BQ25731: IC with NiMH charging completion function

Hi Tiger-san,

Thank you for your support. From the URL you sent me, I would like to choose a product that only supports NiCd and NiMH.

1. Another E2E I sent you before said that products that support multiple cell chemistry cannot support The key end-of-charge detection methods. Am I correct in understanding that there is no charge IC that supports The key end-of-charge detection methods of NiMH?

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1446098/bq25731-multi-chemistry-not-mentioned-on-datasheet/5547421?tisearch=e2e-sitesearch&keymatch=BQ25731%20NiMH#5547421

2. Is there an application note for using NiMH with products that support multiple cell chemistry?

Best Regards,

Nishie

Hi, Nishie,

Good choice to pick a dedicated NiMH charging product, which may provide the key end-of-charge detection. 

I am not aware of such an app note. 

Regards,

Tiger

Hi Tiger-san,

I checked the battery specifications with the customer again, and found the following specifications. I could not meet these specifications with products that only support NiMH, but could you recommend products that support multi-cell chemistry and that can charge and discharge NiMH?

< Specifications >
・6 or 8 NiMH in series
・Charging current is under consideration between 0.2 C and 1 C (Max 3 A)
・Input voltage is assumed to be 12 V or 15 V.

Tiger Zhou said:

I am not aware of such an app note. 

->You do not have any documentation, but could you tell us the component configurations that support multi-cell chemistry and that can charge and discharge NiMH?

Best Regards,

Nishie

Hi, Nishie,

You can check this out. 

https://www.ti.com/product/BQ25792

Regards,

Tiger

Hi Tiger-san,

There is no mention that the BQ25792 supports NiMH, but can it be used for NiMH batteries?

I searched in the data sheet, but I could not find NiMH.

Best Regards,

Nishie

Hi, Nishie,

We have a gap here. 

Yuta Nishie said:

I could not find a Buck-Boost type charging IC that supports NiMH only.

Regards,

Tiger

Hi Tiger-san,

I apologize for my lack of explanation.

There is no longer a requirement for the Buck-Boost control.

Could you introduce a product that can support NiMH that meets the following specifications and has the functions I have talked about so far?

< Specifications >
・6 or 8 NiMH in series
・Charging current is under consideration between 0.2 C and 1 C (Max 3 A)
・Input voltage is assumed to be 12 V or 15 V.

Best Regards,

Nishie

Hi Nishie,

The only part that supports NiMH only is BQ25172.

If you want a higher power part, I recommend BQ25756E and set EN_PRECHG = 0 for NiMH charging.

Regards,

Charles Harthan

Hi Charles-san,

Thank you for introducing the product.

Am I correct in understanding that we can provide the key end-of-charge detection(Delta-V detection, Temperature rise rate, Time-based cut-off) for NiMH by setting EN_PRECHG= 0?

Best Regards,

Nishie

Hi, Nishie,

Yuta Nishie said:

Am I correct in understanding that we can provide the key end-of-charge detection(Delta-V detection, Temperature rise rate, Time-based cut-off) for NiMH by setting EN_PRECHG= 0?

Not provided. 

Regards,

Tiger

Hi Tiger-san,

Could you give me an example of an external circuit to check the charging completion of NiMH using a product that supports multi-chemistry?

Best Regards,

Nishie

Hi Nishie,

I think you need a dedicated high power NiMH charger, which we don't have. 

Regards,

Tiger

Hi Tiger-san,

I found the following article on how to detect NiMH Charge Termination.

NiMH Battery Charger Circuit: What You Need to Know – Flex PCB

Can I use the BQ25820 and the IC below to detect NiMH Charge Termination? Please let me know if you have any other IC you recommend.

・Delta-V detection:INA230
・Temperature monitoring:TMP118
・Timer-based termination:NA555

Best Regards,

Nishie

Hi, Nishie,

Excellent!  Why not?

Regards,

Tiger