STNS01 - battery greater than supplied Fast Charge current

[stevema2]

Hi 

I'm using the part STNS01 with a Li-Polymer batter of 6mAh (nominal capacity).. I've used a 13KΩ resistor for to set current charge limit which provides 15mA as the output for the CCCV charging.

Would there be any issue with using a 6mA battery with the STNS01 set to 15mA (this is the lowest setting)?

I was assuming the battery would only source the current it was capable of using.

Thanks in advance for any assistance. 

[Peter BENSCH]

Welcome @stevema2, to the community!

I can't really understand your assumption. Each battery can supply a maximum of the (short-circuit) current resulting from the cell voltage and the internal resistance. Of course, only the current specified in the data sheet makes sense.

In order to be able to make further statements about your setup, please insert a URL to the data sheet of this battery, alternatively you can attach the PDF.

Regards
/Peter

[Andrew Neil]

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@stevema2 wrote:

I was assuming the battery would only source (sic?) the current it was capable of using.

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"Source" means that the battery is supplying the current to the connected device.

Did you mean, "sink" - ie, the battery receiving current?

https://community.st.com/t5/stm32-mcus/how-to-identify-which-pin-can-sink-most-current-on-any-stm32/tac-p/721074/highlight/true#M1048

But no, a battery won't limit the charge current into it - you need external circuitry to do that.

As @Peter BENSCH said, the battery datasheet will tell you the maximum allowed charge & discharge currents.

[stevema2]

Thank you both for your input, I have attached the datasheet for the battery we intend to use.

My apologies, I did word my statement incorrectly, I should have said 'sink' as the the battery is being charged by the 15mA. 

@Andrew Neil do you know of any reference designs for a circuit to limit the charge current?

[Peter BENSCH]

As you can see from the data sheet, the 6mAh battery may be charged with 1C for ‘Rapid Charge’, i.e. actually with 6mA. The standard charging current is actually only 0.2C = 1.2mA.

At Riset = 13k, the minimum charging current of the STNS01 is 15mA, which is too much for this somewhat fragile battery. Unfortunately, this makes the STNS01 unsuitable because Riset must not exceed 13k and cannot be increased to the 33k required for 6mA.

Regards
/Peter

[Andrew Neil]

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@stevema2 wrote:

do you know of any reference designs for a circuit to limit the charge current?

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You design your charger so that it cannot exceed the battery's maximum charge rate.

As @Peter BENSCH said, the STNS01 is not suitable as it cannot meet your battery's specification.