Tuesday, May 4, 2021

New cordless electric lawn mower

My original solar lawn mower built in 2005

Back in 2005 I converted my neighbor's dead 22 inch Craftsman gas lawnmower to run on a 12 V electric motor using a deep cycle lead acid battery.  It has lasted 11 years and was crazy powerful.  I have had to replace the battery three times in the intervening years at a cost of about $80 per battery plus a $5 fee or recycling the old battery. Back then there were no cordless electric lawnmowers available and due to my commitment to reducing my carbon footprint, this was the only option I could come up with for mowing my lawn.  That mower was charged from solar panels on my shed roof.  You can read more about the construction of it on my blog here.  At 95 pounds, it is kind of a beast and in the peak of summer summer becomes tiring to push around for 20 minutes - fortunately the battery only lasts 20 minutes or so.

old vs new lawn mowers
Over the last several years, almost a dozen companies have introduced cordless electric lawnmowers and last year I started to review them.  The technology has come a long way!  What I find interesting is that there are two newcomers building cordless yard tools, Greenworks and EGO that are both very highly rated.  Cordless lawnmowers are also made by many of the established tool makers like Makita, Black & Decker, etc.  So this spring I did more research and winnowed my choices down to one of those two makes and settled on the Greenworks based on price ($400), size (20" cut width), performance and versatility.

There are several things that are unique about this cordless lawnmower:

  • It has slots for 2 batteries and switches from one to the other when one runs down. (It comes with a 4AH and 2AH batteries).
  • There are inexpensive secondary market batteries available for it with higher capacity than the manufacturer's batteries.
  • Run time with both batteries installed is estimated at about an hour.
  • It has 2 smaller sized blades rather than a single 20" blade.  
  • It weighs about 40 pounds which is much lighter than most gas mowers or my previous one which weighed about 95 pounds.  It is so light that it almost feels like a toy until it cuts through the heavy grass like a champ.
  • It increases its power/speed automatically when it hits heavy grass.
  • Cutting height is set with a single lever.
  • It can be configured either for mulching or a grass catcher on the back.
  • It is almost as quiet as my previous mower, and much quieter than a gas mower.  It has a very high-pitched whine from the dual motors that my neighbor thought sounded like a drone flying overhead until he came by to see it.

old vs new

I have already stripped the old mower for parts.  It turns out that the 3/4HP motor if purchased new today would cost more than the new mower.  So I've listed it on eBay in the hopes that I can sell it for at least half the current retail price.  That big honking gray motor weighs in at 31 pounds so it will be expensive to ship!

The new mower is still solar powered because all of my power comes from solar energy either from my solar panels or the solar farm that I subscribe to.  As Kermit the frog stays: "It's good to be green!"

Sunday, April 25, 2021

My 1st generation Enphase microinverters are failing fast

10 failed microinverters


I was a very early adopter of the Enphase micro-inverter (devices that convert power from solar panels directly to 240 V AC right under the panel on the roof).  I began installing my solar power system in 2009 and added to it over the years to the point that I now have 32 solar panels each with its own micro-inverter.  My installation was the 1239th and there are now literally millions of these micro-inverters in the world.  In the intervening years Enphase have continually revised their products and they are now selling seventh generation microinverters.  Enphase were the pioneers of this technology and remain one of the front runners in the highly competitive field.

To date 10 of these micro-inverters have failed and Enphase have honored their warranty which goes to 15 years. I am now seeing one or more failures every year for the last five years.  The most recent unit to fail is shown in the chart below on the bottom left.  A major advantage of using micro-inverters is that they allow you to monitor each device and its power output in near real time.

Below you can see a recently removed failed device and the new one that looks quite different.  Each new micro-inverter comes with a different set of cable adapters as they evolve the technology and make it backwards compatible with the early models.

Failed, and replacement micro-inverter.

New inverter is smaller lighter and form fits to the components

Every time one of these units fails, I go on to their website and order a replacement - a process that is made quite simple for me as a self installer (rather than end-user).  To replace these inverters, a friend and I need to go up on two ladders, remove the solar panel to access the inverter underneath and then unplug and replace it.  This takes about an hour to do this safely and carefully.

While I am very pleased that the warranty is being honored, I am concerned that I have only four years left on the warranty on some of my older devices and will be left having to buy them at over $200 each when they fail after that.

Sunday, March 28, 2021

DIY install of a Mr Cool heat pump

In March 2021 I received a government stimulus payment of $1400 as part of the Covid-19 recovery.  So I decided to do my civic duty and stimulate the economy by purchasing a DIY Mr. Cool heat pump.  And of course, I am on a mission to reduce my carbon footprint.  I got a very good price from Lowe's of under $1600 for this 240V unit which is rated at 23,000 BTU or 20 SEER for cooling and  25000 BTU for heating (Model: DIY-24-HP-C-230B).  It is rated for 1000 ft.² so it will be sufficient to heat the ground floor of my home which is roughly 27 X 27ft.  It is a split system meaning that it has a condenser outside and an air handler inside connected by wiring and plumbing and can do both air conditioning and heating.  Split heat pumps are known to be very efficient - typically well over 300% efficient, meaning 1000 W of electrical energy gets you over 3000 W of heating or cooling energy.  Yes I know, this sounds like magic, but it's actually just basic physics.

By purchasing the DIY installed unit I am saving over $2000 in markups and installation costs.  Several years ago I got prices from a couple of different local installers that were around $4500.  I did have to buy almost $200 worth of additional parts to complete the installation.  This includes the outside mounting bracket, electrical wire, circuit breaker, outdoor disconnect box, outdoor conduit and a plastic line set cover.  So all in, I'm spending a little over $1800.  It took me many hours of research to identify and select the best prices for all of these components but it was worth it, and I am a geek so this is what I do!

I spent about seven hours doing the actual installation, and if my house had not been built in an unusual way, it would've been a lot easier and faster.  I watched YouTube videos of other people doing installations and some people were able to do it in 4 hours or less. 

Installing line set and mounting bracket

The two biggest challenges were drilling a 3.5" diameter hole through the wall for the plumbing line set, and installing the mounting bracket for the condenser outside.  That hole had to go through 3 2X6 studs and took over an hour to open up!

Here's what the condenser looks like mounted outside my basement door:

and the air handler inside with the remote control:

I made a time lapse video of the installation with subtitles explaining each step:

From studying the energy consumption, I am very disappointed to see that the standby energy use ranges from 37 to 57 Watts.  According to a tech support guy, they need to leave the fan inside running at low speed to continuously sample the temperature for the thermostat.  This is grossly inefficient and there seems to be no way to disable that. 

Since my home, business, and vehicle are largely powered by my self installed solar array, the electricity for this heat pump will come mostly from the sun.  I will keep the Rinnai propane heater in place because heat pumps lose efficiency when temperatures drop below 5°F as they do often here in Maine in winter.  I also use a large wood stove in the basement whenever outside temperatures are below 20°F.  By using up to a cord of locally sourced firewood, I am also reducing my energy needs with a renewable resource.

This Mr. Cool heat pump also comes with a smart phone app and can link to my Amazon echo units so that I can control it by voice by asking Alexa to change the temperature setting etc.  The app lets me set up a schedule of temperatures and also review the history of usage by hours per day.  It has a geo-fencing option that you can use to turn the heat down when you leave home, but since I'm around all the time, I won't be using that.  It also shows a timeline of when settings were changed, all of this really appeals to the geek in me!

Friday, January 22, 2021

Inconvenient trees


I took this photo of my workshop on January 15 to show the way that the trees on the windrow on the south side of my property have grown to shade my solar collectors and panels.  This windrow forms the border between my property and my neighbors.  When I first moved here in 2001, the trees were only 20 feet or so high, now they are nearly double that and in the dead of winter here in Maine when the sun angle is very low (latitude 43) these trees are becoming more and more obnoxious.  So I asked my neighbor how he would feel about my topping them and he was fine with it.  He had just signed up for getting his electricity from a solar farm and bought a Chevy Bolt electric vehicle, so he is fully on board with renewable energy.

So I put a bow saw over my shoulder and climbed up the trees and aggressively trimmed back the branches that were most actively shading the four large solar collectors that I used to heat the building in the winter.  I was able to gain back about an hour of sun in the afternoon which makes a big difference in offsetting propane needed to heat my workshop building.

This photo was taken after my first pass at topping the trees on the left.  It was taken at around 1:30 PM.  I have two other trees to cut, but I will need help from one of my other neighbors to accomplish those since there is some strategy involved.

Below are charts showing the output from my solar electric panels before and after trimming the trees as shown above.  you can see that the trees had been taking a bite out of my beautiful parabola on clear sunny days!  Definitely some improvement here!

I noticed on my community Facebook group that local people with goats were asking for Christmas trees because goats like to eat them, so I offered the cut branches and a couple of people came and picked them up! 

I had two other options; pile them in the backwoods and let them decompose, or burn them.  But both of these options would release carbon into the atmosphere.  I think it is more environmentally responsible to let goats have them don't you?