Scavenging energy to charge coin cell - M24LR16E-R alternatives? - Page 1
Forum section: electronics / projects

author: itsfreerealestate
author_rank: Newbie
timestamp: October 17, 2018, 01:11:38 pm
content: Hi,Long time viewer, first time poster.I have a low power project I'm working on (currently aiming for a single Li coin cell) that will occasionally need a charge (which can take multiple hours if need be). The Qi chargers actually seem overpowered for the application; e.g. the TIDA-00318 low power charger from TI (http://www.ti.com/tool/TIDA-00318) supports charging from 10 - 250mA (the lowest charge current is ten times higher than the C rating of the smaller coin cells). I was looking at NFC transponders, as I may also use NRF for a data drop during charging, and noticed that the M24LR16E-R from STMicro (https://www.st.com/en/nfc/m24lr16e-r.html) also includes an 'analog out' pin, which apparently allows the NFC chip to export harvested power. I was wondering if anyone is aware of any other such solutions for really low and slow wireless charging of coin cells, either with or without NFC.Cheers from the dart!

author: GeoffreyF
author_rank: Regular Contributor
timestamp: October 17, 2018, 03:12:45 pm
content: If you are talking about a coin cell such as the 2032 or 2016 - it is not rechargeable. Attempting to do so could be a hazard.Not every "Lithium" battery actually has the same chemistry. Not all Lithium chemistry is capable and safe of recharging.

author: Benta
author_rank: Super Contributor
timestamp: October 17, 2018, 03:50:47 pm
content: Not to derail your project, but is there any chance you have some significant temperature differences (>10 C) in the environment? If so, you could look at thermal energy harvesting.

author: itsfreerealestate
author_rank: Newbie
timestamp: October 18, 2018, 01:19:48 am
content: Quote from: GeoffreyF on October 17, 2018, 03:12:45 pmI'm aware of this;https://www.digikey.com/products/en/battery-products/batteries-rechargeable-secondary/91Quote from: Benta on October 17, 2018, 03:50:47 pmNo. And this is a terribly inefficient way to harvest energy using current silicon.

author: GeoffreyF
author_rank: Regular Contributor
timestamp: October 18, 2018, 01:09:40 pm
content: Indeed not all of those batteries, I think none of the coin cells, are rechargeable. There are many kinds Lithium battery chemistry. Only some are rechargeable. If you have a specific coin cell that is specified as rechargeable - please post a link to the spec sheet. Rechargeable Lithium batteries also have very specific requirements for charge currents, which also change during the charging cycle. That's another wrinkle for you to work on.DLCC capacitors might be a better way to store harvested electricity.

author: itsfreerealestate
author_rank: Newbie
timestamp: October 18, 2018, 11:15:30 pm
content: Quote from: GeoffreyF on October 18, 2018, 01:09:40 pm"ML414H is a rechargeable, coin type battery with features such as Pb-free reflowable (Peak temperature: 260 C) and high temperature heat resistance."

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 19, 2018, 01:12:56 am
content: https://na.industrial.panasonic.com/products/batteries/rechargeable-batteries/rechargeable-coinhttps://voltaplex.com/lithium-ion-battery/coin-cellhttps://biz.maxell.com/en/rechargeable_batteries/coin-type_lithium.htmlhttps://www.powerstream.com/Ni-Coin-ceLL.htmhttps://products.varta-microbattery.com/en/produkte/batterien-zellen-und-konfigurationen/technologie/wiederaufladbar/lithium-knopfzellen/alle/technologiebeschreibung.html#page/124https://www.master-instruments.com.au/category/Lithium_Rechargeable_Coin_Cell/1158

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 19, 2018, 01:34:54 am
content: As for energy harvesting, NFC would certainly be a way to do it provided that your device can get close to an NFC reader long enough to get substantial amounts of charge.I've used the AS3953 (ams) in one project. Those chips are great. You can handle NFC communication AND get a few mA (up to 5 mA IIRC). Could certainly be used for charging a very small battery.I don't think you can harvest more than a few mA, whatever the solution you use, if it's strictly NFC. That may prove enough for your application. If you need more juice and are still interested in a wireless inductive solution, you may take a look at Qi chips/modules. Works very well.

author: David Hess
author_rank: Super Contributor
timestamp: October 19, 2018, 04:11:50 pm
content: Look for "energy harvesting" ASICs. Linear Technology (Analog Devices now) has a bunch of them.