Powering through 18650 LiPo

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Powering through 18650 LiPo

By Obuw
- Thu Aug 11, 2016 6:10 am #52689 Hello all,

I have plans for a wifi doorbell, which I'm planning to power with a 18650 LiPo battery. Would it be safe to connect one directly, if I can check it beforehand to make sure its voltage is not above 3.7V before connecting it?

Otherwise, what kind of a circuit would be recommended? A diode+stepup? An ldo stepdown? I don't want to overcomplicate things.

I suppose I could just use 3xAA NiMh batteries but it'd be a bit bulkier and harder to recharge.

PS. I'm making the door button power up / power down the 8266 using the idea from here. So the power usage should be minimal.
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Re: Powering through 18650 LiPo

By RFZ
- Fri Aug 12, 2016 7:21 am #52782 You will loose a lot of capacity if you use a LiPo only charged up to 3.7V.
Use a simple cheap linear voltage regulator like AMS1117 or HT7333 (LDO, low power). You can buy 100 of them for less than 10 USD.
Please make also sure that your setup cannot drain the battery too fast if you don't have a battery protection circuit. The ESP can monitor its Vcc and send a warning along with the doorbell signal when the battery gets low.
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Re: Powering through 18650 LiPo

By trackerj
- Fri Aug 12, 2016 9:33 am #52786 Not a very good idea.

You need a 3V-3.3V LDO regulator to be able to run properly your ESP module. The usual LD1117 is not good as it has a voltage dropout around 1V. Look at the Board Schematic from this post, it has a good LDO (MCP1825S), suitable for battery run.
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