Feeding Independent Current-Measurements to Fuel-Gauge Algorithm

[Tyekuhn]

Hello,

In a system that incorporates an nPM1300 (PMIC), we draw large amounts of current from our battery for certain portions of our circuit, and we must bypass the PMIC for this portion of the circuit.  Specifically, we have a high-current DC/DC circuit which has its input directly connected to the battery (bypassing the PMIC, and the VSYS output), however, the rest of the system runs off of the PMIC output (VSYS).  Because of this bypass, we must measure/estimate the battery current draw of this DC/DC circuit independently of the PMIC battery-current measurements, and feed this independent measurement to the fuel-gauge algorithm.

The question is:  Is there any precedent for doing this?  Is it expected that this would succeed or fail, with regards to getting accurate fuel-gauge information?

Thank you,

Ted

[runsiv]

Hi

As this is an unite case we need a bit more information

What kind of battery you are planning to use (chemistry /capacity for ex.)?

Operating temperature range? 

How often such bypassing are made / For how long/ and what's the peak current during such bypass points?

Any estimate of the current consumption/ loading behavior in normal operating mode and device operating time?

Regards

Runar

[Tyekuhn]

Hello,

We are using a LiPo pouch-type battery, 1000mAh, 3.7V nominal...standard LiPo chemistry.

Operating temperature range is ~20C to 40C; this is a wearable application.

This bypassing occurs in the active-mode of our device, so nearly all of the time.  The peak current can get up to about 1200mA (1.2A); and this can last for several minutes as battery voltage gets lower.  Our device is roughly a constant power device, so as battery voltage gets lower, current increases, and vice-versa.  However, nominal current is closer to 800mA; this can last up to 30 minutes.  The normal operational mode of our device has the battery being completely discharged in approximately 60 minutes.  So a 1000mAh battery is nearly discharged in 60 minutes, and then fully charged again before used again.

When our device is not in active-mode, the current draw is far less, <10mA.

Our charge current is set to 500mA right now, if that's of any consequence.

Thanks!

Ted

[runsiv]

Thanks for the update, I have forwarded the information to our developers and will get back to you

Regards

Runar