Running Moteino from 2 x AAA cells

[Felix]

The 800mA is mentioned in the DS - indeed an input current peak limit. But the MCP will exceed the LTC at load current, that is what surprised me. It can do up to 400mA no problem, see the first page and load current efficiency graph on page 2. I analyzed the graphs and the MCP is as good or better than the LTC according to the DS. The quiescent current is almost the same, I think the LTC can do down to an absolute low quiescent current of 7uA whereas the MCP is 19uA. In shutdown the MCP is <1uA. The other feature of having a higher VIN than VOUT is not something I paid attention but I will need to study that. For now I need to order samples and make a PCB and play with these. The savings are incredible though.

I am finding that chinese LiPos underperform and dont work in very cold temps. They drop out at around 20F. That is surprising considering that Lipos are used in electric cars and other environments where extreme cold should be no problem. The chinese LiPo datasheets mention they work down to -20C which is verified to be false information, as usually is. See this sample datasheet, standard discharge rate of 0.2C, that is 200mA (far more than usually used in my motes): https://www.sparkfun.com/datasheets/Batteries/UnionBattery-1000mAh.pdf

So sometimes we trust datasheets but as I thought I already learned, I find myself to keep getting burned with chinese products that are garbage. It feels like sabotage, seriously, especially after investing a lot of time and money in certain infrastructure. Lipos are still nice for being compact and flat and all that. For indoors they are great. The remaining problem is everybody is now used to the low prices on ebay and other places that sell chinese products and when presented with a better quality product at a higher price they throw their hands up in protest. Why is hardware so hard ... people don't get it.

[TomWS]

<...snip>

I am finding that chinese LiPos underperform and dont work in very cold temps. They drop out at around 20F. That is surprising considering that Lipos are used in electric cars and other environments where extreme cold should be no problem. The chinese LiPo datasheets mention they work down to -20C which is verified to be false information, as usually is. See this sample datasheet, standard discharge rate of 0.2C, that is 200mA (far more than usually used in my motes): https://www.sparkfun.com/datasheets/Batteries/UnionBattery-1000mAh.pdf

So sometimes we trust datasheets but as I thought I already learned, I find myself to keep getting burned with chinese products that are garbage. It feels like sabotage, seriously, especially after investing a lot of time and money in certain infrastructure. Lipos are still nice for being compact and flat and all that. For indoors they are great. The remaining problem is everybody is now used to the low prices on ebay and other places that sell chinese products and when presented with a better quality product at a higher price they throw their hands up in protest. Why is hardware so hard ... people don't get it.

I wouldn't touch anything but a name brand LiPo. I'd definitely avoid an off-brand. These devices scare me to death and will only use them when there is no serious alternative - outdoors I'll mostly accept that I need primary cells and for interior battery backup situations I'll try to use SLA.  It's only when I've GOT to fit a reasonably strong rechargeable into a small space will I consider LiPos, and only if they include the protection circuit (which any reputable battery supplier should).

When I was first looking into LiPos I did some research on safety.  I found one report talking about safety in the RC industry.  Expecting to find a few cases where there might have been a fire, I was stunned to see that the report had cited 177 cases of fire or explosion!  Uh, I know RC industry is somewhat big and certainly rough on equipment, but this, alone, convinced me to treat these with TLC.  Also, having recently purchased some from Sparkfun, the packaging and warning labels they used looked like HAZMAT rating 4!
Tom

[Felix]

The LiPos from adafruit/SF and other popular places are the same as I sourced from china, different shapes and sizes and seem to have very similar "protection circuits". I don't have empirical data to test these circuits and I did not really research if those circuits are legit or not. My guess is they will fail in certain scenarios, I think we can safely assume that instead of giving the benefit of the doubt (we're talking china here, level of trust 0). I don't know if adafruit and others would ever reveal disaster scenarios they hear from their customers - if that has ever happened, my guess is not. They would be ethically forced to stop selling them knowing they are bad and be stuck with potentially thousands of cells in stock (they do buy in thousands to get a decent margin). And they would scare off the maker industry away from LiPos if they would do that. But again... its pure speculation, no data to back that up. I would still expect someone out of thousands of customers and cells sold to have some kind of bad/scary/disaster experience, even if not a house burned but 1 explosion under reasonable conditions is enough to make a big deal.
The HAZMAT labels are regulations they are forced to use, and USPS can't ship loose Lipos.

I have a load of lipos I sourced from china, now I am stuck with them not able to sell them because of all the extra regulations for batteries and low temp no-performance I've observed. I've considered UPS but it's just a big unknown so they are basically a lost investment of a few hundred $.

Anyway, if anyone wants to buy a bunch of LiPos that are perfectly fine in other than extreme temperature conditions (verified 1500mAh Lipos that are more compact that anything afafruit/SF can offer), at a better price than those guys, I can ship UPS, you can contact me. These fit perfectly in the MotionOLED Mote kits I make. I should post this on the blog too...

[ulli]

I did some power consumption calculations with the result of 1,6 years lifetime of an Moteino clone with IR-Diode:

RFM69 is partially in idle and listening mode. Info from DS
   (idle 1004ms and listening 2 ms)
--> 0,041 mA/h
Atmega @8MHz partly in sleep and idle mode
   (awake 24 times a day for 1s)
   (Idle ~ 4mA and PowerDown ~35µA)
--> 0,036 mA/h
MCP1640 step up
--> 80% efficiency, therefore overall current consumption + 20%       
IR Diode
--> negligible small

Overall summary: 0,092 mA/h → 1,6 years with a 1200mA Battery

I am pretty surprised about that result. Can anybody give a feedback if that is plausible?

[TomWS]

I did some power consumption calculations with the result of 1,6 years lifetime of an Moteino clone with IR-Diode:

RFM69 is partially in idle and listening mode. Info from DS
   (idle 1004ms and listening 2 ms)
--> 0,041 mA/h
Atmega @8MHz partly in sleep and idle mode
   (awake 24 times a day for 1s)
   (Idle ~ 4mA and PowerDown ~35µA)
--> 0,036 mA/h
MCP1640 step up
--> 80% efficiency, therefore overall current consumption + 20%       
IR Diode
--> negligible small

Overall summary: 0,092 mA/h → 1,6 years with a 1200mA Battery

I am pretty surprised about that result. Can anybody give a feedback if that is plausible?

I see a couple items missing from your calculations:
Transmit power - pretty negligible with 1 hour between transmissions...
Quiescent current of MCP1640 (19uA)
Current multiplication due to step up (I'm assuming 1.5->3.3V) (2.75 multiplier)

However, even with these changes, I come up with roughly 122uA average which will (theoretically) give you 1.122 years with 1200mA battery.

I don't use listen mode so I don't have any empirical data to confirm your data (or DS).  I do think that a 2ms listen time is pretty worthless.  What I do to send data to the mote is queue up requests to motes in the gateway and tell the mote that the gateway has something for it on the next Ack.  The mote sees the ack and stays awake in receive mode for two seconds, giving the gateway time to start a 'conversation'.  The mote stays awake until all data has been sent or the mote suspends the conversation until the next cycle.  Not immediate data out to mote, but reliable and no wasted power...

Tom

[ulli]

Thanks for you remarks!
Regarding the listening mode....I checked again the DS....I thought the listening mode ist active as default...it's unfortunately not 
I calculated the consumption with just the idle Mode of the rfm....got a lifetime of 3 days....damn!

Isn't there a chance to get a rfm running from battery?
Do you have any proposals? How are you running it?

[TomWS]

Thanks for you remarks!
Regarding the listening mode....I checked again the DS....I thought the listening mode ist active as default...it's unfortunately not 
I calculated the consumption with just the idle Mode of the rfm....got a lifetime of 3 days....damn!

Isn't there a chance to get a rfm running from battery?
Do you have any proposals? How are you running it?

I don't understand your question.  I'm running several from batteries...

[ulli]

I am currently building up a moteino clone with a infrared diode.
The moteino should control my TV.....  The moteino gets his commands over the rfm69. (Radio/IR Gateway)
But in that case I do not know how to run this configuration from a battery because the rfm needs so much power in listening mode...


What are your moteinos do in your network?

[TomWS]

I am currently building up a moteino clone with a infrared diode.
The moteino should control my TV.....  The moteino gets his commands over the rfm69. (Radio/IR Gateway)
But in that case I do not know how to run this configuration from a battery because the rfm needs so much power in listening mode...

If I understand your application correctly, you'll have a moteino in the same room as your TV and it drives an IR diode to control it.  The mote receives commands over its RFM69 rf connection and sends the appropriate IR modulation sequence to the diode.  I have two questions:
1. Where does the RFM69 rf signal come from?  - how does that transmitter 'know' what to send to the mote?
2. Why does the TV controller mote need to be battery operated? It sounds as if it's a stationary device, is it physically isolated from a power source (AC outlet)?

I'm still struggling with your comment that battery operation is not possible, but, I suspect, your application needs more 'on' time than a battery will easily allow.  The KEY question you need to answer is: What kind of responsiveness does your TV controller mote need?  If instantaneous, then, um, you might have some 'challenges'.  If you can tolerate seconds of delay, then there are some 'tricks' you might be able to do - those 'tricks' would rely on Listen mode...  Another pertinent factor would be how many other motes would you like to deploy in other applications.  This is relevant because it's all about 'traffic'.  Traffic accomplishes things at the cost of battery life...

Now, if your TV controller Mote is controlled by a server that is handling TV recording schedules, then we've got a scenario we can deal with! 

What are your moteinos do in your network?

Um, it's a long list if you want to know ALL the motes in the 'plan'...

Right now, it's a short list.  I have deployed three motes but they don't have a gateway to talk to since I've had a, shall we say, 'set back' in the gateway deployment project...

But, I think your interest in what motes are battery operated, correct?

The battery operated motes are mostly deployed outdoors:
Soil Moisture Sensor - many of these so my server can decide if it's time to water...
Liquid Level Sensor - two of these - measures water height in my two water features, so I can autofill them.
Irrigation Valve Mote - for the landscaping sprinkler system and autofillers.
TH_Mote  - battery operated Temperature/Humidity sensor that I drop wherever I think it's worthwhile measuring that stuff...

I have a bunch of Landscape Light motes, but these all run off low voltage wiring, so not battery operated.
The Workshop has Dust Collector controller and a BUNCH of current monitor sensors that determine that a piece of equipment in my shop is turned on so the corresponding blast gate is opened and the dust collector is turned on (or off if nothing's been active for some time). 
There are also a few motes that are variants of the current sensors to monitor various pieces of equipment (eg well pump, septic pump, etc) to make sure something is/isn't running properly.  These, obviously, are not battery operated.

Eventually will deploy mailbox monitor and driveway traffic vehicle sensor, but probably won't get these out this year.  Both of those will be battery operated (and VERY long range).

Tom