Can someone please compare the feature set of the Particle Battery Shield as compared to the SparkFun Battery shield. The SparkFun device is half the price of the Particle device so in a cost sensitive volume application there really needs to be an overwhelming advantage to spend twice as much to operate the Photon on battery. In reading over the material, it would appear that the major advantage is that the Photon can read the battery level in the Particle shield which does not appear to be a capability of the SparkFun shield. Is this correct? Are there any other advantages to the Particle shield over the SparkFun shield?
@jmosk, the Sparkfun shield does have an I2C battery gauge. The difference is that the Particle shield is shipped WITH a 400ma LiPo which is not included with the Sparkfun unit. Also, the Particle unit has a screw terminal for external power (wall wart, solar cell) whereas the Sparkfun unit requires an extra barrel jack (not included). Finally, the Particle board is smaller and sits tightly under a Core/Photon. I believe you get value whichever board you chose though Particle provides a ready-to-go solution.
Do you happen to know whether they use the same chip? Also I can’t find the allowable input voltage for the particle power shield
I noted that the Particle Board is using a different model number of the same manufacturers chip on board.
@peekkay - Thanks for the info on the battery shield. I know you were involved in another discussion on Photon power requirements but there were no numbers reported as part of that thread. Do you know what the power consumption of the Photon is with WiFi enabled? My mobile application will not be able to sleep as it will be continually recording external data over its WiFi while in motion. I want to have at least 8 hours of battery power available and have no idea how long a 400ma LiPo is going to last. I will probably need a battery much larger than what comes with the Photon Battery Shield.
Operating Current (Wi-Fi on) IIN avg 80-100 mA
Operating Current (Wi-Fi on) IIN pk 235-430 mA
So a 400mA Lipo will last between 1 and 4 hours at 100% WiFi use depending on conditions, let’s call it 2.5 hours average, but you should really use worst case.
You may want to consider just powering from an external USB ‘Power Bank’ that are commonly available in excess of 10,000 mAh. Just buy a reputable brand not some fake eBay knockoff.
If you are making your own PCB, the basic circuit for charging a LiPo is less than $2 in quantities of 10.
I have got one of those multi meters that can measure USB devices and its about 360 mW average with up to 500 mW peaks though those are rare. I got almost 12 hours from an old Samsung Galaxy Nexus battery that was down to somewhere around 1200 mAh at 3.7 V so about 4.45 Wh. I’m using this battery board http://www.seeedstudio.com/wiki/Lipo_Rider_Pro
By the way I really don’t get why people always quote mA even though that is meaning less without knowing the voltage while Watts is the actual power and Watt hours is the real measure of energy.
Note that the mA numbers for the Photon are with 5V while the mA of the battery are for 3.7 V which is why I’m always using Watts instead.
@jmosk, I think the chip number is a typo. They use the same MCP73831. Realistically, you should expect about 150ma/h consumption if the Photon is always sending data, assuming your sensors are not consuming a lot of power. Based on that, you would need a 2000ma/H battery for about 9 hrs of operation (using a 0.7 “efficiency” factory). There are a lot of factors affecting power consumption including distance to the AP, ambient temperature, etc. You will need to experiment to find what works best for your design.
mAh is a measure of the total current capacity regardless of voltage.
If you think of variable voltage regulators, the output is given in Max current regardless of voltage.
So would the photon use less watt when run at 3.7 V instead of 5 V? I would guess the 100 mA figure for the Photon would only be correct at the 5 V the USB uses which is consistent with my measurements. At 3.7 V it would thus draw a higher current but the same wattage modulo different losses.
The point is you don’t need to know the voltage to know the capacity of the battery. If you are using Watts, you need two pieces of info… but you only need one to know the capacity of the battery, so using Watts complicates the calculations unnecessarily.
The battery is like a gas tank holding gallons of gas; do you buy X number of BTU’s of gas power, or do you buy gallons?
Why do I need 2 things when using watt? My battery has 24.4 Wh thats one thing.
When using mAh is when I need to know two things. A 6600 mAh battery could be 24.4 Wh when it’s 3.7 V meaning it can power my Raspberry Pi for about 10 hours assuming that uses 2.4 W or it could have 79.2 Wh if it’s a 12 V battery e.g. from a car that would power the same Raspberry Pi for 33 hours.
I’m a software guy not an electrical engineer but that’s just how the units work and for example entering things in Wolfram Alpha clearly shows that:
As far as I understand using Ah only works because the voltage is implied. Also I’m definitely paying my electricity bill in kWh
OK… my circuit shows a current consumption of 100mA with an ammeter at the input. How long will a 24.4 Wh last? Now what if I told you that the battery is capable of 1000mAh? Which is easier to calculate?
That calculation assumes that there is no voltage conversion between the battery and the circuit, it’s a simplification and it works as long as that assumption holds but in the case of the Photon running off 5 V USB and buying a 3.7 V battery it really doesn’t hold.
See my comment above, it works and is arguably easier but only as long as the assumption holds that you are talking about the current draw at the same voltage as the battery which isn’t what happens with a battery board that upconverts the 3.7 V from the battery to 5V for the Photon and neither when using e.g. a 12V car battery and down converting.
My last post on this matter.
I connect a battery to my circuit, which is in a black box locked in a safe behind wall in a lead lined room with no lights. Not having a clue what is inside the ‘black box’, I measure 100mA current draw. The battery has a label that says 1000mAh. How long will the battery last?
Let’s agree that there are situations where you need to do mAh/mA to get the time and others where Wh/W is the right thing to do.
Will the battery shield give you data on the voltage INPUT into the device? That is, if I’m using a solar cell to charge the battery can I query the voltage coming out of the panel?