Powering Arduino with LiPo Batteries

Other Hardware Motors, Mechanics, Power and CNC
1

Hello everyone,

For one of my projects, I would like to power an Arduino Board using a 2-cell (2S) 7.4V LiPo battery. The voltage perfectly falls into the board operating region (so there are no issues here), but my main concern regards how to protect the battery from over-discharging and overcurrents. The battery that I am using (https://hobbyking.com/it_it/turnigy-nano-tech-1200mah-2s-25-50c-lipo-airsoft-pack.html) does not have an integrated protection circuit, so I need to add an external one.

And that's what I did. I bought one of these battery protection boards they sell off Amazon (Youmile 5PCS 2S 3A 7.4V 8.4V Scheda di protezione della batteria al litio 18650 Modulo caricatore BMS Scheda di protezione PCB per cella di batteria al litio agli ioni di litio con striscia di nichel : Amazon.it: Elettronica) and tried it, but I have the following issues:

  • The board provides charging protection (I don't need that, I want only discharging protection). This is a source of issues since it seems like the board is by default turned off if, as the battery is connected, it is not charged first. So I cannot connect the battery only for discharge, as I would like. (I apparently solved this by short-circuiting the input and output negative terminals, but I have no idea if this affects the behaviour of the board)

  • The board "needs" all 3 battery terminals (B+, B-, BM), while I have available only B+ and B- (since I do not recharge, I don't care about single-cell control)

So, what I am actually looking for, is a discharging protection board that needs only the two "big" battery terminals, but I cannot find it.

Otherwise, if you have better strategies for powering the Arduino (external buck converter?), I'm all ears.

PS This topic falls into my general problem of "I want to use LiPos to power stuff but I don't know how to implement battery protection". For example, for another project, I would like to power an LED panel with two of these 7.4V batteries in series, but I'm stuck (again) on how to protect them from over-discharging and overcurrents. Also in this case, I would charge the batteries externally using a proper LiPo charger, so I do not mind about the charging but only discharging.

PPS I was thinking about designing my own board, but I'm a mechanical engineer so I don't know where to start. I found some schematics, but I would prefer to find a ready-to-buy board rather than build my own.

Thank you very much in advance
Have a great day!

Luca

2

Power bank would be the easiest choice. Just be aware that some of them have low current detection and switch off if current draw is below threshold.
I have used several, all working fine. And all protections built in.

3

For overcurrent just use a fuse.
For overdischarge connect the battery using a MOSFET or relay and monitor the voltage with the Arduino. When it goes to low turn off the relay or MOSFET

4

If the current requirement is low (you tried a 3A protector) why use a LiPo battery that is capable of circa 60A ?

Safer to use a lower current more stable Lithium ion maybe ?

Agree with the comment about powerbanks, all protection built in, some even have solar charging built in.

5

Answer to

and

I really would like to use Lipos as this is an airsoft-related project, so the idea was to use the same batteries used for airsoft replicas. Also, I have quite of these batteries hanging around.

If for instance I consider the second project, a power bank would not be enough to power a 20-30W LED light panel. This is a more general question, I know.

6

Lot of additional information..
No, power bank is not good for 20-30W load.

7

No problem

8

Use two 1M ohm resistors as a voltage divider. Your battery voltage at the top, the divider goes to an analog input and the bottom to gnd. Periodically check your voltage and give a warning when you reach your desired discharge level.

9

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