Lessons learned: Thrusters, Lithium and SOC

Good day,

Calling all dealers, designers and installers.

Recently I’ve been involved in two technical support cases of which I want to share my insights and the lessons learned.

The first is about Battery State of Charge, and especially for systems that include a Color Control GX or Venus GX. The various options can be quite confusing and initially we didn’t have a manual explaining them. We do now!

See the SOC link below. Please take the time to study this carefully. Anyone involved with advising, designing or troubleshooting systems with the aforementioned devices should know this by heart:
Battery State of Charge (SOC)

The second lesson concerns a typical marine topic: bow and/or stern thrusters and their batteries. The conclusion is simple: don’t put thrusters on the house battery, especially don’t do so when using bms protected lithium for the house battery.
The main reasons for that:

• Combining thrusters on one battery with Multis and other electronics is not a good idea: spikes from thrusters cause issues and/or damage to the connected electronics.
• Another reason why combining thrusters with house loads is not a good idea: using the thruster can empty the battery of the whole boat, instead of only its own battery.
• Having thrusters on a lithium battery with a BMS that will disconnect them in case of any issue is not a good idea either: just imagine a sudden cut out in the middle of a manoeuvre without pre-warning. Note that we do not give warranty on our batteries if there is no BMS with full disconnect installed, which basically rules out Victron lithium batteries for such purpose.

Instead opt for a simple separate battery, without a disconnect BMS. Then the helmsman will automatically be warned when the battery is at a low SOC: in that you’ll feel that the thrusters are losing power, rather than having to do without them, without any pre-warning.

So please make sure not to advise nor accept such installations as a designer, dealer or installer.

Have a good weekend!

Matthijs