Energy Buffering for cr2032 battery

RE: Energy Buffering for cr2032 battery

hmolesworth — Wed, 15 Dec 2021 22:13:41 GMT

The most efficient solution is to throw away schottky diodes, which are too inefficient - 300mV drop on a 3 volt CR2032 loses 10% of battery power over the battery lifetime.

Instead use an Ideal Diode from the coin cell to a local capacitor bank say 100uF (ceramics not Tantalum or SuperCap, derate capacitor voltage by a factor of x2 to avoid loss of capacity, so 100uF 10Volt or 6.3 volt ceramic).. Loads must be connected directly to the coin cell with separate capacitor storage, ceramics say 150uF 10 volt though 6.3 volt is ok. Do not source load power from the MPU pins to avoid draining the nRF52 capacitor bank. Active-low drivers can use the port pin, active-high should be buffered by interface powered from coin cell not nRF52 VCC.

Use PWM to drive loads such as LEDs or mini speakers; tune the PWM to protect the coin cell. Massive voltage drops on the coin cell can be tolerated since the nRF52 is isolated with the local VCC supply. Connect the proximity sensors direct to the battery.

RE: Energy Buffering for cr2032 battery

Jared — Mon, 13 Dec 2021 13:33:14 GMT

done

RE: Energy Buffering for cr2032 battery

Letho — Mon, 13 Dec 2021 11:33:12 GMT

I’ve edited the sensitive information, so I think you can convert it to a public case now. Thank you.

RE: Energy Buffering for cr2032 battery

Jared — Mon, 13 Dec 2021 11:25:28 GMT

If this case doesn't contain any sensitive information, maybe I could convert this case to public? So you could get help from the community?

RE: Energy Buffering for cr2032 battery

Letho — Fri, 10 Dec 2021 11:20:10 GMT

Hi Jared,

As you say, I was thinking of doing a hybrid solution, where I would gradually charge the capacitor with a low current (max 0.2 mA) so the battery would not be stressed as much.

I don't have much experience in this field either. Can you recommend me any alternative electronic forum where someone might have more insight in this type of issues?

Best regards,
Tomas

RE: Energy Buffering for cr2032 battery

Jared — Mon, 06 Dec 2021 12:45:23 GMT

Hi,

[quote user="Letho"]I was wondering if you don't have any idea (or, ideally, more example designs) of how to buffer energy. The only thing I found so far is using buck convertor in combination with super capacitor (as described here: https://www.ti.com/tool/PMP9753) . [/quote]

But would the super capacitor be able to store as much as the coin cell? Or were you thinking of doing a hybrid solution?

I'm sorry, but I'm not that very experienced in exactly this. Maybe you should try posting in some alternative electronic forum?

regards

Jared

RE: Energy Buffering for cr2032 battery

Letho — Sat, 04 Dec 2021 15:15:01 GMT

Hi Jared,

Yes, you described my problem nicely.

The device I'm developing is smart home sensor, which should function for a few years without battery replacement.

It is important to have the device as small as possible, that is why I decided to use the battery CR2032, which has a decent capacity of 240 mAh. The battery CR2032 is small and easily replaceable. As the device can function up to 4-5 years (based on our average power consumption), there is no need to use rechargeable batteries or energy harvesting at this point.

The only issue is that the chemistry of the battery cannot keep up with the power requirements of the sensors pulse. But I think no battery of this size can keep up.

I've checked the design of the beacon you linked, but it seems that the design doesn't take in consideration such problem. The pulse current of the SoC nrf51 is approx 5-7 mA when the beacon is transmitting (based on the online profiler https://devzone.nordicsemi.com/power/w/opp/2/online-power-profiler-for-bluetooth-le ). The pulse current will decrease battery's capacity, as it's mentioned in the study linked in this thread ( https://devzone.nordicsemi.com/f/nordic-q-a/62487/high-pulse-drain-impact-on-cr2032-coin-cell---graph-csv-data )

I was wondering if you don't have any idea (or, ideally, more example designs) of how to buffer energy. The only thing I found so far is using buck convertor in combination with super capacitor (as described here: https://www.ti.com/tool/PMP9753) .

Thank you so much for your help,

Best regards,

Tomas

RE: Energy Buffering for cr2032 battery

Jared — Thu, 02 Dec 2021 12:44:19 GMT

Hi,

I think the main problem is as you say that coin cell batteries are not made to deliver high current due to their low discharge rate. Is there any possibility of using other types of batteries such as Alkaline, Li-ion etc? You write energy buffering, does this mean that you are going to implement some kind of harvesting of energy such as solar panel etc?

A bit outdated but still interesting design is our nrf51 based beacon starter kit.

regards

Jared