Power Supply CR2032 3V Battery Drop Voltage - Page 1
Forum section: electronics / general

author: trungosu
author_rank: Contributor
timestamp: October 04, 2018, 02:27:48 am
content: Hi,I have a question regarding NXP-Zigbee chip power supply. Working range 2V-3.6VWe try to use coin cell CR2032 3V to supply power for the Zigbee.I'm running Serial Communication application on the chip, it works perfectly.When we try to power it at normal room temperature, it works fine. Battery voltage is around 2.8-2.9V.However, when we try to put it in our refrigerator which around 0 degrees.I know the battery drops around to 2.7V. And at the peak current 30mA when transmitting the data. It drops around 0.5 V.It makes the power supply around 2.2-2.1V which I think in a moment, it drops below 2V that's why Zigbee stops transmit data. (unfortunately, I don't have an oscilloscope to test how long it go drop but using multimeter give me those number)I have a parallel capacitor 220uF with power supply but looks like it's not helpful.I'm not sure what is the value of capacitor I should have or how to handle the cold temperature situation.Thank you very much.

author: Sceadwian
author_rank: Unknown
timestamp: October 04, 2018, 03:57:08 am
content: Have you tried a larger cell? You're really pushing what you can expect from a 2032.

author: TheSteve
author_rank: Unknown
timestamp: October 04, 2018, 04:56:16 am
content: A CR2032 is never going to be happy with 30 mAh of current draw.

author: trungosu
author_rank: Contributor
timestamp: October 04, 2018, 07:21:37 pm
content: Quote from: Sceadwian on October 04, 2018, 03:57:08 amYes. It worked fine with a larger cell.But, I saw all of the commercial wireless sensors from Smart thing, Xiaomi, they are using cr2032.I wonder how they did that. I want to make the sensor as small as possible.Thank you very much.

author: trungosu
author_rank: Contributor
timestamp: October 04, 2018, 07:24:13 pm
content: Quote from: TheSteve on October 04, 2018, 04:56:16 amEven with flash of time, maybe 100ms. I know parallel capacitor or super-cap could help to preven voltage drop but I have no idea to start.Thanks.

author: lem_ix
author_rank: Regular Contributor
timestamp: October 04, 2018, 10:16:07 pm
content: Try with a ceramic cap for a start, lets say 10 uF. But indeed this is too much current for 2032, expect reduced capacity.

author: David Hess
author_rank: Super Contributor
timestamp: October 05, 2018, 03:21:06 am
content: The internal resistance of the cell increases at lower temperature affecting both the maximum available power and efficiency. Some cells are better than others.https://www.embedded.com/electronics-blogs/break-points/4429960/How-much-energy-can-you-really-get-from-a-coin-cell-You could improve the situation with some variation of a buck-boost converter to provide a constant minimum voltage to the circuit and a bulk input capacitance.

author: tsman
author_rank: Frequent Contributor
timestamp: October 05, 2018, 03:10:22 pm
content: Quote from: trungosu on October 04, 2018, 07:21:37 pmMost of them use a CR2450 which is a lot bigger physically and higher capacity.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 05, 2018, 04:51:28 pm
content: Quote from: TheSteve on October 04, 2018, 04:56:16 amHere's a CR2032 Energizer datasheet:http://data.energizer.com/pdfs/cr2032.pdfSurprinsingly enough (to me at least), its operating temp range (-30°C to +60°C) is impressive.Typical figures are tested and given @21°C though, so obviously you are on your own when the temperature is a lot lower or higher than this.And yes, the typical drain is given at 0.19 mA and pulse drain at 6.8 mA. So for a 30 mA pulse drain, even at room temperature, it's probably going to have a much lower capacity than the rated ~200 mAh.

author: trungosu
author_rank: Contributor
timestamp: October 05, 2018, 05:02:00 pm
content: Quote from: lem_ix on October 04, 2018, 10:16:07 pmThank you. I tried 220uF ceramic cap but It seems not enough.Yes. It looks too much for 2032. But it's a really good job in industrial that how they could handle that.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 05, 2018, 05:04:31 pm
content: You may be interested in this Nordic paper:https://www.dmcinfo.com/Portals/0/Blog%20Files/High%20pulse%20drain%20impact%20on%20CR2032%20coin%20cell%20battery%20capacity.pdf

author: trungosu
author_rank: Contributor
timestamp: October 05, 2018, 05:07:49 pm
content: Quote from: David Hess on October 05, 2018, 03:21:06 amI also think maybe I should go with a buck-boost converter even it will cost some drain power. Do you have any recommendation buck-boost converter in mind? I usually use TI with around 80% efficiency.

author: trungosu
author_rank: Contributor
timestamp: October 05, 2018, 05:12:16 pm
content: Quote from: SiliconWizard on October 05, 2018, 05:04:31 pmCool. Thank you very much. Yes. I know some products using CR2032 with high drain pulse.I just move from Nordic BLE to NXP Zigbee for my project.That's exactly the paper I need. Thanks

author: trungosu
author_rank: Contributor
timestamp: October 05, 2018, 05:14:44 pm
content: Quote from: tsman on October 05, 2018, 03:10:22 pmThanks. Yes. I will try my best to solve the problem if not, a bigger battery is a great idea.The only problem I have to find a different enclosure which fit with CR2450.

author: Rerouter
author_rank: Super Contributor
timestamp: October 06, 2018, 01:15:08 am
content: Its easy to work around it for small time pulses, but yeah 30mA for 100ms requires a crazy level of capacitance,the ESR of a CR2032 is about 20 ohms at room temperature, down at 0C its close to 75 ohms,I've built my own little RF modules, but I went out of my way to keep the RX/TX time as short as possible (5.5ms @ 11.7mA in my case) That still required a 47uF in parallel to ensure it could transmit down to 0C, your using much more current, for a much longer time, so yeah 220uF will not cut it at all,To work it out, you treat your consumption like a constant current load, with the battery being a voltage supply with 75 Ohms in series, with X sized capacitor in parallel, then work out the size to keep the voltage above your cutout voltage (1.8V in my case), I ended up using Falstads circuit simulator for this, but there are ways to do it with math.For me that 47uF let me discharge the battery all the way down to 2.3ish voltage and able to handle the transmission,http://data.energizer.com/pdfs/cr2032.pdf

author: jesuscf
author_rank: Frequent Contributor
timestamp: October 06, 2018, 06:10:02 pm
content: I have a brand new Energizer CR2032. Open voltage test gives 3.31V. Short circuit test gives 119 mA . The internal resistance is therefore around 28 Ohms (3.31/0.119). With a 30mA load, the internal voltage drop would be around 0.8V; this means that the load will see a voltage of about 2.5V. If you want to reduce the voltage drop, either use a battery with a smaller internal resistance or alternatively put two or more CR2032s in parallel.

author: trungosu
author_rank: Contributor
timestamp: November 26, 2018, 08:55:45 pm
content: That's great information.Yes. I think I have to do some serious calculation in order to handle the transmission.Thank you very muchQuote from: Rerouter on October 06, 2018, 01:15:08 am