Hello, I want to power an ESP32 with 3.7v Lipo battery. The ESP32 is powered at 3.3v can't handle the 4.2v - 2.7v that a Lipo battery typically outputs. I was thinking of just using a 3.3v voltage regulator, but I can't use the rest of the battery after 3.4v - 3.5v even with a relatively low dropout voltage. I also thought about stepping the battery up to 5v then back down to 3.3v. Which do you recommend doing? Also, the ESP32 will be in a 'deep-sleep' mode for 80% of the time. Thanks.
Use a very low dropout voltage regulator (60 mV is not uncommon). The ESP32 is spec'd to run on as low as 2.2V.
@jremington, thanks. One more question, would stepping up 3.7v to 5v and then back down to 3.3v make my battery run time shorter than just using a voltage regulator 3.3v?
Of course the battery lifetime would be worse. You get maybe 85% efficiency in the upconversion, then only 66% on the linear regulation.
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HI,
Have you googled;
lipo 3.7 to 3v3 converter
Tom... 
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There are SEPIC regulators like the LTC3440, which are advertised to be 90-95% efficient, but the expense may not offset the ~89% efficiency of a simple 3.7-3.3V linear regulator.
Something like the APK2210 series of linear regulators would work for the latter. The dropout voltage is only 50 mV. $0.36 each, single quantity! Currently on backorder, like everything else.
The Raspberry Pi Pico uses RT6150A/B which is good also for your purpose.
A 3.0V regulator might make sense. That would let you use all the power the battery has to give, and the ESP32 will use less current at 3V than at 3.3V. A buck regulator in theory would be more efficient than a linear regulator, but that may reverse at deep sleep current levels. Actually, since the ESP32 wakes from deep sleep by doing a full reset, one alternative might be to power down completely if there's a way start up again from that state. What would trigger the wakeup from deep sleep?
Not as accurate as a dedicated regulator, you could consider a small silicon signal diode in series with the battery which will drop the voltage by 0.6v to 0.7v
At 3.4v a typical Lipo is about 96% discharged, so only 4% is left.
So an easy problem to solve, just use a LiPo with 4% more capacity ..............
Hi,
What is the reason you want to power with single Lipo?
Tom...
Why not use an ESP32 board with LiPo port.
Leo..
@Devanshu_Acharya , It looks like it would work, but there out of stock at Digikey and Mouser. I'll look a little more for it.
@ShermanP, I'll try the 3v regulator, thanks.
@TomGeorge, I want to power a remote and don't want it to be tethered to any external power source.
@Wawa, I'm making a custom PCB for a remote.
I looked it for you , found this on Mouser, looks like very similar product:
Note: This will be very hard to solder though....and if you want something simple go for the 3v LDO as @ShermanP suggested. I also suggest using a TP4056 charging and protection board for safety.
Are you trying to make something like a RF remote?
3.7 is the nominal voltage. Fully charged a lipo cell will deliver 4.2 volts, so with the larger drop 0.7 you'd still get 3.5 volts.
Which may or not be OK.
If you need 3 volts, at the other end there's still energy at 3.7 volts SOC, so you'd lose out or be under voltage for the rest of the usable part of the discharge.
Which may or not be OK.
I use 2s or 2 cells in series ("7.4" nominal, 8.4 max) and a good quality step-down "buck" regulator.
But that becomes a bit more involved if long battery life (like using sleep) is part of the plan.
a7
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@Devanshu_Acharya, I think I might try to ISL9110RTNZ. For the charging IC, I think I will use the STC4054GR. It basically the same thing as the TP4056.
Yes.
Just noticed this.
You will get more life out of your lipo and be safer doing if you don’t let the voltage delivered to your circuit (under the full load) drop below something way above 2.7 volts.
I charge to 4.15 volts. The first 0.05 volt goes quickly anyway, and undercharging is appreciated by the cell.
I discharge to 3.3 - 3.5 volts, depending on how much fun I am having and how closely I am heeding the numerous mechanisms I have in place to alert me to a low voltage situation.
The cells typically recover to 3.7, which is what I aim for. That is a perfectly good voltage for leaving a lipo around unused for a protracted period.
Yes - I get shorter flight times. But… I am using lipos that are years old and give me the same performance that I got in their youth.
You should never leave a lipo charged or discharged. I have come across a rule of thumb sez every day you leave a lipo cell sitting at 4.2 volts is like doing a full charge/discharge cycle. IOW it unnecessarily ages the cell.
If I fail to get the recovery voltage, I charge or discharge as required to re-establish the 3.7 storage charge. Even if it is tomorrow I know I’ll be using it again, because tomorrow never knows.
It’s convenient when charging multiple cells connected in parallel at the charger… yes, it is done alla time, alarmed me at first but if you use similar cells with near identical starting SOCs and similar condition it works very well. Knowing all my cells are 3.7 volts (but checking them one by one before placing them on the charger) means I can grab a bunch of packs, charge them and then go to the field.
My use is not atypical. Relatively high current for relatively short times. Like 10s of amperes for single-digit minutes.
Nothing delivers like a lipo cell. Learn that the hard way by ever shorting one or hooking it up backwards. We all have stories, some very sad.
If you do much with lipos, take a few peeks around and develop respect for this wonderful but scary dangerous source of power.
has everything and more about all chemistries.
a7
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Hi everyone
I use a DC to DC module that I made for this. It has an input of up to 5.5V and down to 3.5V, with an output of 5V. I then bring it down to 3.3v with a LDO or leave it at 5V depending on the application.
FYI, I do realize this is a very inefficient way for getting 3.3V from a 3.7V lipo.
Regards
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