How to power the 3.3V ESP32 from a 3.7V Li-ion battery?

rontec
Posts: 17
Joined: Thu Dec 13, 2018 11:06 pm

Re: How to power the 3.3V ESP32 from a 3.7V Li-ion battery?

Postby rontec » Sat Dec 15, 2018 4:58 pm

WiFive wrote:
Fri Dec 14, 2018 10:16 am
For example
M5stack uses EA3036
Odroid-go uses MP2161
Olimex ESP32-DevKit-LiPo uses Silergy SY8089
Thanks. Very helpful.

For the benefit of others:

The EA3036C is under $0.15 per unit
The MP2161 is under $0.10 per unit
The SY8089 is under $0.09 per unit

Perhaps luisonoff will be interested in analyzing their efficiency.

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loboris
Posts: 514
Joined: Wed Dec 21, 2016 7:40 pm

Re: How to power the 3.3V ESP32 from a 3.7V Li-ion battery?

Postby loboris » Sun Dec 16, 2018 9:48 am

rontec wrote:
Sat Dec 15, 2018 4:36 pm
Thanks for the idea. Even a LiFePO4 battery has a voltage which is too high while it is charging.

LiFePO4 battery is charged to 3.6V (or 3.65V) and this is within ESP32 voltage range.
You can limit the charger voltage to 3.5 V and the battery will still be charged to 99% - 100% depending on type.
I've used this in a practical project (with the solar charger) for months without any issue.
This is the only powering method where the full battery capacity can be used, without any losses.

Here is an interesting article.

rontec
Posts: 17
Joined: Thu Dec 13, 2018 11:06 pm

Re: How to power the 3.3V ESP32 from a 3.7V Li-ion battery?

Postby rontec » Sun Dec 16, 2018 8:49 pm

loboris wrote:
Sun Dec 16, 2018 9:48 am
rontec wrote:
Sat Dec 15, 2018 4:36 pm
Thanks for the idea. Even a LiFePO4 battery has a voltage which is too high while it is charging.

LiFePO4 battery is charged to 3.6V (or 3.65V) and this is within ESP32 voltage range.
You can limit the charger voltage to 3.5 V and the battery will still be charged to 99% - 100% depending on type.
I've used this in a practical project (with the solar charger) for months without any issue.
This is the only powering method where the full battery capacity can be used, without any losses.

Here is an interesting article.
Fascinating. I will have a closer look at using LiFePO4 batteries.

What solar charge controller IC do you use?

bobtidey
Posts: 38
Joined: Mon Jun 18, 2018 2:24 pm

Re: How to power the 3.3V ESP32 from a 3.7V Li-ion battery?

Postby bobtidey » Mon Dec 17, 2018 9:05 am

Little bit more info on the XC6203 LDO regulators.

The maximum peak current is 600mA with the sustained output current of 400mA. I use the E series which has no built in current limiter to ensure that doesn't kick in. With a 220uF miniature SMD output capacitor I haven't seen any significant brown out spikes.

There are other regulators in Torex range which are also interesting. The XC6220 has a 1A output also with low quiescent and even lower drop out, but they are a bit more expensive.

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loboris
Posts: 514
Joined: Wed Dec 21, 2016 7:40 pm

Re: How to power the 3.3V ESP32 from a 3.7V Li-ion battery?

Postby loboris » Mon Dec 17, 2018 10:27 am

rontec wrote:
Sun Dec 16, 2018 8:49 pm
What solar charge controller IC do you use?

No special solar charge controller IC is used, just MP2315 switching regulator providing 6V to the TP5000 battery charger setup for LiFePO4 charging and some additional circuit to disconnect the panel on low voltage. Any panel (or other power source) 6V - 24V can be used. Input and battery voltages are measured by ESP32.
You can use cheap modules for charging LiFePO4 battery, like this one.

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