Tempest voltage levels and power save modes, no rain detection etc

We are heading to winter (north side of the world at least) and our sun is giving less power.

Some Tempest devices are sitting in the shade most of the day, some don’t see any sun at all. In summer time this is mostly not a real problem but in winter … The battery can run the Tempest quite some time but without a few hours of sun (more than 300w/m^2) on a regular basis, it will deplete. And as it goes down, the power saving modes kick in to help it stay afloat as long as possible. We hear people say their Tempest doesn’t detect rain … but they didn’t look at the battery voltage. Once it is in mode 3 the haptic sensor is turned off completely, hence no rain detection.

This page explains in more detail the battery from the Tempest and the voltage levels.

Before opening a support ticket or a topic on this forum, please do check your voltage and siting of the Tempest. Often relocating it where it sees direct sunlight is enough to get it going again.

Compare the solar radiation graph and the battery voltage. The battery will really start to charge above 300w/m^2. If your solar radiation graph shows none or very short periods above that level, your battery will not keep up. Several days (cloudy days for ex) should not be a problem. Once the sun shines again, the Tempest will charge quickly to nominal again.

If you still feel it is more than a siting problem, do report here or you can contact customer support and we will help you out.

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Is there a point voltage wise where the unit will not report at all?

Typically right about 2.3V since that is when the Tempest shuts down until it can get charged back up.

thanks… that puts my unit offline until it gets some sun… bummer… its the rainy season in Seattle… not sure it will come back online for a while.

i’ve seen comments of some who put a “lamp” at the solar panels but that seem incredibly inefficient and i don’t really want to take down and put up my system every couple of weeks (as that seems to likely throw off the integrity of my measurements if I have a periodic “bench” period)… curious if anyone else has some suggestions (other than wait for the in-dev power pack)?

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I’m one who used a 250W lamp to charge up a Tempest. It was a very early field test unit which didn’t make it through that really dark time we had last winter. This was before the different power save modes and when I’m think the firmware was still running all of the debugging code.

It looks like your unit was charging fine in the summer. Is it getting some shade now with the sun low in the sky or is it just the cloudy weather?

Its a two part solar challenge…We havent had a nice cloud-free day in two weeks (pnw normal fall storminess) and i live in a forested area where the sun is above the treeline for maybe 4-5 hours daily (i have my sensor on the north end of a clearing centered between the trees). I would get a bit more solar panel sun-time if i lifted the sensor (its currently 2m or so above the ground) so maybe i could relocate it? To the top of my nearby barn. But thats also closer to trees on my property and may have more obstruction influences (always trade-offs). But if it gets me just a bit more power…?

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I wondered if that might be the case. I figured we had somewhat similar weather but thought you might have a bit more fog. I happen to have a relatively clear southern exposure so my Tempests have been hanging in there.

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So if the voltage drops low enough to turn the tempest off entirely (2.33V for me) - will the tempest come back online automatically after enough sun? Or will i need to go through any rebooting / reinitializing process?

I can’t say I ever did nor did one of my Tempest go offline this way but since they come back after a reboot, I suspect they will come back online once there is enough juice in the batteries. Maybe someone with real field experience can tell ?

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Yes, it will come back online after enough sun. Assuming nothing is wrong with the Tempest, of course.

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What type of artificial light will charge a Tempest?

I’m in Washington state, near Portland, OR, and my Tempest has been below 2.3V for the last 3 weeks. I tried tilting it up to get more overhead exposure on the panels but it did not help. I bought this device for rain and wind measurements and in winter months it turns out to be useless. It amazes me there is no provision for an external charger.

I tried bringing it indoors and set up a work light about 10 feet away. All it did was report 110F temps but did not charge at all. There are so many light types, (incandescent, halogen, florescent, LED, etc) but what works best and what frequency light do I need? Perhaps ultraviolet or infrared would work better than visible white.

I used a 250W heat lamp placed far enough away to keep the Tempest temp below 100°F and has a couple of white Styrofoam pieces on each side forming a corner and was able to charge a very early Field Test unit.


I’m in Kelso so we have similar weather. So far all the Tempests since the early one has been staying charged so far. I wouldn’t worry about trying to charge the Tempest until it drops closer to 2.3V because it will mean you get even less data recorded during the artificial charging.

That said, what is your Station ID or link to it to see if maybe it has some charging issue.

I mistyped my voltage and said 3.4V but I meant to type 2.3V (since corrected above).

I do get a small amount of charging on some days, but not enough to turn on rain reporting, again.

If I knew the pin-outs on the 4-pin connector I might try my own charging (using a voltage and current limited power supply). This is a very low-voltage device but a few mA trickle should help. Seems like they could supply a charging adapter so we could buy a few days of operation at a time.

You have to leave the power switch on during charging and you need to leave the hub powered up so you can monitor the charging progress, but that means if you are indoors it’s sending bogus data to Weather Underground unless you deactivate the link. Very annoying.

What is your siting like? Is it getting more shade now than earlier in the year? If it is still getting a good view of the sky then maybe it has charging issue. That is why I asked what your Station ID was.

WF is working on an external power option which I think you’ll like. Not sure when it will be released but the design specs look really good.

For what its worth, 11 days later, my unit got just enough of a recharge to come back on in Mode 3… no interference on my behalf the entire time it was down. Got a notification on my apple watch while i was away from home and did a little public happy dance… now if only it could charge up enough to stay alive.

I agree with @general.delivery , an ability to charge via a wall-wart or a 12v battery and/or the much anticipated power-pack would be welcome as the sensor doesnt seem capable of currently surviving a dark PNW winter in my region surrounded by tall trees. Missing out on the most active weather period for the greater Seattle area is a bummer for me

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Absolutely would be a nice feature to be able to do a charge for a day to buy a week or two in the usual dark, grey, wooded Seattle area. My Tempest has been offline now for a couple of months even while being in the sunniest part of our yard. But sunny is a very relative term when the sun has to cut through 100’ tall Douglas Fir trees because of the low sun angle.

And, yes, an external power charger should trigger an “offline” signal so that data is neither recorded locally nor transmitted to either WeatherUndeground or WeatherFlow’s AI prediction system.

Having same problem with low sun angles/cloudy days. First rain sensor shut down (happened before w/ low power) now, with 2.33 volts - offline

perhaps I should mention my suggestion here as well… add an option to set sampling rate not faster than once every 15 seconds (just as the sky). This should help the tempest unit running longer, before it drops to sampling once a minute or worse. (@dsj).

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I like your last two sentences. I’m patiently waiting for this item to climb aboard the “Tempest Train!”