That performance is about what you should expect from a good stock ST setup. The stock harmonic is good for high capacitance, low PF loads like a low PF charger or cheap welder. An AVR will not work as well for those loads since the cheap ones do not do true RMS voltage regulation.  If you want tighter regulation for normal loads, you will need to connect the AVR to the mains, as your harmonic winding doesn't have extra capacity for the fully loaded situation.  The AVR can only limit the excitation source. 

ST heads which have excessive voltage (unlike yours)  require adding power resistor to reduce harmonic excitation, and can use the harmonic as excitation for an AVR.  They will do well with the AVR on the harmonic (with no resistor) since even under full load the harmonic will have sufficient power.  Some stators (like mine) have harmonic winding configurations that have output waveform distortion called the "harmonic hump" when the harmonic is used.  Some have found adding capacitance to the rectified harmonic output reduces this acceptably.  That may also boost your voltage somewhat (not varied by load). Just remember that the harmonic peak voltage is quite high- (it is spikes, not a sine) and I have measured my ST-3 harmonic voltage peak for starting a well pump load at 400VDC despite a faceplate harmonic voltage of something like 24VDC.  On some heads, capacitors did not change the harmonic hump, but using and AVR off the mains works well.  (Motor run capacitors are the safest to use for this.)

Be careful to check for aluminum rotor windings.  They do not hold up well, and it can be hard to spot with the red electrical varnish.  My neighbor got one of these from CGG, and one rotor winding failed open in less than a year. The bearings need to be replaced with high quality ones like SK.  The "better" Chinesium bearings we got from CGG were noisy under load.

I added info on the common variations of the ST single phase heads in hopes it may help some others new to these simple, cheap workhorses.  I have gotten great service out of mine with some effort but I don't recommend them for newbies without some technical skills as they vary greatly and some are not  problem free.  Stamford clones were recommended here and have been reported  to be trouble free with good waveform, but are expensive relative to the ST heads.

Best Wishes,
BruceM

If you add counterbalance until you just barely start to see fore and aft movement, that will be the ideal weight if you are looking for minimum vertical force.

I had built a temporary wood frame for my Listeroid, which I mounted on 1" thick rubber pads (grooved and glued in place with gorilla glue) on a thickened shed slab- 10 inches thick under the engine area.  Without balancing, despite the rubber pads, it audibly shook the whole steel sided and roofed building and you could feel it through the ground 10 away from the building.  I then used the wheel marking method, which took an entire afternoon of fiddling.  Then I could sit a cup of water on the valve cover and just see some rippling.  On my next engine project for a neighbor I used 38ACs method of matching the flywheels and getting the counterweight centered on the keyway first before adding counterweights.  This made it SO much faster and easier. Maybe 20 minutes to that perfect balance where fore/aft movement is just barely starting and a cup of water is used for the final balancing. The beauty of his method is you just add/subtract counter weight equally on both wheels, and then observe the balance.  It is only a question of too much or too little and you will be using the cup of water pretty quickly.

The only reason for a big slab of concrete is if you'd like to raise the engine for ease of service.  Or you have failed to understand 38ac's simple method.  It's brilliant.

For your new post- I'm not a fan of low voltage systems for just the reasons you state.  But there, balance will be very important.  Some sort of soft mount may help, the ulitmate being sailawayrb's properly engineered system. You will still have sound issues with valve clatter, and will need an earth muffler of some sort.  I like the leachfield exhaust method in a dry location as it also gets rid of exhaust smell.

I've always been a big fan of your Bamfords with their enclosed pushrods and sturdy design. One of the all time great slow speed diesels.  It's very impressive that you've  brought so many back to life, and i have no doubt you are greatly appreciated by your clients!
Best Wishes,
Bruce

Fantastic post mortem results Veggie ! Glad to see your 12V starter motor/generator vindicated, I have always thought it was a great setup you had. 

Next time you'll know to do an anti-corrosion plus wear and lubrication service on the motor/generator when you replace the battery.

Current limiting with a fixed voltage charge is well supported by most commercial PV charge regulators and is not usually not a problem even for older charge regulators.

LFP has to be regularly full charged if you have any hope of having an reliable state of charge indication and to do non-manual balancing.  The cell charge-voltage curve is flat with some variations until you reach around 90% of full charge.  Likewise, LFP cells should only be balanced by your BMS when approaching full voltage (voltage is rising appreciably), very unlike the lithium ion cells.  You can decide how full is full  if you like, but you must pick a value in the nearly full range where the voltage is rising substantially.  Most have so far found that even keeping the cells at full charge is not causing significant degradation over time.  See Will Proust's diysolarform.com to get some decent info. He does his technical homework well before presenting info.

I am not using LFP yet but just 5 months ago was working on an all linear, high voltage BMS design for 38 LFP cells in series with another EE friend.  In my research I found that the differences between LFP and Lithium Ion cells was causing trouble for many early LFP adopters with BMS hardware that was not well suited for them.  Balancing LFP by any means (active or passive, high or low current) at other than near full was always a mess.  The voltage-charge curve is just too flat, and instead of balancing, it was actually unbalancing.

Apparently large balancing current is not needed despite the more limited balancing time window, and 100ma to 1 amp seems to be working fine. The cells are just that good at least when young (under a decade old). 


Best Wishes,
BruceM

Hi Veggie,

That poor Listeroid in the video is so badly out of balance it's pounding itself to pieces.
A serious cruelty, it should be a crime.

An induction motor is a bad match for a starter, low starting torque and huge locked rotor current.
If it's free  and you really want to see it for yourself, just disconnect power manually when it begins to start to stop it from becoming a synchronous generator. You can do that by rpm sensor (I like the cherry hall effect gear tooth sensor for counting my spokes) and an Arduino Nano to do the disconnect automatically.  Or a thousand other ways...

Best Wishes,
Bruce

 Powder Monkey has an ideal, keep it simple application for thermosiphon tank cooling in that he is running 8 hrs a day in a no-freeze location.  No antifreeze needed and the long time for getting up to temperature and potential increased carbon build up are not a problem for his application.

My application was for short runs, typically 30 minutes. (Pump water while running washing machine, or pump air for the shop, or a 30 minute bulk charge of my battery bank.)   I also have the issue of sub zero temperatures in winter which also make the tank method a poor choice ($) as ajaffa1 wisely notes.  I opted for the thermostat and a (exhaust induced draft- no fan required) radiator with thermosiphon flow because of my  anticipated short run times and a design goal to not require generator operation when operating the air compressor compressor only.  (I could not find affordable cast iron radiators here in AZ or I would have used one with a thermostat.)  I have further reduced de-coking labor by adding a water/methanol feed system.  I keep waiting for the cold idle knocking sound which used to signal time (at 200-300 hrs) for de-coking but now it never happens. 

The perfect cooling system for the CS is application and location specific.  (And the desires and design goals of the builder/designer.)  XYZer created a lovely portable CS design for thermosiphon and fanless oversized radiator with convection only air flow. Standard automotive style cooling setups with pump and fan can be more compact and lighter weight while also being quite practical and economical.  Cujet's portable twin CS design is one outstanding example.

Best Wishes,
Bruce M