BQ2004H: NiMH Battery Charger Issue

Farrukh Mehmood

Part Number: BQ2004H
Other Parts Discussed in Thread: BQ2004E,

I designed a battery charger with BQ2004H for 10 cells Nimh battery 8AH. I found the charger will always stop fast-charge before it's completely charged and the time seems shifts in the table in datasheet. For example, I set TM1 and TM2 as low/low, fast charge safety time should be 325min, but it always stopped at 150min, which is for next level setting. But if I changed to Float/Low, which should be 154min, fast-charge will stop at 69min.

So the fast charge time in my experiment is 150min, 69min, 35min, 17min, 9min, 77min, 37min, 9min. All of them are only half of the time supposed to be. Anyone can give me an idea about it?

a) Charge rate : C/8

b)Termination: -ΔV method and C/8

c) Auto discharge and Temperature termination are not using.

over 7 years ago

0 Wang5577 over 7 years ago

TI__Guru 56650 points

I believe your test data. The datasheet could have an error. I ordered an board to check it.

0 Farrukh Mehmood over 7 years ago in reply to Wang5577

Prodigy 60 points

Hi Dear,

Thanks for ur response.

Sorry to mention that the above timings are related to BQ2004E. I am using BQ2004H, the reference values on all the pins are OK. But the fast charge is terminated after some time but Battery never reached full charge. Circuit is totaly based on the evaluation board.

EVB2004E.pdf

0 Wang5577 over 7 years ago in reply to Farrukh Mehmood

TI__Guru 56650 points

I ordered both EVMs.

0 Farrukh Mehmood over 7 years ago in reply to Wang5577

Prodigy 60 points

Hello wang,

Thanks for your time.

Kindly help me on this issue as its an urgent matter.

Regards

0 Wang5577 over 7 years ago in reply to Farrukh Mehmood

TI__Guru 56650 points

Ok. When the board comes, I will let you know the test result. And then, I will ask design team to confirm it.

0 Farrukh Mehmood over 7 years ago in reply to Wang5577

Prodigy 60 points

Hi Wang5577,

Still waitng for your reply.

regards.

0 Wang5577 over 7 years ago in reply to Farrukh Mehmood

TI__Guru 56650 points

Fixed small trouble on the EVM order today. I hope I can get the board soon.

0 Wang5577 over 7 years ago in reply to Wang5577

TI__Guru 56650 points

I got the bq2004H EVM this afternoon and checked the fast charge timer. The fast charger timer is correct.
Would you order an EVM to check the early termination issue? With an EVM, you can confirm it is charger circuit issue or the battery pack issue because the serval termination methods are related to the battery pack.

0 Farrukh Mehmood over 7 years ago in reply to Wang5577

Prodigy 60 points

i have an EVM board DV2004HS1. i have copied the circuit and design a PCB. All the pin voltages in all modes are same on both boards. when disabling the voltage termination mode by connecting VSEL pin to GND or VSS, IC take complete time (650 min) to charge the battery pack. otherwise by leaving VSEL as floating (negative delta voltage termination) IC terminates the fast charge within 10-30 mins.

0 Wang5577 over 7 years ago in reply to Farrukh Mehmood

TI__Guru 56650 points

"leaving VSEL as floating (negative delta voltage termination) IC terminates the fast charge within 10-30 mins."
Does the EVM have the same early termination issue?

0 Farrukh Mehmood over 7 years ago in reply to Wang5577

Prodigy 60 points

Hi Guys,

My problem of Early Termination is resolved. My charger is working perfect now. The problem was that i was using an unregulated VCC for charging IC, replacing this unregulated switching base IC with Linear regulator IC "L78L05" has resolve my issue.

Thanks

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BQ2004H: NiMH Battery Charger Issue