Anyone using a residential HV battery/solar configuration on a boat?

[Insequent]

I moved house a few months ago and am in the process of planning an install of a bunch of panels (22 in all) on my roof. It will also be able to have a battery, and have a bi-directional interconnect with my PHEV car battery, once our regulatory authorities approve such connections. The technology to do it already exists.

The good news is that the residential battery is LFP, and not one of the more dangerous lithium chemistries. In doing a little checking i discovered the battery operates at "300 -660 V". The range in voltage is a puzzle but as we all know higher voltage allows for smaller wires, so I can see that benefit. Given our grid in Australia is 230V nominal there may also be advantage for the inverter and battery to operate at voltages in the same ballpark, rather than at 12 or 24V such as typical for boat solar+house bank configurations.

Now, there is a trend to move towards all-electric boats with large house banks. I can see advantages in having a large high voltage inverter bank to supply AC loads, allowing domestic AC appliances rather than low voltage DC ones that are usually far more expensive. A smaller low voltage DC bank for boat electronics might still be appropriate.

What I'm not clear about is whether ABYC, or other considerations, preclude batteries operating in the 300-600V range for recreational boats in our size range, Superyachts may already do it? The battery proposed for my house is an outdoor unit, IP 66 rated and an 8 kWh battery is only 70kg in weight. Having one or two of those batteries on the boat deck is feasible IMO.

I recall some members considering, and deciding against 48V DC house banks for a number of reasons, but why not go the HV battery route?

 

[mvweebles]

I recall some members considering, and deciding against 48V DC house banks for a number of reasons, but why not go the HV battery route?

How would you charge a 300V-600V battery bank? What problem is being solved?

BTW - here's a recent thread on 48V conversion. 48V Lithium Electrical Upgrade

Peter

 

[rslifkin]

Boats generally don't have to move power as far between the high power DC devices, so the advantage is smaller. And there's the downside of losing the ability to power the bulk of DC equipment directly from the batteries.

 

[twistedtree]

Lots of good questions packed in there, and responding in no particular order....

Grid tied solar systems without batteries have always been higher voltage, at least as long as I've paid attention to them. 300-600V is typical. As we all know it makes the wiring easier and less expansive, but it also does the same for the power conversion electronics. In the absence of batteries forcing the voltages down, all design considerations say to use higher voltages.

Now, battery systems dedicated to grid tied systems are starting to use higher voltage batteries. And cars use higher voltage batteries too. This has now spread over to boats with higher-end electric propulsion systems also using high voltage batteries, often repurposed from the automotive industry. The inventing and borrowing keeps ping ponging back and forth across industries, and it always has. My first land-based solar/battery/inverter system was all based on marine products because that's what was available.

Yes, we are seeing movement towards 48V, but a large part of me thinks that a mis-step and that we should really just jump to higher voltages. Say 100V minimum. But that's just my opinion.

As for ABYC, E-11 covers up to 60V. There is an electric propulsion standard (maybe E-31, but I'm not certain of the number) and it deals with high voltage propulsion system. But it's specific to that application, because that's really the only place it shows up in boats, and even then it's uncommon. ABYC has recently launched an effort to create a more general high voltage standard akin to E-11, recognizing that it's just a matter of time. I have no idea what to expect for an ETA on that work.

If I were building something in the mean time, I would take my guidance from E-11, factor in E-31 where applicable, and also take guidance from the AC power sections of E-11. There are a number of things in E-11 for AC wiring specifically because it's higher voltage. Things like insulation ratings, only making electrical connections in closed boxes, etc.

 

[mvweebles]

.........

Yes, we are seeing movement towards 48V, but a large part of me thinks that a mis-step and that we should really just jump to higher voltages. Say 100V minimum. But that's just my opinion.

There is so much off-the-shelf available for 48v it's hard to imagine going with anything other than 48v except for specialized applications (EV propulsion being one). 48v alternators are even becoming more commonplace.

Cruising boats will mostly need untethered charging which requires more real estate for panels than boats have. Technology will of course evolve but with current development horizon and the robust AC loads boats are requiring, I just don't see why leapfrog the plethora of 48v lot on the market.

Peter

 

[twistedtree]

There is so much off-the-shelf available for 48v it's hard to imagine going with anything other than 48v except for specialized applications (EV propulsion being one). 48v alternators are even becoming more commonplace.

Cruising boats will mostly need untethered charging which requires more real estate for panels than boats have. Technology will of course evolve but with current development horizon and the robust AC loads boats are requiring, I just don't see why leapfrog the plethora of 48v lot on the market.

Peter

That is probably the practical reality of things. But looking at it abstractly, why 48V? Wouldn't 100V or 200V or 300V be even better, just from a technology and design perspective? I think the answer is Yes, it would be better. 48V is really only a magic number because that's what the phone company settled on 100+ years ago. And data centers picked it up for exactly the reason you mention - lots of stuff was already available. In cases where 48V was not an option (EVs) or a restriction (grid tied solar), clean sheet of paper designs jumped to much higher voltages - on the order of 10x rather than 2x.

A mature eco system can be a great asset for progress, and also a major impediment to progress. Just look at the US's refusal to switch to the metric system, even though most of our major industries have already done so on their own.

 

[dannc]

Praxis(Ship automation and navigation systems - Praxis Automation Technology B.V.) and MG Energy(MG Energy Systems | Energy Storage Systems | Modular & Scalable) make batteries, BMS, etc for voltage higher than 48V for marine use. They seem to be aimed at commercial vessels for hybrid or electric propulsion.

For our smaller vessels I don't see the application for higher DC voltages. Seem like it would just be added complexity. The hybrid motors that are of interest to us are 48v. I could see that higher DC voltages would be an advantage but the equipment to use the higher DC voltage does not exist. If one could have radios, chart plotters, radar, etc at 48v that would be great but it is not really happening yet, much less at higher DC voltages.

 

[twistedtree]

If I were to ever pursue a higher voltage DC system, it would be 90% to power inverters, and 10% to power 12V or 24V DC devices via power converters. All high power loads would be AC. My current boat already does this, though I kept the batteries at 24V. But all high power loads except on docking capstain are AC. Big ships are pretty much entirely AC.

 

[Insequent]

How would you charge a 300V-600V battery bank? What problem is being solved?

BTW - here's a recent thread on 48V conversion. 48V Lithium Electrical Upgrade

Peter

Peter - various comments above highlight several advantages and it seems to be an obvious direction to head. It could take a few years to get there. Likely to happen for new boats first or possibly a major refit of an older boat.

For refrigeration, cooking and aircon loads its a big win to be able to select from domestic appliances already out there. I already have 2,720W of solar aboard which provides 10 kWh on a sunny day. Lots of boat have generators plus or minus that size. Charging a HV battery is readily achievable. As TT noted (along with many excellent points), the HV battery is your inverter battery bank.

You could leave the OEM start batteries & alternator system as delivered to run boat electronics. No need to have large capacity 12 or 24V alternators and battery bank.