Well, that SAFT model is quite expensive for that capacity. You can always go directly to the Chinese manufacturers, they are more than willing to send out samples, for instance www.gmbattery.com or www.eemb.com or www.yataenergy.net . I’ve been quoted a price of about $10 for a very large (12cm long) 36Ah 3.6V battery (max constant current 450mA, max pulse current for 15 seconds 1000mA). They quoted about the same for 2 x 14Ah batteries in series (for 14Ah at 7.2V).
However, these are in quantities of 500+ (although they might be persuaded to sell them in smaller quantities).
Question about the April dev board power requirements:
Can it run on 2 x AA ?
The input range for the buck convert (TPS62172DSGT) is 3 to 17v
Non discharge AA battery voltage is typical 1.5 to 1.65v
BUT typical battery voltage (brand dependent) is 1.1 to 1.3 under a continuos 200mA discharge.
Use case: WiFi is ON and downloading new firmware so current draw is 200mA for a few seconds not the typical usec during “normal” operations. Will this not bring down the WiFi as input voltage to the buck converter would be 2.2 to 2.6 volts?
You don’t want to feed 2xAA’s into an april’s power supply, because it’s a buck. You’ll be operating below the supply’s output voltage and as such you’re just burning extra power for no benefit.
As I noted above, you need a boost and you really need to use lithium AA’s for good performance.
Least hassle is the LTC3528, as seen in the flora ref design:
…but trim it to boost to 3.0v instead of 3.3v - this improves efficiency. This, however, is about 12uA Iq so your total sleeping power is almost 20uA. It’s also not a cheap part.
Nora uses a Torex XC9128 which is enabled by a line on the imp; this allows a true 6uA sleep. We’re still updating Nora to rev2, but I’ll see if I can get someone to post the rev1-with-bugfixes design for you.