You only have to convert ~4.6V (peak, when we have direct solar pass-through) down to 3.3V with a device that mostly only consumes around ~2-4mA in Idle. It’s not worth the hassle adding a BB.
The design is also using a very modern LDO that doesn’t consume much power. Also the drop-off under load isn’t that big. It’s no a shitty AMS1117.
Alright, that makes sense! Do you have any power consumption measurements of the board in various RF moments? (rx, tx, idle, bluetooth…)
Thanks!
No long term high precision measurements right now.
Some values I remember: Idle was something around 2-4mA with LoRa RX activated, short LoRa TX peaks up to ~170mA.
Going to add a I2C INA measuring shunt in the future designs. But my project budget is gone for this and next month.
I was finding around 7-9ma in RX with the max boost then 130-160 in transmit for just a moment. Which is comparable to the rakwireless module I’ve been testing. The Ram unit definitely goes to sleep better when used as a tracker, something wrong in the HT-CT firmware not allowing deep sleep.
At about €7 for the HT-Ct and about a euro for the charge controller/LDo module it’s cheap and seems to run well from a 6w 5v solar panel and some cheap 18650. Complete build with antenna, battery, printed enclosure and 3m pole coming at around €30. Cheap enough if they get stolen or destroyed I don’t really care. 
With one of the next revision I’ll replace the CR123A battery with a “classic” 18650. Turns out that there’s no big market for CR123A 3.7V LiPos and the size limits them to a maximum capacity of ~800mAh. Also there are a lot of fakes around.
The BQ25185 should have enough safety feature to even use LiPos without protection circuit. Maybe I’ll going to test this in a metal tub.
Have you done any tests to see what happens when the device runs flat? Does it re-start, when solar charged again, from when it has run flat? Does a protected battery perform differently in this regard to an un-protected one? Thanks for any info. Love the project.
Have you done any tests to see what happens when the device runs flat?
I haven’t tested this yet in detail, but theoretically the ESP32 should start up normally as soon as the brown-out detection isn’t triggered any more.
Does a protected battery perform differently in this regard to an un-protected one?
Unprotected LiPos are way cheaper than protected ons. But they invented these protection circuits for a reason.
I still gonna make the first test runs with protected LiPos because I really don’t want to burn my apartment down.
Will report as soon as I have some tests done.
That looks really cool. Thanks for the update.
Out of interest how are your programming it? Assume can flash firmware to it over the UART connector? Presumably use some sort of CP2102 or similar USB->UART convertor?
I switch the device to the bootloader mode and then flash it via UART. I’m using an old FT2232HL board for this.
Just curious, why not use the native USB?
look nice 
Just curious, why not use the native USB?
I have to flash a device like once a year. So not worth the stress adding it.
Also UART can be run with 921600 so flashing takes 20-30s.
This is not a development board where I need USB-JTAG.
Hm, there’s nothing to add to get native usb. So it’s even simpler than a UART bridge.
You just need to wire Pad18/GPIO19 and Pad17/GPIO18 to USBDP and USBDN respectively. No extra hardware needed (unless you want to add TVS diodes for ESD protection, perhaps)
Good point. If I continue enhancing this PCB I’ll put it on my list.
For now there are two big things for future Meshtastic Router boards
This board is only $14 ? nRF82540 + LR1110 LoRa - ME25LS01 LoRaWAN Module+MX25LE01 Development Kit - MinewSemi Store
Also available as stamp - https://www.aliexpress.com/item/1005006655389454.html
or the previous version https://www.aliexpress.com/item/1005007430412913.html
also added supoort for these already
I added support recently - Add Minewsemi LR1110+nRF52840-ME25LS01 [both 4.2inch e-ink and non e-ink varaint] by markbirss · Pull Request #4387 · meshtastic/firmware · GitHub
That looks really good. Guess I’ll order a bunch of them after my holidays.
Thanks for the info and integrating the platform!
Are there Kicad files around for this thing?
Only
