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I'm looking into the possibility of running a wireless sensor node for up to 10 years on a single battery. I think the average current draw is likely to be around 70uA, with the peak current draw possibly being 20mA(the average takes this into account). System voltage can be between 2.5-3V.

This seems like it might be a requirement in more and more projects as the area of IoT and remote sensors continues to grow. I was hoping to get some suggestions for a few different possible solutions that balance cost and capability.

I thought about a CR123A as a possible battery, or even just a couple of AAA batteries. A li-ion rechargeable cell was also a consideration, but I think maybe the self-discharge might be a factor after that length of time and recharging/energy harvesting might be difficult or costly.

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    \$\begingroup\$ You might look into the batteries used in smoke detectors that are rated for 10 year use. Like the U9VL-XC battery. \$\endgroup\$
    – JRE
    Oct 13, 2016 at 9:53
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    \$\begingroup\$ The very first thing you want to find is a battery which is actually guaranteed by the manufacturer to last 10 years. It is no use designing any circuit at almost no current if the battery is not even going to last that long. The battery chemistry will very likely be a Lithium based primary cell (not rechargeable). Unless you could use a small solar panel to provide extra charge. But anyway, few manufacturers will guarantee 10 years of lifetime for a battery. \$\endgroup\$
    – Bimpelrekkie
    Oct 13, 2016 at 9:54
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    \$\begingroup\$ 70 µA average current over ten years require a battery with more than 6132 mAh capacity. The peak current of 20 mA for one second every hour of the ten years will need another 487 mAh. During 10 years some self discharge will happen, a 10 Ah battery may be not enough. \$\endgroup\$
    – Uwe
    Oct 13, 2016 at 10:14
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    \$\begingroup\$ Primary lithium! \$\endgroup\$
    – winny
    Oct 13, 2016 at 10:23
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    \$\begingroup\$ Are you constrained for size/space? If not you could probably use an array of batteries with high shelf life and some sort of switching system. \$\endgroup\$
    – R.. GitHub STOP HELPING ICE
    Oct 14, 2016 at 2:51

6 Answers 6

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First, let's see how much energy or capacity you need. 70 µA for 10 years comes out to 6.1 Ah, and you say this is at 3 V. That's a lot more than a CRxxxx battery can do.

Another problem is that you need a battery that is good for 10 years regardless of discharge. Many batteries aren't specified for such a long shelf life, let alone service life. For this kind of application, you need to have conversations with field engineers from battery companies. Take a look at Tadiran. They are aiming for this kind of application.

Another option is a lithium rechargeable with a small solar panel. At 70 µA average, a 18650 cell is way more than enough. It could easily ride out a few weeks with no sun at all. Just a few hours of sun a week would be enough with a modest panel.

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    \$\begingroup\$ Solar panel + super cap/smallish battery is definitely the way to go. +1 \$\endgroup\$
    – Vladimir Cravero
    Oct 13, 2016 at 14:34
  • \$\begingroup\$ Yep, picked a fairly arbitrary number and didn't do my maths there! Thanks for the heads up about Tadiran, and I'll explore solar cells more. I know it's a possibility, but some sensors may not have incident sunlight, or even indoor light. \$\endgroup\$
    – Sensors
    Oct 14, 2016 at 11:11
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Long lasting (very low self-discharge) batteries usually doesn't have a very good discharge characteristics.

For example Tadiran SL-360, 14500 form factor offers 2.1AH at 6mA discharge but can not be discharged above 20mA. In the datasheet, you can see it can discharge 10 years at 20uA.

One way to get around it is to use a energy buffering solution: slowly discharge the battery and charge a large capacitor, and use the capacitor to burst out the peak current you need, when you need it, like this energy buffering reference design targeting 15 years battery life for remote sensing application by TI.

I think if you choose your battery based on your peak current requirement, your design will need a very specialized battery that offers both low self discharge and good discharge current, which probably makes it expensive and hard to source.

Energy buffering relaxes the peak current requirement on the battery significantly.

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    \$\begingroup\$ Energy buffering requires a large capacitor with a low leakage current and small internal resistance. The lifetime of some electrolytic capacitors may be less than 10 years. \$\endgroup\$
    – Uwe
    Oct 14, 2016 at 14:17
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As someone posted in the comments, Lithium Thionyl Chloride primary cells are a solution to this problem. Such cells exist in various form factors, from 1/2AA through D, and various battery pack configurations. Certain manufacturers (Saft, Tadiran batteries) guarantee 10 years of shelf life. These cells provide 3.6V, take into account that it is extremely hard to gauge the remaining level of charge with these cells, and there are other phenomena related to the batteries that you will have to consider in your design.

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I believe your best possible solution is non-rechargable (or "primary") Lithium batteries. The self discharge on these is roughly 10% in 5 years - all rechargeable batteries are much higher than this. This is the solution used by Electronics companies for long life wireless sensor nodes. This link has some info on battery discharge, while This one describes non rechargeable battery types.

Finally, this Farnell link has a selection of non-rechargable lithium batteries (of various types!) that should suit your application

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    \$\begingroup\$ I agree Lithium primary cells e.g. CR2 3.00V offer the best affordable long term life with low cost and high energy density with excellent cell voltage regulation. Lithium Thionyl Chloride are good choices for ELT's that need to last 10 yrs as long as short circuit failure is nil with in-built thermal fuses and rigid containers, otherwise they become significant explosive devices if shorted. Ref biz.maxell.com/en/primary_batteries/pdf/ER_15e.pdf \$\endgroup\$
    – Tony Stewart EE75
    Oct 14, 2016 at 15:09
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Nearly 30 years ago I was responsible for the design of sealed non-repairable electronic equipment which was sold with a 5-year unconditional warranty. We used Lithium Thionyl Chloride batteries (Tadiran and Saft, as I remember), in sizes from AA to D, and had no problems with battery life; we had test units which achieved over 8 years operational use (at which time I left the company and so lost contact). I expect battery design has improved over time, so I would suggest this as the likely solution.

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Buy sulfuric acid and plumbum (Pb), make a lead battery large enough. Come into the room and recharge the battery when needed with another battery - non-stop solution (as you want). Size will be big, but you don't have any limitations of that.

Lead batteries are used up to this days when you want very low self-discharge. It stores reserve power for cell networks, computers etc. Because it is reliable, simple and does not harass environment (all components are convertible back to new battery).

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