M Rives

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since May 07, 2021
Electrical engineer living off grid.
Zone 6a
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Recent posts by M Rives

Growing up, the expression "playing chicken" was common, but never fully understood until we got chickens. They were allowed to free range and loved the fresh cut lawn. In fact, they especially loved to run right in front of the lawnmower chasing bugs. The ultimate game of "chicken" as they dodged out of the way at the last possible moment.

I was not so nimble one night when moving their coop. It's on bicycle wheels so it rolls pretty good. The chickens were all locked in for the night and I started rolling it down the road from the barn. Everything was going great as my wife looked on from the top of the hill. The road gets a little more steep about half way down and that's where the trouble started. I was doing everything I could to hold it back and hollering at my wife to help slow it down. Faced with the thought of it crashing out into the field below, I started running in front then beside the coop. That's when my foot went under the edge and down I went. It rolled mostly over me and pushed me to the bottom of the road where it leveled out. That's right, grandpa got run over by the chicken coop! My wife caught up and was yelling to see if I was OK. My head and arms sticking out like the witch's red shoes sticking out from under the house in the Wizard of Oz was too much for her and she almost peed her pants laughing at me. The chickens all slept through the E-Ticket ride.

Speaking of peeing, sometimes I'm known to pee out in the yard (totally committed to permaculture, you know). All the cats and I have a gentleman's agreement and they leave me to it. One particular chicken, not so much. There I was minding my own business when she ran right between my legs, obviously thinking "MUST CATCH SHINY GOLDEN BUGS!" Hilarity ensued. No matter which way I twisted and turned, I could not avoid peeing on the chicken. Fortunately, there is not a video of us dancing around together on the side of the hill Knowing she liked to be petted the only thing left to do was spray her off with the garden hose. I was much more observant of the chickens after that experience.
2 weeks ago

Gilly Burke wrote:iced tea



And its southern relative, Sweet Tea.

Grits are very similar to Polenta so while the name might be different, the texture is similar. A guy I worked with talked about having polenta parties when he was growing up but I think you could substitute grits:

1. Get a big group of family and/or friends together.
2. Scrub a large counter or table clean.
3. Randomly place treats like olives, peppers, veggies, grilled meats, sausage, bacon - whatever you really enjoy - on the counter.
4. Pour a large pot of polenta on the counter in a thin layer surrounding all the treats.
5. Give everyone a fork.
6. You can have any treat you want, but you have to eat all the polenta from the edge to the treat. If someone beats you to the treat you wanted, redirect to another one.

He said things could become rather competitive ;-) I suspect this is something your visitors have never experienced.
1 month ago
You can never go wrong with Rocky Mountain Oysters...

Before I was hired my manager used to take visitors from Asia and Europe to Bruce's Bar in Severance, CO for this 'treat'. Fortunately, I'm still as curious about them as I ever was.
1 month ago
Hi Mike,

Q14: Will a 60A panel and existing wiring be adequate?

Perhaps? It depends on your loads. Looking at your greenhouse info I see you are using some electric heaters which may explain where your 18kWh/day is going. We run some items like a toaster oven, hair dryer, microwave, etc. but only for a short duration. The crock pot only comes out on sunny days. Your welder may be pushing it depending on how many amps it draws. Trying to run a plasma cutter and big air compressor is probably not a good idea. I run a 240V 3HP table saw and it works fine but it requires a huge starting surge (works fine except for the time when the belts were cold and it did not spin up - the pixies escaped from a $180 solid state battery switch on that occasion). Similarly, your well pump may pull a lot of power on startup. It's a good idea to do a load analysis where you document all your loads and how much power they draw. Then consider how many of them may be on at the same time.

A 6kW inverter will output 25A at 240V (6000W/240V=25A) or 50A at 120V (6000W/120V=50A). The Schneider manuals specify 60A breakers into and out of their 6kW inverter. Hopefully you won't use the full output of any 6kW inverter for a prolonged period of time since it will be pulling about 125A from a 48V battery bank (6000W/48V=125A). These are rough numbers since there will be some losses due to the inverter efficiency and wiring. Different inverters support different levels of surge current. The Schneider 6kW can briefly do 3x the rated power. It's also important to balance 120V loads since the inverter may not be happy providing the full 6kW at 120V.

You might find the spreadsheet linked at the top right of this page (look for the download button) along with the discussion useful:

https://diysolarforum.com/resources/system-energy-audit-and-sizing-spread-sheet.12/

I'll also attach an example system diagram from our previous home. It does not include a generator since it was grid tied. There are some notes on wiring sizes, mostly for the PV arrays since they were ground mounted some distance from the house. The inverter was maybe 30-40' from the priority load sub panel which was 60A. I also have a wiring loss calculator spreadsheet somewhere but it might prove more confusing than helpful.

The humidity in the greenhouse might not be too good for the generator. It sounds like a wofati dug in below frost depth might be just the ticket I'll also attach an interesting generator shed drawing I snipped from Hardy Diesel (I did get a water cooled diesel generator, but not from them).


5 months ago

Terry Byrne wrote:
Does this mean that the Web is going to be increasingly monetized, ie. somebodies somewheres are going to charge a fee to encrypt pages/websites even?



Hi Terry, yes, I suspect that the Web will be monetized in every possibly imaginable way

There are an untold number of companies that sell web hosting. You create the content and they provide a web server to host it so anyone can view it. You also need a domain name like somewebpage.com that must be registered and linked to your physical server so people can find your web page. A domain registrar will charge you for this domain name or the hosting provider will be happy to handle it and pass the cost along. The security certificates are sold as an add-on to the hosting service by many of these companies. For example, my web host provides a free certificate for the first year of hosting then sells a renewal each year after that. This is on top of the domain name registration fee that is usually charged annually. They will also let you pay to keep your personal info at the registrar private so you don't get a ton of spam about search engine optimization, web page design, marketing, etc. All of this is relatively low cost but it can add up over time.

Always keep in mind, when it comes to the Internet if you didn't pay for the product, you ARE the product.

Mike Haasl wrote:
I'm still a bit unclear about Question #9.  Can the generator feed juice onto my household grid at a distant subpanel and then the inverter and batteries could be 100 yards away in the house?  Or do I need a dedicated wire that feeds power from the generator to the inverter?



Q9 - No, you cannot normally feed the generator into your house circuitry along with the inverter output. The generator and inverter outputs are not normally connected together. The generator needs to have a dedicated wire to the inverter but it can be 100 yards away with large enough wire. The inverter output will feed a sub-panel with priority loads if you are grid-tied or your main panel if you are off grid. This will allow the inverter/charger to charge the batteries and feed through power to your loads on the inverter output. It also allows the inverter to seamlessly switch your loads from the inverter output to the generator and vice-versa.

My inverter decides what power source is available and uses it to feed the priority loads on the inverter output. If there is grid power, it can feed it through and also charge batteries if needed. The same if generator power is available. If there is no external AC power source, the inverter generates AC from the batteries and / or PV output. Locally generated power can be also sold back to the grid, but only if the grid is up. In a grid failure, your power system MUST NOT feed power back to the grid to protect any power company workers. That's why a transfer switch is required for a generator. The Schneider inverter includes the transfer switch.

You can get a better idea of wiring for a system with PV, batteries and a generator on page 134 of the Schneider XW Pro 6848 Install Guide here:

https://solar.schneider-electric.com/download/xw-pro-iec-user-documentation/?wpdmdl=10331&refresh=6211e4c8d76881645339848&ind=media-10991&filename=ML202007_XW-PRO-NA-Installation-Guide990-91228A-01_rev-A.pdf

Page 128 shows a simplified diagram of what's inside the inverter / charger if you are a glutton for punishment ;-)

Mike Haasl wrote:

Jim Webb wrote:Batteries: I'd avoid lithium batteries, not least because of fire risks.


Jim, this is a bit surprising to me.  I know phones or small batteries sometimes burst into flames but I thought the bigger packs, especially ones that aren't DIY, were safe.  I mean there are two in my wife's prius..  



The Li-Ion batteries initially used by Tesla and other EVs are based on lithium nickel manganese cobalt oxide (NMC). EVs try to make them safe, but there have been cases of EVs burning down houses. This chemistry is more risky than the lithium iron phosphate (LiFePO4) cells which are generally regarded as the safest option. There are videos of people testing LiFePO4 batteries by short circuiting them or drilling holes in them on YouTube. That said, any time you are storing 10's of kW of energy and using 250A DC circuit breakers, caution is advised. Dropping a wrench across a lead acid or LiFePO4 battery pack could certainly ruin your day, even worse if it welded itself to the terminals. It makes sense to take all necessary precautions. Commercial LiFePO4 batteries include a battery management unit to monitor cell voltage, temperature and current. They will disconnect if anything goes out of bounds. The DIY packs I built include these same protective devices.

For comparison:

LiFePO4 batteries charge with a constant current until charged while lead acid batteries charge with a decreasing current and a long absorb phase. That means your generator will run longer to recharge lead acid batteries and the longer it runs, the less efficient it gets since its output will be constantly decreasing.

For longevity, lead acid batteries should only be discharged to about 50% and must be fully recharged to 100% every 5-7 days even if they are still at 90%. LiFePO4 can be cycled from 20% to 90% for maximum life so fewer AH of capacity are required. LiFePO4 are also happy to go for long periods without being charged to 100% so if you have a string of cloudy days, they don't have to be recharged until they have been discharged.

You will also need to add distilled water to the lead acid batteries on a regular basis and provide a vent for the hydrogen generated during charging unless you pay more for AGM or Gel batteries.

So far, I am very happy with the change to LiFePO4 and would not go back to lead acid.

Scott Loren wrote:
How about putting your setup in an insulated building with a waste oil burner to heat it?


My generator is in my shop so when it runs, I get some free heat. It's not too loud and the exhaust is routed outdoors.
5 months ago
It looks like they aren't selling kits anymore, but the greasecar web site might be of interest. Their system starts on diesel then after the engine heats up you can switch to used vegetable oil. The engine heat warms up the vegetable oil so it will flow through the injectors. Before shut down, you must switch back to diesel and purge the vegetable oil. This does not sound very feasible for automatic start / stop but it could probably be done with some effort. A water cooled diesel generator would be needed to preheat the vegetable oil. Here's the link to their web page which includes Technical Resources and FAQ sections:

https://www.greasecar.com/

There is also a book about running cars on vegetable oil, "From the Fryer to the Fuel Tank" by Joshua Tickell.

Q9 - As for system design, the generator will create either 120 volt AC or 240 volt AC power. It can be located a reasonable distance away from the batteries and inverter / charger which are normally close together. If you add some PV modules, their charge controller is also typically close to the batteries. This is driven by the relationship between power, voltage and current. For a given power of 1000W, at 240V the current is 1000/240 = 4.2A but for 1000W at 12V (battery voltage) 1000/12 = 83.3A. The higher the current, the thicker the wires need to be to prevent power loss and voltage drop. Higher power systems usually use 48V battery banks for this reason.

My system uses Schneider (formerly Xantrex) equipment. It includes an automatic generator start (AGS) controller. This unit allows setting different generator triggers for start / stop. Mine starts the generator when the batteries drop to a programmable voltage setpoint. As soon as the inverter/charger sees the generator come on, it waits for it to stabilize then automatically switches over and starts charging the batteries. The inverter also passes the generator power through to all the loads. If a heavy load starts the generator may slow down causing the inverter to disconnect it briefly then reconnect. When the generator stops the system goes back to the inverter output automatically. This is all transparent to the loads so computers don't crash, etc.

The generator is water cooled diesel based on a Kubota tractor engine. It includes a start control module which handles all the glow plug preheat timing, cool down, etc. You might be able to use something like it to handle the switch over from diesel to vegetable oil. The Schneider AGS might also be able to do this, it has a lot of options. The AGS in my system just closes a relay to short the start wires together when the generator should run. The inverter talks to the AGS so you can set it to stop the generator with a few different options. Mine turns off when the charger ends the absorb phase indicating the batteries are charged.

Q10 - We are totally off grid and this setup has run without issues for over 5 years using lead acid batteries. I just switched over the LiFePO4 batteries and only had to change the setpoints for charging voltage and the automatic generator start. It has programmable quiet hours when the generator won't run. Otherwise, it only runs when it needs to rather than on a specific schedule. That is probably better for battery and generator lifetime.

As Andrew said, Will Prowse has a lot of good info. Be sure to check out his forum site where you will find lots of good stuff and people willing to help you with specific questions:

https://diysolarforum.com/

Some food for thought: 18kWh is a lot of power to generate and store each day. You'll probably need to run a 48V system with at least a 6kW 120V/240V inverter. A DIY LiFePO4 battery bank of 16 280AH cells can store 14kWh. For maximum lifetime, normally you only want to use less than 80% of that so you'd need twice as many batteries. One set costs around $3,000 if you build it yourself from decent quality Chinese cells shipped from US stock. Commercial LiFePO4 batteries will be a lot more expensive. The water cooled diesel generator I bought should run for 25,000 hours with routine maintenance since it turns at 1800 rpm. The air cooled diesel generators turn faster and probably only run for 5,000 hours. A Lister will probably run forever but I'm not sure about getting 12kW out of one. If you run for 2 hours a day, 5,000 hours is about 7 years. If you get a portable gas or LPG generator for around $1,000 and run it that much it might last 2-3 years before the inverter will stop accepting its power. I'm not sure if a diesel generator will have that issue (declining power quality). A separate AC powered battery charger would probably work OK for longer but the inverter inputs are finicky. Anything you can do to reduce power consumption is going to be worthwhile.
5 months ago
Skip this unless you want to know more about httpS vs. http web pages

Just FYI, the httpS means that your connection to the web site is Secured by encryption. This is very important if you are doing anything you don't want others to be able to see. For example, filling in a form with your credit card info.

There is a move toward making all web browser connections secure using https so at least some web browsers will default to using https. For example, if you just type somewebpage.com in the address bar, your browser will automatically try to go to https://somewebpage.com where it used to go to http://somewebpage.com.

In this specific case, the real content is at http://www.stoves2.com (which then points to http://www.woodburningstoves2.com). The weirdness happens because there is also an httpS://www.stoves2.com. The problem is with the security of the https page.  In order to prove the connection is secure, the web page needs the right credentials (called a certificate) which must be purchased from a known legit source. https://www.stoves2.com has a security certificate, but they created it themselves rather than purchasing it from a known source. This means the connection is encrypted and cannot be eavesdropped by anyone but it does not provide any assurance that the web site is who it claims to be, hence the warning of an insecure site.

Michael Qulek wrote:In terms of other Li battery based things, I see variable results that are temperature dependent.  I have a wireless weather station, powered by Li AA batteries, and I can see that the outside temperature sensor stops working when the outside temp drops below about 45F.  The next day, when the temperature warms back up, the sensor will start reading again.



Hi Michael,

The Davis weather station I have showed the same problem. The Lithium AA battery (which is not a rechargeable Li-ion in my case) provides backup. The main power comes from a super capacitor that is charged by a solar panel. After some time, the super capacitor wore out. Replacing it allowed the weather station to transmit all the time again. If you've tried replacing the battery and it still stops reporting when cold this might help your problem, too.

Now we're totally off the original topic. Is that OK here?
7 months ago

Denise Cares wrote:I checked my little solar lights and they indeed have Li-ion battery a rather large/oversized AA almost a double one in a plastic wrap (but it is not double AA), so not sure what size to call it. I have charged new lights outside and it is 30deg now and they seem to work. I think you're right they are designed to be used outdoors. So temperature extremes cold/hot may shorten the life of batteries but it may be a variable thing with some types of batteries more sensitive than others (maybe a manufacturing flaw in the short lived/malfunctioning ones?).



Hi Denise,

Thanks for confirming that you have Li-ion batteries in the small solar lights. They may be 18650 size, 18mm diameter (just under 3/4") x 650mm long (about 2 9/16"). These can be ordered in styles with a small button top or a flat top so keep that in mind if you need to replace them.

For more info on the temperature issue, the following forum entry discusses a paper that tested Li-ion batteries for 100 cycles at various temperatures. The summary seems to be that the batteries have lower capacity at lower temperature but that the capacity recovers after the batteries warm up. They are charging at a low current like your solar lights with a small solar panel which probably helps prevent damage.

https://diysolarforum.com/threads/why-you-cannot-charge-lifepo4-below-0-degrees-celsius.2912/post-370147

As Michael said, this is a much bigger concern in a larger solar power system. Large LiFePO4 cells can be pretty spendy so erring on the side of caution is a good idea. The small 18650 cells can be found for about $3 so replacing them after a few years is doable.
7 months ago