Permanent Magnet Generator on Propshaft

[CaptainRivet]

???
We have the topic of shaft gen to charge your battery bank as alternative power generation while sailing. To run an AC of this is far out what can be harvest from or done with a freewheeling prop shaft on boats our sizes.
Also don't need an AC while sailing but on a hot windstill day it might be handy. And for that you need a fully charged big housebank.
How to charge it under way when 1/2 of your solar is covered by sails, the wind gen is not really working due to forewind course but you do 7kn and your propshaft is spinning with 500rpm anyhow?

[Seafarer7]

Originally Posted by CaptainRivet

What happens if your battery is fully charged?
If the pulley is still turning and the MPPT stops charging without load it creates a spike that kills your MPPT.
How did you solve this?
Carl (See above) solved this with a clutch disengaging the pulley. Also if your drag is too big in eg light winds to stop energy production. Like that solution too and combine it with yours. Disengage the link belt wouldn’t be practical.
Was looking for a clutch but cannot find one. Wrote Carl a PM too but no answer so far.

Good question: so far I haven’t had that problem. On my last ocean crossing, energy was well balanced between consumption and generation (solar plus pair of shaft generators). Since then I increased solar to more than 1kw so this issue will likely come up, with solar plus the two shaft gens.

There are two or three solutions I have for it:
1. I intentionally chose the TriStar MPPT 150 series because it can handle an open circuit voltage of up to 150volts. So when the battery gets fully charged and the PMDC generator starts to rise, the hope is that at all cruising speeds the 72v motors/generators would not exceed 150v open circuit under no load. I do monitor the motor output voltages very carefully (haven’t see much more than 60v under load). If this option fails and open circuit voltages approach the 150v limit, there are two back up plans:

2. On demand loading: there are a number of on demand loads that can be quickly engaged if battery is full and the open circuit voltage of the PMDC motors begins to approach 150v. Eg hot water heater via inverter, electric kettle, induction cooker, water maker, etc. Some are useful and some just plain wasteful, but enough quick-on loads exist to ensure fast escape from rising voltage.

3. Lock the shaft in reverse and/or Remove the belts from the pulley driving the PMDC motors. This is normally not difficult to do, however the fast boat is going, the more the effort required to manually hold and slow down the shafts enough to engage reverse, stop rotation and remove the belt. A clutch would be a great addition but so far I’ve done it manually. The adjustable belt is easy to roll on and off

[Seafarer7]

Originally Posted by CaptainRivet

Also do you run the shaft gen while motoring or how do you solve that?

I would never do that. Scary to think of what could happen there. The prop shaft turns so much faster when motoring, I would guess a few thousand rpm, versus just the few hundreds when free wheeling. So it would be so easy / quick to exceed the MPPT open circuit voltage limit and damage it. Also easy to exceed the limits for the PMDC motor itself (lost one this way during early phase experiments). An alternator is a much better piece of gear to run off an engine vs a PMDC motor, as alternators are designed to handle thousands of rpm.

[Seafarer7]

With twin engines, I would only engage both shaft generators when sailing extended periods. If motoring is anticipated, I may leave one belt on, motor with one engine and lock the other shaft in reverse while motoring.
On the CA to Hawaii pacific crossing there were stretches of several days where solar plus both props ran non stop (solar intermittent, props non stop), supplying all energy. My boat does not have a diesel or gas generator. The quiet was much appreciated

[CaptainRivet]

Originally Posted by Seafarer7

Good question: so far I haven’t had that problem. On my last ocean crossing, energy was well balanced between consumption and generation (solar plus pair of shaft generators). Since then I increased solar to more than 1kw so this issue will likely come up, with solar plus the two shaft gens.

There are two or three solutions I have for it:
1. I intentionally chose the TriStar MPPT 150 series because it can handle an open circuit voltage of up to 150volts. So when the battery gets fully charged and the PMDC generator starts to rise, the hope is that at all cruising speeds the 72v motors/generators would not exceed 150v open circuit under no load. I do monitor the motor output voltages very carefully (haven’t see much more than 60v under load). If this option fails and open circuit voltages approach the 150v limit, there are two back up plans:

2. On demand loading: there are a number of on demand loads that can be quickly engaged if battery is full and the open circuit voltage of the PMDC motors begins to approach 150v. Eg hot water heater via inverter, electric kettle, induction cooker, water maker, etc. Some are useful and some just plain wasteful, but enough quick-on loads exist to ensure fast escape from rising voltage.

3. Lock the shaft in reverse and/or Remove the belts from the pulley driving the PMDC motors. This is normally not difficult to do, however the fast boat is going, the more the effort required to manually hold and slow down the shafts enough to engage reverse, stop rotation and remove the belt. A clutch would be a great addition but so far I’ve done it manually. The adjustable belt is easy to roll on and off

To 1) it depends on your type of battery setup if you get a high voltage spike (Lithium/LTO) or a constant rising (lead acid/agm) voltage when they go from 95% to fully charged. With Lead your save but with Li/LTO the spike will be above 150V and you won’t be fast enough adding a load if you hit 100%...you could set a voltage warning at the bat monitor and if at 95%
add your No2 backup loads like water maker or heater. Means bank will be never fully charged
To 2) I will have only LTO and maybe Li-ion Tesla modules as housebank,so spike will kill the MPPT. Ok with 3 Tesla modules=18.3kwh bank will be in 99% cases not fully charged, with 440A LTO yes often 100% charged and the spike will be high...in a millisecond from 50 to over 400V as LTO has extremely low resistance and takes up to 10C charge in which will be switched off from 100% to 0% immediately when full. So on demand won’t really work.

To 3) solution for me must be a “flip the switch” or “pull a lever” solution. Have one shaft which is always turning. in reverse lock cost me 1kn speed and forget stopping/slowing shaft down by hand. Taking the belt off not practical either.
This is my challenge to solve here...

[CaptainRivet]

Originally Posted by Seafarer7

I would never do that. Scary to think of what could happen there. The prop shaft turns so much faster when motoring, I would guess a few thousand rpm, versus just the few hundreds when free wheeling. So it would be so easy / quick to exceed the MPPT open circuit voltage limit and damage it. Also easy to exceed the limits for the PMDC motor itself (lost one this way during early phase experiments). An alternator is a much better piece of gear to run off an engine vs a PMDC motor, as alternators are designed to handle thousands of rpm.

Imagine that there is a high difference between motoring and freewheeling. Cannot measure as I sit in Switzerland and cannot get to my boat in Canaries due to lockdown. But I have access to machine shop and measured the mechanical parts where the shaft gen should be installed so I can fabricate what I need.
so there is a need for disengaging the shaft gen manually with a clutch or some other pull the lever/Flip a switch solution.
Maybe you could change the gearing with a mountain bicycle like solution from 1:2 to eg 3:1 while motoring but never saw something like this.
Carl’s 12V clutch pulley would be a very good solution just to dis-/engage it.

With a normal alternator used as shaft gen the energy production is switched on/off by the initial magnetization load but that creates 5 A waste/lost for 5A energy. Not acceptable.

[Seafarer7]

Originally Posted by CaptainRivet

To 1) it depends on your type of battery setup if you get a high voltage spike (Lithium/LTO) or a constant rising (lead acid/agm) voltage when they go from 95% to fully charged. With Lead your save but with Li/LTO the spike will be above 150V and you won’t be fast enough adding a load if you hit 100%...you could set a voltage warning at the bat monitor and if at 95%

add your No2 backup loads like water maker or heater. Means bank will be never fully charged

There are two voltages to monitor: (1) the output voltage from the shaft generator (0v to 72v during normal operations, tied to the input side to the MPPT controller), and (2) the output voltage from the MPPT, which is the battery voltage. Although you never have to worry about voltage #2 (since the charge controller does it for you, and does a good job of it, based on the configuration settings for battery type) it still gives you a heads up on the situation. It’s the #1 voltage that is of primary concern. I have both voltages and MPPT charge phase monitored via a computer/server tied in to the charge controllers serial bus. During “bulk charge” phase the MPPT controller take all the energy it can get from the shaft generators, so no problem with voltage #2 at that point. It is only during the “absorption” and “float” charge phases, when the battery is near full, that the MPPT controller begins to reject some of the incoming energy. As energy draw is lowered the voltage of the charge sources increases (applies to both solar and PMDC hydro). Max open circuit voltage for solar is known - it is whatever the specs on the panel array say. But for hydro the open circuit voltage is directly proportional to shaft rotation speed. So unless you can calibrate for all sailing speeds - including surfing (I have exceeded 15knots boat speed sailing/surfing) this voltage is unknown and potentially the danger point. Your batteries are always protected - they are on the other side of the MPPT controller, but the controller itself and possibly the PMDC motor may exceed spec if the no-load PMDC voltage gets too high.

The trick is to act quick if you ever get to the “absorption” phase, while the MPPT is still drawing some, but not all energy from the charge source (and therefore still keeping those voltages down).

[Seafarer7]

Originally Posted by CaptainRivet

Imagine that there is a high difference between motoring and freewheeling. Cannot measure as I sit in Switzerland and cannot get to my boat in Canaries due to lockdown. But I have access to machine shop and measured the mechanical parts where the shaft gen should be installed so I can fabricate what I need.

so there is a need for disengaging the shaft gen manually with a clutch or some other pull the lever/Flip a switch solution.

Maybe you could change the gearing with a mountain bicycle like solution from 1:2 to eg 3:1 while motoring but never saw something like this.

Carl’s 12V clutch pulley would be a very good solution just to dis-/engage it.



With a normal alternator used as shaft gen the energy production is switched on/off by the initial magnetization load but that creates 5 A waste/lost for 5A energy. Not acceptable.

Like your boat, mine was designed somewhat as a motorsailer/powersailer, and manufacturer OKs leaving the prop to freewheel while sailing. I get about 200 to 300 rpm going 4 to 5 kts - I used this inexpensive laser tachometer to measure:

uxcell RPM Tachometer Photo Non Contact Rotation Meter - 2.5 to 99,999, Photoelectric, DT-2234A https://www.amazon.com/dp/B0711B4QWJ..._vpAygBgzA4OgO


I don’t have Lithium but on second review I think what you are saying is that your Lithiums go from bulk charge to 100% full in a split second, with no absorption...

In that case I would recommend the TriStar MPPT 600 (ie any 600+ MPPT) instead of 150v, if your boat speed calibrations show that your selected PMDC motor OC voltage can potentially exceed your systems safe voltages. TriStar MPPT 600 handles up to 600 volts input voltages.

[QuentinC]

Towed arrays are expensive. Some people do not have 5000 to buy a towed array.

[QuentinC]

Originally Posted by CaptainRivet

Awesome
Exactly what I was looking for. Awesome how you avoided to disassemble shaft. had the same idea but was not sure if that works and you proof it does.
My hull speed is 8kn and I have a 21x15 fixed prop, shaft starts turning from 1.5kn on. And was turning the last 36years without any problem, it’s a motor sailor that sails well and was designed like this from the beginning. A fellow with the same boat converted to a folding propeller and gained 0.25kn speed at most...I keep the fixed, invest in energy production and make use of the energy instead.

What happens if your battery is fully charged?
If the pulley is still turning and the MPPT stops charging without load it creates a spike that kills your MPPT.
How did you solve this?
Carl (See above) solved this with a clutch disengaging the pulley. Also if your drag is too big in eg light winds to stop energy production. Like that solution too and combine it with yours. Disengage the link belt wouldn’t be practical.
Was looking for a clutch but cannot find one. Wrote Carl a PM too but no answer so far.

If you go to a napa or oriellys parts store ask to see their ac parts replacement catalog. You can find many ac clutches for replacement in this catalog, they also have a heavy duty catalog for big trucks and farm equipment. Lot of the replacement clutches have specs on shaft size and depth. After that you may find the right size or one that will work after machine the shaft or make an adapter.

[CaptainRivet]

Originally Posted by QuentinC

If you go to a napa or oriellys parts store ask to see their ac parts replacement catalog. You can find many ac clutches for replacement in this catalog, they also have a heavy duty catalog for big trucks and farm equipment. Lot of the replacement clutches have specs on shaft size and depth. After that you may find the right size or one that will work after machine the shaft or make an adapter.

Thank you for the hint.
To be honest I have no idea what exact typ of AC12V or maybe better DC12V clutch and what spec I need for that application. Thats why I hoped Carl could tell me what he used, so I see what typ&specs I roughly need. Also about the durability I need, clutch will be in slip mode for a long time and must be able to withstand the 2500 rpm’s for 72h straight motoring in a storm...like I had that once in the street of Biscaya...

2nd To define the shaft size needed I need the PMA as the AC clutch goes on the shaft of the PMA like Carl done it. Disengage the clutch slips and PMA shaft is not driven, engage and PMA shaft starts turning.
A 2 piece split pulley goes on the prop shaft like seafarer did it. It’s half a moon landing operation to get my prop shaft aligned after dismantling it, so I definitely avoid that.

I am in Switzerland at the moment and boat is in Gran canary, so Napa or orellys are not within my reach. Hope to find a Fitting clutch that I can order online.

[QuentinC]

I used to own an independent parts store. https://www.4s.com/en
This is the company that most parts store distributors buy ac parts from. You will not be able to buy direct from them.
I had to think for a bit, its been several years ago. Look in their ecatalog online. Then any parts store should be able to interchange their part no.
Also have a look at this youtube video.
https://youtu.be/er9op2FdMN8
He has a lot of videos on wind generators, wiring and where to purchase parts.
I would like a small favor in return. I had bought a C&C 38 sailboat. I was learning how to sail, doing some work on it. I was planning to have to bottom cleaned and painted. I had to quit work, was diagnosed with cancer. I was really wanting to set this up on my boat but I had to put the boat up for sale. If you decide to do this would you send me pics and data? I have been excited about this for a year now. Maybe later i can buy a boat again.
Also had a thought. Pick the pma that you want then pick the ac clutch you want to use. You can always take the pma shaft to a machine shop and they can make the shaft how you need it.
Thanks quentin