Lithium version 3.0 in our Swan 431 CAID

[ihe2]

Hi You all!

I started designing and implementing the system four years ago and now I can finally say it's finished! Because of my background in software business, I call it version 3.0 - that's usually when the teething troubles are over and the system is working as intended.

I started the project by reading all the related information from here and other sources. My eyes opened and it wasn't such a piece of cake I assumed! For starters I decided connecting 320AH LiFePO4 cells in parallel with the lead acid battery and monitoring the system with Batrium's BMS and software. The Lithium battery was simply disconnected from the rest of the power system using a bipolar relay in case of any problem. The system worked fine without any HVE or LVE happening during normal operation. Of course, I had carefully tested that disconnection/connection would actually occur if necessary. The mains charger is a Victron 120A/3000VA Quattro and the new Beta 50hp engine had a Balmar 100A version with MC614 as the charger.

The following year I added a lithium backup battery and completely removed the 4 year old deep discharge LA batteries and put in a 100Ah basic LA battery to take over the loaddump when needed. I rewired all the battery wiring to be more rigid and removed all the old Nautor installed switches, gauges, etc. I installed BEP brand motorised switches to separate the different batteries and designed and made a control panel in aluminium for them. Now I turn the power on and off, select batteries etc with small rotary switches on the panel. They have been workin fine. Of course, all the Bep motorized switches etc can also be operated manually. The BMS also monitors and controls the BEP switches ofcourse.

Everything still worked fine and the following summer I added a Balmar 180A XT charger still controlled by the MC614. I gave up the Batrium BMS and got a new BMS with more control options from GWL.

Now in my latest version (pic) the battery has been replaced with new Winston 400Ah cells while retaining the old lithium backup battery. All charging sources and latching relays etc are controlled by the BMS in analogue with very low consumption relays, opto-isolators or similar. The new 500A BiPolar BlueSea relays switch the charge and discharge busbars on and off under the analog control of the BMS (off, if HVE and LVE continue for more than 15 seconds). They can also be controlled manually.

Balmar XT is connected directly between the lead acid battery and the charge busbar for loaddump reasons and the final protection is to open the Bep motorised switches by the BMS if a significant overvoltage condition (HVE+0.3V) persists for more than 2 seconds. The system also has a Sterling charger protection device for this situation. That has never happened so far. Last winter I also replaced the main power panels on the 12VDC and 240VAC sides (photos) with new ones of my own design and added a Victro Cerbo GX unit plus other Victron stuff to the system. At the same time, the boat's ethernet network was completely rebuilt with a view to the future planned Starlink installation.

So why did I end up controlling the system by analogue means even though my background is strongly in computer science? Actually, this is exactly why. It's quite hard to say what to fix on the fly if something unexpected happens on the CAN bus and despite the BMS's best efforts the battery is charged or discharged outside its comfort zone. In an analogue system, everything can be operated manually if necessary and troubleshooted with a multimeter. I’ve had no troubles at all during these 4 years so I’d like to think our system is reliable enough. And, of someone will naturally remind me that different batteryy chemistrys are not allowed in a boat lifepo system (ABYC). I know that and I’m willing to take the risk as it simplifies a lot of the system design and implementation.

Below are some pictures of the system. Dawnings are only made for my own use, so please forgive me if something is shown amateurishly! Have a nice spring for everyone!







IHe from Finland

[BaccaSean]

Looks definitely very nice! Thanks for sharing.

Can you give us an overview of the terminal block layout?

[ihe2]

Thank You for those kind words of Yours.

The upper bar gives ground for those sual boat accessories and also for all the different signals and to the circuits of the panel itself.

The middle bar is mainly for different signals between the panel and those devices it either controls or receives signals from. It has some other uses also. For example It has a bank of connectors for dedicated devices which are always on, even if this panel itself is turned off. There are two pushbuttons at the panel which swithes these devices (BMS, bilge pumps, radio memory, barograph, etc) on and off using a 120ADC bipolar relay. When this EVERYTHING OFF button is pushed, all of the boat's electrical systems are disconnected from any energy source. Only one item, the similar ON button is active and still connected to get the systems up again.

The lower bar is for accessories switched on and off from this main panel. Lights, navigation instruments, radios and so on.

It wasn't exactly an easy job to do. I spent at least 200h in designing the system and assembling/testing the panel at my home"lab" last winter and spring. After 4 long days at the boat last spring the panel was finally connected and functional. And at least 5 more days with our new BMS, Victron devices and ethernet implementation.

After all, it is very satisfactory to do something real and visible for a chance.