Battery questions for outdoor products

[thefatmoop]

Hi,

To very briefly summarize the product i'm working on: It's a sensor box that's placed in a particular environment where they need a lot of them monitoring lots of different things. They're placed outdoors, customer doesn't want to run power to them, must be wireless, run for years on a battery. I've got everything working like a charm with a pcbs/working with a supplier IP67 enclosures.

Here's my dilemma. The company wants hundreds and the batteries will only last 2-3 years. What kind of battery is rechargeable, and can sit outdoors? From my brief research lipo batterys can't stand outdoor extreme cold temperatures. Currently i'm planning to use 3AA batteries, but that's just a crime throwing out thousands of batteries. With lipo I could integrate a small solar panel to charge it using a lipo charger ic, or nicad, or currently i'm leaning towards a super capacitor and ensuring that the electronics can run a couple days off it.


Any ideas? If you have particular products in mind, please include part numbers/supplier whatever.

[janekm]

No rechargeable, but Lithium Thionyl Chloride batteries are the standard for this kind of application. They have low enough self-discharge for >20 year operation. Very high capacity too so you can get by with not replacing the batteries as often.  Tadiran and SAFT are two well-known brands.
The normal kind don't like high discharge currents but there are special versions for high pulse loads.

[helius]

LiSOCl₂ can operate down to very cold temperatures with relatively low increase in internal resistance. Varta and Eagle-Pitcher are also suppliers from what I remember.
Lithium-ion batteries may also be suitable if you select a type with extended temperature specs. Read the datasheets!

[Nusa]

The problem with solar chargers is that unmaintained small solar panels also have an operational lifetime of a few years. Mostly they need to be cleaned a couple times a year. And if you oversize and spring for large panels to compensate, they are visible and attractive to thieves.

If you've already designed for AA batteries, I suggest something like this as a drop-in replacement: http://data.energizer.com/pdfs/l91.pdf
It meets your cold-weather specs, but they're not rechargeable. If regular AA's were going to last 2-3 years, I'd expect these to run at least 10 years, maybe much more. How long is long enough for this project?

[DBecker]

Many solar lights have continued to use NiCd cells.  They tend to be 'unambitious', accepting lower specific capacity in exchange for robustness, temperature tolerance, and longevity.

Solar cells are always a challenge.  Surface treated glass is good for long life and a bit of self-cleaning, but more expensive and difficult to seal.  Plastics all have vulnerabilities, with UV and chemical being common.  You think you have the perfect enclosure, and then someone's cleaning crew uses ammonia to wipe down everything clear.  Or Goof-Off to wipe away paint drips.

[thefatmoop]

I know there's nicad charger ICs, but can nicads just be connected to a solar panel then just like a zener + resistor to prevent overcharge? I think the solar is out because I can't find high quality small panels distributed in USA for a good price. I always feel iffy on the offers and big distributers like digikey charge an arm and 2 legs. Everything is so pricey on digikey it'd cost about the same to go with a solar panel + 100F capacitor

I saw Tadirans and that looked good but price was out of the question from digikey. This battery from xeno is likely what i'll go with. It says AA, sorry dumb question but that's standard AA alkaline form factor?


http://www.atbatt.com/xeno-energy-xl-060f-aa-36v-lithium-battery.asp

Should power my application for 5+ years

[Nusa]

AA specification is 1.5V, so it's not AA. But it is AA-sized. Looking at their spec sheet confirms that: http://www.atbatt.com/amfilerating/file/download/file_id/515/

It appears you're looking at the button-top version of the battery. You might consider asking if they will sell in AX, T2, or T3 forms. AX = axial leads, T2 = solder pins (1 at each end), T3 = solder pins (1 at + end, 2 at - end). Soldered in batterys are more reliable than battery contacts.
Here's a better spec sheet: https://cdn.sos.sk/productdata/66/ad/0b50ce7c/xl-060f-ls14500.pdf

[Zero999]

Hi,

To very briefly summarize the product i'm working on: It's a sensor box that's placed in a particular environment where they need a lot of them monitoring lots of different things. They're placed outdoors, customer doesn't want to run power to them, must be wireless, run for years on a battery. I've got everything working like a charm with a pcbs/working with a supplier IP67 enclosures.

Here's my dilemma. The company wants hundreds and the batteries will only last 2-3 years. What kind of battery is rechargeable, and can sit outdoors? From my brief research lipo batterys can't stand outdoor extreme cold temperatures. Currently i'm planning to use 3AA batteries, but that's just a crime throwing out thousands of batteries. With lipo I could integrate a small solar panel to charge it using a lipo charger ic, or nicad, or currently i'm leaning towards a super capacitor and ensuring that the electronics can run a couple days off it.


Any ideas? If you have particular products in mind, please include part numbers/supplier whatever.

How cold is cold? 15^oC is cold for the equator, -15^oC is cold for the most of the UK but not for continental climates.

How much sun will this thing get? What about a small wind turbine?

[mariush]

Would a small 6v lead acid  /  lead crystal battery work for you ? You can find them from about 10$ and should be fairly easy to charge using solar power, and buck regulators could be more efficient than boosting from 1.5v to whatever your circuit uses.

Only downside would be the volume the battery has.

(and they should be recyclable, after all the infrastructure should be there to handle car batteries right? may even get money back for them and should be easy to replace in the field)

// or can you shove 2-3 alkaline C or D sized batteries? Those should have A LOT of capacity and may be cheap if you buy in volume.

[james_s]

The outdoor unit of my weather station uses a combination of a super capacitor charged by a solar panel and a CR123 lithium primary cell as backup. In most cases the capacitor is enough to power the unit through the night, at least in the summer. The lithium backup cell then lasts anywhere from a year to several years.

Apparently the super capacitors do fail more frequently than one would like though so that's worth consideration.

[jh15]

NO! NO!

Seal the battery in so not user repairable replaceable.

Have a monthly fee, discounted for a year in advance of course. An Einstein on a John Deer tractor.

Have a service contract up front for about 50 % the cost of replacement.

Slightly increase the features of new models, and make them anorexic.

Slow progress by buying up raw materials plant and production stifling competition.

Make sure liquid damage is not covered in service contract.