1 cell battery charging circuit

Thread Starter

Jonathan1256

Joined Aug 25, 2020
4
Hey everyone,
I am currently working on designing a one-cell battery charge and protect circuit for a simple project I'm working on but don't have too much expertise in this area. Below is an image of the schematic I designed. Charging the battery will use a USB-C port located on the board, and will be limited to 0.5A using R26. What I am unsure about is if both of these ICs are required or if the charging IC has enough safety protections built into it to be sufficient. My main concern is over-discharge protection. Also, if I were to swap the USB c port for a solar panel and adjust R26 according to the solar panel output, would the rest of the circuit be able to be powered while charging the battery? Any other comments regarding the circuit would be appreciated. Thank you!

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You still need the protection IC. The charger has no way to disconnect the battery in an over-discharge situation. How could it?
Certainly you can use a solar panel or a Mr Fusion for the input as long as you respect the max Vin of the charger. Which I think is 5 volts. Yes, you can modulate the current, but again, limited by the capacity of the chip.

But your charger is a linear device so it can't transform power. Higher input voltage won't make it charge faster, it will just turn the excess power into heat. But higher available current would mean you can turn up the charge rate by reducing the value of R26.
 

Thread Starter

Jonathan1256

Joined Aug 25, 2020
4
You still need the protection IC. The charger has no way to disconnect the battery in an over-discharge situation. How could it?
Certainly you can use a solar panel or a Mr Fusion for the input as long as you respect the max Vin of the charger. Which I think is 5 volts. Yes, you can modulate the current, but again, limited by the capacity of the chip.

But your charger is a linear device so it can't transform power. Higher input voltage won't make it charge faster, it will just turn the excess power into heat. But higher available current would mean you can turn up the charge rate by reducing the value of R26.
That's very helpful. Thank you!
 

Ya’akov

Joined Jan 27, 2019
6,853
Just a picky comment for those following at home.

A battery is a set of cells connected together. So you really can't have a "one cell battery". It is certainly true that common usage has lost this distinction, but in a technical context it is still good to preserve it.

Fun fact: we get the term "battery" from Benjamin Franklin who was a very distinguished, internationally recognized researcher in electricity. It comes from an artillery battery. The idea being that one cell is weak but combined they have great power.

He also gave us the confusing positive and negative notation. He had a 50/50 chance and the coin landed the wrong way. The physics of the situation makes it that current flows from negative to positive which is not very intuitive. The conventional current model gets around this by saying current flow is the direction a positive charge would go, which looks like to the negative. What a mess.

His insight about there being a distinction was spot on, though.
 
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