Input voltage range for Wemos D1 board

Question

What's the input voltage range for a Wemos D1 board?

I have a battery pack of 4 AA batteries. This makes 41.5 V = 6 V, but I think they can drop as low as 41.2 V = 4.8 V. Can I hook the battery pack directly to the input voltage socket? Or is this to much?

What happens when I connect the D1 to the USB to program it? Must I disconnect the battery pack first? Sometimes it would be handy to let the USB cable connected to the debug output on the serial monitor.

I'm aware of Power Wemos D1 mini from battery but that only answers whether 3 batteries are enough.

Answer 1

It's 3.3V linear low drop out regulator has a drop out voltage of up to 0.3V.

The 5V regulator from VIN is unlabeled in the schematic so we can't say. Depending on how much it drops at 4.8V, the 3.3V should still be powered. But at 4.8V, your 4 AA pack is dead anyway.

The board uses a comparator to disable the USB power input when the DC jack is used, so no, it would not work that way without you disconnecting the battery pack.

As listed on the website, it says the DC input is 9V to 24V. There is a SS24 diode in the way, so that will drop about 0.3V at the currents used by the Wemos. Again, without knowing the 5V LDO's drop out voltage, then it may need much more than 6V.

Frankly, you should inject the batteries to the 5V rail, through a 1n400x diode. That would work nicely, as the 5V is only used to power the 3.3V regulator.

Answer 2

Searching infos to the Wemos D1, I landed here.

Sadly the links given in OP don't work anymore, so I'm a little confused. Though I know this is a 4 year old post, I want to answer.

The broken link named "Wemos D1 mini V2.0" as exactly this product name has a regulator (ME6211) behind the 5V pin that accepts at max 5.5V. It won't explode immediately if you feed it with 5,6V, but powering it with 6V is probably not the best idea.

I don't know where the above mentioned maximum 24V come from. There is another ESP called NodeMCU (that's not a D1 Mini!) Some of those boards have an SPX3819M5 regulator that can handle up to 16V.

From running multiple D1 with li-ion batteries, I can say it still works with voltages down to 2,8V on the 5V pin. The decreasing voltage while discharging is not a problem at all.

I suggest instead of using 4x1.5V use 3x1.5, so the maximum is just 4.5V and it will work even if the batteries are almost discharged (then it's 3,6V.)

Another alternative I already have in use is running 3xAA rechargable batteries, which fully loaded provide up to 4.3V. I usually recharge them when they reach 3.6-3.5V.