Category Archives: Green

Going Lopy

Darren, g0hww has attempted to persuade me several times over the last year or two that I really needed to try some of the devices from Pycom.

I resisted for quite a while, but finally broke a few weeks ago. I was looking out at our Polytunnel while it was raining and was wondering what the temperature was in the tunnel. Sure, I could walk out in the rain and check on the thermometer, but that would require effort, and the potential to get wet etc.

So I caved, and ordered some Lopy4’s and accessories including a Pysense 2.0X.

Darren gave me a copy of his code for his own project, and after some bodging (principally around getting the deep sleep to work correctly), I had enough done for an initial deployment.

Initial Deployment
Test deployment

I used my Powermonkey Extreme from to power it up and left it run over night. On checking it the following morning, I was slightly surprised and disappointed at how quickly the Powermonkey battery seemed to drop given the LoPy4 shouldn’t be using all that much power from the power bank(33.3WH), however the low temperatures are probably a major factor in this. The power consumption is approximately 0.95 of an hour at 13mA and 0.05 of an hour at 130mA, which comes to about 20mAh or about 0.1Wh at 5 Volts.

After looking around my ‘stores’ I found some other bits to make the deployment it a bit more practical. A recycled 12v PV panel and Victron Bluesolar PWM Light Charge Controller (thanks @floatsam for both of those), a recycled 7Ah SLA from a decommissioned UPS in work, and a DC/DC converter.

Phase 2
PV Panel ,Charge controller, and SLA added.
Phase 2 close-up
A closer look.

It worked very well at this location, but now it was in danger of getting watered along with some seedlings, so it had to move. A few screws, a bit of board and some Galvoband, and he-presto a new shelf.

Final location
LoPy4 in its current position.

The LoPy itself is close enough to the house that WiFi is working fine, no need for LoRa. So I spun up a Virtual Machine on my Proxmox server, installed a Mosquitto MQTT Broker, bodged some more Python, threw in a bit of influxdb, grafana and pushover. And now, as well as having some nice graphs, I’ll get an alert if the temperature goes to high or too low.

Screenshot from 2021-04-04 16-48-12


Shack 2.0

So, several months later, house move complete and it is time to get a shack operational again.

I am a fan of keeping things running when the power goes out. From a Amateur Radio Communications perspective, I have had a 80Ah battery in the shack for over 10 years and I have been using a West Mountain Radio Super PWRgate PG40S and Rigrunner 4010S to power my radio equipment and to keep the battery charged. My current ‘desktop’ is based on a Intel NUC 7i7BNH these along with their LCD’s are running off an older APC Smart UPS 1500, which gives between one and two hours of run-time should the power go out.

While everything was in boxes, I purchased a West Mountain Radio EPIC PWRgate (I wonder what adjective will be used to describe the 4th Generation!) this device can charge Lead Acid, AGM/GEL and LiFePO4 Lithium battery types, and, what attracted me to it is that it has a built in Photovoltaic (PV) Charge Controller. Which removes the need for a dedicated Charge Controller.

Sometime during the move, the old AGM battery died (Ophelia was its final ‘performance’). New shack, new battery, a Trojan EverExceed ST-1280 was ordered from O’Connell Batteries in Cork and duly arrived.

Plug-and-play? well not-exactly. After looking at the specs, the default ‘AGM’ setting in the Epic PWRgate needed some adjusting to avoid overcharging the battery. The battery specifications say 2.35 Volts per cell (for 12 hours), so the ‘Max charge voltage’ needed to be dropped from 14.4 to 14.1 volts, and the PSU set to 14.2. On Linux, the Epic PWRgate appears as /dev/ttyACM0, guessing I used 115200, N81, no handshaking and its console immediately popped up.

Battery:  1-Disable, 2-Gel, 3-AGM, 4-LiFePo4, 5-Other:    <3>: 3                
Reset to default values (Y,N):   (Y,N) <Y>? n                                   
Max charge voltage in Volts:    <14.10>:                                        
Max charge current in Amps:    <10.00>:                                         
Min charge current in Amps:    <1.00>:                                          
Trickle current in Amps:    <0.25>:                                             
Recharge voltage in Volts:    <13.49>:                                          
Max charge (minutes):    <720>:                                                 
Retry after abort (minutes):    <240>:                                          
Min supply voltage for charging in Volts:    <14.15>:                           

Once out of setup mode, it spits out readings about once per second. This includes what the state of the chargers is, the power supply voltage (PS), Battery voltage and charging current (Bat), Solar Panel voltage (Sol), Number of minutes in this charging state (Min)

 Trickle   PS=14.22V Bat=13.61V,  0.05A  Sol= 0.04V   Min=962  PWM=337  adc=6                                                    
 Trickle   PS=14.22V Bat=13.61V,  0.05A  Sol= 0.04V   Min=962  PWM=338  adc=6                                                    
 Trickle   PS=14.22V Bat=13.61V,  0.05A  Sol= 0.04V   Min=962  PWM=339  adc=6                                                    
 Trickle   PS=14.20V Bat=13.62V,  0.05A  Sol= 0.08V   Min=962  PWM=339  adc=6  

Hopefully the battery is as reliable and lasts as long as the last one!

Irish Summers getting brighter?

I’ve been recording the “Monthly Average” output from my PV system for a while (Since 2011). Looking at the figures for this summer.  The “Sunniest” month was June (91 Watts), followed by August (83 Watts) and then July (81 Watts).

Ok, so July sucked, I think we all knew that.  However what surprised me was when I looked at the results from previous years. It appears that the system has produced more power on average this year than any previous year.

To be continued…

Micro PV

So, having moved the garden shed and the PV panels in August/September 2011 to a more sun friendly position, I was pretty sure that there would be more output from the system over the next 12 months. Now, that 12 month interval is just coming to an end.

When I checked this evening, the average power generated 24×7 for the last 12 months as per rrdtool is 40 Watts, with a peak of 357 Watts. Which equates to approximately 350kWh, or somewhere between 70 and 90 Euro worth of Electricity for the year.

So in short, yes there was an increase in output, an approximate 42% increase in average power and a 100% increase in peak power. At least now I can tell myself it was worth the effort!

Micro PV two years on.

Some changes since last year. Firstly the panels have a different orientation from last year.  I moved the shed last August/September and both panels are now facing South West (220deg), still at the tilt of about 5-10 degrees (which I really must measure), not ideal but better than before.

The same two Evergreen panels are in use, but I’ve a new Mastervolt Soladin Inverter from Nigel in Mysolarshop. Unfortunately I accidentally let the magic smoke out of the Steca, when moving things around and it had to be replaced. I might try and get the smoke back in some rainy afternoon when I’m bored. The measurement set-up is still the same using the Envi CC-128.

So for the last 12 months rrdtool is saying an ‘average’ of 28 watts is produced every day. So from the back-of-an-envelope, we get 0.028*24*365 or approximately 245 kWh produced, with a value of approximately €49.

However, I have reason to believe that output will be better this year. The first picture below is from the 3rd of June last year.

This one is from today:

Two things are immediately obvious. The peak instantaneous value, and the average are both higher. This should help increase the output from the system for 2012.

The experiment continues!

iPhone and charging

I (deliberately) flattened my iPhone today so I could charge it with its own charger. I about 19:00 I plugged it in to my kill a watt meter to see how much power it uses.  I’m assuming the meter isn’t all that accurate, and as it is designed to measure typical household loads its display is in kilowatt hours.

With it plugged in for 19 hours with no load, the kill a watt claims to have consumed 240 watt hours. Which means that it would consume approximately 31.5 watt hours for a 3 hour iPhone charge time.

After charging for 3 hours the iPhone apparently used 40 watt hours, subtracting the 31.5 above gives a results of approximately 8.5 watt hours.

Given the inaccuracy of the devices, that is close enough to the 10 in my previous post for me to say about 10 and roughly in the ballpark of the previous test. Time to go looking for more accurate measuring devices.

iPhone and PV charging

A few weeks ago I was looking around the lab at the remnants of old projects and realised that we probably had enough bits to put together a solar powered charging station for phones. I.e. a 30 Watt PV panel (don’t buy from Farnell), a 12Volt Battery, and a PV charge controller.

I got an old 3 way cigarette lighter socket in Halfords, chopped the cable, added powerpoles, a fused connection to the battery and I now can charge my iPhone at my desk in work.

So, at break yesterday I was asked how much I was saving by charging my iPhone via solar energy.  I had no clue, so I let my iPhone die completely last night and re-charged it while checking the charge current on a Watt’s up meter.  I got tired of looking at it after 3 hours, but you can see the results on the graph below.

For the first 2 minutes, it stayed steady at 360mA, then the phone switched on and it started charging normally.  About 45 minutes at 340mA, before the current started to drop away.  At 20ma charging current I stopped the experiment.  If we allow a fudge factor for the accuracy of the Watt’s up meter, and the efficiency of the Apple charger  (I was running the test off a DC supply) and say about 10watt/hours, that translates to 0.00129 cent per charge or thereabouts.

Micro PV, one year on.

So, after 12 months, what do the numbers say?

Well first a quick reminder of what I have running. A Steca Grid 300 from, fed from two Evergreen ES-180RL 180 watt PV panels on the roof of the shed.  They are fairly flat on the shed and not in an ideal location. There is about 5-10 degree of tilt on the panels.  One of them is ‘facing’ South East, the other North West. So a very non-ideal situation, but useful nonetheless.

I’m using rrtdool to graph the output from an Envi CC128. The CC128 is measuring the output of the Steca grid-tie inverter.

So for the last 12 months rrdtool is saying an ‘average’ of 35 watts is produced every day. So from the back-of-an-envelope, we get 0.035*24*365 or approximately 306 kWh produced, with a value of approximately €55. Not a whole lot really.

Looking at the ‘average’ consumed by the house. It is now showing as 391 Watts (down from 455 the last time I looked). Giving 0.391 *24*365 or approximately 3425kWh (approx €620).

In short, its knocking about 10% off the electricty bill at present, not a lot, but given the panels don’t receive any direct sunlight in mid winter, it isn’t bad at all.

The experiment continues.


Winter is most definitely on the way, slight frost on the car this morning, and the weather station run by the South Eastern Amateur Radio Group showing a significant dip last night, though it was colder on Sunday night. Strangely though, I’m looking forward to getting a nice fire going on our new stove. And seeing how well it can heat the sitting room and the rest of the house.

First Light

I finished off the rewiring i mentioned in a previous post.  This was mostly just a tidy up of the cables around the inverter. The inverter itself is an older model Powermaster PM-1500SL-24, however the battery charging circuit generates terrible Radio Frequency interference. This means that the shortwave bands are completely obliterated when charging is taking place (from either solar or mains/generator power), so I leave the inverter off unless I need it. I use a Steca PR3030 and two 80watt panels, facing roughly South, to keep the battery bank topped up.

I have tested the system it by running the central heating, fridge-freezer and chest freezer off the inverter for a few hours, but I must give it a more thorough test at some stage in the near future.  The batteries are no longer new and, should there be a power cut, I’d better be able to keep the TV running or the boss will not be pleased!