4.2. VP2 & Vue Station ‘Low battery’ warnings

Overview

This topic refers only to low battery warnings from Vue and VP2 wireless transmitters (or what are reported as messages similar to ‘Low battery on station #1’). A station low battery warning is obviously only ever seen with wireless stations and not with cabled units, which have no transmitter battery. The clue is in the word ‘station’ that appears in the warning message. Console low battery warnings are dealt with in the console section.

These warnings will be seen in the message or ticker area of the VP2 and Vue console display, but analogous warnings can also be seen if you’re running the Weatherlink software and look in the Alarm and Battery Status option available on the main Window menu.

Wireless repeater units will report similar low battery warnings, in which case the message in the console ticker will be eg ‘Low battery on repeater A’

Background

*Wireless transmitter battery: The most obvious cause of a low battery warning is of course that the transmitter battery needs replacing! The battery required is a CR123 (sometimes labelled CR123/A) type which is a lithium battery of a small cylindrical torch-cell type often used in digital cameras and other digital devices. It should be fairly readily available from most battery outlets, including e.g. larger supermarkets, Boots, camera shops and the like. It’s is also readily available from online shops, but do buy from reputable sources and not e.g. eBay where low quality copies may be sold. Note that this is not a rechargeable battery; rechargeable CR123 cells can be found but should not be used – they have a different voltage characteristic and in any event the Davis transmitter circuitry cannot recharge them.

All modern Davis wireless transmitters (ISS; Supplementary wireless transmitters such as the Anemometer Transmitter; and wireless repeater units) are powered in a similar fashion: The circuitry typically has three three sources of power: a small solar panel; a ‘supercapacitor’ (‘supercap’) component; and a backup lithium battery. (NB The 6372 and 6382 Supplementary Temp and Temp/Hum stations originally had no solar panel door as standard, although one may optionally be fitted, and in recent years 6382 was given the solar door. Now that 6372/6382 have been discontinued in favour of the 6332 multi-sensor transmitter, any new supplementary transmitter will automatically have a solar door.) These three power sources work together in harness as follows:

When the sun is shining brightly then the solar panel provides power for the circuitry. Any surplus power is used to charge up the supercapacitor, which, as a 10 Farad component, can hold a considerable amount of charge for its size.

As night falls, the solar panel can no longer provide any power and the circuitry switches to use the supercap as its primary power source. The supercap can hold enough charge after a bright day in summer time (long days and short nights) to power the transmitter for the whole of the night-time. But for much of the year, the supercap will be exhausted after a few hours of operation and the circuitry will then switch automatically to use the backup battery as the power source. At dawn, the solar panel will start to function again and will take over from the battery.

The transmitter circuitry is very efficient and the back-up battery will last a considerable period. Indeed even without solar panel input (eg as in the 6372/6382 transmitters) the battery can last 6-9 months. The role of the solar panel is effectively to extend this battery life still further, typically to 18-24 months. But nonetheless the battery will of course eventually expire and need replacing, which is clearly when the Station ‘Low battery’ warnings are designed to show and alert the user to the need to change the battery in the relevant transmitter. In normal operation there is usually no need to panic when the station low battery warning appears – typically the unit will not stop transmitting overnight for at least 1-2 weeks.

In stations with just a single transmitter then obviously there can only be one transmitter battery that needs changing. In multi-transmitter configurations then care must be taken to read the ‘Low battery on station #1’ message accurately. The digit after the # sign will indicate which channel number is flagging up the low battery condition and hence the fading transmitter can be identified.

Troubleshooting transmitter battery issues

*Note: Once triggered, a low battery warning does not reset automatically until midnight. So even if you’ve inserted a brand new battery, the warning may not disappear until the next day – this is perfectly normal. Occasionally the first midnight reset doesn’t work and it may take 2-3 days before the warning disappears – provided the outside data is being received normally this is not a cause for concern.

*New stations: The wireless transmitter can start to transmit once significant sunlight reaches the solar panel. If this happens before the battery tab is pulled to allow the battery to start operating then a transient low battery warning may be triggered. This is just a quirk of the set-up procedure and can be ignored (unless of course it continues for days after the initial set-up).

*Do be sure to check that the transmitter battery is making good contact with its holder and of course is the correct way round.. It is not unknown for the battery contacts to become tarnished or bent a little such that they no longer make firm contact with the battery. So even though a good new battery may have been installed the power may not be flowing adequately to the transmitter cicuitry.

*On VP2 stations, ensure that DIP switch #4 on the SIM board is in the OFF position. The ON position should be used only for troubleshooting wireless reception issues. If switch #4 is inadvertently left on when not required this will steadily drain the battery and hence cause early but genuine low battery warnings. This issue does not arise with Vue stations (unless the channel selection/check button is somehow stuck at the in position.)

Low battery warnings can be genuine (ie the battery really is running low) or spurious (the battery is actually fine, but a false warning has been triggered). It is important to distinguish between these two possibilities – a spurious warning is a minor nuisance but the station will continue to operate perfectly well. Even genuine low battery warnings typically happen well before the battery is actually exhausted and so there is no need to panic if a warning is noticed – you will usually have a week or two in which to swap out the old battery with a new one (but obviously do not wait too long!).

The reason that spurious warnings might happen is as follows: Data packets are transmitted continuously by the ISS every 2.5 seconds or so and any data packet can contain a low battery warning flag. Once even a single such warning packet has been received then the console may display the low station battery warning until midnight of that day, when an automatic reset should occur. So if there’s a voltage misread in any one of the ~34,000 data packets transmitted daily then the console low battery warning may remain activated after the trigger packet has been received until midnight of that day.

If a transmitter is left too long after a genuine warning without changing the battery then you will notice the sensor data from that transmitter dropping out overnight. (During daylight hours, unless the light levels are very low, the solar panel will provide sufficient power to maintain data transmissions.) For many users, the main ISS will be their only sensor transmitter and so the chief symptom will be that all outside data goes missing at some point overnight, but with inside data and pressure readings still being recorded OK. But if you have eg an anemometer transmitter or other supplementary transmitters then it will be data from that specific transmitter that is not being received overnight.

If you start to see repeated low battery warnings with a short battery life (weeks to a few months) and you conclude that the warnings are genuine (data starts to go missing if you don’t change the transmitter battery) then you probably have a supercap problem – see the supercap faults topic.

*Note: it is also always worth double-checking that the battery is firmly in place and that the battery contacts are not dirty or corroded – this is uncommon, especially if the unit has always had its battery in place, but can be more prevalent with older stations, particularly Vue models, or if used in a more corrosive environment, eg at a coastal location.

Vantage Vue station low battery warnings

The voltage monitoring circuit on Vue transmitters seems somehow to be set too sensitive on some Vue stations and may have a tendency to generate spurious station low battery warnings. Of course you need to satisfy yourself that the warnings are spurious and not genuine, as outlined above. But if the battery is relatively new and ISS readings show no sign of dropping out overnight, even after eg 3-4 weeks, then the warnings probably are spurious.

If you have an older Vue console which is still running the original firmware then one solution that might help is to download and install firmware v3.00 from the Davis website . NB But do not download firmware later than v3.00 (eg v4.18) unless you have a console of MB or later hardware revision. v3.00 firmware requires that the console receive multiple low battery flags before it activates the console display warning and this largely, although not entirely, alleviates the problem.

On a few Vue systems the low battery warning can remain persistently though spuriously activated even if a newer firmware version is installed. Once you’ve concluded that the warnings really are spurious then on such systems there is regrettably little more that can be done, short of replacing the Vue ISS wiring harness (and thus effectively fitting a new voltage monitoring circuit). If the station is continuing to run perfectly well then these low battery warnings are best ignored – the continuing warnings are certainly an annoyance but nothing more. The transmitter battery can be replaced at eg annual or 18-month intervals to keep the transmitter running normally.

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