Cumulus Support

I suspect this topic has been touched on before. I last changed the Tx batteries 10 weeks ago and this morning the Tx low battery warning is showing in the console.

Does 10 weeks seem like a reasonable lifetime for brand spanking new, not bought at the local market, Duracell AA batteries?

If the general consensus is 'yes' then I can feel an experiment with Ni-MH batteries and solar cells coming on...

Mark(I never knew I had vertigo until I got a weather station)B

I seem to remember someone else posting recently about poor battery life.

Steve

steve wrote:I seem to remember someone else posting recently about poor battery life.Steve

This one is an excellent Solar Power post

https://cumulus.hosiene.co.uk/viewtopic.php?f=13&t=629

but that only implies poor battery life...

and this one:

https://cumulus.hosiene.co.uk/viewtopic.php?f=13&t=536

but that references mainly the Rx unit...


Additional:

I've found a circuit that adds on to a solar powered garden light that claims to be able to produce a regulated 5v output at 10mA. I'm going to make some mods to it and I reckon it *SHOULD* produce 15-20mA at 3v. I *THINK* that might just sneak enough to run the Tx unit - Watch this space!

The Solar PSU results are in! See further down the thread.

If it's of any help, first set of Duracels (as it happens) on mine lasted about 6 weeks. Now a set of Energiser Ultra Alkalines have lasted 4 months so far and seem ok.

Energizer, 3 months and it's ok.

Six months so far for all batteries. Can't remember if they were supplied ones or other alkalines. I have Lithiums waiting in tthe wings.
Dave

Be aware that Lithium cells suffer badly from low temperatures, voltage and current availability dips.

Whatever cells came with the unit back in May or June of 2008 and still working fine.

Solar PSU results:

The results don't look too encouraging at the moment! Not quite the hoped for 15-20mA @ 3v
(Maybe my cheap solar garden lights are too cheap!)
Anyone care to hazard a guess what the current requirement of the Tx unit might be?

Where did I leave that drawing board?...

MarkB wrote:The results don't look too encouraging at the moment! Not quite the hoped for 15-20mA @ 3v
(Maybe my cheap solar garden lights are too cheap!)
Anyone care to hazard a guess what the current requirement of the Tx unit might be?

Where did I leave that drawing board?...

Guess at the milliamp/hour rating of the normal battery and divide that by one year or so they are supposed to last.

Call them 2000mAH / 8760 hours = 0.2283mA or 228uA, but also keep in mind that NiCads are 1.2V whereas the usual cells are 1.5v. Which might mean the Tx range is reduced, also that in cold conditions the voltage might fall even more.

Thanks harrym1byt; I've been thinking down those lines too - although with much more pessimistic assumptions. I'm currently (pun very intended) trying to find out how much power there is in a AA battery. (Discharge it through a 6 inch nail maybe). Could even try to measure the current draw on the Tx (but that's a bit tricky without major surgery).

Using your guestimate (2000mAH) and my observation (10 weeks = 1680 hours) gives about 1.2mA - this thing might just work

Oh darn it! I'm going to have to find out empirically... (I'll wait for a fine, still day though)

I'll post details if it works...

From Wikipedia;

Alkaline battery
An AA-sized alkaline battery might have an effective capacity of 3000 mAh at low power, but at a load of 1000 mA, which is common for digital cameras, the capacity could be as little as 700 mAh

MarkB wrote:Thanks harrym1byt; I've been thinking down those lines too - although with much more pessimistic assumptions. I'm currently (pun very intended) trying to find out how much power there is in a AA battery. (Discharge it through a 6 inch nail maybe). Could even try to measure the current draw on the Tx (but that's a bit tricky without major surgery).

...

Actual amp hour capacity depends on the discharge rate - high discharge rate means low capacity. As already said, mine has now run for 8 to 10 months on the original cells.

Your idea to measure the Tx current flow is probably doomed to failure, because it will vary a great deal between its normal current and the draw when it transmits the batch of data. No need for major surgery - take a small piece of double sided PCB the same size as the cells, add a short wire connection soldered to each side and slip this between any cells connection point.

harrym1byt wrote:take a small piece of double sided PCB

The simplest ideas are usually the best - I hadn't thought of that! Thanks!
You're right about the 'transmission pulse' - I'd never record that without an oscilloscope...

Incidentally; The Fine Offset website claims a run time of up to 2 years on alkaline batteries and nobody has yet corroborated that!

Well I've done the test and there simply isn't enough current from the circuit I am using. But I've learned a lot from the experiment so I'll keep banging on at it because I am sure there is a solution out there. (It's very probably next to the truth...)

I'll post it when I've got it.

Mark