Micro CoGen.

We've decided to stick with a Listeroid for my new neighbors off grid generator/air compressor...copy of my setup except if I can do it, he'd like to use propane.
I found a propane carb and a cdi igntion, will try the injector hole method.

Dieselgman has a few 8/1's left and I think that might be a good match as with the loss of power from reduced compression and propane, I suspect 650 rpm will no longer be adequate.

Anyone able to make a good guess as to a target operating rpm for 6-6.6 hp on propane?  (I've got to order a genset pulley.)

Most small engines run about 9.5:1 compression so I assume that's about it for propane.  Could anyone guess what shim thickness under the cylinder would that be?

I'd appreciate some ideas for a low speed (<=1200 rpm) engine to run on propane, about 6 hp.   Something with parts readily available would be ideal.

The intended application is for an off grid homestead, for well pumping, washer, air compressor.  Rarely some battery bank charging. My Listeroid 6/1 is doing this same service admirably, but I'd like to find something to run on propane for some new neighbors that don't want to handle diesel fuel.

Any thoughts?

I just got an email from jsaphotonics.com.  They are offering their fiber optic specific gravity sensors, electrolyte level sensors, and cell temperature sensors in small quantities for experimenters.  The SG or SOC battery cap sensor is about $40. $30 as an oem style unit. Plenty of options, reasonably priced.  It seems like a few of these would be handy for someone with a diy system.  There's nothing more reliable than SG for wet lead batteries.

Hi Guys,
I'm finishing construction of my big (128SF) drainback solar panel for hot water heating (space and domestic).  I have built the 700 gallon insulated storage tank, ready to put in the liner.  My water pressure is just 12 psi, from a hill mounted tank. 

I'm interested in the "batch" tank within my tank heat exchanger for my domestic hot water, but am having a hard timing finding an affordable tank. I can't use a water heat tank since the outside of those tanks would corrode when submerged.  New galvanized steel tanks are out of sight, cost wise, and stainless steel pressure tanks seem insane as well.

My last resort is a copper tube exchanger, but in winter my incoming water is near freezing, so according to the figures I've seen, I would need at least 180 feet of 1/2" copper ( as 6-8 coils in parallel) at 2 GPM.  (38F to 105F).  This is $360 just for the soft copper, perhaps $420 all together for copper cost.  I think that even 180 feet is marginal.

Any ideas would be appreciated.

PS-  I can't use a big coil of 1" pex as the exchanger/batch heater as I don't tolerate hot water from pex for showers. Too much plasticizers smell, especially the first year. 

SteveU requested that I start this separate thread.  Here's the post from another battery thread:

"I love my 120VDC system with cheap Walmart 12V marine batteries, using individual battery shunt regulators. (A scheme developed my Manzanita Power for electric cars with AGM batteries.) There's virtually no water loss, no need for protracted equalization, and a premature death in the 3rd year can be replaced without having to worry about age matching.  (My 2 battery losses were both due to prototype hardware failures due to corrosion on unsealed boards with too fine a clearance around traces.)  At the end of 4 years, the charge efficiency was noticeably poor, so I retired the whole set when I had a cell loss last fall. I'm too lazy to work hard to save an aged $67 battery.  Twice a year I check all the cells SG, and add water.  I'm ready to go to once a year now; I'm not adding hardly any water, and have had almost no variation in water consumption between cells or batteries.  I do mini-equalization charges (2 hours) monthly.  The Manazanita Power approach to charging long series strings is a real winner in my book.  I realize I'm well outside the mainstream with 120VDC, but someday this will be much more common, unless the battery technology picture changes."

You can read more about Manzanita's strategy for charging high voltage strings of lead acid batteries here:
http://www.manzanitamicro.com/products?page=shop.product_details&flypage=flypage.tpl&product_id=87&category_id=22

The manual is downloadable and has more good information.

I use a similar strategy, but with PV charging knowing when the batteries are full requires a bit more thought, due to such things as a passing cloud. My battery regulators are analog, and limit the battery voltage to one of three selected temperature compensated voltages, float, bulk charge, and equalize. Two bits of output from the PicAxe battery bank charge controller (BBCC) selects which voltage all the battery regulators see via their opto isolators. Feedback to the PicAxe is a single analog signal from each of the ten battery regulators (an opto-isolated analog signal) proportional to the amount of current the battery regulator is shunting in order to maintain the selected voltage.  The BBCC also reads PV charge, Load, and AC charge currents, and controls an analog PV charge controller
which regulates my 875 watt PV array (120VDC nominal) to charging at either full power, 2.5, or 0.5 amps of net charge.  The PV charge regulator is a small board mounted on a big aluminum heat sink.  

I don't do pulsed regulation despite the small size and efficiency because my epilepsy is aggravated by high frequency EMI.  Even the micropower processor is in a shielded enclosure with filtered connectors; a 1200 baud signal is the fastest that can be used.  So in general my design would not be something the general public is interested in.  

I've found 120VDC to be very handy.  Most switching supplies will work fine, and universal motors without triac speed controls will work fine.  There's a nice RV park type diaphram pump that works on 120VDC.  My entire low power computing system and rear projection display all use stock supplies.  I have to filter the heck out of them to keep the 120VDC clean, and the house power is separately filtered with a military grade, Filtron -120dB filter (RFIcorp).

I use no AC except for washing machine and water well pump, and (rarely) some AC tools for the shop.  My wood shop and hand tools are all pneumatic, as I can't work near AC motors. I run my Listeroid 6/1 to pump air to a 500 gallon receiver and to do run an AC washer plus pump water from my well (1/2 hp submersible pumping from 200 ft).  I have 12psi via gravity feed, which is perfectly adequate with oversized pipes.  I use a propane refrigerator modified to be sealed combustion and have a Peerless propane range modified to be piezo start.  All my lighting is 120VDC incandescent and halogen, as I don't tolerate the EMI from any of the new lighting, and can't tolerate the light quality (spectrum) of fluorescent lights of any kind (including the phosphor based white LEDs).  Someday I'd like to experiment with RGB LED lighting, to see if a custom panel array of LEDs might be useable.  But the heat loss of the incandescents is NOT a loss for me in the winter, when I use the most lighting, and at 25 cents a bulb they are hard to beat.

I changed my 6/1 to induced draft, ala the Rumely Oil Pull line of tractors, with their induced-draft cooling systems.  The exhaust is directed into the 8" galvanized duct, and extends up to within about 16 inches of the top of the top pipe.  The cap is a standard vent cap, for rain protection. It reduces the air flow , but it still pulls plenty of air.

This works very well, requiring no AC power, which is nice when I'm just running my air compressor.

From the second photo you can see that only about 6x11 inches of radiator is being used- which works fine for full load at 80F.  This is a thermosiphon cooling system also, so now I'm looking for an appropriately small radiator with large inlet and outlet.  So far, the Geo Metro (12x12) is the smallest I can find with adequate inlet and outlet for thermosiphon.  Any tips for a very small, non-plastic radiator would appreciated.

I previously had no fan at all, just the large radiator, which worked fine except for the rare day here  with dead calm air and a long run time at full load, when I'd start to boil off some coolant.

The Rumely method was something I wanted to try for fun.  If I was starting over with an engine room now, I'd put a small radiator near the ceiling (near horizontal, outlet tilted down a bit), with the exhaust line faired into 8" duct connected to the radiator, and go up through the roof with 8 inch duct.  Then the induced draft system would also pull the hot ceiling air out of the engine room.  (I presently use wind turbines for that now.)

Bruce
Metro 6/1
Off grid near Concho, AZ

I did some experiments with an LED T8 tube light and have found that the warm white LEDs (yellowish phosphor blob over blue/UV LED) bother my epilepsy as badly as CFLs-  I guess it's the spiky light spectrum. 

I'm wondering if the white light generated by red, green, and blue LEDs might be more tolerable, but haven't had any luck in finding a panel, tube or bulb light to check out. 

Anyone know of a source for a non-phosphor, white via RGB LED light?

The 1000w unit looks very interesting- high voltage 3 phase output at just 200 rpm. 

http://www.ginlong.com/wind-turbine-pmg-pma-permanent-magnet-generator-alternator.htm

For a rack closer, or governor "nudger" or flat out electronic governor, this servo looks like a great deal.  It's metal gear, coreless motor, high torque and speed.  $34 incl. shiipping!  Note the satisfaction guaranty, including return shipping.  Impressive.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220481888243

Because of some health issues and treatment run afoul, I may be less active here for a while.  I've asked Daryl, aka Crumpite to be co-moderator, and thankfully, he has agreed.  Please welcome him, and thanks to all our contributors for your interesting projects, questions, and creative ideas.

WJ has inspired me with his determined quest for sensors;  so here's my new quest:

Lead acid battery state of charge (SOC) can be computed on the fly with by currents in and out, with some "resets" on charge complete and sanity checking the resting voltage whenever that happens.

But if I had a way to read specific gravity from just one battery cell, I'd be much more confident-  SG is the "gold standard" for wet batteries SOC. 

I've thought about a tiny magnet in a glass tube as a float, with one of the Allegro Microsystems switched bias, analog output hall effect sensors as the pickup.  The switched bias (50KHz) types are stable over time.  The tube would need a bulb on the bottom, as there's not much depth of acid over the plates, and all I can think to do is have it sitting up out of one cap hole.

I'm hoping someone will have some better ideas on how to do a real time specific gravity measurement on a lead acid battery.

Any thoughts?

In researching engineering articles and battery charging techniques for my own 120VDC battery bank, I found that long series strings of batteries, even well matched, are notorious for problems using a typical series charger.  The early electric car folks did most of the pioneering work in this area, as they were often using strings well over 150 volts. They ruined a lot of batteries so that we don't have to, if we pay attention to their work.

For a serial string, over time, some batteries get overcharged, and some chronically undercharged.  The latter get sulfate build up and loose capacity, the overcharged batteries eat away one plate and fail.  Equalizing by protracted, slow overcharging can reduce the problem, but the better performing batteries still suffer some plate erosion during equalization. (Which is also a big waste of energy.)

The reason is because of variation in materials and manufacturing- each battery has slightly different characteristic charge and discharge impedance.  Without very frequent equalization, the difference in state of charge of the fastest charging batteries vs the slowest becomes enough to destroy both.

The solution is to use shunt regulators on every battery.  Manzanitamicro.com is one company that did some pioneering work in this approach. By adding a simple shunt regulator to each battery, and reducing charge current once one of the battery shunt regulators signals that it is shunting current, fast charging batteries are saved, and the current is shunted to the adjacent slower batteries (not entirely wasted as heat).  The shunt method of serial charging is also very valuable for AGM batteries, which can't be equalization charged heavily without shortening their life.  (Heavy service batteries with heavy plates can take a lot of equalization charging.)

With an intelligent charge controller, you can monitor and log the time delay between batteries reaching charge, so as to identify batteries which may need attention. (Desulfation, cycling, or replacement).

I built my own linear battery shunt regulator which is temperature compensated (probe on each battery).  Temperature compensation is critical, as colder temperature charging requires a much higher cyclic charge voltage. When I see chargers with fixed voltages, I cringe.  The regulators have bussed opto-isolated controls to select float, cyclic, or equalization charging (two signals).  Each regulator has an opto-isolated output that is an analog signal proportional to the shunt current. (one analog signal per battery)

While I am still working on the smart, datalogging controller, I have used this system manually on my 10 string battery and am very impressed. In just a few discharge/charge cycles, the disparity in charging times between batteries reduces- to less than a minute on year old (crap marine) batteries.  Equalization is not needed on a regular basis, though I will add a very brief equalization period after peak charge daily if PV or Wind power permit.

Hopefully new 24 and 48V charge controllers in the future will incorporate this approach. Without it, very high quality batteries (well matched impedance for charge and discharge) and lots of equalization are needed.

Parallel batteries have their own serious problems with charging, but there is no practical way correct the problem through the charger. It can only be mitigated by battery matching (same age, condition, charge/discharge impedance) and frequent equalization charging. The practice of paralleling a bunch of small batteries has a well documented, poor outcome.

Hopefully someday soon we'll see the shunt regulation scheme of series batteries being applied to the 48 and (later) higher voltage battery bank commercial charge controllers.  

Optimistic news for folks who don't like CFL's with some blurbs on various new incandescent technologies. 

http://www.nytimes.com/2009/07/06/business/energy-environment/06bulbs.html

Working on some software for my 120VDC battery bank controller I finally ran into a stumbling block with the Picaxe 40X1; it is limited to 16 bit unsigned integer maths.  Alas, for state of charge (SOC), calculated every couple seconds throughout the day, this just won't do it.  I need 32 bit integer or at least 32 bit floating point.  

There are about 8 compiler choices (Basic or C) that support the same 16F887 processor, so I won't have to change my processor board, but I will miss the utter simplicity of the Picaxe as I wade through compiler and programmer choices.