Batteries / Solar power

[KarlS]

Three weeks ago I installed a National Geographic 265NC weather station and I already had to replace the fresh alkaline batteries I used to set it up.

Here is the problem: I live in central British Columbia, Canada, and we already had a few days of -25°C and below. I know that these temperatures are very hard on batteries, so I was thinking of connecting the transmitter to an appropriate mains source. But even this won't help as we are prone to repeated and prolonged power outages (up to 5 days at times). Possible solution: installing a small solar panel to power the station during the day and charge a set of NiCad AA's to get it through the night.

I'm a retired software engineer and the last time I used a soldering iron was probably 25 years ago. Does anyone have an easy to follow "recipe" on how to build and connect such a device? Or does anyone have a better solution.

Cheers

Karl

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My Weather website http://www.friendsofbridgelake.org/page.php?id=91

[Station House]

Hi

I can't advise on how to build one (I'm not that clever!) however some versions now have a solar panel with a built in battery which (I think) supplements the AA batteries in the transmitter

Have also seen threads about experimenting with the panels that you get with those small LED garden lights - if i recall correctly people were mounting them well away from the transmitter (to ensure in full sun) and putting a couple in series and then connecting them into the transmitter battery compartment terminals.

I'll see if I can find those threads

Good luck!

[Station House]

A couple of threads below - suspect there are more!

https://cumulus.hosiene.co.uk/viewtopic.p ... lar#p33064

https://cumulus.hosiene.co.uk/viewtopic.p ... ilit=solar

Would be interested to read what ideas Gina has - from her postings she is certainly the inventor/experimenter type!

[Gina]

Lithium batteries are considered to be much better in cold climates and they maintain their voltage better as they age. It's what I use.

I did consider a mains supply but decided it wasn't worth the bother.

[KarlS]

Thank you guys for your replies. I've got an order in for an 8-pack of lithium batteries, so let's see how they will hold up when the mercury hits -40. I will keep you posted.

[bnwrx]

Lithium batteries are considered to be much better in cold climates and they maintain their voltage better as they age. It's what I use.

I did consider a mains supply but decided it wasn't worth the bother.

I concur, It stays cold here in Colorado at 8600' and Lithium's seem to work well and for a long time. They should be fine for you.
Good Luck

[Charlie]

I plan to use the lithium cells when my cheap aklalines die. It's now been a year and they are still going strong, which leads me to believe they are not being depleted much, but rather dying of shelf life because the amount of power used is so low. So lithiums should last a decade, at least.
However, a number of folks have also reported that the transmitter range is a function of battery voltage. A bit or experimenting confirmed this for my 265NC too. So, if you are set up on the hairy edge of range (given wall construction materials, trees, other obstructions as well as actual distance), that would explain your batteries apparently going south so quickly. The voltage gets slowly lower as the cells lose power and the cells may be fine for another application like a flashlight or camera, but the voltage is not quite high enough for enough transmitter range for your signal to get through.
If this is the case, you would get far more benefit out of locating the transmitter / display pair physically closer, than from different batteries.
There is no way your batteries should die in 3 weeks, unless they sat on the shelf of the store for a couple years before you bought them. Try them in something else and I bet they are fine. If they are not fine, then you should return the weather station fast - it has a major defect.

[philcdav]

i guys.

at these temps (< -10) any batteries will struggle so what about insulation ?

It would be easy to extend the battery pack connection and fit some insulation. Maybe encase the whole unit in a foam block. Its easily removed.

And the foam could be free christmas packing or skip hopping produce

My Duracells lasted 2 years without dying and coped with -10

[sanramonrover]

Hi again all,
Just got my system set up in Costa Rica yesterday. No problem with freezing batteries here.
Before leaving Canada I modded my unit as follows.
1- took the solar cells off two of those cheap sidewalk LED lights.
2 - wired them in series (one red to one black lead, leaving a red and black free)
3 - wired them to a dual AA battery pack (red to red, black to black)
4 - glued the two solar cells to the top of a plastic pastille box (it just happened to be the right size, but forgot the brand.)
5 - mounted a power supply socket in the side of the case
6 - installed two rechargable batteries in this case, removed the ones in the remote unit. I can mount this case in a more suitable location than up a 10'pole,


7 - opened the remote unit - had to split it with a knife (as posted elsewhere) as there are no screws holding this together.
8 - wired a lead cut from a small power supply (AKA wallwort?) to the two top battery terminals (pos to pos, neg to neg)
9 - filed a small hole in the bottom joint of the remote unit to allow the lead to exit.
10 - re-closed the remote unit with elastic bands - in case I need to open it again
11. - plug the plug from the remote unit into the socket on the pastille case, and hey presto it works.

Getting 2.75V at the remote unit in morning sun.

I did not use blocking diodes - there seems to be a debate as to whether they are necessary.
I know the plug usually goes on the power source, and the socket on the appliance, but there just wasn't room to put the socket in the remote unit, so my wiring is backwards from standard

As usual here (8 degrees N Lat) we get 12 hrs dark and 12 hrs daylight - not taking into account the very cloudy weather at the moment. So far its working OK.

[Charlie]

Hi philcdav,
Not a good idea. Insulation won't help.
Isulation does not generate heat, it only keeps it in. There is not enough power drawn by this circuit to keep anything warm.
Insulation will, however, cause problems for the instruments - humidity, pressure, and at least the response time of temperature will all be messed up if you encase the transmitter unit in something.

[Gina]

Yes, you need the temperature/humidity unit mounted where it can get plenty of air blowing round it but well sheltered from sunlight ie. a decent Stevenson screen.

[philcdav]

Hi Charlie.

think i might have misled you somewhat.

The idea was to extend the battery pack cable and encapsulate a battery pack remotely from the main kit.

However, you may be correct in that it wont generate heat BUT it might keep the cold out.

That said, i have had no power issues down to - 10C and thats about our limit here in Liverpool

[Gina]

As I recall, lithium batteries are fine at -10C.

[bnwrx]

As I recall, lithium batteries are fine at -10C.

They keep working at -21F also, I have seen proof on my setup..

[Charlie]

As I recall, lithium batteries are fine at -10C.

They keep working at -21F also, I have seen proof on my setup..

And I recorded -29C (-20F) last winter happily with Alkalines. I'm a big fan of lithiums, but as I mentioned earlier, the distance between transmitter and receiver has far more impact, and really drives what voltage you need from the batteries.