Need advices on suitable battery type with high lifetime for IoT devices - Page 1
Forum section: electronics / beginners

author: JL34
author_rank: Contributor
timestamp: December 27, 2020, 02:50:06 pm
content: Hello,As I have understand in oneother post, battery-free IoT devices are difficult to achieve in home indoor environnement.So I am looking for advice on selecting a battery type with high lifetime (<10 years) to powering ultra low power IoT devices in home environnement.Those devices will haverest energy from indoor electical lights.I have found some types but no suitable for this usage :-lithium have little lifetime (depending on number of charge cycle)-supercapacitor have lifetime less than 10 years.-solid state battery seems to have good lifetime but are not easy to find.Anyone have some advices on this subject ?Thanks

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: December 27, 2020, 10:49:21 pm
content: Li-ion will last for more cycles if you operate it near the middle of its capacity. E.g.charge to 60% and discharge to 40% (a depth of discharge of 20%) and it will last roughly 15 times as longas if you charged to 100% and discharged to 0%.Of course, during this time it will still degrade due to high temperature and general ageing. Also note that quality of the cell matters; cheap Li-ions aren't going to last long regardless.

author: nuclearcat
author_rank: Unknown
timestamp: December 27, 2020, 11:11:21 pm
content: LiSoCL2, lithium thionyl chloride battery, huge capacity and lifetime but they are not rechargeable and pricey. You might avoid pricey energy harvesting and just go with this type of battery.Eneloop NiMH can last surprisingly long time, depends on use.Supercaps are pretty durable, it depends (again) where and how you use them . Unlikely any accessible batteries will last 10 years at 85C.Supercaps lifetime chart dependence attached.

author: JL34
author_rank: Contributor
timestamp: December 28, 2020, 12:53:24 am
content: Thanks for those replies.Quote from: I wanted a rude username on December 27, 2020, 10:49:21 pmThis may be achieved with stopping energy harvesting at 60%, but it let only 20% of full battery capacity before reach 40%. Interesting, not impossible, but a little less convenient. But a lifespan based on the number of cycles is always less practical than if it is based on time. At least for long lifetime's devices that should work while being forgotten, like IoT sensors.Quote from: nuclearcat on December 27, 2020, 11:11:21 pmLiSoCL2 could be a good primary cell, that permit to not use an energy harvesting circuitry. Depending on usage and consumption, it could be a good solution.If supercaps could reach 15-20years of lifetime, this seems to be a very interesting solution. I don't known it could be so high. It requires energy harvesting, but this is not very limiting.I still have to think about the consumption and use of my devices (mainly defining data transmission frequency and calculate corresponding daily consumption).In those type of case (indoor IoT sensors with minimal maintenance), what strategy would you choose ? Primary cells or secondary cells with energy harvesting ? Why this choice ?Thanks for share your experience ;-)

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: December 28, 2020, 02:56:55 am
content: My decision process:Can I get power consumption low enough for a primary cell or battery of the right size? If so, prefer lithium button cell,AA, AAA, and Li-SOCl2, in that order.Is energy storage infeasible (e.g. high power consumption) or unnecessary? If so, prefer power delivery via USB-C, wiring to automotive 12 V, etc.For everything else, use Li-ion prismatic.Note that rechargeable is the last option. Why? Because it adds complexity, unreliability, and development time. So I prefer to avoid it.A sensor may be low power enough to allow a primary supply for its lifetime. That would be optimal. If the cell can be replaced by the user (even if it requires undoing a few screws to change the Li-SOCl2 cell once every decade), you don't even have to worry about allegations of waste and planned obsolescence.

author: amyk
author_rank: Super Contributor
timestamp: December 28, 2020, 02:58:11 am
content: Lithium thionyl is proven for this sort of application. A lot of products use them as backup batteries for calibration RAMs and RTCs. They definitely last a decade or more, but the drawback is they are not suitable for high currents.

author: nuclearcat
author_rank: Unknown
timestamp: December 28, 2020, 10:39:48 am
content: Quote from: JL34 on December 28, 2020, 12:53:24 amIt really depends on the project. It worth only if device is entirely hard to reach, like TPMS sensor. If your device is using ambient light - it sounds like accessibleFor 10 years you need to hunt for each nA, and any new leakage that appears during operation will severely affect device. Sometimes it can be something really nasty and hard to reproduce stuff, like flux residue degradation, components aging, etc. You might need even to do accelerated aging tests, which are time and money.And it's not only about power, it's about everything in your design, and in my opinion it is not trivial and very expensive to design device that is guaranteed to last 10 years without servicing , and sometimes its better choice designing with option of servicing device each X month or years(including battery change).

author: JL34
author_rank: Contributor
timestamp: December 28, 2020, 01:43:22 pm
content: Quote from: I wanted a rude username on December 28, 2020, 02:56:55 amIt makes sens and is a good argument to primary cell.Quote from: nuclearcat on December 28, 2020, 10:39:48 amThis seems obvious presented like that. But as a hobbyist and not an embedded system engineer, I haven't those type of experiences/knowledges. Very interesting sharing, thanks for this.I still have to do some experiment with my Silab Gecko starter kit, but after some search and calculation it seems that DIY Zigbee sensors could be achieved with average current consumption maintained below 50-100mAh per year (2µA sleep current with 10ms wake-up time to transmit @10mA with SiLabs mgm12p02f1024ga-v4). It is theoretical, some quiescent and leakage currents should be added, but magnitude order remain the same.Going with lithium coin cells should permit reaching a few years of lifetime. And even more with Li-SOCl2 cells, close or more than a decade.It opens a huge playground to me, in home IoT sensors

author: MadScientist
author_rank: Frequent Contributor
timestamp: January 02, 2021, 09:04:47 pm
content: LiFePO4 chemistry will give you longer life and more cycles , as the cost of sone energy density

author: tszaboo
author_rank: Super Contributor
timestamp: January 02, 2021, 10:46:45 pm
content: Yeah, but in the home environment, why dont you just put two AAA cell in it, or a coin cell, and let the user take care about the rest. I know about these systems, because it is mayor PITA to handle these batteries in a hard to reach, hard to disassemble industrial environment.Having a battery-free product is a gimmick, that shouldn't be the mayor selling point of a product. The only parts I've seen in a home environment with unreplaceable LiSOCl battery is gas meters and smoke alarms.

author: JL34
author_rank: Contributor
timestamp: January 02, 2021, 11:49:28 pm
content: I am not trying to develop any sellable products. I just try to develop a sensor network for my own usage at home, avoiding PITA to replace the batteries every few months.Originally I planned to use rechargeable batteries with indoor light energy harvesting. Using supercapacitors cells could permit reaching 5-10 years of lifetime, it would be nice. But it is a more complex solution.So I have looked at primary cells side. Good energy managing with primary cells capacity could permit reaching 5 years lifetime.I have not made any choice yet, and I still have to study costs and feasibility

author: ElektroHS
author_rank: Contributor
timestamp: March 16, 2021, 12:52:28 pm
content: I'm developing IoT products with battery solutions at the moment where is possibly.In case of outdoor devices - solar panel + energy storage - these devices aren't small. Also, there is nuances in case of your outdoor environment can have -5-10C and less...Indoor devices with small size - battery CR-series. Microcontroller sleeps the most of time to minimise battery usage.