BQ34Z100EVM: Learning Cycle Questions

nima shirazi

Part Number: BQ34Z100EVM

Hi, I have determined the Chem ID of my cells as specified in: https://www.ti.com/lit/an/slva725a/slva725a.pdf?ts=1694198175782

Now, I am attempting the learning cycle specified in: https://www.tij.co.jp/jp/lit/an/slua903/slua903.pdf?_ticdt=MTY4OTg5NDI0OXwwMTg3ZGQ4NzMwZWIwMDgyNzk4ZmU1MTJlMmQ4MDUwNmYwMDIwMDY3MDBiZDB8R0ExLjIuMTQwMDY3NTYyMS4xNjgzMDQ4ODM4

First, I'd like to make sure that both of these documents outline currently-used procedures (there isn't a better document I should be following) as I've had this issue before with TI documentation.

Regarding the learning cycle:

Can I let the relax stage run longer than recommended? This is because the whole cycle takes around 20hrs and I cant be attending it for the whole duration. I was hoping after the initial charge, I could wait until the next day as opposed to 2hrs to start the discharge
It is specified that Qmax is not updated if the following occurs: If Temperature is outside of the range 10°C to 40°C. My charger IC uses both dV/dt and dT/dt termination to detect when the NiMH battery is charged, however this consistently results in max recorded temperature values between 40 and 50 degrees. Should I just insulate the battery from the dev board, or should I terminate charging before this point?

Thanks for your time and attention.

over 1 year ago

0 Steven Yao over 1 year ago

TI__Genius 12215 points

nima shirazi

Customer typically use some programmable charge and discharge machine to do the learning cycle, like Arbin or Marco.

The Qmax update shall happen under relax mode, you only need to assure the temperature is OK when when VOK clears in relax mode.

0 nima shirazi over 1 year ago in reply to Steven Yao

Prodigy 50 points

Yao,

thanks for your response, however I still have the same questions:

does it matter if the battery is in the relax state for longer than is needed?

I understand that temperature needs to be OK, I'm asking for your expert opinion on whether manually halting charging (to prevent excess heat) is advisable?

+1 Steven Yao over 1 year ago in reply to nima shirazi

TI__Genius 12215 points

nima shirazi

In principle, long relax should be OK, but needs to assure below rule is not violated:

4.9uV / Rsense * Qmax Time / 16 * 3600 < 1.5% * Design Capacity

Manually halting charging shall be fine as long as Charge Termination Detection process is not interfered

0 nima shirazi over 1 year ago in reply to Steven Yao

Prodigy 50 points

Yao, thank you for answering my questions. I just wanted to clarify what the Qmax Time variable is. I cant find it in the BQ34 datasheet, nor can i find it in the learning cycle documentation.

0 Steven Yao over 1 year ago in reply to nima shirazi

TI__Genius 12215 points

nima shirazi

Qmax Time is the timer started from the moment when Qmax is updated, the unit is hr/16

Power management

Power management forum

BQ34Z100EVM: Learning Cycle Questions