My conversion to Lithium (and Cerbo) – by Stefanie
Yacht Taku Moe – electrical refit
Sailors and recreational vehicle adventurers will remember Stefanie’s last year’s blog, entitled Sailing with Signal K.
In it she described her implemention of data coms connectivity – allowing her yacht’s various electronic devices to talk to each other …and to her.
During Lockdown she’s been busy again – converting her yacht to Lithium, and exploring the extensive range of communication ports on her new Cerbo GX which lies at the heart of this system.
First of all she tells us – Why Lithium?
- Almost double the usable energy with the same capacity
- high energy density
- Up to 70% weight savings compared to lead-acid batteries
- almost loss-free charging of the lithium batteries (99% efficiency)
- high charging and discharging currents (ideal for inductive off-grid cooking)
- very low self-discharge
- significantly extended service life with up to 5000 charging cycles
- absolutely maintenance-free
- makes gas on board superfluous (induction cooking – no propane makes me feel much safer)
Stefanie also cites arguments against a conversion:
- high investment costs that will only pay for themselves over the years
- significantly increased installation effort
- Cannot be charged at temperatures below 5°C
- needs an arsenal of safeguards
- old charging technology partly no longer usable
Stefanie says: For us, the advantages outweighed the disadvantages, as I am familiar with the technology and can do the installation myself. That saves a lot of money and time. In addition, I trust no one more than myself 🙂 .
At sea, under sail Stefanie generates power from a solar array offering 510Wp – which she can augment with a portable array offering a further 200Wp, which she deploys on cloudy days. When she is motoring her power comes from a Balmar 6-series 100A alternator. We will hear about her alternator installation, and how she controls all that charging power, in a couple of weeks.
This week she generously details her whole installation and the reasoning behind her choices:
…At the end of January, Heike and I visited Boot in Düsseldorf to get a few missing items, but especially to look for a supplier for the retrofitting.
The Victron Energy brand was obvious from the start, because I’ve only had the best experiences with Victron. I don’t have experience of the competition, for example Mastervolt, but I swear by Victron. In addition, I occasionally test new firmware for Victron on various devices and believe that there can be no better support. Which manufacturer already has such a large community and reacts to bugs with an immediate update? Most of it is now even open source.
We had contact with Transwatt GmbH from Soest a few years ago when Lunatronic equipped us with Victron equipment and AGM batteries. They were always contact person # 1 for small problems. Transwatt also had a booth at the fair, so we met their managing director, Mr. Mischkowski, for a discussion. Since I had clear ideas about the new system, the rough design was created quickly. I later sketched more details in a diagram.
Despite Corona, delivery was made almost on time at the beginning of May. The sheer number of components made me swallow hard. Is that all supposed to go on board? Where?
Of course I’d thought about it beforehand, but it only becomes real when you have everything in front of you.
The AGM battery bank including charging technology, inverter etc. was quickly removed and I was able to start the installation.
First I sunk the four Victron SmartLithium 12.8 100Ah into the battery compartment. While one of the four AGM batteries weighed 33kg, the new ones were only 15kg. Even with my badly damaged back, that’s still manageable. The space savings are also enormous when you compare the two installations:
Each of the four lithium batteries goes to a Lynx Power In. All cables, positive and negative, are exactly the same length. This is particularly important because the internal resistance of lithium is very small. Any additional resistance – be it due to different cable lengths, badly pressed tubular cable lugs or incorrectly screwed contacts / corrosion – adds up and creates an imbalance. The positive connections are each protected with a 150A ANL fuse. Of course, a parallel connection can also be implemented more easily. But it was particularly important to me to make the system reasonably clear and to secure it. This works particularly well with the Lynx Distributor or the Lynx Power In (can easily be converted as a distributor).
Between another Lynx Power In, the BMV-702‘s shunt is on the negative side and a main battery switch on the positive side. Main battery switch under the saloon bunk? Yeah right. With this switch I can close down the entire system. That would be important, for example, when servicing the MultiPlus or other system components; or when we leave the ship for a long period of time. In the latter case, absolutely nothing should be attached to the batteries. With an absolutely minimal self-discharge rate, this is the best way to protect the batteries during your absence. Otherwise, however, the system monitoring needs electricity, and nothing would be worse in the long run than if someone accidentally turned this switch on or off “just for fun”. Basically, however, the switch is always on.
I also converted the second Lynx Power In into a distributor. Connected there are, among other things, all chargers (Victron SmartSolar MPPT 150/35 and 75/15; Victron Orion Tr-smart 12 / 12-18; Victron MultiPlus 12/3000 / 120-50), as well as the output to the loads on the switch panel of Taku Moe.
The chargers are connected via a Victron Smart BatteryProtect 12V / 65A. The Victron VE.Bus BMS decouples the chargers in the event of a “charge disconnect” caused by an increased cell voltage and thus prevents a further increase in the cell voltage, which would otherwise cause the batteries to die quickly. If the cell voltage falls below an adjustable level, the chargers are switched on again.
All 12V consumers (with the exception of the Victron VE.Bus BMS) are run via a Victron Smart BatteryProtect 12V / 220Ah. If the cell voltage is too low – which in the worst case scenario can also end fatally for the expensive lithium batteries – the VE.Bus BMS with its “Load Disconnect” ensures that all loads are switched off and the batteries are no further discharged. Only when an adjustable cell voltage is restored are the consumers switched on again.
Not a nice scenario, but absolutely necessary. If the cell voltage is too low, however, it should be an absolute exception, which 1. does not come as a surprise if you have your system under control and 2. does not really endanger the safety of the ship or the crew, even if there is no more electricity on board. Sure, the autopilot, plotter and all its relatives on board are indispensable, but in an emergency we can do without them – at least for a short time, during which either the defective battery is removed from the system or the error has been eliminated.
The Victron MultiPlus 12/3000 / 120-50, our inverter and shore power charger at the same time, is also connected to the second Lynx Power In. With up to 120A charging current, the batteries are charged in an astonishingly short time 😉 .
The VE.Bus BMS is connected to a so-called AC Mains Detector. The latter registers an existing shore power connection and, controlled via the VE.Bus BMS, switches on the MultiPlus’s charger if the cell voltage is too low. Otherwise, the inverter reliably supplies us with up to 3kW power from the lithium batteries. Enough for inductive cooking or other power-hungry 230V devices.
For smaller AC loads I installed a Victron Phoenix 12/375 inverter. It works much more efficiently with small consumers (laptop chargers etc.).
Almost all devices are connected to the Victron Cerbo GX. The Cerbo is like our control and information centre. Via the GX Touch 50 display, all relevant values can be read immediately and, in some cases, devices can be switched on and off, and their parameters changed.
The Cerbo GX has a complete arsenal of different entrances and exits and is always accessible via the internet with our ship router. So we have almost full control over the processes in the ship with regard to the electrical system.
Victron has continuously developed VenusOS over the past few years. There is now also a version with the so-called “large image”. In addition to the actual VenusOS operating system, this version also contains an implemented version of Node-Red and Signal K.
Last year I made a lot of effort to enable the most complete control and monitoring of the ship navigation data and electronics with Raspberry Pi’s, now all of this is done by the Cerbo GX! And if a function has not yet been implemented, this usually happens in the next firmware update or you play about with Node-Red and build the feature yourself.
The Cerbo GX is connected directly to the NMEA2000 network via one of the VE.CAN ports, so that all data from NMEA2000 is also available on our iPhones / MacBooks via Signal K. In addition, the Cerbo also provides the Victron system data on connected batteries, charge controllers, and the like. Ready for the chart plotter. Modern MFD’s have already integrated the Victron HTML5 app in order to receive information about the Victron system on the chart plotter. Older MFDs, on the other hand, may offer maximum battery voltage and current. In any case, the Raspberry Pi’s disappeared in the moth box. At least until I can think of something new to use 🙂 .
Gone are the days of adapting signal K to the system to a large extent or of laboriously programming it. Most of the data is automatically available, for example, in the WilhelmSK APP. Plug and play.
Only a small selection of display options – WilhelmSK on the iPad
That was essentially it with the conversion. It all took a while, but the installation was also a lot of fun.
In the next post, however, it goes a little further. Our good old alternator is to be exchanged for a high-performance alternator.
I would particularly like to thank Victron Energy, Transwatt GmbH with Mr. Wischkowski and Mr. Hupfeld for the great support in realizing this project.
German speakers will certainly wish to follow Stefanie’s blog.
By Justin Tyers