SX35 External stern thruster 12V w/controller unit

Are Lithium-ion (Li-ion), LiFePO4 or Lithium batteries a good solution for thruster battery banks?

Not necessarily. These systems typically come with a Battery Management System (BMS) that will disconnect the thruster in case of any issue with the battery (for instance, if the thruster draws more current than the BMS allows). Just imagine a sudden cut-out in the middle of a maneuver without any pre-warning.

At Sleipner, we recommend a solution with a simple, separate battery and without a disconnect BMS system (such as the lead acid bank frequently used for starting or similar). The helmsman will then be warned when the battery is getting low and feel that the thrusters are gradually losing power, which is significantly better than losing your thrusters without any pre-warning.

Disclaimer: Ensure battery/energy source is installed according to CE/ISO current rules and regulations and by licensed electricians.

Can I use LiFePO4, Lithium or Lithium-ion batteries for my thrusters?

Yes, you can, but not without taking some precautions. Sleipner produces two product lines of thrusters that will work well with high-capacity batteries and one product line which should be used with caution in combination with LiFePO4, Lithium, Li-ion, or similar batteries, which may be capable of delivering higher voltage under load than traditional batteries (such as lead-acid, AGM, gel or similar).

All Sleipner proportional thrusters will work well with Li-ion or LiFePO4 batteries, as the included PPC unit will control the output voltage to a safe level for the thruster. Make sure, though, that you actually get a good battery intended for maritime use. NB – make sure you have the latest embedded software installed.

All Sleipner eVision thrusters have built-in functionality to limit the maximum voltage delivered to the thruster. Again, make sure your battery is intended for maritime use.

Traditional DC on/off thrusters may be damaged or have a reduced life expectancy if operated at voltage levels outside their specifications.

Disclaimer: Ensure battery/energy source is installed according to CE/ISO current rules and regulations and by licensed electricians.

Can the thruster cause the BMS (Battery Management System) to disconnect the batteries?

Yes. Most engineers would tell you that it is not ideal for connecting the bow thrusters to a service bank protected by a Battery Management System. Thrusters are heavy consumers, and they may create sudden peaks in current draw, which again may cause the BMS to disconnect the batteries if the thruster draws more current than allowed. If this happens in the middle of a maneuver, you would be left without thrusters and may lose control of the boat.

Hence, Sleipner recommends that the thrusters be connected to a separate battery bank (that is not lithium) without a Battery Management System that can disconnect the batteries (and consequently the thrusters).

Disclaimer: Ensure battery/energy source is installed according to CE/ISO current rules and regulations and by licensed electricians.

What happens if I connect a Lithium, Li-ion or similar battery to my “on/off” DC thruster?

A Lithium or Li-ion battery may maintain a significantly higher voltage and higher current under load than a lead-acid, gel or AGM battery. This will provide significantly more power to the thruster motor and give some undesired side effects:

• The propeller will rotate significantly faster and with higher power than what they are designed for, increasing the risk of cavitation and following damages in the tunnel and at the thruster.
• The thruster risks overheating and will have shorter run times. This can cause the thruster to stop in the middle of a maneuver.
• Over time, the thruster may be damaged and you may have a reduced life expectancy.

Sleipners speed controlled thrusters will not be impacted by Lithium, Li-ion or similar battery times providing a steady high voltage.

Disclaimer: Ensure battery/energy source is installed according to CE/ISO current rules and regulations and by licensed electricians.

What is IPC (Intelligent Power Control)?

This is a unique patented Sleipner safety feature supplied with all standard (on/off) DC electric Sleipner thrusters. The IPC functionality provides two unique features:

1. It will detect “flapping” of the solenoid (typically caused by badly charged batteries that are subject to a huge current draw and voltage drop when the thruster motor is engaged), and will stop trying to run the thruster, preventing excess solenoid contact tip wear and dramatically reducing the risk for a weld-in situation of the solenoid. A ‘weld in’ (run away) situation is when a thruster continues operating without a signal from the operator at the control panel.
2. Even if the solenoid has a weld-in situation, which even with the IPC prevention actions is still possible, as all mechanical switches can weld-in at a point, the unique IPC function will STOP THE THRUSTER, without active action by the operator. This will give the operator time to locate and Select OFF on the thruster system Isolation/Main Switch.

What type of batteries are recommended for thrusters?

Sleipner recommends that the thrusters are connected to a battery bank that is not protected by a Battery Management System (BMS). Typically this means lead-acid, AGM, gel, or similar kinds of batteries. This is important because thrusters draw a lot of currents quickly, and the high amp draw may lead the BMS system to think that there is an issue with the system and consequently disconnect the batteries from the circuit, in which case you would lose maneuverability.

If you have Lithium batteries powering your thrusters, the best advice we can give you is to check the actual voltage measured on the thrusters during operation. Sleipner thrusters are designed to operate within a specific voltage range, and as long as you are within these boundaries, it doesn’t matter for the thruster if the current is delivered by this or that battery pack.

It may also be a very good idea to check the actual current drawn from the battery during full power at the thruster to see that you are not at the limit for the BMS to avoid sudden loss of maneuverability if the BMS disconnects the battery.

With installations where the battery pack is far from the thruster, the higher voltage delivered by LiFePO4 or similar batteries might not be a problem as you will experience a voltage drop through the long cables.

Always make sure you measure your voltage on the thruster to avoid the risk of early thruster wear.

As battery technology is changing rapidly, we always recommend consulting a professional battery supplier.

Disclaimer: Ensure battery/energy source is installed according to CE/ISO current rules and regulations and by licensed electricians.