3V battery for door sensor node.

[ahmedadelhosni]

Good topic. I have been lazy since a month to ask the same question regarding best batteries do people use for battery powered nodes ?

I have thought of using AAA batteries but I really do not know which categories do I go with. Lithuim or Alkaline ?

If you check this link https://d2ei442zrkqy2u.cloudfront.net/wp-content/uploads/2016/03/MN2400_US_CT1.pdf

You find that the Alkaline battery can operate till it reaches 1.0 v for more than 1200 service hours. So two in Series will give me 2v which are still above 1.9 for the atmega and nrf to run.

But also if you check lithuim batteries.
http://data.energizer.com/pdfs/l92.pdf

It also operates for 1200 service hours at 1.4v before the battery dies quickly.

My question. Why would I choose a more expensive option (which is Lithuim) although I can use the Alkaline which is much cheaper and may be half the price ? Will the performance is better with steady voltage using lithuim ?

Thanks.

[mfalkvidd]

@ahmedadelhosni with most low-power nodes, we're talking >10,000 service hours. With those low drains, the self discharge of the battery becomes much more important than how much they can deliver at 1mA drain. Unfortunately, neither of the datasheets you link to contain self discharge. I don't know why they don't include it. The ENERGIZER L92 specified a shelf life of 20 years though.

https://en.wikipedia.org/wiki/Self-discharge#Typical_self-discharge_by_battery_type lists typical self discharge for some battery types though. Lithium-metal is better than alkaline batteries, which is better than (rechargeable) Lithium-ion which is better than (rechargeable) NiMh.

In short, yes it is probably better to choose a Lithium battery because the alkaline battery will have self-discharged after ~5 years while the Lithium battery can go 10 (or more).

[Nca78]

In addition to what @mfalkvidd said, when you use nrf24, the lower the voltage the lower the emitting power, so the quality of your radio link can decrease and you can lose messages, meaning your sensor could appear unreliable or have to resend the message a lot a lot meaning shorter battery life.

But if you have a really low power node you will have a very long battery life (2-3+ years) with standard AAA so I would go for a good quality alcaline (not a cheap one to avoid leaks ruining your sensors). And if you see you have range problems when voltage goes lower then switch to lithium version.

[scalz]

@Nca78

Any good suggestion for that ? I'm making a breakout for TPS61098 to test, but if you have other suggestions of similar chips I'm interested :)

I was thinking to these boosters. They are nice, I used them in a old multisensors project I showed here.
Hmm.. it's not at all handsolderable, what happens ?! :stuck_out_tongue_winking_eye:
I'm kidding ;) I'm the same, I don't like to be limited by parts choice.

This booster is very small, but 6 pins only if i remember. better use good parts, good shielded inductor, good planes etc to reduce emi, improve efficiency etc.
I moved to different battery types because I wanted more discrete nodes, or simplicity, and between AA/AAA there is not a big profile difference. But I still have a recent design with this booster, for a usecase.

[gohan]

@scalz you forgot to add some links :D

[scalz]

@gohan which links ?

[gohan]

@scalz said in 3V battery for door sensor node.:

TPS61098

where you referring to this booster? I thought you were talking about another one you had

[scalz]

@gohan
yes these one; I have different variants but the family is TPS6109x.
I made a multisensor two years ago with this booster (published a preview in the forum). works well, but finally I published an other multisensor, which was cheaper, on coincell. But still not enough cheap for people ;)
Now I prefer to have just a few projects&revisions, than too much. to save time and support. So I carefully sort my stuff :)

[Nca78]

@scalz said in 3V battery for door sensor node.:

This booster is very small, but 6 pins only if i remember. better use good parts, good shielded inductor, good planes etc to reduce emi, improve efficiency etc.

Yes I sticked to what is suggested in the datasheet and bought everything from arrow. But in the end it takes more space than expected so I'm not sure I'll make the board...

[scalz]

@nca78 said in 3V battery for door sensor node.:

Yes I sticked to what is suggested in the datasheet and bought everything from arrow. But in the end it takes more space than expected so I'm not sure I'll make the board...

yep it was another point i forgot to mention..

[skywatch]

Thanks for all the input and ideas - I'll go with cr2032 and see how it goes. Batteries, holders and ceramic caps are all on their way, so time will tell on this one.

Thanks all! :)