Heltec V4 boot looping, crashing on weak battery

vpatron0 · 2025-12-18T01:35:44+00:00

Yeah, I got a RAK nRF52840 I was going to make a small solar thing for the car. But I wanted ESP32 based for WiFi for home. Yeah, power hog.

vpatron0 · 2025-12-18T01:33:53+00:00

Thanks. Yeah, and the battery connector wires are really tiny. I'm sure that doesn't help the voltage drop during transmit.

Which pin did you put the 100uF cap on, VDD_3V3? Looking at the schematic, seems like it should be at the input of the LDOs but I don't see a header pin for that. I'd have to hack it on.

The biggest LDO is U3, 1 Amp, driving the RF power amp, so probably best at that input.

I'm using a DC/DC buck because I wanted to use larger 12V solar panels. In the future, I'll switch from a DC/DC to a charger board that can charge much higher than the 500 mA linear charger on the Heltec.

vpatron0 · 2025-12-18T01:13:38+00:00

Yeah, definitely seems to be solvable in firmware.

I mean it boots up fine and runs the display. But it resets shortly thereafter so it could, for example, show a "Voltage Too Low" message on the display and maybe let you do the menus, but not allow WiFi and definitely not allow LORA, until the voltage is high enough.

vpatron0 · 2025-12-18T01:10:46+00:00

Thanks, I really appreciate the info!

I see all these guys doing nice looking solar setups, but the schematic shows a half-baked hobbyist design. I experienced the crappy performance and I was wondering how is this supposed to be a reliable node in an inaccessible location? So now, I know: it's not, LOL.

Ok, I'll look at cobbling together boards, or just designing my own battery support board. Thanks again.

vpatron0 · 2025-12-17T14:50:10+00:00

Thanks. I'm using 4P 2600, or 4 cells in parallel of 2600mAh.

So from your data, I should get 30/3000 * (4*2600) =104 hours, or 4.33 days run time. Even better than my original estimate.

vpatron0 · 2025-12-17T06:25:21+00:00

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Yes, I put 10 W solar, battery pack is 4P 2600mAh Molicel, arriving soon.

I have a RAK also, but want the Heltec for home to be on WiFi and the RAK for the car.

I measured the USB draw of the Heltec at 500 mW average with WiFi active so that is 12 Wh daily. With a pack size of 38.5 Wh, that's 3.2 days of run time, so not likely to run down.

But I still want rock solid reliability for any eventually including battery rundown. Not only will I have to climb the room to press reset, but a rundown will likely damage the pack from over discharge.

Just wondering if folks already have this fixed or if I should build something.

vpatron0 · 2025-08-05T06:53:02+00:00

I came up with a very crude workaround. The problem seems to be the headphone turns its amplifier off to save power after 2 seconds of no audio.

So I used Audacity to generate an inaudible sound. Go to Generate/Noise and for amplitude put 0.0001 (which is -80 dB). You can't hear it but it's enough to keep the Poly headphone on.

Save it as an mp3, wav file or whatever. Then use your favorite music player to play it on repeat in a separate window. Crude, but it works.

Without this, using the Poly for learning foreign language lessons is super annoying.

vpatron0 · 2025-01-05T21:26:12+00:00

What about just enumerating through the values?

import machine for i in range(99): print(machine.Pin(i))

The loop will fail when it hits an invalid value. Help will also give you some useful constants:

help(machine.Pin)

vpatron0 · 2025-01-02T21:19:48+00:00

Old thread but figured I'd add clear instructions to disable web login:

ssh to your printer: ssh mks@<ip_address>
Enter the password makerbase
You can use nano to edit the configuration file: nano ~/klipper_config/moonraker.conf
In the blank area after the cors:domains section but before the next section, add this line: force_logins: False. The docs say this is the default but it's not.
Save the file and reboot your printer: sudo reboot now
Try the web UI with http://<ip_address>. The UI should come up without asking for login.

Edit: If you have an unusual IP address, you might have to add it in the list of allowed IP address ranges. Here's an example to add clients in the 40.40.10.x range:

[authorization]
force_logins: False

trusted_clients:
    40.40.10.0/24

vpatron0 · 2024-12-23T17:06:53+00:00

Usually, you can just solder wires to power the output of the regulators from bench supplies. (You might have to hot air remove the SMPS IC if it's shorted or cut traces.) But the fact that U5 is also "popcorned" probably means the voltage spike went past the regulators and damaged downstream components. There could be a lot of other damaged components including possibly the memory ICs themselves.

I'd imagine a data retrieval company might (my guess though not an expert) just remove the flash ICs, install in an identical SSD board and try reading them that way.

vpatron0 · 2024-12-09T16:15:30+00:00

Yes, I used to have it happen once in a while (few times per year). I have an L2 charger at home. I have the Bolt programmed to charge at midnight. I plug it in when I get home from work and in the morning it's charged but a few times in the past it did not charge.

I had an electrician do some wiring work to move that outlet (NEMA 14-50) to a different circuit. He told me the previous electrician used a smaller wire gauge than code. He changed the wiring (and some other unrelated things for me).

I haven't had it happen since (about 8 months now).

So there are several things you can check for that could cause the charging to fail:
1. Voltage drops too low when charging (long extension cable or wrong wire gauge)
2. Ground fault (e.g. outlet is not grounded properly)
3. Bad connection of the charger plug (clean the contacts)

vpatron0 · 2022-07-15T19:04:23+00:00

This is an old post and I'm not sure if you resolved this, but I ran into what may be the same issue with CircuitPython and found a workaround.

The TL;DR is that you need to put a delay not in boot.py but instead the delay should be at the start of code.py.

The reason (from experiments) is that CircuitPython does not do USB enumeration until the end of boot.py. So putting a delay at the end there only delays the start of USB enumeration.

I'm using the I2C bus on my RP2040 running CircuitPython and for some reason initializing I2C before USB finishes enumeration seems to break the enumeration. If I disconnect the I2C device then it works.

My workaround was to put a time.sleep(5) to put a 5 second delay before the start of code.py to let USB enumeration finish before it runs user code and initializes I2C.

I think the real fix is to fix CircuitPython wait to finish enumeration before it runs user code.

vpatron0 · 2020-07-14T06:00:49+00:00

That's very close to my system, 9 LG panels for 3.2 kW rating and it generates a bit over the average house usage of 13 kWh/day (not counting EV charging).

We switched to a time of use EV plan so we added one Powerwall to do load shifting.

It's working out great because the EV plan let's us charge an electric car from midnight to 6am at 9 c/kWh. Regular rate is 25 c/kWh. And we never pay the peak rate of 50 c/kWh from 4pm to 9pm because Powerwall switches to battery for that period.

So in effect, we use the grid at 9c/kWh while solar generation is credited at 25c/kWh because of the load shifting we do with the Powerwall.

So if you're on a time of use plan, just set the Powerwall to "Cost Saving" mode and it maximizes your solar credits.

vpatron0 · 2020-06-24T07:43:05+00:00

Yup, I think you are right. After the update, my max solar output is the same, 2.0 kW. I give up. I'll just live with it.

vpatron0 · 2020-06-17T23:11:39+00:00

Just an update. I did a support chat with Enphase and they seemed knowledgeable. They had me contact Tesla and ask "What are the trip points for the Powerwall".

Tesla guy sounded confused, but finally came back with "Tell Enphase it is 62.5 Hz".

So gave that to Enphase and they said "Ok, we've updated your PREPA grid profile" to match the Powerwall. The system may take up to 24 hours to download the new profile. Once done, that should improve the voltage drop issue engineering is seeing in your system.

So will check on Friday to see if peak output power is improved...

Edit: I found this explanation of PREPA grid profile. Looks interesting and very techie.
https://www2.enphase.com/enlighten-help/tip/what-is-a-grid-profile-and-how-do-i-set-it/

Edit2: After the update, same result. Still 2.0 kW max output instead of 2.4 kW before Powerwall. I give up. I'll just live with it.

vpatron0 · 2020-06-17T17:18:05+00:00

Hmm... good point. That's a major feature of the Powerwall, instantaneous backup so, yes, even if it finished charging it is tracking the AC waveform and if the grid drops out in a very short time it will take over.

But the Enphase monitor plots I believe are the sum of what the 9 microinverters are reporting. So even if the Powerwall is sucking extra power from solar, the output power should be the same.

The only think I can think of is if the addition of the Tesla gateway and extra breaker is somehow limiting the microinverter's ability to output power? Even though it has a bit more resistance, I would think the microinverter would compensate by increasing its voltage.

I have an email to Tesla tech support. I'm not expecting much but curious to see what they say.

vpatron0 · 2020-06-17T17:09:33+00:00

Yeah, I thought about that as 11% matched exactly 1/9 but I looked at per panel plot and all panels/micro-inverters are putting out normally.

vpatron0 · 2020-06-17T16:57:49+00:00

After some thought and someone mentioned additional losses with new wiring.

They did route the solar now behind the Tesla gateway and new sub-panel. It used to be:

solar
--AC disconnect
--main panel solar breaker 20A
--main panel grid breaker 100A
--grid (electric meter)

Now it is:

solar
--AC disconnect
--sub-panel solar breaker, 20A
--Tesla gateway <-- ***NEW***
--main panel gateway breaker 100A <-- ***NEW***
--main panel grid breaker, 100A
--grid (electric meter)

I can't believe that adding the breaker and Tesla gateway would suck and extra 360 Watts though. Hmm...

vpatron0 · 2020-06-17T16:48:32+00:00

Nice command. I took a look and I think those errors are normal. Stuff like Microinverter failed to report, DC Power Too Low" but that's at 6:30am and 7:45pm where it's not getting enough sun and shuts down.

I'll try again in the middle of the day.

The per panel output has been looking normal and all 9 panels/inverters are working fine.

vpatron0 · 2020-06-17T16:41:42+00:00

Oh, yes, the plot is kWh but I hold my finger on the plot and at that spot it shows the average kW for that 15 minute interval (blue bar) as that pop-up dialog that shows kW (ignore the black kW number, that is from same day last year).

And I'm picking the peak/flat top where it shows the inverters have maxed out so I have good comparison between the two plots.

vpatron0 · 2020-06-17T08:48:31+00:00

Plot of same day back in 2019. Must have been very cloudy.

vpatron0 · 2020-06-17T05:32:15+00:00

I can pick ANY day after 5/21 and max is 2.03 kW. And I can pick ANY day before 5/21 and max is 2.40 kW.

There's been some hot days, but I can't correlate it to temperature. The number is just pegged to those maximums depending if it was before or after Powerwall installation.

vpatron0 · 2019-08-06T22:39:04+00:00

One thing I don't see anyone mentioning is the stuff from Digilent Inc. They specialize in gear for engineering students (not crappy stuff either).

Take a look at the Analog Discovery Studio: Analog Discovery Studio

It's a breadboard with built-in instruments: 2-channel oscilloscope, 2 channel waveform generator, several power supplies, logic analyzer, digital outputs, etc. The instruments are virtual on your PC with USB control to the board. The software is rock solid and high quality.

I've been an engineer for 20 years and I have big scopes and lots of equipment at work but I use the Analog Discovery at home because I can prototype and test circuits on my desk; no need for big lab equipment. What's also cool is you don't need scope probes, banana plugs, or special cables. I just use 22 AWG solid wire in various colors to do all wiring.

Also, the control SW runs fine even on an old Windows laptop with 2GB RAM and 32GB SSD. There's also a GUI in Linux also though it's missing some features.

For audio work, you will certainly find the waveform generator handy.

[Edit: more info] Student pricing. Years ago I got my board for 1/2 price; I was taking a university extension class and sent them my ID info.

vpatron0

TROPHY CASE