I would like some help figuring out how long a typical single AA battery (2000mAh) will last connected to a 3.3V step up converter without any load. This is the converter I'm using. There's datasheet but I'm not entirely sure how to get information that I need to determine battery life.
Datasheet gives operating current for each variant, the 3V3 one is 45uA, typical.
2000mAh / 45uA = 5 years. Your battery will self-discharge much faster than that.
MarkT:
Datasheet gives operating current for each variant, the 3V3 one is 45uA, typical.
2000mAh / 45uA = 5 years. Your battery will self-discharge much faster than that.
Excellent! Thank you very much! Out of curious where did you find 45uA number? I don't see it in the Datasheet...
You also have to figure that powerout = powerin minus some loss.
Spec on the part is
"High Efficiency 85% (Vin = 2.0 V, VOUT = 3.0 V, 70 mA)"
So powerout = 2000mAH * 0.85 = 1700mA roughly.
What's your current draw going to be like?
More to the point a 2000mAh battery will rarely exhibit that capacity in real life unless its brand new
and you boost-charge then trickle-charge and then immediately discharge at the 20hour rate to a rather
impractically low final voltage. Call it 1000mAh and you're less likely to be dissapointed.
CrossRoads:
You also have to figure that powerout = powerin minus some loss.
Spec on the part is"High Efficiency 85% (Vin = 2.0 V, VOUT = 3.0 V, 70 mA)"
So powerout = 2000mAH * 0.85 = 1700mA roughly.
What's your current draw going to be like?
Thanks! Draw should be pretty low but I haven't calculated it yet. I'm powering Moteino w/ RFM12B transmitter and DS18B20 temp sensor. Without putting chip to sleep and sending readings every 30 seconds I my AA lasted just a little under 1 week. So I wanted to figure out if step-up converter might be burning much of the juice. My goal is for battery to last at least a year. I plan to try using Watchdog timer and only transmit readings once every 5 minutes. Also I might use 2 AA...
Or a C or D, lot more capacity there.
Excellent! Thank you very much! Out of curious where did you find 45uA number? I don't see it in the Datasheet...
Fig 57
CrossRoads:
Or a C or D, lot more capacity there.
No that's too big. Sensor needs to be pretty small so I can fit between window and bug screen
Worst case, 9V battery, but then I have to find very efficient voltage regulator...
pito:
Fig 57
Ah, there it is! Thanks!
Or LiPos, they are available in flat packages. Can you run on 3.7 to 4.2V directly?
No it needs to be 3.3V
So a small step down regulator then. I don't know if efficiency is any better that way.
This little one is 1000mAH.
Examples of higher capacity thin LiPos
http://www.all-battery.com/li-polymersinglecells.aspx
I got some of the fancy 18650 lithiums. They're putting out 4 volts charged, and are rated at 3.7. So I'm having a hard time finding something efficient that will cut it down to 3.3v. LDOs have higher dropouts than that, or quiescent currents way too high. Buck converters that I have found do as well. If you find something that works, I would like to hear about it.
Since the battery still has useful life @ 3V2 a single 18650 or any single Lithium battery is going to be an issue. Better to use a 2S combination and a buck mode switcher. Better still is to use the sleep modes supplied in the Low Power Labs library. The power savings in sleep are better than the self-discharge rate of the battery. Much bwetter.
Doc
sonnyyu:
cmkpl:
It is more common that we can use a portable USB power supply for charging up mobile phones. I know that Arduino accepts USB power as its power supply. By reading the schematic, I found that there is no voltage regulator for USB power supply.My question is, how can I make a regulator for input voltage 4-5V and output voltage is more or less 5.0V for arduino? Or can we buy directly from eBay or somewhere else?
It is useful as I have one USB phone charger.
Thanks.
What you ask is SEPIC or Buck–Boost dc converter, Google it.
Buck (Step-down) - The output voltage is lower than the input voltage
Boost (Step-up) - The output voltage is higher than the input voltage
SEPIC - The output voltage can be lower or higher than the input voltage or equal to input voltage
Buck–Boost converter - The output voltage is of the same polarity of the input, and can be lower or higher than the input or equal to input.or u could make up u own one, use 1 Buck + 1 Boost or 1 Boost + 1 Buck or isolated ?uk or -5V + ?uk converter ...
electronics is art.
We need SEPIC or Buck–Boost dc converter circuit since Li-Ion fully charged has 4.3 v and fully discharged has 3.0 v.
High Efficient Li-Ion to 3.3-V Conversion IC TPS6113X from TI
Need free sample?
Very useful link,
Speaking of art of electronics I have cheap Atomic clock with wireless external temperature sensor. That sensor sits outside my window and runs of 2 AA. Besides transmitting temperature it has built in small LCD display and LED. It's there in freezing winter temperatures or hot summer days, yet it works on same set of batteries for 2-3 years. I don't know how the heck they managed to achieve such crazy efficiency (magic?), but I'm really tempted to take it apart
No magic, It is battery management. It sleep then wake up when needed. One day we might be able put ourself to sleep a long time then wake up in future. Or lowering the core body temperature extends life spans
Lowering the core body temperature of mice let them live an average of 15 percent longer, researchers report.
http://news.healingwell.com/?p=news1&id=535876
Now it is human life management.