Can I power nodemcu with 2 Li-Ion Single Cell Battery (series connection) ?

Thread Starter

M3D0

Joined Oct 8, 2020
53
I'm working on a project where I need to power my nodemcu with an external battery and I have three (electrical magnet 5vdc) connected to the nodemcu which I will control (on/off).
So I was thinking to have two independent power sources, one for the nodemcu (which consists of 2 Li-Ion Single Cell Battery), and one for components which they will get their power from an independent power source as well but the signal from the nodemcu.
My Questions:
1- Can I power the nodemcu with 2 Li-Ion Single Cell Battery (series connection) ?
2-what is the voltage and current needed for the (electrical magnet 5vdc) ? and can I use the Li-Ion Single Cell Battery too as the power source?
Components used:
https://ram-e-shop.com/product/bt-051425p-220mah/
https://ram-e-shop.com/product/electrical-magnet-5vdc-lifting-magnet-2-5kg-holding/
https://ram-e-shop.com/product/kit-node-mcu/

Thanks in advance!
 

Geologic

Joined Sep 10, 2020
10
From the specs, nodemcu can be powered by External Supply Pin with input voltage: 7-12V
2 li-ion bateries in series will be 8,4V when fully charged and around 5,5V when discharged, so i think the answer for the first question is no. Instead, you can use or make a step-down switching circuit to 3,3V and use it on the 3V3 pin.

For the 2nd question, your magnet is rated @5V, so a single li-ion battery will not work (4,2V to 2,75V), you will nedd a step-up switching circuit to 5V. Be aware of current consumption, that magnet is rated @ 220mA.

Remember you cannot use nodemcu to drive directly the magnets, you shouls use nodemcu to drive a switch (like a MOSFET), that will drive the magnets.
 

Thread Starter

M3D0

Joined Oct 8, 2020
53
From the specs, nodemcu can be powered by External Supply Pin with input voltage: 7-12V
2 li-ion bateries in series will be 8,4V when fully charged and around 5,5V when discharged, so i think the answer for the first question is no. Instead, you can use or make a step-down switching circuit to 3,3V and use it on the 3V3 pin.

For the 2nd question, your magnet is rated @5V, so a single li-ion battery will not work (4,2V to 2,75V), you will nedd a step-up switching circuit to 5V. Be aware of current consumption, that magnet is rated @ 220mA.

Remember you cannot use nodemcu to drive directly the magnets, you shouls use nodemcu to drive a switch (like a MOSFET), that will drive the magnets.
Thank you this was really helpful!
 

Thread Starter

M3D0

Joined Oct 8, 2020
53
From the specs, nodemcu can be powered by External Supply Pin with input voltage: 7-12V
2 li-ion bateries in series will be 8,4V when fully charged and around 5,5V when discharged, so i think the answer for the first question is no. Instead, you can use or make a step-down switching circuit to 3,3V and use it on the 3V3 pin.
So I've been reading about batteries for the past few days, but I really can't understand how did you know that both batteries of (8.4V) will produce/discharge (5.5V)??
Because the way I think of it that if the batteries are (8.4V) they will produce (8.4V) or something less than that (like 0.3V difference for example) because of the resistance in the circuit.
 

Geologic

Joined Sep 10, 2020
10
So I've been reading about batteries for the past few days, but I really can't understand how did you know that both batteries of (8.4V) will produce/discharge (5.5V)??
Because the way I think of it that if the batteries are (8.4V) they will produce (8.4V) or something less than that (like 0.3V difference for example) because of the resistance in the circuit.
Common Li-ion batteries are rated @ 3,7V, but when they are fully charged, they can go up to 4,2V. This kind of batteries shouldn't be discharged lower than a safe value, normally 2,7V, because bellow that voltage some chemical instability will reduce battery lifetime.
So, for 2 cells in series, you will have 8,4V when fully charged, and you shouldn't use them below 5,5V.

For that reason i always use protected li-ion batteries, they have a built-in circuit that disconnects them in case of short circuit (they can catch fire) or deep discharge.
 
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