Hi,
I spent 10+ hours researching on this forum before asking this question. I need to clarify my findings before i "burn down the house".
I have arduino uno which I want to run from protected 18650 batteries.
I want to connect the batteries as I found here (3X18650 with 3xTP4056)
and then plug them in power connector.
Is it safe ?
During charging the Uno is not going to be in usage. I want to use Uno due it is a “school” project so easy for kids to assembly (other boards are to small) it with few different small sensors, buzzer etc. different combination no motors.
The way shown is NOT good. Don't put the TP4056's in parallel. Unbalance in battery voltage will cause trouble.
Using the barrel jack with batteries is very wasteful for power but it should work if the voltage is high enough. With 18650's in parallel it's not, you just have the same voltage as from a single cell.
But why do you want batteries instead of USB (via PC or powerbank / charger)?
And why 18650?
How are you intending to connect the 18650s? In this video, they all have a common ground so you cannot connect them in series, and they all have separate chargers on their + terminals, so you cannot connect them in parallel.
The video shows something that can only be used as a battery charger. The cells must be removed from the holders to be used together.
Want to make it "mobile" that is why i can not use 12V 7,2Ah accu which is cc 2 kg.
18650 is available, 3 of them have voltage of ~12v when full and when empty around 7v so had idea that it "fits". they are also easy to charge...
You could use one 18650 and a switch mode voltage converter to step it up to 5V.
Or use a balance/protection circuit designed for the number of cells you are using. Then use a switch mode converter to step it down to 5V. The linear regulator on the Arduino just wastes power, every extra cell that takes you over 5V is waste heat.
An easy option would be an 18650 with a small boost converter with USB out. Serves two purposes. Easy to connect and you can not connect the battery together with the computer (which can damage the computer).
yes after programed going to be used only from battery,
very good suggestion not to connect it to pc e.g. to take measurement data, was not thinking about it. thnx
ok i understand boost converter (so to use 1 instead 2 batteries)
and if i want to put also a charger TP4056 how to connect 3 of them (converter, TP and 18650)?
If you already use protected LiPo's I see no reason whatsoever for the insurance to whine. Every person carries at least one on his/her body most of the day. All you actually made was a small power bank