Running from a 18650 battery

I have an esp set up and running directly from a 18650 battery.

Being a li ion battery, is there any concern with long term use in terms of the battery going under a recommended voltage and potentially being dangerous?

I'm not sure if this battery is an issue, like a lipo, that can be an issue if undercharged, do I need any special considerations for the 18650?

Currently the esp is wired directly and running fine. Do I need to add anything between the battery and device? Regulator or something to detect under voltage?

Thanks

There are 'protected' 18650....which are slightly longer. Maybe you can try those.

Regardless of what lipo we have.... just don't short circuit them.

Li-ion batteries are 4.2V when fully charged, so in theory this is too high for the esp. Many people report that their ESP's run fine at this voltage, but damage could be slow and cumulative causing eventual failure. So a regulator is a good idea. Make it a low-dropout type to maximise battery life. I have used Wemos Mini in many projects with Li-ion batteries. The Wemos uses an me6211 regulator. But it may be more convenient to find a thru-hole LDO regulator.

Over-discharging unprotected Li-ion cells can damage them. They can be damaged, resulting in danger of explosion or fire when you try to re-charge them.

If you have purchased unprotected batteries and need to add an external protection circuit, you can buy inexpensive charger modules with built-in protection.
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I have those charging modules but couldn't find any details on how exactly they're supposed to be used.

Obviously the battery connections are clear. Do you then use out+/- for the load?
And what about charging while something is connected? I thought you couldn't do that but with no info on the board, I don't know if it manages that itself?

steven_191:
Do you then use out+/- for the load?
And what about charging while something is connected?

Yes.
The input voltage when using a usb connector is normally 5V. As long as your circuit is ok with a 5V supply, you can charge at the same time. If anything in your circuit cannot run at 5V, you need to regulate the supply down to a safe voltage.

so just so I understand this, because I cant find this info anywhere,

I connect the load to out+/- and the battery to batt+/-.
If I plug in the USB for charging at the same time, the load can still be powered, while the charger charges the battery, and these dont interfere with each other?

Ive just measured the input/output voltages on all of the terminals and batt and out have the same battery voltage ~3.7v
If I plug in the USB, everything raises to ~4.4v.

This tell me everything is connected right?

But does this mean that the load connected to out+/- is using the voltage from the USB, not from the charging circuit? Because if its extra load on the charging circuit, that could lead to battery failure as the charging circuit see the load as part of the battery, when it isnt.

I havent found any documented proof that running and load and charging at the same time are ok in this set up. I can only find info that says plug this into a battery to charge it. Nothing more.

Worse case scenario, I can wire an inline switch so that only the battery charging, or load discharging from the battery are active at any time.

steven_191:
Ive just measured the input/output voltages on all of the terminals and batt and out have the same battery voltage ~3.7v
If I plug in the USB, everything raises to ~4.4v.

It should probably rise to ~4.2V, the charging voltage of the battery. Test the voltage of the battery, if you read 4.4V there, decide if your DMM is shit or if you rather want to take cover.

Anyway, you are talking about LiPo protection here. Your ESP will not like the voltage in any case. I successfully used an HT7333 with the ESP multiple times. Some caps are advised and there is not much headroom for periphery.

I have an esp running for a few days now on the battery.

It seems fine with battery only but I don't know if the battery will continue to drop voltage and eventually cause damage to itself.

Will the ht7333 cut the output if the battery goes low?

steven_191:
Will the ht7333 cut the output if the battery goes low?

No. You have been told how to protect the battery. Buy a protected the or the mentioned module. And yes, this is necessary if you ever want to charge it savely again.

The HT7333 is an LDO regulator that protects your ESP from running it grossly out of spec.

I have already said that I have those charging modules. I then questioned if those modules protect the battery from excessive discharge.

If you have any datasheets on those modules can you share them because I haven't been able to find them. I believe the modules part number is TE420.

I can see that the Ht7333 will protect against over voltage being a regulator but haven't read anything yet about protecting again under voltage. Other than buy a new battery.

steven_191:
I then questioned if those modules protect the battery from excessive discharge.

Yes

steven_191:
I can see that the Ht7333 will protect against over voltage being a regulator but haven't read anything yet about protecting again under voltage. Other than buy a new battery.

The ht7333 protects the ESP against over-voltage from either the battery (between 3.8~4.2V) or from the 5V from USB. The ESP won't be damaged from under-voltage as far as I know, it will just refuse to work. But even then it will continue to drain the battery, possibly damaging it. The ht7333 cannot protect the battery from over-discharge.

So you really need both the charge module, to safely charge the battery from USB (or a 5V solar pannel) and to protect the battery from over-discharge, plus a 3.3V LDO regulator to supply the ESP with the correct voltage from the output terminals of the charge module.

PaulRB:
Yes
The ht7333 protects the ESP against over-voltage from either the battery (between 3.8~4.2V) or from the 5V from USB. The ESP won't be damaged from under-voltage as far as I know, it will just refuse to work. But even then it will continue to drain the battery, possibly damaging it. The ht7333 cannot protect the battery from over-discharge.

So you really need both the charge module, to safely charge the battery from USB (or a 5V solar pannel) and to protect the battery from over-discharge, plus a 3.3V LDO regulator to supply the ESP with the correct voltage from the output terminals of the charge module.

thanks, thats what I wanted to know, but still not able to find a datasheet on that charging module which is a bit annoying.

This product page links the datasheet to both ICs involved.

This is on the website

- Important! Disconnect load when charging

I dont know if this is because the out+/- would be receiving the full charging voltage or because this adds load to the charging circuit, and would cause premature damage to the battery.

Has anyone had experience charging while a load is connected via a regulator?

The datasheets also suggest this would be used on a mobile phone application, and who turns the phone off while charging?? Surely it must be able to cope but I cant see anything explicit.

I think ill just put in a switch to allow either charging or load.