Has anyone used a 9V battery to power the April Board / Imp?
I’ve seen examples of a 3 or 4 cell (AA battery) battery packs, but not a 9V battery clip. After all, there is a voltage regulator on the April Board. I can’t see why it wouldn’t work, but I want to make sure before wrecking an imp.
you can power your board up to 17 V if I recall correctly.
9v battery will work fine - in fact, we have various devices made of a 9v battery and an april 
So I did some online searching …
I’m thinking that using 4 AA batteries will last longer than a 9V battery.
So I bought a 4-cell battery container at Radio Shack.
Maybe I should do a comparison and see which lasts longer using the same program, I/O, and components.
a typical 9V battery is 500mA/h, at 9V = 4.5W/h
a typical AA battery is 2000mA/h, *4 = 6V = 12W/h
Remcohn you should consider using lithium AA as standard AA drop their voltage over time. Hugo might laugh at this but I’ve been bypassing the voilage regulator on the April and feeding imp direct on 3.3v op pins with 2 AA cellsI have 4 imps running this way for months.
http://www.powerstream.com/AA-tests.htm
Well, there’s the answer about 9V batteries … not even a close race.
Thanks for the info. I’ll stick with my AA batteries (and switch to Lithiums also).
@controlCloud yes, lithium AA’s rock - and powering an imp directly from two of them works well - the problems only come when someone puts plain alkalines in there (or NiMHs)!
Hugo hoping Nora-batty 2 might help with that sure to happen scenario?
One further question I know voltage isn’t a good indicator as to the state of battery but want to do a crude indicator but can’t find a good rule of thumb voltage for a empty AA lithium?
//NiMH
1.2 V = Full
1.16 V = Empty, Recharge
// lithium AA’s
1.5 V = full
1.XX V = Empty
Thanks as always
I suppose you could use an A/D pin on the imp to report battery level to a server. Scale the 0-6V with an op-amp and misc. components. But you would be using-up another pin. A spent lithium battery would crash the imp before it would know it was too low? perhaps.
The best indicator is a test - log hardware.voltage() and see when it falls over, then work back a bit! We have noticed voltage changes quite a bit with ambient temperature though.
If you google energizer L91 datasheet, there are discharge curves in there.
Yes, nora2 deals with this. We’re cycling it right now with different battery types, hundreds of thousands of wake cycles.
can someone tell me how to attach battery power to an April board? I have a project for a remote light switch (homegrown home automation), but I don’t have any way to use the USB input from a computer to power it. I have a 9V battery in the project now.
If you used USB, there is a jumper between these pins: USB and VIN
Remove that jumper.
These two pins are next to each other …
Pin called: GND = black wire or (-)
Pin called: VIN = red wire (+)
Connect battery clip or battery pack to those two terminals.
The April board has a built-in voltage regulator that supplies 3.3V to the imp.
You can use a 9V battery, but you’ll get poor performance (battery life).
You’re better off getting a battery holder for 4-AA batteries (6 volts).
You can get one at Radio Shack for under $3.00 and it even has a cover over
the batteries. Amp Hours for 4-AA batteries is much longer than a 9-volt.
The only problem with using 2 Alkaline AA’s bypassing the regulator…
Wifi will stop working at around 2.95v? Much of the battery capacity remains.
Not a good choice because only a small % is used.
Would be great without Wifi!
This beats a 3.7v Li-ion if you’re sleeping most of the time because…
6ua is much less than the 25ua I measured on the April board.
Understand? I could explain further.
I’m comparing Li-ion to Alkaline (without regulator)
Li-ion self discharge is measured in months, not years as Alkaline is.
so wouldn’t I move the jumper from USB position to BAT? So I can use VIN and GND to connect the battery? What are the P+ and P- pads for?
VIN is the same as P+? GND=P-? Is there any difference?
I’m confused now … I thought he wanted to use the April board. So I’m not sure where the 2 akaline AA batteries bypassing the regulator discussion comes from.
I’ve ran an April board with a 4-AA battery holder (6 volts) for a couple months now and I’ve never had to replace them yet.
You remove the USB jumper and have NO jumper there. I use the GND and VIN pins that are on the same row as the other pins. I have the whole row of pins with leads soldered in them and stuck into a breadboard. It makes it easy to mess around with different circuits.
thanks for the clarification mlseim, that’s what I needed to know!
Controlcloud mentioned Lithium AA’s. I didn’t have any of those handy. Bypassing the regulator uses 1/4 the power, if you’re sleeping. 1/40th when the voltage gets lower and the regulator changes modes.
oh, I see what you’re talking about. That might be true, but I think the voltage regulation, and using other components in the circuit outweighs the hassle and risk of bypassing the regulator. Maybe if the final circuit is tested and found to be robust and stable, you may be able to determine ways to make battery life more efficient and longer lasting. Your first goal is to just get a working model (of any kind).