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A little over a year ago, I replaced my nearly stock Amel 54 “comfort package” lead acid system with a nearly complete LifePo4, aka lithium battery system. The system was designed with the help of Victron engineers and of course a marine electrician, but I will say that many marine electricians today try to apply lead acid thinking to lithium and it leads to many unintended consequences. I promised many of you a writeup on my 1 year experience with my system, what works and what could be better.
I’ll start by saying that lithium truly is life changing. All of the 230v appliances we ran earlier, we can run without genset. On battery, we can cook with induction, run aft aircon all night, heat water, run the boiler, wash clothes and dishes and moreover, charging just got a 20-25% boost due to lithium’s charging efficiency. The only thing that won’t run is that I can’t start up the scuba compressor on inverter power, probably due to startup spike. I can probably install a capacitor to fix that, but it’s low priority and I’m fine starting the genset for that. Despite the cost of my system, I would do it again in a heartbeat. It is the best change we have made on the boat, without question.
I’ll also preface by saying what I’ve said many a time before - I am not an engineer by any means but I simply research, ask questions, execute and then test extensively. I rely on people smarter than me to advise me on things I don’t understand, of which there are many. It’s not a cheap system but given that we are at the front end of a multi-year circumnavigation, I believe the amortized cost is lower than using flooded lead acid/gel/agm. That is, if you don’t kill the batteries, which an improperly setup system may very well do.
My old system consisted of the following:
- Twelve 100AH 12v gel batteries, wired in serial pairs to make 24v and then wired in parallel to make 600 amp hours.
- Dolphin 100amp primary and 30amp secondary charger
- Mastervolt 110amp 24v changer on the main engine with Alpha Pro 1 regulator
- Xantrex power monitor
I’ll start by listing the components of my current electrical system, specifically items related to my lithium installation:
- Six Victron Smart lithium 150ah 12.8v batteries, wired in serial pairs to make 25.6v and then wired in parallel to make 450AH.
- Victron VE.BUS BMS
- Victron Quattro 24v/5000va/120amp charger/inverter
- Victron Skylla-i 24/80 (3) charger with correct adaptor to allow it to talk to the VE.BUS BMS
- Mastervolt 110amp 24v changer on the main engine with Alpha Pro 2 regulator
- Three LG Neon2 320watt solar panels for a total of 960w wired in parallel
- Victron BlueSolar 150/35 MPPT charger with the correct adaptor to allow it to talk to the VE.BUS BMS
- Victron BMV-712 battery monitor
Let’s walk through the individual components and why I chose them, what I like about them and what could be better. The system is NOT perfect and some of the problems I’m trying to solve for are still outstanding. Part of this writeup is to ask for your help, especially those of you who studied/worked with this stuff, and to explain my decision making and have you tell me, with a reasoned argument and evidence, why a different way is better. Or provide solutions for holes in my system - I’ll be the first to say that they exist.
You will note heavy representation by one brand - Victron. That was intentional because one of my biggest fears is that the batteries die and if I had lots of different brands for the various components, they will each point fingers at the other and I would be left holding the bag. Victron has a great reputation and my experience with them has been great. I’m sure Mastervolt or Battle Born or XXXXYYY brand is great, so don’t take my component selection as saying that Victron is the best and no other brand will work.
Batteries: We’ll start with the battery selection. Because lithium can easily go 2000 cycles even with 80% DOD, you don’t need as much bank capacity to equal usable capacity compared to lead acid. With my original 600AH setup and no more than the recommended 40% DOD, the usable AH is 600*.4=240AH. Given the batteries are 12.8v, you need an even number of them to make 25.6v, so I could have gone with 4 of them and had the same usable capacity (300*.8 = 240AH) as the original 600AH setup. But I went for 6 batteries and got 450AH and (450*.8=360AH) usable capacity. Sure, even more is nice, but the reality is that my solar array only puts out about 200-250AH a day, so additional battery bank capacity would simply extend the interval for running the generator and 230v chargers. I probably won’t install a wind generator for various reasons. Each pair of batteries is connected serially using copper bars. The Electrican tried battery cables as jumper wires (“but this worked fine on every other <lead acid> setup I’ve installed!”) but the current going through them caused the cables to overheat. The copper bars aren’t perfect because they can exert force on the battery posts, but that’s the best solution I’ve found to date. Note that each pair is wired to the Amel installed +ve and -ve post in the battery compartment using equal length battery cables.
The Victron Smart lithium 150AH batteries fit in the stock battery location under the passage berth. They were nearly the perfect size, only requiring me to trim a bit of the wooden bracing under the “lid” of the passage berth bed. Some may put larger batteries horizontally, but Victron explicitly cautions against that. For warranty reasons, I will follow their advice. The batteries are considerably lighter than my previous gel batteries - I lost 258kg in battery weight alone. That’s actually a bit of a problem because now we list about 1-1.5 degrees to port and my port side gelcoat is under the waterline and requires weekly scrubbing! Nearly half the battery compartment is empty but I’m too afraid to put anything in the same location as those expensive batteries.
I also added 3 fuses, 450 amps each.
My understanding is that Amel didn’t install battery bank fuses because they didn’t want you to lose bow thruster, windlass or other critical high draw components when voltage drops and consequently amperage skyrockets. This is not really a concern with lithium, where the voltage drop is negligible even when I draw 200amps from them. I can easily run the bow thruster or the windlass with engine/genset off. Even to my non-engineer mind, having non-fused big batteries like this just sounds dangerous. Hearing about a few Amel battery bank explosions reinforces my fear, so I went for the fuses. I zip tie backup fuses and also jumper wires nearby in case the installed fuses fail to handle the currents Amel 54s require. No problems so far.
BMS: With Victron, I went for the VE.BUS BMS system. All the pigtails from the six batteries run in serial to the BMS. As you may know, the BMS monitors the battery condition, down to the cell level.
230v Charger/Inverter: I chose the Quattro 24/5000/120 because it barely fit into the spot where the old Dolphin 100A charger sat, in the engine room. This gives me 5000va (watts, more or less, depending on the 230v appliance) of inverter capacity and can charge at up to 120amps. With lithium, the batteries can take nearly the full charging current up until high 90s state of charge, so I opted for lots of charging capacity for shorter genset runtime. We aren’t on shore power much, so I can’t comment except to say that much of the time, your shore power connection can’t handle that much amperage, so you’ll be limited by that.
The inverter capacity allows us to run virtually everything on the boat. The admiral has been known to run the toaster, microwave and induction cooker at the same time. While the batteries can easily handle that in terms of current delivery, if you draw 200amps like that, you’ll drain the battery bank in about 2.5 hours. Note that lithium capacity does not drop dramatically like lead acid with increasing current. For lead acid, when they say 100amp hours, they mean 5 amps an hour for 20 hours (test load=capacity/20hrs). If you draw 100amps on a lead acid battery, it will probably last 10 minutes and result in a massive voltage drop, increasing your amperage even more. That is not the case with lithium.
Why did I choose the 5000va Quattro and not 3000va model or the 8000va model?
Well for the 3000va model, I figured there would be times where the admiral or crew overload the inverter. It’s not the end of the world if you have a 3000va inverter, but since the batteries can easily handle 5000va of draw, I figured why not? Also the ratings are made for operation at 25 degrees Celsius. It might get a bit hotter on my boat so I wanted excess capacity. Additionally the 5000va fits perfectly, albeit sideways, where the old Dolphin 100amp charger fit. We had to add a wood board for backing, but it fits perfectly and takes advantage of the ventilation provided by Amel to the original Dolphin 100amp. After a year of usage, I have never noted output nor charging current reduction due to heat. The 8000va model is larger and heavier and I am not sure it will fit in the stock Dolphin 100 location. Additionally, the standby draw is twice (2 amps+) the standby draw of the 5000va. There is some power save mode but that makes my analog Amel voltmeter jump constantly, which I avoided for longevity reasons. For me, the Quattro 24/5000/120 was the goldilocks solution.
By using the Quattro, you take the original Amel 230v automatic switch out of the system as the Quattro does it internally. There are advantages to that, as you will see later.
Installing the Quattro requires an ethernet cable and FOUR 50mm^2 battery cables from the engine room to the battery compartment. That means you need to break the epoxy seal between the engine compartment and the passage berth, located on the floor on the forward end of the “passage”. After this, you will re-epoxy the hole so the watertight separation is re-established. I also ran an additional ethernet cable in case of failure of the original cable.
I also added a Victron Skylla-i 24/80 charger. This is intentional for two reasons: (1) If the main Quattro fails, I can easily rewire the shore power lead and run the Skylla. This duplicates the redundancy we had with the original Dolphin 100amp / 30 amp separate chargers. (2) Additionally, this gives me a way to plug-in at marinas that are primarily 110v and then double them up to produce 220v. This is common in the Americas. The problem with this system is that it still retains 60hz, but many of the appliances in our 54 do not run on 60hz. So the concept is that we can use the Skylla to charge the lithium batteries and have the Quattro provide 230v/50hz power via the inverter. The Skylla is wired using the old cables that were connected to the Dolphin 100amp charger. If Amel believes the cables can handle 100amps, I presume it can handle 80amps. The Skylla fits where the old Dolphin 30 amp charger fit, right next to the Quattro.
When the Quattro detects mains/genset power, it will immediately pass it through to the boat’s internal 230v wiring. If that shore power is 60hz, you have a problem. I specifically asked Victron if I could force the Quattro to just charge and not pass through shore power and the answer was a definitive NO. So the Skylla solves that problem if the situation ever arises where we need to plug in for longer periods in locations that only provide 60hz power. I’m sure an expensive frequency converter would be more seamless, but we don’t anticipate many if any long periods of plugging in in the Americas.
Alternator and Charge Controller: The original Mastervolt Alpha Pro 1 alternator charge controller does not have a lithium charging profile and had to be replaced with a newer model. Unfortunately Victron does not make alternators nor alternator charge controllers. Note that most alternators will burn up when subjected to the charging loads imposed by lithium. With lead acid, the maximum current is only required for a short period as lead acid cannot accept full charging current once you get above say 60% state of charge. So your typical 100 amp alternator will only be required to output 100amps for a short period. With lithium, it will be required to output the full amperage until the battery bank is nearly full. Many alternators cannot handle the heat generated from this and will burn out quickly. Speaking to Mastervolt engineers, they were adamant that the Mastervolt 24/110 can easily handle outputting the full current for long periods as lithium requires. For extra measure, I installed a temperature sensor on the alternator to reduce output if the alternator overheats. Additionally, I limited maximum output to 90 amps. This is done via an ethernet adaptor from Mastervolt.
Renewable power generation: I installed a stainless arch above my davits and mounted LG Neon2 panels. I wanted the 350w model but they only had 320w in stock. Note that the size is exactly the same, it’s just some panels have higher yield than others. This gives me 960w total. I opted to connect them in parallel, which requires thicker cables (13mm2) and more of them, but given my research, I believe parallel will allow higher daily total output when there is partial shading from sails/masts. Electricians often push for serial wiring as it’s easier. The solution we came up with is to have a pair of wires from each panel to a junction/switch in the lazarette and then a single pair from there to the MPPT charge controller.
For charge controlling, I opted for the Victron BlueSolar 150/35 MPPT controller. The 150v gives me the voltage capacity in case I decide to re-wire the panels to serial and the 35 amps is just at the level recommended for 1000 watts of solar.
The electricians installed it in the same passage berth compartment as the main switches, which after a while, I realized was not ideal. More about that later.
Finally, I installed a Victron BMV-712 battery monitor in the same location as the original Xantrex monitor, on the Amel 24v panel. It fit perfectly.
Lithium thinking is very different from conventional lead acid thinking. The batteries do not like to be kept at 100%, in fact, for optimal lifetime, you should keep them at 40-50% state of charge. I generally try to keep them between 40-80%. The renewables will add on average, 200-250 amp hours a day in tropical areas. That almost covers my daily usage. But energy is like money, you will never have enough and if you’re not careful, you will end up using more than you have!
With lithium, you can think of the batteries as a “gas tank” for energy. After a year’s usage, the amount I put in via charging is only 2.5% less than the amount drawn out. That 2.5% is charging inefficiency. With lead acid, the charging inefficiency/loss around 10x as much, so when you draw 20 amps, you need to put in 25 amps to replace it! That means the same 1000 watt solar array with lithium is effectively a 750watt array with lead acid. And given that lithium can accept full charge current up to high 90s SOC, very little generated solar power is "wasted" by batteries not being able to accept full current at high SOC, a common problem with lead acid. With the thousands of cycles available in lithium and the charging efficiency, my primary concern is keeping the batteries between 40-80%.
Right now, every 3 days, on overage, I’ll start up the genset and run both chargers (200amp total) for around 30 minutes. My procedure is that I’ll turn off all the chargers (not simple on the Quattro as you need to login via the MK3-USB connector and use the VE-Config software and reduce charging current to zero amps. Then I’ll start the Onan 11kw and run it for 30 seconds before turning on all the chargers to allow oil to circulate. The Skylla 80 amp is wired into the original 230v panel switch for the 100amp Dolphin. I haven’t gotten around to changing the label yet. :) I wire that to AC output 2 on the Quattro, so the Skylla only runs on shorepower/genset, rather than inverter. It also delays switching on by 2 minutes, I believe. Everything else is wired to run off the inverter. Yes, even the water heater and aircon.
To turn off the genset, I’ll turn off all the chargers and then let the genset run with no load for 1 minute before shutting it down. This cool down procedure is probably overkill, but specifically recommended by Onan. Then I’ll reset the Quattro to max charging power in case the laptop dies and I’m unable to increase it later. This procedure, while it occurs only twice a week or so, is something I’m trying to eliminate. I’ll talk about that later.
One disadvantage of pairing up the batteries to produce the required 24v is that these serial pairs can become imbalanced. Same with lead acid, so nothing new here. Most people just let it be, but I am a bit more careful. Once a year or whenever I have good shore power, I’ll use the Quattro to fully charge the battery bank and then disconnect all the batteries. If I’m still living aboard, the Skylla provides clean enough output that I can use it to provide 24v in the absence of a battery bank. I will take my small 12.8v lithium specific charger (1.5amps), which you can buy for $30 on Amazon and charge each 12.8v battery individually. By topping them off individually in this manner, when I pair them back up, they are re-balanced. The Victron batteries have balancing capabilities within the cells of each individual battery, but NOT across a serial pair. While this is probably not necessary, the cost of the batteries is making me do whatever I can do ensure they are happy. I went nearly a year before this balancing procedure and the batteries remained quite balanced - again my procedure is probably overkill.
All is not perfect on our system. With lithium, each 12.8v battery is composed of 4cells. If any of those cells drop below a certain voltage or go above a certain voltage or overheat, they will be damaged irreparably. That’s why you have a BMS to monitor all the cells individually. However, the BMS only warns of dangerous conditions - you need something to act on that warning.
You need a device to disconnect loads when the voltage is low, as indicated by the BMS. Initially I installed the Victron BP-220 which can handle 220 amps continuous and a lot more for short periods, supposedly. It was a reminder never to trust the marketing material without testing. The first time I used my hydraulic passarelle, the BP-220 melted. The Amel was not initially wired with lithium in mind, so the “control” wires that are connected to switches and have low current are not separated from the “power supply” wires when they get to the main switches. If you could take the time to separate that out, 220 amp capacity of the BP-220 would be plenty, but as is, it’s not sufficient.
My current solution involves not letting the battery bank state of charge drop below 25%. I’ve confirmed with Victron that this will make it very very unlikely that you’ll have a cell low voltage condition. Moreover, the inverter will stop inverting if the BMS indicates a cell low voltage condition.
Does anyone have a solenoid they can suggest? The VE.BUS BMS load disconnect functions by sending out a signal at battery voltage (eg - 25.8v) when all is good and drops to open circuit when the load needs to be disconnected. The VE.BUS BMS can power a solenoid that requires up to 2amps but obviously I would prefer something that is bi-stable so it doesn’t draw power continuously when all is good. I would prefer something that can handle at least 600amps continuous.
To prevent cell over temperature or over voltage, there needs to be a way to cut off charging. The VE.BUS BMS communicates with the Quattro, the Skylla and the MPPT. If the BMS signals a problem, the Victron devices will stop charging.
The Mastervolt alternator, however, is not controlled by the VE.BUS BMS. According to Victron documentation, the VE.BUS BMS has an output that provides 10mA of power to control a simple relay in response to battery over voltage conditions. The Mastervolt controller has a “reg-on” brown wire that allows you to safely cut off charging on the Mastervolt alternator. All you need to do is disconnect it. Mastervolt provides this functionality and states that you can wire it to a switch and use it to safely turn off the alternator to give additional motoring power when needed. So it’s safe for the alternator, per Mastervolt. But, despite trying 24v relays and even 12v relays, the VE.BUS BMS could not power a relay to control the reg-on and consequently turn off the alternator if necessary.
I had a long discussion with Victron engineers and they suggested I try this very low current relay.
Any thoughts on this? It needs to require a lower power draw to activate than a normal 24 or 12v Hella automotive relay.
In the meantime, the Victron engineers suggested I set the absorption voltage on the Mastervolt to 27.5 volts. By doing that, it does not fully charge the lithium bank and with that low of absorption voltage, the likelihood we have a cell overvoltage condition is very very small. In fact, given lithium’s distaste of persistent high state of charge, I may lower the absorption voltage further so I don’t keep the batteries at high SOC during extended motoring.
Shorepower charging and state of charge:
Another problem I have tried to solve is regarding state of charge while plugged in for long periods. Personally I don’t like to plug in because of horror stories I’ve heard regarding bad wiring at marinas and zincs disappearing very quickly. In fact, I’ve been tied up for 2 months during this hurricane season and I have not even bothered to plug in - I just let the solar array take care of the batteries. We even run AC when it’s too hot.
Now the challenge when you’re either plugged in or not using much energy as is the case when you’re not moving much is how to keep the batteries from sitting at 100%. Lead acid thinking requires you to keep the batteries fully charged - in the lithium world that will reduce their lifespan.
One solution is to set a lower absorption voltage when you’re plugged into shore power for a long time, so that the chargers stop charging at say, 60% state of charge. This is done through trial and error because one of the advantages of lithium is very little voltage drop with respect to state of charge. That, of course, makes it hard to determine state of charge. But trial enough or more accurately, error enough and you’ll figure it out.
MPPT choice and location:
If I could do it again, I would have bought the SmartSolar vs. the BlueSolar. I like monitoring and tracking and the SmartSolar has the bluetooth transmitter built in. The BlueSolar does not and requires that I add in a bluetooth transmitter, which is fine except for the fact that the same data comm port on the MPPT is used by the charging cutoff signal from the VE.BUS BMS.
I also don’t like the current location of the BlueSolar MPPT as it heats up the main battery switch compartment where it’s located. I don’t want to vent it to the passage berth area as we don't want to add more heat to our living spaces. I also don’t want to vent it outside using the existing battery vent because I would rather not have salt mist enter a compartment full of wires. I’m sure Amel thought of that when they installed the vent in the engine room - I am not going to take unnecessary risk with my expensive lithium setup by altering the vent system in the battery compartment. What I will likely do is mount it in the engine room and use the old wiring for the Dolphin 30 amp charger to extend the solar panel feed to the MPPT. Then I’ll just use the same 2 pairs of 50mm2 wires that the Quattro uses in order to feed solar charging current to the batteries.
Safety, Better Batteries, Drop In Solutions, Replacing Batteries.
A few final notes - LifePo4 is very different and far safer than the lithium batteries that you hear about blowing up in phones and laptops. You can research it, so I’ll leave it at that. Some have suggested that cheaper and better battery technologies are right around the corner. To me, I could wait until next year to buy a computer and I might get a faster one, but then I will not have a computer for a year. We are circumnavigating now and really enjoy having a functioning power system now. After experiencing life on lithium, I would never go back to lead acid/gel/agm. Moreover, I knew some people when I was back in grad school (known for their engineering department) who were talking about solid state batteries and that wasn’t last year. :) The statements I’ve read about solid state batteries being right around the corner have been from the same institution. Perhaps this time, it’s true, but I am not holding my breath.
Some companies are selling you drop in solutions. Just buy their lithium batteries and you can use your existing charging system and it just works. Hopefully after reading this description of my experience with lithium, you will not send money to them. Otherwise you’ll probably be sending more money once your batteries die unexpectedly.
Finally, some have wondered what happens if a battery fails in the middle of the Tuomotus, stating that you can’t find a lithium replacement out there and you’re screwed. Well, while I agree you won’t find a lithium replacement in every harbor in the world, you aren’t really screwed. All of my chargers can handle standard gel/lead acid/agm batteries and if necessary, you can replace them with lead acid and just change the charging profile. But the reality is that with the ability for lithium to take deep discharges with no damage, I would probably just take a battery pair out of my bank and keep going. But this does highlight the fact that you should be able to change the charging profile yourself. It’s not rocket science and if I can do it, anyone can.
Next steps for me:
As I mentioned, I am not 100% happy with the alternator charge (high voltage) disconnect situation and the missing low voltage load disconnect solution. I’m all ears on how I can fix those.
The next project for me, which could be easy or cause intense brain damage is wiring the Onan generator to automatically start at 30% SOC and turn off at 75% SOC. It’s relatively easy to get the Onan generator to start with the Victron system, but I want the generator to start, with no load for 30 seconds, then turn on the chargers, run for the necessary time to charge up to 75% SOC and then turn off chargers and run the generator for an additional 60 seconds to cool down before shutting off the generator.
I think I’ve found a solution in the programmable relays in the Quattro paired with the relay in the BMV-712, but I need to consult with my smart friends first before I try this solution. With it implemented, my system would remove one of the heretofore seemingly unavoidable annoyances of sailing an electricity hungry sailboat - constantly monitoring the battery SOC. The solar would provide most of my power and if that proves not enough, the generator would automatically kick in, maintaining the built in protections (overheat/oil pressure/etc) that the Onan has.
Anyways, this post is far too long already. Hopefully this opens up a discussion and I’m happy to answer any questions on things that I have not explained clearly or omitted, which I’m sure there are many.
2007 A54 #69