If there is a single thing that I regret with this complete project was the decision to use Lithium batteries...
On the surface of it they seemed like the answer for this type of application...and if they lived up to the claims of the promoters of the batteries they would be. Lets face it...light weight, fast charging, virtually non existant discharge when not in use, about 5 times the cycling life of conventional batteries. But, as with many things in life, the hype sometimes doesn't match the reality.
Now, please appreciate that the following is only my own personal opinion after having 'lived' with them on the ocean for about 11,000 kms.
My opinion is that the technology of these batteries are not at a stage in which they can be relied upon in the marine environment. They need very sophisticated battery management systems and these systems are prone to failures.
If you have a bank of these batteries and several cells fail in one battery it brings the entire bank down. This is why we got stranded 200 miles south of Singapore. One of the circuit boards in the battery management system failed. That in turn caused a couple of cells to fail which led to a complete shut down of the 48volt bank system...thus no propulsion.
Part of the problem may be due to the higher ambiant temperatures in the tropics. The batteries were getting extremely hot. This was something that the manufacturers did not warn about. It wasn't a problem in New Zealand but it sure was in the tropics.
Four times the boat was disabled...and each time it was due to these batteries. Maybe they would be OK for a boat just cruising around the coast of a country where there are technicians available who understand this technology but outside of those regions it is still unknown technology. Nonetheless each time the costs to fix them or replace them are pretty excessive!
Four times I had to fly my technician to various countries to carry our repairs. Support from the manufacturer is virtually non exisitent even though I opted for the best and most expensive brand.
When the last failure occured in Langkawi I could not contact my technician so in desperation I tossed out all the lithium batteries and replaced them with AGM's. On hindsight I should have done that a long time ago. I now have a reliable system that works and any electrician can understand...hey, even I can understand it.
I will do a seperate post on what I have done with the electrical system. By the way, I am happy with the electric motors and although I had a lot of teething problems they are all sorted and had I and others had had experience with them most of those problems could have been avoided.
So, if you are considering usiing lithium batteries in your boat you may like to drop me a note for more into. One consolation which doesn't make me feel so stupid in persevering with them is that Boeing also made a mistake with these batteries in their new Dreamliner airplanes. :)