Modern lithium setup for boats

[s/v Jedi]

With the increased interest in lithium batteries as pricing comes down, I find many sailors don’t realize how a modern setup works. They also don’t realize why Victron equipment is so popular. So I decided to write this post, hopefully explaining the key points of such a system.

Imagine you have a “power system” that provides DC power at several voltages, like 12V, 24V or even 48V, all simultaneously and automatically. Also, it provides AC power to run a high power, all electric galley as well as a small phone charger. For US boats, it provides 120V as well as 240V AC, while EU boats enjoy the familiar 230V system.

Power doesn’t come by itself, it needs to be generated and we can use several sources like solar panels, diesel or gasoline fueled generators, engine mounted alternators, wind generators and shore power. A modern system allows all of these and is able to run them in any combination, automatically (even though many, including me, like to keep some manual control).

The generated power is put into our power system, independent of whatever power is currently used and taken from the power system. When you run a 2kW generator, you don’t have to worry about switching on a 3kW air conditioner, which used to stall the generator immediately. We can even start multiple such high loads simultaneously regardless of the generator running or not.

This doesn’t mean that the power system has inefficiencies like running everything from batteries and power input just charging those batteries. No, when AC power from a generator or shore power is fed into the system, it is directly switched to the output to feed appliances. The system is smart enough to augment that output with inverter power when required and it can adapt fast enough that we don’t even notice.

This amazing power system is easy to build, from small to large scale. So what do we need?

1. LiFePO4 batteries. This is the safe lithium chemistry, unlike the cobalt variants that are in the headlines about lithium battery fires. These won’t ignite and unlike even the old lead-acid batteries, they don’t go into thermal runaway under any realistic scenario.
For most cruisers who want to eliminate propane gas from their galley, the minimum size battery needed is 7kWh. You can achieve that by buying batteries that add up to that amount in a manufacturer recommended setup, or you can build one yourself for which you need eight of the popular 280Ah cells in series, creating a 24V battery or battery bank.
now you need to add some accessories: a class-T fuse, a battery switch and a battery monitor. I recommend BlueSea Systems fuse and their Remote Battery Switch and the Victron Smart BMV monitor.
Now here comes the catch: you need to create two of these battery banks, with all the accessories duplicated as well. This provides redundancy as well as extra capacity for periods where less power can be generated (low solar output etc.)

2. A powerful inverter/charger system. Most of the features from the above description are implemented by this system and you need to scale it to your power requirements. This is where the Victron Multiplus systems get their popularity from because they provide the features that can prevent overloading generators or shore power as well as boosting that generator or shore power with inverter power. Also, they can help “soft starting” appliances like air conditioners that have a high inrush current.
For most cruisers I recommend to use two Multiplus 3000 units in parallel service. Large boats can use three or even use higher power models but make sure to always have at least two. This allows for redundancy but also some special setups for dealing with foreign shore power, like an EU boat in the US etc.
There’s one more recommendation for US boats and that is to buy the EU 230V 50Hz models. You can easily reprogram these to 240V 60Hz and on the output add a Victron Auto-Transformer to create the US standard 120/240V service. This allows 240V appliances that run much better than equivalent 120V appliances (A/C, cooktops, watermakers etc.)

3. Solar panels. You want to be as much independent from generators and shore power as possible and solar panels are the #1 candidate to achieve that. If you don’t fancy the looks of large solar arrays on boats then you need big diesel gensets or stay with propane fuel. For most cruisers the minimum target to achieve energy independence is a 2kW array. This is easy for catamarans but not so easy for monohulls. You can achieve a 2kW array with four Renogy bifacial 450W panels. That array is 175” x 75” surface area. Being a monohull, we built a sliding system that is 185” x 75” deployed but only 95” by 75” with the outer panels retracted, which still generates 900W power (you block the bifacial surface with the retractable panels).
This array is connected to a Victron Smart MPPT controller. I recommend the 150/85 VE.Can unit that can handle the whole array but you would want a spare aboard for cruising areas without Amazon Prime delivery ;-)

4. Shore power is something that can seriously hurt not just the crew (electrocution) but also the boat (galvanic corrosion). This is why I recommend to use it for one thing only: power an isolation transformer. The popular Victron 3.6kW transformer is enough for most cruisers and it can adapt voltages for boats in foreign waters. The output of the transformer isn’t shore power anymore: it is a new power source that is fed by a magnetic field that was generated by shore power. All risks surrounding shore power are eliminated by the transformer, but of course we still have a potentially dangerous voltage so the electrical installation aboard still requires professional level.

5. Victron Cerbo GX is the management system that synchronizes systems and connects it to the boat’s NMEA2000 network as well as to the Victron Portal where all statistics are kept and management tasks are performed. Note that the VE.Can solar controller also connects to NMEA2000.

Even though the system described above is extensive, it does eliminate the propane fuel from the boat which isn’t just dangerous but also a pain to refill while cruising. I include three diagrams, one that matches the system described for US boats, another one for EU boats and also a basic system that fits the smallest cruisers while still providing the important features described and allowing a single induction cooktop for when propane runs out.
The last diagram is for the DC side.

[rslifkin]

I don't see anything above 12V on the DC side in that diagram?

Personally, I'm a bit torn on the DC voltage issue. When I upgrade batteries at some point and probably want to go bigger on the inverter(s), it would start to make sense to switch to a 24V house system. But at the same time, converting an existing boat from 12V -> 24V is a pain. Some stuff is easy, just spend money and replace it with a 24V version (such as the windlass motor and bilge pumps). And some stuff will already run on either voltage. But I'd still be forced to split to 2 DC panels and run DC-DC converters to supply loads that are stuck at 12v and can't be switched over.

[Chotu]

this is a beautiful state of the art system. Honestly, well done. it is basically the picture of perfection.

I noticed that you very carefully planned everything out and document it. Is there a chance you documented the price of all the components? So someone could see what a system like this might cost them?

because I think that’s the only reason someone might not go for it. Budgetary reasons.

you can achieve most of what is being done here by separating the items out. A battery charger. Isolation transformer. Inverter. Generator. Solar charge controllers.

if you have all of these as separate components, it still works the same way. The inverter will dip into your battery bank, which is being charged by a generator or solar or whatever, allowing you the soft start capability.

you might manually have to switch between generator and shore power using a transfer switch however. But if you always run everything through your battery charger and pull all of your loads off the inverter and DC system, it behaves the same way as yours. That’s how I have mine set up at i think a small fraction of the price.

Note: i did not size it for my massive air conditioning loads. those go straight from the generator, not through the DC system.

[rslifkin]

You could do it with separate components, but at least for the Victron stuff, the inverter/charger combo gives a few benefits beyond auto-transfer. You can set a limit to how much it can draw from shore or generator power. As you approach that limit with loads, it will reduce the battery charge rate to keep you within the power budget. And you can have it also draw from the batteries to supplement input power if you've got short term loads beyond what the shore/gen supply can support.

[s/v Jedi]

Originally Posted by rslifkin

I don't see anything above 12V on the DC side in that diagram?

Personally, I'm a bit torn on the DC voltage issue. When I upgrade batteries at some point and probably want to go bigger on the inverter(s), it would start to make sense to switch to a 24V house system. But at the same time, converting an existing boat from 12V -> 24V is a pain. Some stuff is easy, just spend money and replace it with a 24V version (such as the windlass motor and bilge pumps). And some stuff will already run on either voltage. But I'd still be forced to split to 2 DC panels and run DC-DC converters to supply loads that are stuck at 12v and can't be switched over.

Yes, for some stupidity reason I put up the 12V diagram instead of the 24V diagram

But if you imagine the LFP batteries are 24V and the 12V LFP busbar says 24V LFP then it’s good. The dc-dc converters are there.

It isn’t a problem at all to switch to 24V. You install an extra 24V busbar, fusebox and that’s it on the main side of things. On the distribution side, your breaker probably has busbars directly attached to the input of the breakers. You simply remove that and wire breakers to either a new, small 12V busbar or 24V busbar. You can still group some if it plays out well but I have a separate feed to each breaker and both busbars at equal distance so I can easily move from one to the other.

[s/v Jedi]

Here is the correct 24V diagram

[rslifkin]

Originally Posted by s/v Jedi

Yes, for some stupidity reason I put up the 12V diagram instead of the 24V diagram

But if you imagine the LFP batteries are 24V and the 12V LFP busbar says 24V LFP then it’s good. The dc-dc converters are there.

It isn’t a problem at all to switch to 24V. You install an extra 24V busbar, fusebox and that’s it on the main side of things. On the distribution side, your breaker probably has busbars directly attached to the input of the breakers. You simply remove that and wire breakers to either a new, small 12V busbar or 24V busbar. You can still group some if it plays out well but I have a separate feed to each breaker and both busbars at equal distance so I can easily move from one to the other.

That makes sense and fits with how I was picturing a conversion on my boat. Either just an oversized set of 24V -> 12V converters feeding the 12v portion of the panel, or throw an AGM in there somewhere as a buffer. And in my case, it would have 12V -> 24V converters for alternator to house bank charging unless I add a second alternator to each engine (as the engines will remain 12v with separate start batteries).

[s/v Jedi]

Originally Posted by rslifkin

That makes sense and fits with how I was picturing a conversion on my boat. Either just an oversized set of 24V -> 12V converters feeding the 12v portion of the panel, or throw an AGM in there somewhere as a buffer. And in my case, it would have 12V -> 24V converters for alternator to house bank charging unless I add a second alternator to each engine (as the engines will remain 12v with separate start batteries).

I converted my start battery to a general 12V bank battery that’s also used for starting. This is fine because there’s a couple dc-dc chargers keeping that battery in float which normally supply all 12V power, with the battery just helping for peak loads.

[s/v Jedi]

Originally Posted by Chotu

this is a beautiful state of the art system. Honestly, well done. it is basically the picture of perfection.

I noticed that you very carefully planned everything out and document it. Is there a chance you documented the price of all the components? So someone could see what a system like this might cost them?

because I think that’s the only reason someone might not go for it. Budgetary reasons.

you can achieve most of what is being done here by separating the items out. A battery charger. Isolation transformer. Inverter. Generator. Solar charge controllers.

if you have all of these as separate components, it still works the same way. The inverter will dip into your battery bank, which is being charged by a generator or solar or whatever, allowing you the soft start capability.

you might manually have to switch between generator and shore power using a transfer switch however. But if you always run everything through your battery charger and pull all of your loads off the inverter and DC system, it behaves the same way as yours. That’s how I have mine set up at i think a small fraction of the price.

Note: i did not size it for my massive air conditioning loads. those go straight from the generator, not through the DC system.

It’s very hard to price out as for batteries alone you get wild variance. A shop like pkys allows quickly pricing all components. I have no commercial interest in any of this so I don’t bother with pricing

[Mal Reynolds]

Thank you, Jedi. Awesome as always.

A big missing piece you didn't mention is the alternator/regulator integration (Wakespeed & Zeus) with the BMS such that the BMS controls the regulator also. With newer high output alternators at 24 & 48 volts, charge rates can go up dramatically. Even large banks can get topped off just by motoring in & out of an anchorage.

[s/v Jedi]

Originally Posted by Chotu

Note: i did not size it for my massive air conditioning loads. those go straight from the generator, not through the DC system.

Then you did it wrong You missed the key points that I start about. It shouldn’t matter if your generator is running or not for switching loads on/off. The generator has a supporting role as power generation plant and the Cerbo can fully automate running it when needed (for high loads as well as for battery charging… all simultaneously)

[Chotu]

Originally Posted by s/v Jedi

Then you did it wrong You missed the key points that I start about. It shouldn’t matter if your generator is running or not for switching loads on/off. The generator has a supporting role as power generation plant and the Cerbo can fully automate running it when needed (for high loads as well as for battery charging… all simultaneously)

In an ideal world, yes. I agree.

Price tag $20,000? $30,000?

i’m merely suggesting a workaround that is in the $1000s and delivers most of the same functionality.

Mine works mostly like yours for all but air conditioning because I decided the load was too infrequent and didn’t need to be supported on a regular basis.

don’t get me wrong. You have created a work of art. It’s perfect. There is no better way to do it. There are just some cheaper ways to get most of the functionality for those who may not have $30k available for their electrical refit.

Also, I applaud you for creating this thread and the other battery testing thread. These are great resources for people to learn from.

[rslifkin]

Originally Posted by s/v Jedi

Then you did it wrong You missed the key points that I start about. It shouldn’t matter if your generator is running or not for switching loads on/off. The generator has a supporting role as power generation plant and the Cerbo can fully automate running it when needed (for high loads as well as for battery charging… all simultaneously)

It depends on your shore / generator side of the power architecture. I've got the one scenario Victron doesn't adequately support that would force me to make changes for running everything through the inverters to be possible.

Currently, I have 2x 50A / 120V (3 wire) inlets and 2x 120V panel legs. The generator outputs single phase 120V and feeds both panel legs in parallel.

Victron's equipment supports units paralleled on a single phase, or run in a split phase setup. And it can accommodate a floating angle between those split phases. But it cannot accept both legs being in phase when configured that way. They could easily fix this in software, but so far they haven't offered it as an option.

I could re-configure the boat to use the more modern 50A 120/240V (4 wire) inlets and re-wire the generator for split phase output. But then I have to worry about balancing load between the 2 generator legs and if I have to connect the boat to 30A shore power with an adapter, I need to find 2 outlets that are out of phase (or I'll only be able to power 1 leg from shore power). I could solve the generator balancing issue with an auto-transformer, but that takes up space that I'm already short on. Although running the HVAC through an inverter and being able to use the dynamic current limiter to buffer HVAC loads would have an upside. Currently my Multiplus momentarily drops the generator input when the 16k BTU A/C kicks on, as there's a quick frequency dip. The generator has no trouble starting the load, but the Multiplus doesn't like what the power looks like when the gen takes a sudden big load.

In light of that, the path I've been going down is to slightly alter the equipment distribution between the L1 and L2 sides of the panel. Currently L1 is sub-paneled for inverter loads, but as I make further upgrades, I'll re-wire so all of the L1 side goes through the inverter(s). And L2 will be fed directly from the L2 shore input or the generator and only have loads that I never need to run from the inverter. So basically, L2 will power the engine battery charger and HVAC, L1 will power everything else (not quite sure on how I'm planning to power the water heater yet).

The only gotcha with this planned setup is that when on generator power, the input power limit for the inverters needs to be adjusted based on how much HVAC is being run (if any), as that load is invisible to the inverters, but still pulls from the same pool of available generator power.

[s/v Jedi]

Originally Posted by rslifkin

It depends on your shore / generator side of the power architecture. I've got the one scenario Victron doesn't adequately support that would force me to make changes for running everything through the inverters to be possible.

Currently, I have 2x 50A / 120V (3 wire) inlets and 2x 120V panel legs. The generator outputs single phase 120V and feeds both panel legs in parallel.

Victron's equipment supports units paralleled on a single phase, or run in a split phase setup. And it can accommodate a floating angle between those split phases. But it cannot accept both legs being in phase when configured that way. They could easily fix this in software, but so far they haven't offered it as an option.

I could re-configure the boat to use the more modern 50A 120/240V (4 wire) inlets and re-wire the generator for split phase output. But then I have to worry about balancing load between the 2 generator legs and if I have to connect the boat to 30A shore power with an adapter, I need to find 2 outlets that are out of phase (or I'll only be able to power 1 leg from shore power). I could solve the generator balancing issue with an auto-transformer, but that takes up space that I'm already short on. Although running the HVAC through an inverter and being able to use the dynamic current limiter to buffer HVAC loads would have an upside. Currently my Multiplus momentarily drops the generator input when the 16k BTU A/C kicks on, as there's a quick frequency dip. The generator has no trouble starting the load, but the Multiplus doesn't like what the power looks like when the gen takes a sudden big load.

In light of that, the path I've been going down is to slightly alter the equipment distribution between the L1 and L2 sides of the panel. Currently L1 is sub-paneled for inverter loads, but as I make further upgrades, I'll re-wire so all of the L1 side goes through the inverter(s). And L2 will be fed directly from the L2 shore input or the generator and only have loads that I never need to run from the inverter. So basically, L2 will power the engine battery charger and HVAC, L1 will power everything else (not quite sure on how I'm planning to power the water heater yet).

The only gotcha with this planned setup is that when on generator power, the input power limit for the inverters needs to be adjusted based on how much HVAC is being run (if any), as that load is invisible to the inverters, but still pulls from the same pool of available generator power.

Please re-read my OP of this thread. For your setup you use 240V units and the first time 120V appears is after the Auto transformer(s). At 240V you only have L1 and L2, no neutral. From the genset you only take L1 and L2 240V. Same for shore power; you can take 120V and let the isolation transformer make 240 from that.

That’s the proper way of doing this for higher power. For your distribution you get two legs again as the auto transformer creates a new Neutral for L1 and L2. It’s in the diagram I posted

[s/v Jedi]

Originally Posted by Chotu

In an ideal world, yes. I agree.

Price tag $20,000? $30,000?

i’m merely suggesting a workaround that is in the $1000s and delivers most of the same functionality.

Mine works mostly like yours for all but air conditioning because I decided the load was too infrequent and didn’t need to be supported on a regular basis.

don’t get me wrong. You have created a work of art. It’s perfect. There is no better way to do it. There are just some cheaper ways to get most of the functionality for those who may not have $30k available for their electrical refit.

Also, I applaud you for creating this thread and the other battery testing thread. These are great resources for people to learn from.

No, it doesn’t cost much extra. How many kW are your A/C’s combined? I think you have three times 16,000btu? Then you simply take three Multiplus 3000’s in parallel, which is just one extra that cost what, $1,400? If the Cerbo programming decides the load is unsustainable from battery it will simply start the generator for assist.