If you have a lead acid battery in the motorhome and it needs to be replaced or if you simply want to upgrade your electrical set-up with a lithium battery, there are a number of points to pay close attention to. You cannot simply replace a lead acid battery with a lithium battery. In this blog we explain what you should pay attention to when purchasing a new battery and how you can make your current electrical installation in the motorhome suitable for a lithium battery.
A lithium battery has many advantages compared to a lead acid battery. For example, a lithium battery is lighter in weight, you can discharge it more deeply and it can easily deliver larger currents. In this blog about which battery in a motorhome you will find more about the advantages and disadvantages of a lithium battery. If you are already convinced of your choice for a lithium battery, read more about how you can make your installation suitable if you want to replace a lead acid battery with lithium.
Purchase lithium motorhome battery
You may have already purchased a lithium battery, but otherwise we would first like to give you some tips on what to look out for when you start looking for a lithium battery. One lithium battery is not the other and because of the for safety you would rather not buy junk or buy the wrong lithium battery. To start with, it is therefore advisable to purchase a lithium battery of the LiFePO4 type. With this type of battery, the cathode (positive terminal) is made of lithium-iron-phosphate, which makes it much more stable (and therefore safer) than other lithium-ion variants.
A LiFePO4 lithium battery is the most common and safe for use in motorhomes, but even within this type of battery there are still a number of choices to be made or things to watch out for. Think of the voltage (12 Volt or 24 Volt), with or without a built-in BMS, the discharge current and of course the capacity. For the required battery capacity, it is good to know that a lithium battery can be discharged deeper (up to 10% remaining) than a lead acid battery (up to 50% or 30% remaining). With the same AHs (Amperes per hour) as your current lead acid battery, you have more capacity available. If you would like to switch to lithium because you want to use more power, for example because you often run out of power, want to use more equipment or want to use equipment which require larger capacities, then you can consider opting for a lithium battery with more capacity. When choosing a lithium battery, you may also want to pay attention to the maximum discharge current if you want to use large capacities, for example because you want to cook on induction in the motorhome.. Not every lithium battery is suitable for this.
Furthermore, with a lithium battery it is important to work with a BMS. BMS stands for Battery Management System and is a special protection module for lithium batteries. The BMS monitors the condition of the battery, especially cell voltage and temperature, and can keep the battery ‘healthy’ by balancing the cells. If the BMS detects that the cells are no longer balanced, the battery is being overcharged, the capacity is too low or the temperature is too low or too high, it will switch off consumers and/or stop battery chargers such as the battery charger, MPPT and DC/DC charger. to prevent irreparable damage to the battery. The BMS is therefore an extra check to protect the lithium battery, so that it has a longer service life. There are both lithium batteries with a built-in BMS and with an external BMS. Those with a built-in BMS are easier to replace with the old lead acid battery, but have the disadvantage that they often have a lower maximum discharge current. Good to pay attention to if you want to use larger capacities and therefore possibly need a higher discharge current.
NOTE* Also make sure that the inverter, 12V consumers that can demand a lot of power and battery chargers (a large battery charger on its own or combined when they are on at the same time, such as the solar panels and the DC/DC Charger while driving) do not exceed the maximum -) charging current of the battery. A BMS will always try to protect the battery against these kinds of factors and can fall into some form of protection. This results in a (usually temporary) non-working battery. Sometimes it is necessary to perform a number of steps to remove the battery from this protection. For example, it may be necessary to disconnect all consumers and battery chargers from the battery in order to activate it again.
Finally, it is good to take into account the minimum temperature for charging a lithium battery. You can use (discharge) a lithium battery at temperatures below freezing, but charging is only possible at temperatures above 5°C. Some manufacturers have built in a heating element for this, but if your motorhome is well insulated and you can keep it warm inside using a heater. for example a diesel heater, then it is not absolutely necessary to choose such a lithium battery if you plan to travel to colder countries. We have traveled to Scandinavia several times in winter with our motorhome with temperatures down to -25°C and have never had any problems charging our lithium battery (without heating element) because it was always warm enough inside the motorhome.
Mount and connect lithium battery
Mount a lithium battery preferably upright with the battery terminals upwards (unless the manual indicates that a different position is also allowed and this is more convenient for you) and pay attention to the position of the battery terminals in connection with the current. the current cable length towards the old lead acid battery. Secure the battery firmly to the floor, for example with wooden beams or angle profiles and straps, so that it cannot slide or bounce while driving. A lithium battery does not suffer from gas forming during charging and therefore does not need to be ventilated to the outside. Some heat development, most manufacturers advise to keep some space (often about 10 cm, but check the manual for the final dimensions) around the battery.
Good to know is that the battery poles (the plus and minus connections on the battery) on a lithium battery are often of a different type than on a lead acid battery. Lithium batteries are usually supplied with an M6 or M8 bolt connection to which you can directly connect a press cable eye. Although adapters are available it is better to connect a new crimp eyelet if the current one does not match. You are then more certain of a good connection. A bad connection can cause strange disturbances and also poses a risk of fire if a lot of current flows through it.
NOTE* If you are going to use larger capacities or if you take a lithium battery with a large battery capacity than before, there is a good chance that you will also have to replace other components in your electrical system. Think of a larger inverter, fuses with a higher fuse rating and thicker cabling. You may therefore have to replace a much larger part of your installation.
Settings for Lithium usage
After mounting and connecting the new lithium battery, it is important to set up all equipment for use with a lithium battery. This must be charged with a different voltage than a lead acid battery. It is especially important to set the battery chargers correctly. If you do not do this, the battery will be charged with the wrong voltage and you might damage the battery. Therefore, set the battery charger or battery charger/inverter and the MPPT to lithium battery. If your battery charger is not suitable for a lithium battery, you must replace it with another one that is suitable.
If you also want to be able to charge the lithium battery via the alternator while driving, install a DC/DC Charger if you don’t already have one. You may already have these in your current installation due to a smart alternator, but if you have a relay such as a Cyrix, you should replace it with a DC/DC Charger. This limits the current to the battery and also ensures a stable and correct charging voltage so the battery cannot be damaged by too high charging voltages.
Any battery monitor such as a BMV should also be set differently, otherwise it will no longer be reliable in keeping track of the current battery capacity and other battery data that is being monitored. An important adjustment here is the Peukert exponent. This is much lower for lithium batteries than for lead acid batteries and, together with other settings, can result in an unreliable battery monitor. Because this setting can differ greatly per battery brand, it is best to contact the manufacturer or supplier for the correct settings.
NOTE* There may be other components within your current electrical installation that need to be set differently if you want to replace a lead acid battery with a lithium battery. Consider, for example, a Battery Protect.
Checklist replacing leadacid battery with lithium
Just a quick overview of what you should pay attention to when you want to replace a motorhome lead battery for a lithium battery:
- The choice for a lithium LiFePO4 battery (12 or 24 volts, with or without built-in BMS and how much capacity in Ah)
- Check whether the maximum allowed discharge current of this lithium battery is sufficient to supply heavy consumers, such as an induction hob
- Are you going for a larger battery capacity and/or do you want to use larger capacities? Then check whether other components in your installation also need to be replaced. Think of a larger inverter, thicker cabling and fuses with a higher fuse rating
- Make sure that all battery chargers (battery charger, charger+inverter in one, DC/DC-charger and MPPT) are lithium-capable and set to lithium. Also make sure that they do not exceed the maximum charge current
- Replace a relay for a DC/DC charger to be able to charge a lithium battery while driving and set it to lithium
- Also set any other equipment, such as a battery monitor and battery guard, to lithium