Hi John.
The Propulsion Marine drives generate as much energy via regeneration as any of the other systems (Electric Yacht, ASMO, etc.) discussed in this group. Virtually all of the commercially available drive systems have regen capabilities.
The two to one time conversion for regen to motoring might be true for a very rare set of conditions, but the statement is largely misleading because the speeds are completely different. The math has been discussed in this group a number of times before. For monohulls in the 30 foot range, the ratio is closer to 40 to 1, that is 10 hours of sailing at 5kts (30W-35W of regen) to replace 15 minutes of motoring at 4kts (320Wh of energy used). Push your average sailing speed to 6kts and the ratio is now 12 to 1, or 4 hours of sailing at 6kts (80W of regen) to replace 15 minutes of motoring at 4kts (320Wh of energy used). Of course, you need to ask yourself, just how fast do you typically sail your boat today? Not just the peaks, how fast do you average under sail for hours at a time?
Multihulls are a special case due to their higher speed potential. And spending 4 hours sailing at 10-12kts might replace the energy used by 2 hours of motoring at 4kts, but I haven't seen any objective performance data (watts to knots) related to regen or motoring power demand for the big cats that would support that claim.
I'm glad that the electric drive vendors are downplaying the regen aspects of electric conversions, because in all but a few cases, regen will not recharge a traction battery any significant amount. Longer monohulls (35'-45') that can sail consistantly closer to 7 or 8kts can do a pretty good job of covering their houseloads with regen, but typically need an external power source (Solar, shore power, IC generator, etc.) to replenish their traction banks.
From my post #21218 from March 28, 2012: "The point is that I'm trying to share my practical experience to help people set realistic expecations of their electric conversions. We had another thread last year that discussed the article "Ditching Electric" from the magazine Classic Boat. The owners of the boat "Siandra" were removing their electric drive after three years. It appears that their biggest complaint was that their system did not regenerate as much energy as they expected and therefore their electric drive did not support their particular use case. Perhaps if they had been told how much power they would really get from regeneration, they would have found other ways to mitigate their energy deficit. As it was, they believed their salesperson, spent considerable money converting to electric, wrote a supportive article about electric coversion in 2008, got dissatisfied, spent considerable money converting back to diesel and wrote a more negative article in 2011. I'm sure that their experience and exposure to their story hurt the electric boat community more than it helped. All stemming from unrealistic expectations."
Here's some of the math from the same post: "If your boat can sail at sustained speeds of 7 or 8kts or more, regen can become a significant source of energy. But for sailboats in the 30' range (the sweet spot for electric drive systems with 5-6kW of power and battery packs around 10kWh or 500 lbs), hull speed is about 6.5kts and 6kts is about all you can average in winds less than Beaufort 6. So the energy from regeneration on most of our boats is limited.
Here's what I posted last September (post #19662) "Since you brought up regen, I'll say it again. I haven't seen any substantiated report of 60W @ 5kts. Push the boat up to 6kts and I would be very surprised to see 120W of regen. I've seen brief moments of 60-70W while sailing my boat at 6kts but nothing consistent. Once a boat hits a consistent 8kts+ (big boats and multihulls), then regen starts to cover more than conservative house loads.
It's the data that nobody likes to hear, but if one motors at 4kts, you typically have to sail 40 times as long at 5kts to recover all the used energy. That means 15 minutes motoring at 4kts will take 10 hours at 5 knots to recharge the traction bank, longer if you're using any of the energy for house loads like lights, radio, or an autopilot. At 6kts, the time to recharge 15 minutes of 4kts motoring drops to 4 hours. Again, adding in any house loads extends the recharge time. But on a long passage, 100W for 24 hours does come to 2.4kWh. If you can keep your house usage to half of that, then 1.2kWh could end up back in your batteries. It will rarely be of any significant value during coastal hopping or gunkholing. I still want somebody to prove me wrong, I've been waiting for a while now...."
Mark from Santa Cruz just posted some preliminary figures after his recent prop change. He observed 1.8-2.2A (we'll call it 2A average) at 50-51V (we'll call it 51V) at 6kts. And the results are (drum roll please)........ 102W at 6kts. Hmmmm. I guess that I'm still waiting....
The bottom line is that I'm OK with these numbers. But this is not the impression that potential electric converts get when they read "Generates power while under sail" or "Most boats will start regenerating at 3.5 to 4 knots boat speed. When at, or near hull speed, the charging current should be around 4A to 6A." in an electric drive product description. While these figures might be true for some boats (as discussed earlier) it's not really true for most of the boats that these systems are sized for. Another vendor states "Not all boats will be able to achieve regeneration. The amount of power generated should be considered supplemental and comparable to what you can achieve through wind and solar chargers." This sounds closer to my personal experience."
My point is that one has to be very careful in designing conversions based on advertising claims. There may be no actual lies, but the truth might not be obvious in the way that things are worded.
Fair winds,
Eric
1964 Bermuda 30 ketch, 5.5kW Propulsion Marine drive (with regen), 8kWh Lithium batteries
Marina del Rey, CA
PS. My car goes 120mph and gets 35mpg, but it does not get 35mpg at 120mph.
--- In electricboats@yahoogroups.com, "John" <thistle411@...> wrote:
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> Regarding charging systems: I did not see regeneration mentioned. Electric Yacht's system provides for that.
>
> The electric powered 42 foot catamaran that Lagoon built a few of used re-gen, claiming that 2 hours of sailing, with the prop being spun by passing water, would provide charging used by one hour motoring. Ie: Motor out an hour, sail four hours, motor in an hour,= zero amps used.
>
> Here in Seattle, I know of an older Columbia 30 footer, that sounds a lot like your project. He's using the Electric Yacht system with re-gen and lithium batteries.
>
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