A UNO and 18650 thnx

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.

Thank you.

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.

Ahh, yeah. I watched it quick an thought he paralleled the output's. But indeed, paralleling the inputs to make a charger makes more sense

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...

If you have any suggestion please share.

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.

voltage buster like ? "Matek DC-DC Voltage Booster 1S Lipo"

So, only mobile after programming I guess?

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).

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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)?

"Good luck with getting insurance for using LiPO batteries in a school!"

no no not in closed space, garden data collection is a target

but it is a good remark, if you would use it in closed space and it still needs to remain small what rechargeable source would you use for A uno ?

jegesd:
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)?

Connect the TP4056 to the 18650. Connect the voltage converter to the output of the TP4056.

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If you charge while the circuit is powered on, it will just charge more slowly, presuming the circuit does not draw more than the 1A charging current.

Thank You

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

yes technically it is a small power bank.

can someone recommend other way to provide power then 18650 ?

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In case of AA batteries how you charge them without taking them out of the "box" ?

idea is to 3d print a box, put a battery inside and charge it via USB phone charger.

spycatcher2k:
and was told in no uncertain terms that the schools do not have insurance for the children to operate anything powered by LiPO battery.

Good luck banning phones, cameras, fidget spinners, (smart) watches, Wii's.... :

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