Ego 21″ mower (LM2100SP) 3rd self propel motor failure & repair report

My Ego 21′′ self propelled electric lawnmower started on its third self propel unit failure back in June of 2019.  For those keeping track, I bought the Ego 21′′ mower back in April 2017, and it’s self propel unit failed in October of 2017 I took it to Home Depot to be repaired (which took 6 weeks) and the repaired self propel unit lasted until July of 2018. Ego customer support was nice enough to send out a replacement mower that time, so my downtime was only 10-15 days, and I was hopeful that the replacement mower might have a better self propel unit in it. Unfortunately, that one started to fail in June of 2019, so it looks like the lifespan of my self propel units are 4 months, 10 months and 11-16 months.

So, back in June 2019, the self propel unit just stopped working much like it had previously. I called Ego customer support and they offered to ship me a replacement mower. We had that all set up, but the next day I went out to push-mow the rest of my lawn, and lo-and-behold, the self propel unit had “reset” and was working again! So I called Ego back and canceled the replacement.   Unfortunately, although the self propel unit had not totally failed, it had not fully recovered, and still had some issues that got gradually worse over time. Specifically, the top speed was reduced, and over the next several months, the power and top speed appeared to keep dropping. Eventually it got to a point where it would not propel the mower up a slight hill without me assisting. Eventually, in January of 2020, the self propel unit failed completely, and did not “reset” itself.

Ego shipped me a replacement mower and I shipped the bad mower (my 2nd) to them, so I am now on my 3rd Ego mower (and year 3 of my 5 year warranty). However, for the first time in 3 self-propel failures the SP unit is different! The new mower (manufacture date October 2019) has a different style of self propel unit when compared to the three units that had failed on it in the past. The old unit had a gearbox on the drive shaft and the motor body stuck upwards at a 90 degree angle. The new unit has the motor body above but parallel (horizontal) to the drive shaft. I don’t know if the old unit had a fan, but the new unit has a fan clearly visible.

Older Self Propel Unit

 

New Self Propel Unit

Objectively, the new self propel drive unit doesn’t look as impressive as the older unit, but given the number of failures I have had with the old style, I’m excited to have something change (and hopefully improve). From a performance standpoint, the new self propel unit works just as well as the old style, so there is no loss in performance. I just hope that it will have more longevity than the older units.

I suspect that the size of my yard (which is large enough that it takes me two 7.5 AH batteries to mow it in the fall/winter, and up to four 7.5 AH battery charges in the heat of summer) may be the reason the self propel unit’s are failing. I suspect I’m putting a lot more “miles” on the SP unit than most Ego owners, plus they seem to be failing in the heat of the summer. I’m not sure if that is due to heat related problems, or if it’s due to the grass growing more in the summer.

2020 Over The Air (OTA) HDTV Channels in Orlando, Florida

After the FCC auctioned off some of the HDTV spectrum for cell phone (5G) use, a few stations had to change their channel allocations. Here is a list of the over the air (OTA) channels I can pick up from the west side of Orlando.

  • 2_1 – NBC (WESH-DT) VHF-11
    • 2_2 – Me TV
  • 6_1 – CBS (WKMG-DT)
    • 6_2 – Dabl  WKMG-DT
    • 6_3 – Cozi
    • 6_4 – Start TV
    • 6_5 – Decades
  • 9_1 – WFTV-HD  (ABC) (UHF-35)
    • 9_2 – LAFF
    • 9_3 – Escape
  • 10_1 – Diya TV (Indian? classic cinema) [Schedules Direct does not have a lineup yet]
    • 10_2 – Orange (county government TV)
    • 10_3 – Vision  (orange TV)  (WLOQ?)
    • 10_4 – This TV
    • 10_5 – News Net
    • 10_6 – JTV
    • 10_9 – open
  • 15_1 – WDSC-HD (PBS 15 – Daytona Beach)
    • 15_2 – WDSC-ED The Florida Channel
    • 15_3 – WDSC-WV (Worldview)
  • 18_1 – WKCF-DT  CW
    • 18_2 Justice
    • 18_3 estrell
  • 24_1 – WUCF-HD (PBS 24 UHF -34)
    • 24_2 create
    • 24_3 kids
  • 27-2 – 27 – WRDQ
    • 27_2 – Antenna
    • 27_4 – Grit TV
  • 31_1 – T31 WTMO CD (TeleMundo Orlando )
    • 31_2 – WTMO-SD
    • 31_3 – TELEXITOS (Xitos)
  • 35_1 – WOFL-DT (FOX)
    • 35_2 – LIGHT
  • 43_1 WVEN-TV (Univision) UHF-22
    • 43_2 – GET TV
    • 43_3 – Bounce
    • 43_4 – Escape
    • 43_5 – Quest
  • 52_1  TBN-HD (Trinity Broadcasting Network) (WHVL-TV Digital 52, UHF 32)
    • 52_2 Hillsng (Hillsing)
    • 52_3 – Smile
    • 52_4 – Enlace
    • 52_5 – JUCE
  • 55_1 WACX-D1 (SuperChannel )
    • 55_2 – WAXC-D2
    • 55_3 – WACX-D3
    • 55_4 – WACX-D4
    • 55_5 – WACX-D5
    • 55_6 – WACX-D6
    • 55_7 – WACX-D7
    • 55_8 – WACX-D8
    • 55_9 – WACX-D9
  • 56_1 – ION (WOPX)  Physical Channel 48
    • 56_2 – QUBO
    • 56_3 – ION Plus
    • 56_4 – Shop (sponsored Television programming)
    • 56_5 – QVC
    • 56_6 – HSN
  • 65_1 – WRBW-DT   UHF-28 (fox 35 plus, my network TV)
    • 65_2 Movies!
    • 65_3 H&I
    • 65_4 Buzzr
  • 68_1 – WEFS-HD Educational  (Eastern Florida State College) [minimal signal, can’t receive reliably]
    • 68_2 – WEFS-CL (Classic Arts)
    • 68_3 – WEFS-NS (NASA Educational)
    • 68_4 – WEFS-FL (Florida Channel)

Salvage 2013 Nissan Leaf modules – 7 year old range update

Back in January of 2016 I put a set of battery modules harvested from a salvage 2013 Nissan Leaf into my S-10 conversion electric pickup. In march of 2016 I drove the truck for a while to see what its range was. [More than 46 miles, as I got tried of driving. The pack had a capacity of at least 15 kWh at that point in time.]

37.4 miles on trip meter.

Today I drove the truck for 35.8 miles before the low cell warning beeper from the BMS started to alert. After I got home [37.4 miles total], the average cell voltage of the pack was 3.75, while my (one) lowest cell was down at 3.3 volts. As it turned out, that cell must have started the trip out at a lower state of charge / voltage from the other cells, as it was still low when charging finished and I had to manually add charge to it individually. [My BMS does a good job of alerting at high/low voltage conditions, but does not do much for balancing the pack.]

According to my JuiceBox, the pack required 14.74 kWh to recharge, which is a good estimate on the battery pack’s current capacity. [This is almost exactly the same amount of power that I used in the trip in 2016, but I didn’t go as far due to different driving conditions. And I also hit the bottom of (at least one cell’s) state of charge.

The 2016 trip averaged 322 watt-hr/mile. This trip consisted of a lot of stop & go city driving as well as a few lengthier stretches of 49 mph arterial streets, and I wasn’t light on the accelerator. My measured watt-hour / mile (from the wall, including charger losses) was: 394 watt-hr/mile

Assuming that the pack has a 15 kWh capacity, this is 63% of the brand new 24 kWh capacity, which means I lost 37 % of the capacity over 7 years. (Some of that was in the original Nissan Leaf, but most of it was in my s-10 conversion.)

I’ll repeat the test after balancing my cells a bit better and see how things go.

Update: I drove the truck until the low cell beeper came on again. I went a total of 38.5 miles, and recharged the pack with 16.69 kWh (16690 watt-hours). The relatively higher  433 watt/hours per mile number is a result of the weather being a lot cooler so I was running the heater in the truck and more 45 mph roads. Balancing the cells got the usable pack capacity (measured from the wall with charging inefficiencies) to 16.69 kWh (which could have theoretically gotten me to 42 miles at 394 watt-hour/mi or 51 miles at 322 watt-hr/mile)

The main take-away is that at 16.5 kWh, I still have access to 68% of the brand new 24 kWh capacity Leaf pack, which isn’t too shabby for a 7 year old battery.

 

 

 

12 Month Grid-Tie Solar system report

Over a year ago we installed a 10.4 kW grid tie solar system.  You can read about the shakedown period here.  This post will cover all of 2019, the first full year the solar system was operational. [Technically, it covers the period between Dec 12th 2018 through Dec 11th 2019, as Duke Energy bills us mid-month.]

In this 12 month period, we consumed 16,695 kWh of power at our house (a 3 bed 2 bath ranch with all electric utilities + two electric vehicles). [We used 16,796 kWh the prior 12 months, so our usage did not appreciably change due to installing the solar system.]

Of this total electrical usage, our solar system produced 15,252 kWh or 91.4% of our total electrical usage, while we purchased 1,443 kWh from Duke Energy and the electrical grid. [There are no economic benefits to producing more than we use, so the ideal system would hit 99.9% of actual usage. We were aiming for 90% when we designed our system.]

Over the year, we paid Duke Energy $314.49 ($130.80 for required connection charges, and $183.69 for the electricity we imported from the grid, averaging 12.7 cents per kWh.)  This compares to our previous yearly cost for power of $2,211.13, giving a yearly cost savings of $1,896.64.  After the EIC tax credit, our solar system cost us $17,439.20, which gives a payback period of 9.19 years. (I’m deliberately ignoring the interest we could have earned by investing the money we paid for the solar system in the stock market, which counteracts the fact that I’m also ignoring the fact that Duke energy raises their rates every so often.)

As the solar system is expected to have a working lifespan of 15-25 years, any energy it produces after the payoff period will be pure profit. So yes, a solar system does make economic sense, in addition to the environmental, social and political benefits.

 

 

BEME Erod remote control repair (crystal oscillator replacement)

I dropped the remote control for my E-Rod electrically operated drapes, and it stopped controlling the receiver/drape unit. I had another remote that still worked, so I knew the problem was with the remote, and not the drape motor unit. The IR transmitters were still flashing a signal, and on the oscilloscope the signal looked reasonable, but the carrier frequency was at 62.7 kHz.

I eventually traced the problem to the crystal oscillator, and bought a 10-pack of them for $5 online (with a month wait time….). Replacing the oscillator restored the carrier frequency to 38 kHz and restored proper operation of the remote.

 

Ego Battery degradation over time (2 year mark)

I’ve been tracking how much power it takes to charge my Ego batteries since I purchased them. I’m using this as a stand in for how much capacity they retain over time. You should know that I have a large lawn (in Florida) and cycle these batteries at least once a week (more in the summer) so these batteries are getting more of a workout than if you had a small city lot that you could mow a few times before charging the battery.

I have two 7.5 AH batteries (one bought before the other). They took 410 watt hours to recharge when new. After one year of usage, the remaining capacity was (78% 320 w/h and 82% 340 w/h) on the two batteries. My older battery has two years of use, and has 70% of it’s original capacity (290 w/h).  So it looks like they drop between 18 and 22% of their capacity the first year, and an additional 8% the 2nd year for a total loss of 30% of their capacity after the 2nd year of usage. [The batteries have a 3 year warranty.]

30% capacity loss in 2 years

Thermoelectric cooler mark 3.5

I took my version 3 prototype ThermoElectric cooler and removed two of the four TEC modules, bypassing them in the cooling loop, to reduce the power draw.

Running two TEC’s at 12v each (in parallel, a sort of “turbo” mode) the whole system draws 136 watts. When I put the TEC’s in series (6v each, or “eco” mode) the whole systems draws 46 watts. This breaks down at 5 watts for the power supply, 11 watts for the fans & pump, and 30 watts for the two TEC’s.

Later on, I also moved the fans to 6v each and reduced the total power draw to 41 watts (the fans went down 5 watts when I reduced their voltage by half).

I’m using a cheap low-efficiency 12v power supply that draws 5 watts all on it’s own just idle, so we could get a 4 watt savings by running if off of a nicer power supply, or a 5 watt savings by running it from a 12v battery directly.

The cooling power is significantly reduced from the 4 TEC version, but I think that having a “turbo/eco” switch that would allow the unit to go from 12v operation on the TEC’s and fans to 6v operation (jumping from 136 watts down to 41 watts) would give the user flexibility to either cool things down when excess power is available, or just maintain temperature when operating off of battery power.  However, even in “eco” mode it takes almost a kWh per day of operation.  But at least it outperforms the Chefman TEC.

 

 

Insulation & heat loss of my DIY cooler

My DIY TEC Cooler has an interior volume of 480 cubic inches (6x8x10) and an interior surface area of 376 square inches (2.61 sq ft). It has an exterior volume of 1.55 cubic feet (12x14x16) and an exterior surface area of 1168 square inches (8.11 sq ft).  It generally has 3 layers of 3/4″ poly-iso insulation (R5) plus a small amount of one-part urethane expanding foam (say, R2?) in some areas, for an estimated R 17 insulation value (sorry, I’m using imperial units here as my insulation comes with R values….)

To calculate the amount of heat that will escape from inside my cooler to the outside (the amount of heat loss I need to counteract with the TEC system to maintain a set 34°F temperature on a 77°F day), we need to know the thermal delta between the inside and outside of the fridge.  (I’ll use 34°F for a good refrigeration value, and 77°F for the exterior temperature).

I’ll also use the average value of the interior and exterior surface area ((2.61+8.1) / 2) = 5.36 sq ft for this calculation. As a reminder, the equation to calculate heat loss in BTU/h is:

equation for calculating heat loss in btu/hours

In imperial measurements:
[5.36 * (77-34) ] / 17 = 13.55 BTU/h

13.55 BTU/h  divided by  3.41 = 3.97 watts

Using the SI system with things translated appropriately gives similar numbers:
0.49796 (25-1) / 2.99 = 3.99 watts

Of course, the above numbers may be completely incorrect, so I also did an experiment after building the cooler:

At 4:45pm I placed 3 refrigerated 12oz (355ml) cans of generic Dr. Pepper in my homemade DIY cooler with a temperature of 3.8°C.  [The active TEC elements were turned off, as I was just testing the insulation properties.]

At 4:21am the next day (11 hours 36 minutes later, rounded to 11.5 hours hereafter) I opened the cooler and one can, measuring the interior temperature at 14.6°C. [we’ll assume all three cans gained the same amount of heat…I only wanted to drink one can.]

So, 36 fl oz (1065 ml) of (basically) water gained enough energy to raise its temperature 10.8°C in 11.5 hours. The specific heat of water is 4.184 J/g-K. 1065ml = 1065 grams of water, or just about 1 kg. Nice how that works out.

4.184 J/g-C * 1065 g * 10.8 C = 48124.3680 Jules = 48.124 kJ = 0.0134 kWh = 13.4 Watt/hour

13.4 wh / 11.5 h = 1.1652173913 watts of continuous energy transfer from the outside to the inside of my cooler (heat gain, or cold loss).

You might notice that the calculated 3.9 watts is not equal to the observed 1.16 watts.
The main reason for this is that the interior of my cooler was never at 34 °F. It started at 3.8°C (39°F) and then raised up to 14.6°C (58°F) over 11.5 hours. It spends more time a higher temperatures, as the rate of heat transfer decreases as the thermal delta decreases. [Also, the ambient temperature was closer to 71.6°F, so the difference between the interior and the exterior was significantly smaller than in my previous calculations.]

For example:
[5.36 * (71-39) ] / 17 = 10.09 BTU/h / 3.41 = 2.95 watts
[5.36 * (71-58) ] / 17 = 4.099 BTU/h / 3.41 = 1.20 watts

However, the integration of the above numbers over 11.5 hours would still give me more heat loss than I observed. So either my experimental measures had a flaw, or the R value of my cooler is higher than the estimated 17.

However, as the results are of the right order of magnitude (4 watts vs 1.1 watts), I’m happy with my calculations and the experiment, and feel that the 4  watts of cooling power needed to maintain a 34°F interior temperature is a good upper bound on the performance needed by my TEC system to maintain temperature.