Tech Note 130 - Solar Power for Projects (Arduino/ESP8266/ESP32)

Arduino a solar panel to your Arduino/ESP8266 or ESp32 projects can make them self-sufficient for power and makes them ideal for remote operation.
Code: github.com/G6E... (MS-EXCEL or OPENOFFICE)
Components: www.banggood.c...
TP4056: www.banggood.c...
Battery: www.banggood.c...
Battery Holder: www.banggood.c...
Solar Panel: www.banggood.c...

[@AmmarLegato]

I really cant describe my gratitude for the Excel sheet you made to calculate all the needed, thats alone is a huge donation to all of us that we will always be thnakful to you.

[@G6EJD]

I am pleased to hear of your gratitude and hope you find it useful.

[@MrBobWareham]

Hi David, you cease to amaze me with your depth of electronic knowledge. It seems endless, we all appreciate you sharing your brain with us, thank you so much.

[@haljones8028]

Brilliant! Exactly what I was looking for. Thank you for taking the time to put this together. Much appreciated!

[@deangreenhough3479]

A most excellent and in-depth analysis. The spreadsheet is a super aid in understanding how best to configure and setup our devices. I for one, will be exploring this over the coming weeks. Thank you so much for helping others 👍🏴󠁧󠁢󠁥󠁮󠁧󠁿

[@andywaring12]

Thank you for this brilliant video and in particular for sharing your calculator which has helped me enormously. I really appreciate the time and trouble you take to make your clear and info-dense videos.

[@retroip]

Thank you for this content, it is very well done. Especially that power consumption calculations, this helped me a lot to plan my solar powered ESP stuff. Thanks a lot.

[@VideoDetection]

Just started putting together a weather station to upload data to ThingSpeak. I found the TP4056 and then Googled solar charger to use it in my project and I found yet another one of your brilliant videos. Thank you for the Calc spreadsheet as it makes working everything out a breeze. You also gave me the idea of adding battery voltage data to ThingSpeak along with the environmental data. I will certainly be monitoring the battery's voltage to see how it performs. Looking to use an ESP32, sleep for 1hr and then approx 10S to collect and send data over WiFi. I will be using a 1 Watt solar cell and a Samsung 35E which has a capacity of 3500mAh. Now to see what your calculator can tell me about my component choice.

[@devtasingh]

Wonderfull explanation, and a lot of thanks for sharing this, including the calculator. Thanks a lot, This is going to help me to design my own devices power supply with solar pannels.

[@newburypi]

Many thanks for this video and access to your spreadsheet. Can't wait to get home and check it out.

[@muttBunch]

This is amazing. Thank you for this. There’s so many things we can do with this

[@namulit]

Many, many thanks. Your videos are atreasure trove for me!

[@warrenmusselman9173]

Very clear, very useful and I'm very grateful. Thank you.

[@mairswartz]

Wow! In depth and well explained. Thank you very much

[@sergiosouza8230]

Brilhante trabalho, voce ajuda a muitas pessoas ! Obrigado

[@josegomez1956]

Thanks, I love your videos, and this simulation in excel is great

[@johneagle4384]

Thank. This is a very well-done tutorial.

[@G6EJD]

Glad it was helpful!

[@NiceEyeballs]

You sir are intelligent.

[@cad3175]

..fantastic analysis mate, thank you

Note that the battery bank has to be large enough to remain between 3.9v to 4.2v

[@G6EJD]

Agreed...

[@Stoparik2001]

Thanks! Excellent and informative video. I will use the information in my projects.

[@DavideAntonioMautone]

Thank you very much sir. I'll use your excel file for my outdoor weather station.

[@edgaromarreynatorres3940]

nice nice project Sr, thanks a lot for the files and information. GOD bless you

[@sblantipodi]

ESP8266 is still a rock solid chip, I prefer it to the ESP32 for low powered applications.

[@G6EJD]

Davide, I agree and to be honest the compiler support is slowly getting better and catching up the ESP32 variant. Yes there is little to choose between the two and there is almost certainly more commercial products using the ESP8266 than the ESP32!

[@JohnTinic]

helped me in many ways with upcominc projects. i ordered some 4056s before i watched your video and it sais Vin max 5V - so i wasnt sure if a 6v solarpanel would work longterm without step-down. after watching i ordered immediately some panels😂😂 thanks

[@G6EJD]

TP4056 data sheet says: Input Supply Voltage(VCC):-0.3V~8V ·TEMP:-0.3V~10V so nominal I put max is 8v and for short durations 10v ideal for a 6v solar panel.

[@JohnTinic]

@@G6EJD true. i found different sheets. the last one i found said 6.5v. anyways... you inspired me to doublecheck them and go with solarpanels :)

[@sblantipodi]

@G6EJD: thanks for the video but how can this work well? solar panel can go over 5V and the TP4056 shut off the charge on input greater than 5V, this can easily waste a lot of energy from the sun and from the battery. how well the ESP8266 works with a such voltage deviations coming from the battery? doesn't it need a voltage regulator?

[@uweri_3851]

Perfect video. I love your videos. A lot of helpful informations. One of my ideas was: Wouldn't it be great to combine results from video 130 with video 108 ? Maybe with a sun tracker we get more efficiency.

[@G6EJD]

I can tell you already that a solar panel pointing south and angled to suit your latitude will be close to optimal or at least 70% of optimal for most of the daily sun transit, yes it would be more efficient to track the sun depending on time of the year, but it’s a lot of complexity to gain a relatively small advantage. Adding the sun tracking algorithm to a project would not be that difficult as the routine / function is standalone requiring just time and date.

[@gsge]

Thank you for this excellent useful tool.

[@TuncayKandemir]

great work, thank you Mr david....

[@davidherriman448]

Thanks for the video. I would subscribe if it were without the ads in the middle.

[@sultanfikri1779]

Terimakaseh belonggo pakcik

[@GaryMcKinnonUFO]

Thanks for the detail, liked and subbed :)

[@gaetanlord]

Really interesting, I d like the fact that you do not rush to provide your information so we could ingest easily. Any chance you could provide banggood link to the parts used in the project. I'm more concern about good battery, because some are fake and you might have a reference for good one.

[@G6EJD]

In general make sure is a pink colour made by Samsung or EBL, signs of fakes are capacities of more than 3400mAHr or more typically 2600mAHr , the rest is a gamble. There is a large e-cigarette market for them so that widens the market.

[@G6EJD]

[US$22.83 18% OFF]4PCS Sumsung INR18650-30Q 3000mAh Unprotected Button Top 18650 Battery Flashlight from Lights & Lighting on banggood.com Battery: banggood.app.link/Ij849oS2qX Battery holder: uk.banggood.com/search/18650-battery-holder.html TP4056: uk.banggood.com/search/tp4056.html Solar Panel: uk.banggood.com/search/solar-panel-6v.html

[@marcrives279]

ESP8266 30uA in deep sleep ? True... for the chip alone! Keep in mind many development boards are using more than 10mA in that stage! That could be a real show stopper for solar projects.

[@G6EJD]

Marc Rives I’ve got a Wemos D1 Mini in front of me now with an attached BME280 and when both are in sleep mode the current consumption is 60uA according to my Fluke 87 which I trust. I only use the Wemos D1 Mini or Lolin D32 which have neat identical regulators and use s low power UART so those are the boards I quoted and measured. I agree some poorly designed boards consume a relatively large amount of power in sleep mode, but even a small 1Watt solar panel will keep them going in most climates. I’m going to do a video on power reduction techniques because a lot of people have asked me, there are some techniques that can be employed to minimise power usage.

[@marcrives279]

@@G6EJD That was my point, you have to choose carefully your board, as USB bridge may be always on and LDO not that efficient during sleep. As a side note, small solar panel are far from 100% efficiency. Your method is great, although numbers may be too optimistic. I can't wait your next video!

[@G6EJD]

Marc, I agree that numbers can be seen as optimistic that why I didn’t go for panel efficiency but losses, plus with a limit market range there is little point in working out solar watts/m^2 and then solar output just assume a 1watt panel will deliver 166mA which they do.

[@toastedregret1601]

Great video David, thumbs up - everything but one slight detail was clear to me after watching the video: I'm wondering if the ESP32 can operate while charging? To put it another way, you mention charge and discharge cycles, but I didn't catch if the ESP32 is still in operation when charging. Appreciate it.

[@G6EJD]

Yes the ESP32 runs continuously whilst charging the charge circuits are always independent

[@mohamedaitmouali895]

energiy available 5*0.75=3.75 not 4.7 ???????

[@LatinDanceVideos]

This is good. Thanks!!!

[@TheAstronomyDude]

Would hooking up a 1.2V solar panel to the lolin board while it has a lipo plugged in do anything? I found a scrap solar light and its tiny brown solar panel outputs 1.5v in max daylight. It says 1.2V 0.1W on the back of the light.

[@G6EJD]

This would not work as the solar panel needs to generate at least 3.8v with sufficient power to charge a battery, you’d need a panel that could generate ideally 4v in full sun with say a 1 watt capacity. Alternatively if you had 4 of the panels you have you could wire them in series.

[@TheAstronomyDude]

@@G6EJD Thank you!

[@ionescuveronel5011]

i am using a 12v panel...it's enough to use a buck converter before tp 4056 without damaging something:)? thank you sir!

[@G6EJD]

Depending on the buck converter output as the tp4056 maximum input voltage is 6v, ideally use a 5v variant but either 5 or 6 volt output would do.

[@wingman1392]

Very interesting and thank you for the work you did to produce this video. I am looking at making a few temp/humidity/pressure sensors for use at home. One of my concerns is the ambient temperture of the sensor battery. I understand that Lithium batteries will only charge above 0C,. Have you had any issues round this? I am guessing that althought the ambient temperature is below 0C, when the sun comes up, if the battery is in a black box, it will heat up above 0C using solar gain. 73

[@G6EJD]

I have 3 sensors that have run continuously using lipo batteries and have not had issues but then I tend to oversize the batteries to make the most of solar energy and operate the sensors during overcast winter periods. If you use an 18650 battery then you should get at least 3-months from a full charge. In terms of the electro-chemical process you will find that lipo will still charge albeit with lower efficiency.

[@rev.kenshostad2888]

Couldn't one use a capacitor, in this system, to increase the uptime?

[@G6EJD]

Only if you can store (and charge!) a suitable value, you’d be surprised how much energy needs to be stored and that requires many farads. So yes feasible it…

[@ahmedawny7236]

thanks a lot for the informative presentation

[@ivanivanov-ml8jn]

I made this circuit with Wemos D1 Mini. In the absence of sunlight and the battery is discharged below 2.5 V, Wemos stops working. The problem is that after charging and voltage of 4.2 V, Wemos does not turn on - a reboot is required, etc. until the next discharge. Is there a way to avoid this problem? Thanks!

[@G6EJD]

How are you applying power to the Wemos, you can use 3.3v as there is a regulator fitted on the board. So you have to use a nominal 5v source on the 5v pin or via the micro usb connector. The regulator has a 0.5v drop out, so the input voltage range is 3.8 to 6v, therefore if using a lipo battery with a nominal 3.8v then you have to maintain it in a charged state. Clearly your solar panel is not providing enough energy to maintain a battery charge and therefore keep the Wemos running. Increase the solar cell capacity.

[@mpty2022]

thanks for sharing your work

[@ThingsMadeOfOtherThings]

Thank you very much for sharing the spreadsheet! I have just one question regarding the battery's charge cycles - in order to extend the life of the battery, should we aim to fully cycle the battery? ie take it down to ~20-25% capacity each day before charging begins? Or is this concern secondary to reliable uptime? Thanks again for helping me to get a grasp of these concepts.

[@G6EJD]

Interesting question, most battery management chips like the tp4057 do not implement any form of life extension routines, but luckily, modern LiPo and LiFePO4 chemistries are as susceptible to the memory effects that used to plague rechargeable batteries, so I think it’s no-longer needed. It will really depend on the manufacturer recommendations or in any event you could engineer the charge level to ensure the charge drops every day or week, the compromise is whether the battery has sufficient capacity to cover dull days when there is insufficient solar energy to sustain operations.

[@popocolocoi6082]

Thank you for this content. I hope this technology will reduce our carbon footprint to stone age levels.

[@G6EJD]

Indeed yes, every little helps!

[@hulkensteinX]

Thank you bro

[@nipoanz7865]

Muy interesante, de verdad que esta informacion sirve mucho cuando las aplicaciones deoenden de baterias

[@G6EJD]

Me complace que lo haya encontrado útil, además de que no es tan difícil de hacer y de bajo costo.

[@mareskavaclav908]

Cool! Super nice calculations! But I am still thinking... Would it worth to put for example some step-up convertor between solar panel and TP4056? Just to use even small amounts of solar voltages to still charge TP4056, its output or even battery?

[@G6EJD]

You could do yes, but it’s all down to efficiency of conversion and the power remains the same so as voltage is stepped up, current falls.energy,, but worth a try. The important thing is not to exceed the 4056 input voltage.

[@psykopat81]

Hi, thank you very much for the video. What method should be used to charge a phone with a solar panel? Should we charge 18650 batteries with the MPPT device and connect a powerbank module to its output? Do powerbank modules keeps charging (if the phone is fully charged) , or disconnect from load? if so, how can we prevent this?

[@G6EJD]

MPPT chargers need to be chosen for for the battery type and voltage and a phone has its own in-built battery manager so no need to be concerned about charging it.

[@psykopat81]

@@G6EJD my solar panel charges two 18650 batteries with mppt module. I connected a powerbank module (5v booster) to batteries and charging my phone with this module (through usb port). The phone charges fine during the day, but when the sun goes out in the evening, it stops charging, the battery percentage drops and it does not start charging again in the morning. If I disconnect the USB cable from the phone and plug it in again, it starts charging again. do you have any suggestion for this problem ?

[@G6EJD]

@@psykopat81It will be due to the charging logic, are you sure the 18650 batteries have been depleted, the charging should not restart until the battery voltage drops to about 3.65/battery, it will damage the battery to keep it at full charge. So you should expect charging to restart at 3.65v or thereabouts and then stop at 4.2v then the process will repeat.

[@psykopat81]

@@G6EJD cn3791 mppt module has battery protection, it starts charging on 3.6v and stops at 4v. Is it the phone's charging circuit that causes the charging to stop at night?

[@G6EJD]

Then it is almost certainly your phone that’s preventing charging until its battery gets low.

[@sunny-il5uq]

you saved me man.. this thing is hard xD solo final year project

[@G6EJD]

Sanya Delaila, I’m happy to help, especially when it’s towards your education. If you need more let me know.

[@sunny-il5uq]

@@G6EJD do u know how to monitor the battery voltage using esp32 (through programming an app)

[@G6EJD]

Sanya Delaila, it depends what board you use, the Lolin D32 has an on-board voltage monitor/divider connected to pin 35 which is a default ADC input wired line this: Vbat | | 100K | Pin 35 | 100K | | Gnd This gives a divide by 2 voltage divider allowing the ADC to measure up to 6v In code terms: Float voltage = analogRead(35); Or Float voltage = analogRead(35) * calibration factor usually about 7 for 4.2v maximum reading the same as an 18650 battery

[@sunny-il5uq]

@@G6EJD thx ill learn more on what u just said 😂

[@r3icon]

Hello, I would like to know if Vusb pin is just 5V pin, becouse I have an older one ESP32 lolin32 v1.0.0 with on-board TP4054 and there I can not see the Vbus pin but there is 5V pin. So if I understend this, I can connet directly the solar pannel to 5V and GND pin on the board and then battery to the JST-PH-2 connector. Thank You for Your respond and have a nice day.

[@G6EJD]

Yes the pins are often labelled differently but are essentially the same all connected to the 5v of the microUSB connector. So yes attached say a 6v solar panel to the 5v pin and it will keep the battery charged but depending on panel size only if the ESP32 spends time in deep sleep to reduce average power demand.

[@technodruid]

4V is too low for Vin on some nodemcu boards

[@G6EJD]

Yes, some are poorly designed, which is why I only use the Lolin D32, it has a very low drop-out regulator and can operate down to 3.4v easily.

[@s.husain6125]

I think it is better to use buck converter also to supply constant current to esp board

[@G6EJD]

You can’t use a constant current supply as the ESP varies the load all the time and that would force the CC regulator to increase or decrease voltage to compensate. I’ve not seen a buck converter together with a battery management device on the market. A battery management device is essential for solar panels to cut-off charge when the battery is full.

[@s.husain6125]

@@G6EJD yes you are right sir but when there is no sufficient sun light and battery drains out on this stage buck converter play major role to supply 4-5 volt constantly if battery voltage as low as 2v buck converter will boost this to 5 volt.... I'm using same Feature in my iot product which will available in market soon....

[@G6EJD]

Yes, It is an option to disable the on-board regulator using the EN pin and then use an external regulator, it would of course need to be a 3.3v buck regulator as using 5v to then down regulate to 3.3v would be wasteful of power, but doing all this increases cost. On the D32 and D32 Pro with on-board battery management using an external regulator would not be as easy. Incidentally allowing a Li-ion/Lipo battery to discharge to 2v would effectively destroy the battery and significantly reduce its service life.

[@sheminjohn123]

Fantastic.

[@mr.bianchirider8126]

I have made a nearly identical solar weather station using a NodeMCU 8266 and a 6V 2W solar panel with deep sleep inside a birdhouse. It has been somewhat successful but I have too many trees ! I started the project in the fall, worked great, some issues with cold in the winter (0 degrees F), but when the leaves started to sprout, the downward spiral of the voltage commenced. Maybe include a chainsaw in the bill of materials ?

[@G6EJD]

Sometimes a chain saw is required. Every little energy saving trick is required to help out the power budget - if using WiFi are you switching it on and off at the last minute and as soon as you’ve finished with it? It makes a huge difference, plus if using a sensor like a bme280 if not placed in sleep mode it consumes about 0.5mA continuously, I’ve submitted a change to the Adafruit library called sensorSleep that enables that, those two modifications alone should give you about 30% capacity. If using an ESP 8266 it should easily run, providing there’s some sleep time indefinitely if it’s got done solar support. Try the calculator and see what it says, maybe increase the losses.

[@mr.bianchirider8126]

G6EJD I deep sleep the 8266 as soon as it is done. It’s on for 10 to 12 seconds. I used 30 followed up with 45 minute intervals. I’ll try to power off the BME 280 but I think it’s a lack of sunlight. Short of putting it on the roof (against the will of my wife “you’re too da** old to be climbing on the roof !”) I am considering LoWa (will it work?) and sticking it in a neighbor’s near treeless yard.

[@G6EJD]

It’s the Nodemcu it consumes lots of power in relative terms when asleep, the UART and regulator are the cause, a Wemos D1 Mini (not a copy) would easily achieve close to 200 days on a full charge because it consumes so little. LoRa is ok but it consumes lots of power plus of all the devices I’ve used it’s difficult to get them into sleep mode, so something to be aware of. Also many of the modules sold have for some bizarre reason wired the hardware sleep/enable such that the Lora module is permanently on.

[@ristomatti]

@@G6EJD I've been thinking it'd be a great service to the DYI community as a whole if some of the talented open hardware PCB designers would send their improvement suggestions straight to the Chinese clone manufacturers instead of only selling their boards at Tindie to a handful of supporters. :) Most hobbyists will never reach the level SMD soldering.

[@G6EJD]

I agree, as some of the supplier boards like TTGO need s lot of improvement to be of practical use. It just needs the makes to start doing this. There is already a sort of open source approach to this on Easyeda all my pcb s ste open source on there and I never design with smd components because it’s too difficult to solder, that said, I can solder ESP32 and ESP8266 bare boards to pcbs without too many difficulties but you need a fine soldering iron bit!

[@Javier_Corado]

Men, you only have a few videos but they are really helpful. Again I just have a few questions. Where did you get the Daily Solar Replenishment formula and also how does the Calculations sheet work?

[@G6EJD]

I created the formula and if you download the spreadsheet you can see all the calculations in there, it’s all open.

[@Javier_Corado]

@@G6EJD You are just brilliant, keep up the good work!

[@e024576]

Is a diode needed between solar panel and tp4056?

[@MPElectronique]

Please Dave, can you make a video how to mesure the power consumption of the ESP32. I think im not the only one i would like to have it. Thanks. Good night :-) Marc.

[@G6EJD]

It is not easy, because the so-called burden voltage of a typical DVM prevents operation, but some DVMs do give reasonable results. You can use a series R of 1ohm and measure the voltage across it, so e.g. 75uA would give 75uV but you need a DVM that can measure up lots and not many do. A good technique is to short out the DVM input until the cpu has started, then the burden voltage won’t affect supply voltage and after start-up, remove the short circuit and current is then measurable. I’ll think about a video on this topic, it’s a good idea.

[@G6EJD]

Marc, our of interest I’ve just purchased an Owon B41T+ DVM with Bluetooth it’s about £60 / $80 but easily measured down to 0.1uA, it’s a 22000 count DVM so can measure from uA to 200mA without changing scales.

[@mr.techinventor3463]

Great

[@simonmerrett]

David, thanks for creating the calculator. When reading around this topic, I have seen several concerns raised about a constant load, such as the ESP boards when not in sleep mode, causing the CC-CV and final cut-off sensing for the TP4056 to be delayed and risk damaging the lithium cells (perhaps leading to dangerous failures like setting fire to itself). Have you seen anything that convinces you that the charge cutoff is happening at a safe point in your set up?

[@G6EJD]

Simon, I’ve not seen any evidence that charge cut-off does not happen, the TO405x series of charge management devices are used widely and I’ve never seen any adverse comments about them. Yes it’s possible for the ESP device to place a constant load on the battery and hence initiate charging but this would be what is in effect a balancing charge to replenish the demand. In fact I see this every day in my solar powered sensors the sun charges the battery and then charge cuts off at about 4.2v then the voltage falls throughout the day but interestingly charging does not restart until the lower threshold is reached (3.9v) when carving starts again, so in battery terminal voltage terms there’s a nice daily saw-tooth waveform as this repeats. Similarly, if there was no charging the tp4054 does not remove the load and so under voltage can occur, but that is a rare event. Overall I think it’s a good battery manager.

[@simonmerrett]

@@G6EJD thanks David. I wonder if you have ever measured the charging current for your setup in bright and overcast conditions. My 6v 3.5W panel is barely managing 120mA directly into an admittedly poor quality cell in bright sun, from the TP4056 through a standard multimeter. This was at a cell voltage below CV charging phase. It is partly interesting because the TP4056 is supposed to stop the CV charge when the current drops to 10% of its nominal CC current (from what I understand). My setup is constantly fluctuating between just over to well below the 1A nominal CC current. This just doesn't seem like a good way to treat a lithium cell! I've ordered a larger panel but the sizing calcs make a lot of assumptions about the efficiency from the panel, through the charger, to the cell.

[@G6EJD]

Simon, have you set the charge limiting resistor to limit the charge current, sounds like you have the value set too high, typically 500mA. I doubt your panel is capable of supplying sufficient voltage and current levels of 1amp or more because it’s internal resistance would prevent that (4.2x1=4.2W for example even say your battery was low at 3.6v then the VA would be 3.5 at 1amp) but there would be insufficient voltage to actuate the 4056 into charge mode. You do have something wrong somewhere because unless your ESP is permanently awake a 3.5W panel should be more than enough, I use a 6v 1W panel and the 4054 spends all its time trickle charging the battery I can see that as the battery voltage climbs to 4.15v then falls away during a sunny day as the charge is cutoff and so it repeats. What does my calculator say the outcome is with your load and panel size. In simple terms an ESP32 with WiFi on requires 3.5whrs/day and a 3.5W panel should deliver for 8-hours of daylight ~14whrs assuming 50% of the 8hours is sunlight, giving you an over-capacity of x4 so where is the energy going? Your sunlight open circuit voltage should be about 6v, if your battery is discharged at 3.7v expect a charge limited panel current if 500mA and a typical sunny day should easily recharge a 2600mAHr battery 8x500mH = 4000mAHr so in fact your 4056 would have stopped the charging at 2600mAhr or when cell voltage reaches 4.15v Either way there’s s problem most likely with the battery no holding the charge.

[@simonmerrett]

@@G6EJD David, I do agree there's something wrong - I have not adjusted the Rprog as the panel voltage remained 5V at the TP4056 input terminals when the battery was connected (no load) so I took this as a sign the current wasn't pulling the voltage out of the MPP of the panel. However, as my test is only the battery, TP4056 (with protection DW01) and the panel - and NO load - we can definitely say something is wrong. I will change Rprog and also put a reliable 18650 in the battery holder - I have a feeling I may have fallen foul of the "trustfire" lottery (having thought I had taken a cell from the "usable" pile). In the end, I will be using this to power a pump at night to water the greenhouse. Found a great little pump on eBay that runs on 3-6V, so one 18650 is all that's required. The pump works fine, just need to sort the energy conversion and storage!

[@G6EJD]

Simon, I too have some Trustfure batteries that are labelled as 3400mAHr but have a real capacity of 980mAHr, now I know, you can tell them apart (real v fake) by their weight. I would measure the open circuit voltage of the panel then fit a known good battery and confirm the voltage drops on load and that battery voltage is starting to climb, if even slightly discharged you should detect the increased voltage quite quickly, then you’ll know if all is correct. With that size panel you have plenty of reserves for maybe 4-5 days of dull weather, but as always it does depend on your load current.

[@eclecticlife]

Probably this is a dumb question. My Li-Po 18650 batteries say 9000mAh. That means that they provide more hours of energy, isn't it? What about using a diode to prevent that the batteries don't discharge at night? Great video and information. Thank you.

[@G6EJD]

John Smith, yes if that’s the true capacity the higher the Maher figure the longer the battery will drive the board, the largest 18650 battery you can buy (genuine) is 3000mAhr so you should have 3 in parallel, there is no need for a diode unless you connect two battery packs together in parallel to prevent one pack affecting the other. Some solar panels include a Diode.

[@eclecticlife]

@@G6EJD Thanks for your response. I have automated blinds with solar panels and one 18650. The NodeMcu wakes up every 30 minutes, checks the level of luminosity and the status of the blinds and if needed opens/closes the blinds. When opening/closing the blinds the usage goes up to 0.45 Amps for two seconds. The battery last for about a week but then it dies. I have a 1 watt/ 6 volt panel for each blind. The servos really are used twice a day, so the rest of the time the usage is the normal for a NodeMcu for 5 seconds. Any ideas why my batteries are not recharging? Thanks again for all the information you provided.

[@G6EJD]

John, the NodeMCU takes a relative lot of power when in sleep mode about 60mA a Lolin D32 would take about 20uA by comparison, the Nodemcu has lots of peripheral components that continue to run in sleep mode. I have an 18650 battery that is marked as 9800mAhr but in reality it’s true capacity is 980mAhr many 18650 has false capacities, so I would look at the battery first. If the capacity was 9000 and every hour the current drawn was 60mA, then the battery would last: 9000/60=150 hrs or 6.25 days, next assume time to operate the blinds is 15/secs then mAhr drawn is 450*15/60=113mAh and this happens 2x per day or 226mAhr needed/day to operate the blinds plus 60mAhr sleep current of the nodemcu, then total daily demand = 226 + 60* 24= 1440/day and a 9000 battery would last 9000/1666=5.4 days so your battery life is correct! If you were using a Lolin D32 your battery life would be about 9000/230=39 days so sleep current is quite dominant! Hope this helps. You will know the blind operating time to get more accurate results

[@eclecticlife]

@@G6EJD Excellent explanation!! I really appreciate the time you took to write all that. You truly are a huge help to the community of makers like me. Thanks again

[@michaels8297]

If I were to add control of a 12v .5amp solenoid to be used 15 minutes a day. Would it be best to use a boost converter to keep cost down. Or purchase a 12v 10 ah batter? Also does this charge controller switch off the circuit if it goes below a threshold?

[@G6EJD]

The tp4054/4056 charge controller is designed for lipo battery management but does not remove power at the lower end, so operation will continue down to 3.3v or lower, the limiting factor is the (usually) on-board LDO regulator which typically has a drop out voltage of 0.15v setting the lowest discharge voltage to 2.7v of the ESP32 + 0.15 or 2.85, but by that time the battery would be entering its region of cell damage. You can get relays rated at 240v 10A nearly anywhere with an on-board driver that can operate on 3.3 or 5v. Something like this 1 Channel Relay Board Relay Module with Optocoupler Low Level Trigger Expansion Board for Arduino 5V/12V/24V(12V) www.amazon.co.uk/dp/B07Q1H63D6/ref=cm_sw_r_cp_api_i_HYXxFbBFMRDG7 being optically isolated gives S good safe interface if going beyond 50v.

[@G6EJD]

Adding a battery of sufficient capacity to meet your daily power needs is essential and you will need capacity for dull days/winter, so I’d recommend getting a battery of the size you mention.

[@michaels8297]

Ok great. So so main the purpose of the relay would be to cut power from the battery if it drops too low? My main concern is not having to power the relay all day while there is enough power. I feel like it will contribute to power loss, but maybe there’s a way power the relay only when I need it. How would I monitor the battery voltage from a 12v 12ah battery ? Maybe a Voltage divider connected to the relay? Turning on the relay for only a short while for battery measurements?

[@G6EJD]

@@michaels8297yes, using an ADC to measure battery voltage would be easily achieved and I did a video on pre-calculated resistance values for 12v although a fully charged leadacid be 13.6 so use a 15v range.

[@michaels8297]

G6EJD - David awesome thank you. It’s my first solar project so your advice and videos go a long way. Thank you

[@vishalanand3921]

Nice... #solartechinsider

[@marcrives279]

Hello again, you have told that official minimum Vin is 3.9v for NodeMCU. I'm pretty sure you are right, but can you give your source please?

[@G6EJD]

Well, what is a NodeMcu 32 ? There are so many clones it’s difficult to say exactly but the Do-it brand at V3 is what I’m referring to as the widely available ‘nodemcu 32s’ of which I have 5, and they use a spx3819 regulator which has a drop-out voltage of 0.45v @ 150mA but as this value is load dependent as it can be down to 0.14v, enabling the board to operate down to 3.45v, so with an ESP32 taking ~145mA with WiFi on, and according to the data sheets, the minimum usable voltage will be (3.3+0.45) 3.75v. Because I have 5 of the devices, I programmed each with a sketch that put the WiFi on and blinked the LED, and the average voltage of when they stopped working was 3.9v. This can be explained by the variability of the load at any given moment and the production spread of the devices both ESP32 and spx3819. The nodemcu32 is the worst performing board I have used, the Lolin D32 is far superior in all regards, especially its use of a high performance LDO regulator. There will never be an official source of a ‘nodemcu 32’ drop-out voltage, mainly because no-one ever publishes such specifications, so all you can do is look at the schematic and make test measurements, which is what I did. Noting I chose the worst board that I could find to quote 3.9v as nearly all other brands are far superior in this parameter.

[@G6EJD]

BTW, what do you think the minimum Vin is please? How would you determine it?

[@marcrives279]

@@G6EJD Great and detailled answer! I was looking for min Vin on NodeMCU v2 (ESP8266). It has an AMS1117 3.3*L*, whose dropout is around 0.25v @100mA (didn't find any datasheet for this L version). So, with WiFi on, at normal temperature, my board is working well around 3.6v

[@G6EJD]

The suffix (e.g. L) usually denotes the package type. Given the 1117 has a drop-out of 1.3v max at 0.8A and there is no data given on Vin-Vout characteristics, you could work on a simple linear relationship giving a ratio of 145/800 x 1.3 = 0.24v then 3.3 + 0.24 = 3.54 which is what your seeing. It was a poor choice of regulator IMO on the v2 board, v3 is only slightly better.

[@marcrives279]

@@G6EJD And I think this is how you get 3.9v : When you power the board via USB, here is *often* a (protection?) diode. USB voltage is 5v +/- 10%. As Vin bypasses diode, worst safe case is then Vin = Vmin(USB) - Vmax(diode) = 4.5V - 0.6V = 3.9V. I'll keep in mind the simple linear relationship!

[@Edmorbus]

can you help me to make circuit schematics and code I want to read voltage with an isolated ground Mine setup is 4x 12v battery and 4x simple solar controllers Aliexpress Every battery have the own Solar controller I use the Esp32 and 1x ADS1115 ADS1115 is a 16-bit, 860-SPS, 4-channel, delta-sigma ADC with PGA, oscillator, VREF, comparator and I2C. I use voltage divider 4x 6.44 K %1 and 30 K %1 The Solar controllers have switched ground if i connect the ground together i get errors The controllers are good it is charging the Batterys good. Please help me with this setup

[@G6EJD]

This is easy to solve, just use some linear opto-isolators, then you can have a common ground on the ESP32 side.

[@Edmorbus]

Have you link for schematics@@G6EJD

[@Edmorbus]

@@G6EJD Please help me what to use witch iC etc

[@G6EJD]

@@Edmorbusyou’ll need a IL300 per battery here’s the data sheet with example circuits www.vishay.com/docs/83708/appnote50.pdf

[@Edmorbus]

@@G6EJD thanks

[@almutasemalbaadani8986]

Thanks for the information. I have a question regarding tp4056 that it is a linear charger and there are some other chargers like cn3065 and also I found different circuits for tp4056 and solar panels. Is it efficient use tp4056, is there any other components needed to connect to output or input or battery so that it works probably like capacitators. please anyone guide me with this as I am using solar energy for my sensor node design

[@G6EJD]

If you can design the circuit and mount the components onto a pcb then yes there are probably better devices around and should be used, but for a good balance of efficiency and practicality these ready made tp4056 modules offer the best solution to keep a battery charged from solar: ￡0.27 | DIY USB Charger TP4056 5V 1A Micro USB 18650 Lithium Battery Charging Board Charger Module+Protection Dual Functions TP 4056 star.aliexpress.com/share/share.htm?image=U1a0fedaa47d54b2eb0cb37443fbf7a70f.jpg&businessType=ProductDetail&title=%EF%BF%A10.27%20%7C%20DIY%20USB%20Charger%20TP4056%205V%201A%20Micro%20USB%2018650%20Lithium%20Battery%20Charging%20Board%20Charger%20Module%2BProtection%20Dual%20Functions%20TP%204056&platform=AE&redirectUrl=https%3A%2F%2Fwww.aliexpress.com%2Fitem%2F1005001727918511.html%3F%26srcSns%3Dsns_Copy%26tid%3Dwhite_backgroup_101%26businessType%3DProductDetail%26spreadType%3DsocialShare

[@G6EJD]

Also the ready made boards have all the required smoothing capacitors required to provide a stable power source.

[@almutasemalbaadani8986]

@@G6EJD Thanks a lot I will be using TP 4056 as I implemented 30 minutes deep sleep and 10 second for sending the data , I really appreciate your response, keep up the amazing videos

[@G6EJD]

@@almutasemalbaadani8986 I’ve got a Lolin D32 powered by one of these connected to an 18650 battery and it’s got a 6v solar battery on the tp4056 input pins and it’s been running for over 2-years now, works perfectly providing there’s sun light, on overcast days there’s enough battery capacity to last for about 3-months or more, the battery then absorbs excess solar power when it comes.

[@almutasemalbaadani8986]

@@G6EJD That's amazing I will be designing a case for it and make an angel for the solar panel, should it be 200 ma or 100 ma for 30 minutes sleeping and using wifi?

[@MPElectronique]

Esp8266 Will not run for a long time on battery... :(

[@G6EJD]

Not if the WiFi is on, about twice as long if off. 2600/75=35-hours with WiFi On and about 60-hours with it off. Make it sleep a bit and the difference is significant.

[@MPElectronique]

@@G6EJD even with nodemcu??

[@G6EJD]

Best ESP32 product for sleep current is the Lolin D32, reliable too. For the ESP8266 the Wemos D1 Mini is very good as it shares a lot of the design with the D32. I regularly get 6-months of battery life from an 18650 using a Wemos D1 Mini plus s bme280 both in sleep fir about 10-mins and awake for 3-secs. Nodemcu either 8266 or 32 are poor performers on battery power.

[@MPElectronique]

@@G6EJD i thought it was firebeetle 32?

[@G6EJD]

Marc, designs improve and for me the Lolin D32 (not a copy) is close to perfect. The Firebeetle 32 has been redesigned the first was very unreliable in programming mode, second version hasn’t really addressed the problems in the first like ADC battery monitoring has values that are too high to enable the ADC to take a valid reading.

[@andyandyfrogy1113]

Hi David, how can I contact you? Thank you.

[@G6EJD]

g6ejd.dynu.com/ then contact

[@andyandyfrogy1113]

@@G6EJD Hi David thank you for replying, but I've tried many times and I get: ''There was an error trying to send your message. Please try again later.''

[@G6EJD]

Andy, Gmail is now blocking my webserver, I need to update the security settings, so for now you can contact me on: [e-mail]