediately make a reservation that a standard V-belt is enough only for generators up to 75 A. If this value is higher or even “flew into space”, then you need to buy a high-strength belt.
To date, only LFP batteries on a yacht can provide current levels of power consumption. Other lithium-ion batteries are difficult to get along on yachts.
The next time you upgrade your yacht, you should take a closer look at the installation of such batteries. Fast charging, large charge capacity, longer service life and operation, the ability to keep batteries for a long time without recharging - this is not a complete list of the advantages of LFP. Well, such batteries will work complete with solar panels. Even if they are small.
Naturally, each boat is unique, as is its owner. Such manipulations should be carried out only after receiving a sufficient amount of theoretical information. The best thing to do is to consult a professional who will point you in the right direction.
We hope that with a short review article we were able to push you to the right thoughts. Do not forget to rate the material, and you can find other interesting articles at the links below or in the "News" section!
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