Weather Data Backfill After Power Loss

I have owned a Tempest Weather Station and a Tempest Hub Power Bank for several years. During this time, I have had two time periods where power was lost for several days. In both of these cases, I got some data backfill but nothing anywhere close to the amount that was ultimately missed.

For example: As a result of the recent storms in Houston, I lost power at around 6:15 PM on Thursday, May 16, 2024. I did not get power back until around 9:47 PM on Saturday, May 18, 2024. However, my data was only backfilled to 8:22 PM on Saturday, May 18, 2024. Needless to say, this was quite disappointing.

Has the data backfill after a power loss been thoroughly tested? Can anyone explain why my unit was only able to backfill a little over an hour’s worth of data when it was ultimately missing over two day’s worth of data?

Does the tempest hub correctly wait for both wifi and internet connectivity to be obtained before attempting to backfill data? Does the tempest hub “handshake” each and every backfill data item to ensure it has been properly received before moving on to the next item?

At this point, my hub power bank seems like a fairly worthless purchase. According to the tempest website, a hub with a power bank should be able to store up to seven days worth of data during a power loss. Clearly, I am not getting anything anywhere close to this!

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There have been one or two long discussions on this over the years. The Tempest stores some data if it can’t reach the Hub. The Hub stores some data if it can’t reach the WF servers across Internet.

If you lose power, your Tempest can’t reach the Hub (unless that is on a UPS) so you’re in that scenario.

Bottom line - you need your Hub on a UPS to be power-loss-safe…

The FAQ has the details -

"* Will I lose data if my Hub/station experiences an outage?
Power Outage
Sensor devices can store about an hour worth of data and will continue pinging the Hub to reconnect. Once power to the Hub is reestablished and the devices reconnect, stored device data will be offloaded to the Hub for publication.
Tip: In the event of a prolonged power outage, you can power the Hub with an external power bank. The hub requires a minimum 5-Watt (1 Amp @ 5 volts) power supply. Make sure the power bank you select has pass through charging ability, meaning it will charge itself (from the wall) at the same time it powers the Hub. For reference, a 10,000mAh battery capacity can power the Hub for over 72 hours.
Internet Outage
Sensor devices will continue transmitting data to the Hub. The Hub can store about a week of data from one Tempest. Once internet connection is restored to the Hub, it will publish the data. Tip: The Hub is able to publish the data locally (UDP, BLE) as long as it has power (setup UDP broadcast and/or leave the app open on a Bluetooth connected device).

Sorry, I think your response has me a little confused. As I clearly mentioned in my original message, I have a Tempest Hub Power Bank (i.e. Unless I am not understanding something, I am fairly certain this device should be able to allow me to have data backfill up to seven days upon a power loss.

Additionally, I did get some data backfill after my power loss – just not nearly as much as what should have been provided given the existence of my tempest hub power bank.

House Power Off = Thursday, May 16, 2024 at 6:15 PM
House Power On = Saturday, May 18, 2024 at 9:47 PM

The Tempest app shows no data after the power loss until Saturday, May 18, 2024 at 8:22 PM. As such, I did get some data backfill (specifically, 1 Hour and 25 Minutes). But, I was obviously expecting much more data backfill (specifically, 2 Days, 3 Hours, and 32 Minutes).

What possible explanation could there be for receiving some but not nearly all of the expected data backfill?

Have you opened an issue with the WF support team? Certainly the backfill should do better than this (I personally have seen better), but only WF can really dig in and understand why you are not seeing the same performance.

I assume at no point during the power outage did the hub loose power? Not even for a few seconds? You got 1 hour 25 mins which sounds like the sort of backfill you would expect when the hub is powered down, but the Tempest device remains active

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ahhh - I must have misread things - I thought you meant the power booster on the Tempest (I guess)

The 85 minutes of backfill makes me think (wild guess) that your power bank might have not been charged or it had somehow been failed and you didn’t know it. But that’s just a complete guess.

I unplugged my hub yesterday by accident. Last night I remembered to return the plug. All systems perfect!
Zero data loss that I can find, most impressed

@peter - Yes, I have opened an issue with the support team. So far, they just asked to me send pictures of the hub power bank when it is plugged in and when it is not plugged in. When the hub power bank is plugged in, all four of its leds are lit and the hub’s led is green. When the hub power bank is not plugged in, all four of its leds are again lit and the hub’s led is red. As to whether or not the hub ever lost power, I can only say it was plugged into the hub power bank during the entire power loss.

@vinceskahan - The hub power bank is always plugged in to an outlet. As such, it definitely should have been completely charged during the power loss. If it wasn’t charged (or was not completely charged initially), I would think there would have been no data backfill rather than some backfill. After all, it’s going to lose charge and not gain charge during the power loss!

I do find the last sentence in the section of the faq you copied to be “interesting”. Specifically, I can think of several interesting scenarios that may not be typical but still should be able to be handled without any issue. Here is one…

  1. House power (along with wifi and thus internet) turns off (for some non-zero time).
  2. House power turns on (but wifi and thus internet is still not on for some non-zero time).
  3. Wifi turns on but internet remains off for some non-zero time.
  4. Wifi remains on and internet finally turns on.

Based on the faq info, it sounds like the hub might publish backfill data locally after Step 3. But, it should hold off on sending the backfill data back to the tempest servers until after Step 4. But…does it???

@john.butt - Please note that the scenario above is probably at least a little if not a lot different than the scenario you mentioned. Specifically, I suspect your hub was able to connect to wifi and the internet almost immediately after your plugged back in your hub. In my case, I know it takes several minutes for wifi to get up and running after a power loss. Moreover, I know that it usually takes my internet several minutes beyond that to get up and running. Is the hub able to properly deal with the wifi taking a non-trivial amount of time to get up and running once power has been reapplied to the hub and does the hub also correctly wait for internet connectivity to return before attempting to backfill to the tempest servers (or at least get stalled until it does)?

No idea. There were a lot of discussions about backfill scenarios a couple/few years ago but best of luck battling the forum software to find those discussions.

It would be nice if WF had an API for querying the Hub and Sensor for their cached data. I know weewx supports backfill to ‘its’ db for gear supporting querying for all cached values (Davis datalogger which saves a week+, to name one).

This is the part that might be the issue. At least on the first batch of Hub Power Banks, the output power would cycle off when it lost power. I haven’t gone hunting for mine to test what happens when it is plugged back in. I know several of us complained about this behavior so maybe WF changed the design of the output to be always on. If the output loses power when the Power Bank is reenergized, that would wipe all the data stored in the hub, leaving only what the Tempest had stored for backfill.

That being said, my sister had her Wi-Fi set to be off between around 11pm and 6am and the backfill of data never completely filled the void. I’m suspicious that some hubs were fitted with less backup memory that they were supposed to have.

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@gizmoev - Yes, I recall reading about the hub power bank’s output power being cycled upon losing power several years ago. At that time, I assumed this was no big deal since the tempest folks would presumably only sell us an item they had fully tested and qualified to guarantee proper backup operation of the hub. Unfortunately, I now think this was a rather bad assumption on my part.

I can easily envision a scenario where power might turn on and off several times before it stabilizes after a long power loss. Since I was not at home, I don’t know whether or not this happened during my most recent power loss. But, I have definitely seen this occur during other power losses at my home. If the power does not come up and stay up for at least as long as it takes the hub to upload its backfill, it is easy to see how the data could get lost. Frankly, I pretty much view the tempest hub power bank as almost completely useless since it seems it cannot handle this situation (which often occurs in my experience at my house). Currently, I am thinking this is the most likely reason for my most recent data loss.

Can anyone suggest a good usb power bank that provides passthru power capability and does not cycle its output power when it loses power?