BQ27426: The change of RM between new battery and aged battery

chengxiaobin

Intellectual 300 points

Part Number: BQ27426

Tool/software:

Hi TI teams

根据TI的资料，我们了解到RM = (DODfinal - DODpresent) * Qmax，而在充放电过程中，DODpresent = DOD0 + PassedCharge/Qmax。

那么，如果我同时给一个老化的电池和一个新电池放出相同的电量，电量计如何确保两者的RM变化量保持一致呢？

我认为，由于老化电池的DODfinal和Qmax都会减少，这将导致计算得到的RM变化量增大。

如果在上面场景下，电量计输出的RM变化量确实不一样的话，那RM和实际放出的电量之间的关系是什么？

According to TI, RM = (DODfinal - DODpresent) * Qmax, and during charge and discharge, DODpresent = DOD0 + PassedCharge/Qmax.

So, if I discharge the same amount of power to an aged battery and a new battery at the same time, how can the fuel gauge ensure that the RM change of the two batteries is consistent?

I think that since the DODfinal and Qmax of the aged battery will decrease, this will cause the calculated RM change to increase.

If the RM change output by the fuel gauge is indeed different in the above scenario, what is the relationship between RM and the actual amount of power discharged?

23 days ago

0 Dominik Hartl11 22 days ago

TI__Guru 55826 points

Qmax will be lower for an aged battery --> FCC will be lower --> RM will be lower --> SOC will drop faster for the same current vs. for a new cell.

0 chengxiaobin 22 days ago in reply to Dominik Hartl11

Intellectual 300 points

Thanks for your reply.

DOD0 is not changed between new battery and aged battery?\

How about DODpresent?

0 Dominik Hartl11 22 days ago in reply to chengxiaobin

TI__Guru 55826 points

DOD0 doesn't depend on age. DOD present does because it's a function of Qmax.

0 chengxiaobin 22 days ago in reply to Dominik Hartl11

Intellectual 300 points

so you means during relaxing mode, the DOD0 is cacluate by the function of OCV and tempature.

If the OCV and temperature of the aged battery and the new battery are the same, the fuelgauge will give the same DOD0?

0 Dominik Hartl11 22 days ago in reply to chengxiaobin

TI__Guru 55826 points

yes.

0 chengxiaobin 22 days ago in reply to Dominik Hartl11

Intellectual 300 points

DODfinal 在老化电池上会变小，对吗？

如果是的话，那在 RM = (DODfinal - DOD0) * Qmax的公式下，老化电池充入固定的电量后，(DODfinal - DOD0)会变小，Qmax也因为老化电池变小。那此时RM值会比新电池充入固定电量的变化量小一些，这个理解对吗？

DODfinal will become smaller on aging batteries, right?

If so, under the formula RM=(DODfinal - DOD0) * Qmax, when an aging battery is charged with a fixed amount of electricity, (DODfinal - DOD0) will decrease, and Qmax will also decrease due to the aging battery. At this point, the RM value will have a slightly smaller change compared to the fixed amount of electricity charged into the new battery. Is this understanding correct?

0 chengxiaobin 21 days ago in reply to chengxiaobin

Intellectual 300 points

Hi TI teams

Could you answer this question? thanks.

0 Dominik Hartl11 20 days ago in reply to chengxiaobin

TI__Guru 55826 points

This goes beyond what we will share online. Why do you need this information?

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

Power management

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BQ27426: The change of RM between new battery and aged battery