When we refer to lithium battery in this post, we mean LFP/LiFePO4 and no other lithium technologies.
We often get the question, "do lithium batteries fit in my boat?". The simple answer is yes , but there are a few things that are important to consider, as all boats are different after all.
There is very little right or wrong when installing and using LiFePO4 batteries in your boat. But there are an incredible number of variations on electrical installations in boats and how you should use your boat and your system. For example: holiday use or sailing around the world, guest harbor versus natural harbor. That's why I thought I'd share my experience from 10 years of use with boats and batteries.
Mastervolt, Dometic and other electrical systems
Boats within the same family may have several different electrical systems, depending on model year and equipment. One thing they have in common is that most have a 12V or 24V system and regardless of the electrical system you have in your boat, you can switch to lithium batteries. If you have a boat, where the charger or solar cell regulator does not have lithium settings, that is not a problem either.
Make sure the charger is set for GEL battery 14.2 – 14.3V or AGM battery 14.4V. It is often said that lithium batteries should have a 14.6V charge, but it is a maximum of 14.6V, it works just as well with 14.2–14.4V. You can control or change the charging voltage on most chargers. If you don't have a GEL or AGM mode, then choose to set the charger to 14.2V - 14.4V or the closest voltage below 14.6V. The advantages of lower charging voltage are that you charge the battery a little more gently and that you can charge both the starter and the living area battery with the same charger. The disadvantage is that it takes a little longer to charge the battery. Exactly the same applies to the solar cell regulator.
If you have a 24V system in the car, exactly the same applies, you set the charging voltage to 28.4V or 28.8V, of course 28.6V works just as well. Max charge for lithium batteries 24V is 29.2V.
Generator and DC/DC charging booster
"Is there a risk of burning the generator if I have a lithium battery?"
The short answer to that question is yes , and one of the reasons is that lithium batteries do not suck power out of the generator, but instead take whatever the generator can deliver. The difference between AGM, Gel batteries and LiFePO4 batteries is that LiFePO4 has a very low internal resistance compared to traditional batteries, where the resistance increases. A generator has a regulator, just as you have a regulator between your solar cells and batteries. The regulator regulates the current output from the generator based on what resistance (inertia) the regulator senses. What affects the resistance is not only the inertia of the battery, but cable area, connections, charging relay, cable length, etc. An example is the Volvo Penta KAD engines (the entire KAD series). In the factory, a 10mm 2 cable was connected between the generator and the starter motor. A 35-50mm2 cable was usually used from the starter motor to the battery, depending on the distance between the battery and the motor. This means that the cable area to the starter motor was sufficient, but the 10mm2 cable between generator and starter motor means that you will never get what the generator is capable of delivering. It will be impossible to "burn" the generator because the resistance in the cable will limit the charge current from the regulator.
When talking about a clean installation, it is important to have as short and thick cables as possible between the generator/regulator and the battery. For example half a meter long and 90 mm2 thick and no connections in between, if you have it and plug in LiFePO4 batteries, you will with a high probability "burn" the generator, because the resistance is so low. There are extremely few boats that have a clean setup or even come close to a clean setup.
As previously mentioned, there are very few right or wrong. Even if you don't have a clean installation. then you can put in a DC/DC charger, that's not wrong. Most boats already have a built-in resistance due to cable area, length and connections. In many cases, you may want to increase the cable area to get more charge out of your generator/regulator.
If the cables from the generator to the battery are far too thin (flimsy) and the resistance becomes too high for the generator to catch fire or be destroyed. The problem is that you don't get more than 18-20A, which means that it takes time to charge the passenger compartment battery when driving. If you want to increase the amperage, you can connect a DC/DC charger so that you can get 30-50 A depending on the DC/DC charger. You can also install stronger cables from the generator to the starter battery and on to the EBL and the living room battery.
Solar cells on your boat
Do you have a solar cell or cells on your boat today? What you need to keep in mind is that the solar cell regulator (MPPT) should be set to a maximum charge voltage of 14.6V, but the lithium battery is actually better charged with 14.2 to 14.4V, the same as GEL or AGM batteries. You do not need to change the solar cell regulator to change to lithium batteries, if you set the voltage (Volt) to 14.2V or 14.4V the battery will be fully charged, it just takes a little longer.
Wondering something else? Many answers can be found this spring battery guide!