nPM1100-EK red LED lighting and a sealed battery

[p143]

Hi All.
I am testing a 4.2v Li-Ion battery charger mock-up with a Wireless Power Transfer having an nPM1100-EK at the end of the Secondary Stage and using its VOUTB 3v buck output to charge the application circuit. Everything works as expected except for one detail.
If I don't use the device for a long time, let's say one month, and even with no load in the VOUTB output, VBAT goes too low, and when I switch back the system, your nPM1100-EK turns on the red LED, apparently preventing the recharge.
The only way to come around the problem I've found was to remove the battery from the mock-up and charge it directly with an external CC/CV wired power supply till I reach VBAT above 3 volts. Then, if I place the battery back on the wireless charging device, the green LED goes on, seamlessly completing the charging cycle as many times as I need.
The bad news is that the final product will have the battery permanently sealed, so you can't physically reach it, and even if you could, the outcome would not be commercially viable.
Any suggestion?
Thanks

[p143]

Hello Kazi.

After thoroughly reading Nodic's nPM1100 Product Specifications document, I think I've found the reason behind the failure.
Being VBATchargemin 2.1v during charge,

and "Battery voltage lower than VBATchargemin after battery detection due to a fault with the battery" one of the reasons for the Charge Error Condition, it is obvious that the Charger Block is going to prevent Vbat from charging the battery after an extended time on the shelf.

Certainly, after let's say six months, of not being used and by natural discharge, any li-ion will get below 2.1v, meaning -if I'm not wrong- that your nPM1100 wouldn't be able to charge it again.

If this is the case (I hope not), in any Use Case in which the battery should be sealed inside the object to be fed, your PMIC wouldn't be compatible, and this, despite the battery being in perfect condition, as it is in my case, since I can charge the same battery seamlessly, with a conventional CC/CV wired power supply not having this VBATchargemin restriction.

My question is. Could this VBATchargemin restriction be somehow avoided, or the battery fault detector be improved so the flaw mentioned above could be solved?
Thanks.
Best regards,

Juan

[Kazi Afroza Sultana]

Hello Juan,

The charger error mentioned in that sections can be solved by disconnecting and the reconnecting VBUS again. 

''Could this VBATchargemin restriction be somehow avoided, or the battery fault detector be improved so the flaw mentioned above could be solved?'' In our latest PIMC (nPM1300), VBATCHARGEMIN is not even mentioned. 
I am not entirely sure if this is the only reason for your case. I have asked developer and will come back to you shortly.

[Kazi Afroza Sultana]

Hello Juan,

Here is the feedback from our team.

''

if battery voltage is below 2.1V nPM1100 will not charge it.

If the product is left unused for a long time, e.g. on the self before a customer buys it, it is recommended to use ship mode to reduce the current consumption (ref section 7.7 in nPM1100 product spec). 

For most batteries they should last a long time in ship mode (460nA), and the battery self discharge is much higher.

''

[p143]

Hello Kazi.

I understand.

But the problem I have, as I mentioned before, is that in my Use Case, the battery and all the feeding electronics must be completely sealed inside the final product, so the user can´t set this Ship mode on, other than in the production phase. Is that right?

Thanks.

Best regards,

Juan

[Kazi Afroza Sultana]

Hello Juan,

Unfortunately, its not possible to set the Ship mode in your condition when product is in a sealed condition. 

You may think of using nPM1300; it can continue charging even the battery goes below 2.1V. This PMIPC also has the hibernation mode which is similar to the ship mode; except you can set a timer for it to wake in every 2ms to 3 days (in 2 ms steps).

Thanks.

Regards,

Kazi