OK, I think it might be time to have a more detailed discussion of the electric power plant on the Lagoon 420
. My local Lagoon dealer was nice enough to provide me with a document that takes all the Lagoon marketing
info, presentations etc and clearly answers most of the questions one might have about this technology. Lagoon publicly claims that they have taken orders for about 75 420's already and even today, there are still some questions outstanding about regeneration boat
speed and gel vs acid batteries. There is a lot of excitement about the 420 but I am in a wait and see mode. If I were to buy a 420 for local sailing I think the electrics are an interesting option. For cruising or circumnavigation
, I just dont get it. Here are some of the things I am concerned about. I am very anxious to understand this power plant better so any debate, new information or pointing out of inaccuracies would be helpful: (pm me if you would like a copy of the document)
1. Motor battery
charging, Motor Operating, house battery
charging and all AC power is provided by the 1 generator
. If this dies, you have lost
all ability to motor or have any form of electricity on your boat, even to operate instruments
. Yes you can regenerate or perhaps use solar panels
but I am not sure how well all of that works. With 2 diesels, you have a full backup to charging of your batteries, powering the boat and providing AC power through an inverter
. I would hate to be in the middle of nowhere with a storm coming and not be able to motor out of the way because my generator was not working.
2. The electric motors run off the batteries until they reach 80%. At 80% the generator automatically comes on and powers the boat with the batteries either in charge mode or offline. The time to get the batteries from 100% to 80% is anywhere from 1 - 2.5 hours depending on how fast you are going. The 2.5 hours is at 5 kts and 1 hour at 6.5 kts. They say "The best way to keep the batteries in excellent condition is to not sail using exclusively the batteries for more than 12.5 miles". The bottom line is that you may be running the diesel
generator more often than not which defeats the purpose.
3. If the generator is being used so often I looked at fuel consumption
. There are a few data points given that are based on load. Load varies depending on whether you are charging the batteries or not, whether you are charging the house batteries, or operating AC appliances
. In these modes you use anywhere from .9 to 1.9 gal per hour. I read an article on the first Solomon powered 410 and they said the generator burned 1.5 gallons per hour while motoring. How much do diesel powered Cats burn per hour and do you use both engines? It looks like you could be using almost as much fuel
in the electric configuration as with two diesels. What do you Cat owners find your fuel consumption is?
4. It was already mentioned that there is no redundancy when it comes to the generator and what happens if it dies. The electric power plant has some very complex electronics
associated with it for power management, load protection and charging. Is there a concern about what happens to these circuit boards when there are lightening strikes in the area?
5. Battery cycle count is another item of interest to me. I have not seen any information on how many charge/discharge cycles the batteries can withstand which gives you a good idea of their lifetime. They say that you should not let them go below 80% to assure longer life, but how many times can you do this? Each time a battery goes through a discharge cycle it loses some of its depth
of cycle. I am wondering how often these batteries have to be replaced and how much this costs.
6. One of the selling points is that the batteries can be regenerated by the props. Regeneration only takes place when the boat is moving faster than 4.5 kts and its estimated that 8.5 kts is when you have maximum regeneration. Considering that the props reduce your speed by about 1 kt, it seems you have to be moving at 5.5 kts or more to use the wind
to regenerate. At the miami
show I spoke to the engineer
who designed the system and he claimed that his personal system takes about a day to charge back up to 100% with his solar panels
assuming a very clear day. I have not seen any documents that show a way to hook solar panels
up into the 420's main battery banks. Lagoon has no plans to offer solar or wind
options at this time.
There are a lot of positives about having electric motors, but this system seems to still be very dependent on having a large diesel generator which still needs to be maintained like your existing diesel engines. You seem to lose quite a bit of safety
associated with redundancy when you go to this electric drive system with not much saving in fuel. Incidently, I asked and there is not an option to add a backup generator. Its probably too big and heavy anyway.
So do I have it all wrong? Comments or clarifications are welcome.