Sky battery life

sky
battery
lithium

#21

That would make sense. We had snow that was ontop of it and it did melt off. It shows 2.7v battery but says error on air. It says its online. The software just has dashes for windspeed and uv/lux. I am going up the tower tomorrow. Shud i change the batteries. The last time i changed the batteries I opened the battery compartment and closed it and it seemed to reconnect to the hub but I change the batteries anyways. Should I change the batteries this time or just try to open the battery compartment door Andre close it and see if it reconnects and try it that way


#22

Please contact support@weatherflow.com or http://got.wf/contact and they’ll help you troubleshoot more and can ship you a new SKY unit if necessary.


#23

When I first received my Sky I put in Energizer battery’s. I was a little surprised when they went flat in less than 2 weeks. On recommendations I bought the Ultimate Lithium at AUD$4.50 each . They have been is service for more than 6 month, through winter and into summer. Initially the voltage was around 3.45 but over winter slowly dropped to 3.30. Now it warmer (ok hot) the voltage has risen up to just over 3.50.


#24

I just replaced my Sky batteries. Four were just under .5v and four were just under 1.5v. Not sure if it matters where the four under .5v were positioned and I did not pay attention. All eight batteries were positioned positive end facing down. I think its interesting that there were four bad ones and four pretty good ones at 6.5 months. Original 8 lithium ultimate came from a single 8 pack.
All in all I am very happy with my WeatherFlow station.


#25

I agree this seems non-intuitive until you understand the discharge profile of the lithium batteries. It is nearly flat for a long time and then drops extremely quickly - the voltage output “falls off a cliff”. The point where the SKY stops operating is when enough of the batteries drop off the cliff, but they don’t all hit the cliff at the same point, thanks to normal variability in the batteries. So, your 0.5V batteries have already fallen off the cliff and the batteries that are just under 1.5V are likely to be near the edge of the cliff:

image
By contrast, alkaline batteries have a much smoother discharge curve and drop below 1.5V in the “flat” section, so your “dead” batteries would be more likely to have similar voltage levels:

image

(graphs are from http://data.energizer.com/pdfs/l91.pdf and http://data.energizer.com/pdfs/e91.pdf)


How long do Batteries last?
#26

On the 25th of Jan the battery voltage in my SKY decreased rapidly.
It went from 2.76v to 1.95v before the SKY and hub lost contact.
I’m using the recommended batteries and have power save mode enabled for sample data.
Any ideas?

Last night I got to the unit and checked the batteries - all were inserted correctly, but two read 0.5v.
I binned them and put in two others, unit is back on line - but the voltage has jumped from 2.68v to 3.07v since last night - will see how they fare out.
My station id is:2638

-Coley.


#27

Hello Coley

I moved your post in this thread, the answer is the post just above yours …

Hope this helps to understand why is falls of the cliff.


#28

damn I missed that and I thought I had searched thanks for linking.
how long are they expected to last? - I see above ~1yr
The first set were alkaline but lasted longer than the second set, lithium ones, granted most are good and reading ~1.7v

-Coley.


#29

depends, I have a sky running for 214 days now (not in safe mode, so full throttle) and batteries are sill giving 3.11. My other sky (admitted a test version giving way more data) lives hardly 10 weeks

We have seen both cases with production nits.

How long did they last for you ? And what were conditions mostly ? Extreme cold periods ??


#30

The alkaline set lasted from 24Jul to 25Nov.
The lithium group of 8 (as only two have fallen off the cliff) lasted from 27Nov to 25Jan.
But the remaining six from that pack are still operational now.

No real cold extremes most temps haven’t been below 0degC

-Coley.


#31

seems pretty short to me

Maybe the lithiums had a bad lot in them … would be surprising but never say never they told me …
Keep a close eye and if they fail again to soon, then maybe time to ask support to have a look. Maybe the sky drains to much power (some units had the problem and were replaced)


#32

It would seem that at least one of the cells is that pack was defective. What you experienced is not typical.


#33

I actually am starting to think that it is typical. I am growing increasingly suspicious that there is a booming gray market for rejects and seconds from Energizer’s factory, and even major retailers like Amazon (direct, not resellers) are being sold the rejects without knowing about it.

This bunny is not amused…

image


#34

Hi @coley.curtin
I also had trouble searching for this thread in the past and only just found it now due to the ‘new’ posts.
I live in a slightly warmer climate than you where it never freezes so I find Alkaline very satisfactory and much more economic. The lithiums are required where it freezes but otherwise Alkaline work perfectly. I have discussed my findings in this thread:


cheers Ian :slight_smile:


#35

That’s where ‘tags’ come in handy. One can search for “battery” and find some useful posts.


#36

Hi @GaryFunk,
I had previously read about the reference to the cliff voltage drop of Lithium and had tried to find the discussion using search and for graph examples by looking at actual weather station public voltage graphs. I searched for ‘Lithium’ but didnt find THIS thread. Now when I search ‘Lithium’ this thread is still 15 down the list. When I now search ‘battery’ it is nearer to the top but I guess I was specifically looking for the lithium cliff so probably didnt search on battery which I thought would appear in many threads. What do you mean ‘tags’?
cheers Ian :slight_smile:


#37

This topic is tagged with sky and battery. In the old days, they were called ‘keywords.’

To search tags, in the search bar enter

tags:battery


#38

Nothing new to report that is not already here - Sky voltage went bye-bye Sat eve.
Batteries were Lithium and 5 months old.
Typical curve for Lithium batteries - was hoping for longer than 5 months.


#39

When my Sky’s batteries died after 8 months, they were down to about 2 volts. What I thought was weird, was that half of the batteries registered as dead; and the other half were not yet to the “Replace” point on my battery checker. I saved the ones that were’t dead. I’m thinking they could be used in my AIR, as a backup.


#40

See above. Unlike alkalines, the Ultimate Lithium discharge curve is very steep: they chug along for a long time at a “good” voltage" and then they “fall off the cliff” all of a sudden. The ones that still looked good are likely almost dead!