BQ34Z100-G1: Maximum nominal energy

Kevin Picot

Prodigy 80 points

Part Number: BQ34Z100-G1

Hi,

I'am using BQ34Z100-G1 on BQ34Z1xxEVM and EV2300 adapter.

I'm trying to set up the correct registers values for a pack. i'am struggling with the following values :

Configuration/Data/Design Capacity

My pack is a 1S8P LiFePo4 assembly (8 x 18650 1500mAh LifePo4 cells)

Nominal voltage 3.3V

Nominal capacity 12.8Ahr

Nominal energy 42.24 Whr

As a first approach, I used Chem ID 0426 (not the exact brand/model, but seems close enough at first sight)

The datasheet is stating that max supported battery capacity is 29Ahr, so I should be ok on this point and set for my case '12800'

However, the field Design energy seems to be limited to a maximum value of '32767' (mWhr) as per the datasheet.

Is there something i did'nt get, or I cannot sense the whole energy capacity of my battery pack with the BQ34Z100-G1 ?

I did'nt run the optimisation cycle yet, but assuming I run it, can I get a Qmax value bigger than the 'Design Energy' value ?

Thanks for your help

Regards

over 8 years ago

0 Haidar Hamoo over 8 years ago

TI__Expert 4065 points

Hi Kevin,
You need to use parameter scaling for your battery pack, please refer to bq34Z100-G1 application note for high cell count battery pack below for further details.
www.ti.com/.../slua760.pdf
Regards,
Haidar

0 Kevin Picot over 8 years ago in reply to Haidar Hamoo

Prodigy 80 points

Hi Haidar,

Thanks for you fast answer !
Just a confirmation required after reading the application note :

There is only one adjustable scale factor, which apply to all parameters.
I mean if I set a "Design Energy Scale", this value will also scale the capacity and the current on all the readings. Right ?

I can't choose to scale only the Design Energy ? (My system is quite high energy/capacity but low voltage and current, and I want to preserve the resolution and accuracy).

Regards

Kevin

0 Haidar Hamoo over 8 years ago in reply to Kevin Picot

TI__Expert 4065 points

Hi Kevin,

Yes, you are correct, when you scale the capacity you have to scale current as well with the same scaling factor, as for the voltage, you don't have to scale it with the same factor but keep in mind that VBAT voltage must be less than 1V (typically 900mV). The scaling will not affect the resolution of the gauge's measurement since IT algorithm that bq34Z100-G1 gauges uses sees the pack as a single cell.

Regards,

Haidar

0 Kevin Picot over 8 years ago in reply to Haidar Hamoo

Prodigy 80 points

Hi Haidar,

Thanks for your help ! Everything clear now !

Regards

Kevin

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BQ34Z100-G1: Maximum nominal energy