Heltec LoRa 32 v3 not fully charging to 4.2v

#1

I have 3 Heltec LoRa v3 boards and none of them fully charge to 4.2v. Mostly, ~4.111, which is about ~90%.

Should the go to 4.2v and the nominal of 3.7v?

At what voltage will it start recharging on depletion?

TIA

#2

I have several different Heltec boards and they charge variously to somewhere between 4.03 – 4.19 volts. They [Wifi Lora 32, Wireless Stick Lite, CubeCell and CubeCell Plus] pretty much all use the same charging circuit and I’m using the same Li-Ion batteries in each case. I would put the difference down to little more than variations in components—the battery itself, the resistors in the voltage dividers used in measuring the voltage and the charging system itself. In my experience, if the battery voltage is staying above 4.00V (all of my applications use a solar panel to recharge the battery during daylight hours) I’m happy. In fact, as long as the battery wasn’t generally discharging over time I think I’d be happy.

As far as recharging goes, my batteries deplete by 0.1 – 0.2V overnight and are generally fully recharged within an hour or two of sunlight then next day. The voltage drop is a little more during heavily overcast conditions but the charging system is still active even in relatively low light conditions.

#3

Thanks for the reply. I was thinking maybe they didn’t want the batteries fully charging for protection of battery life. I am using 5v 5w (~8.5”x11” solar panels and am charged in ~2 hours in the morning.

#4

Unique Pete,

I’m new to Meshtastic. I have a couple Heltec Lora32 v3s on the way. I want to run one as the client and the other on top of my house. I’m thinking I will have two 18650s and a 6v solar panel setup. I have been trying to figure out where to connect the solar panels. I’ve considered a twin pigtail USB-C connected to the solar panel. I think that should be interpreted as “connected to USB” and would charge the 18650s when the sun is out.

I’m thinking two 18650s. I’m in Texas, it will be plenty hot up there on the roof. I’m going use a large roomy enclosure and have lots of air circulating around all contents. No foam.

Where or how do you have your solar panel connected?

Alan
Ki5ETN

#5

You need at least 4-6 3000mah 18650 cells. You can get solar panels with USB-A connector which then can be plugged to the board’s USB-C port. I recommend a 5v/6w panel.

#6

My solar panel is connected through the 5V pin on the board, with a protection diode for good measure. If you look at the board schematic, the only difference between that and the USB connector is the fuse that sits between the USB port and the 5V ‘supply point’.