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--- kit:mod_battery_power [2019/01/19 16:34] – [Power Bank Capacity] - true capacity steve
+++ kit:mod_battery_power [2019/01/19 18:12] (current) – [Power Bank Capacity] steve
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-  January 19, 2019 - This article is still being authored. This information is not yet ready to use!!!
+  January 19, 2019 - This article is still being authored. This information is not
+  yet ready for use!
 ====== Introduction ======
@@ Line 33: / Line 34: @@
 ====== Short Term Power Plan ======
 This section describes what you'll need to do in order to convert a CrowBox to run on short term power.
+===== Required Parts =====
+Here's a good thing- you only two need parts to convert a CrowBox to run from a USB power bank. Even better, one of these parts is the power bank itself! We'll talk more about choosing a power bank in moment.
+The other part you need is called a "micro USB breakout board" or "micro USB pinboard". This is a small micro USB socket with some standard pin headers attached to make it easy to wire up to projects like the CrowBox so that you can plug in a power bank. This is very inexpensive part and they are easy to find on amazon and eBay. These are so inexpensive that you usually have to buy 10 or more in a lot for around $5 USD, so you'll end up with some extras.
+**NOTE:** Be sure that the USB breakout boards that you buy are "micro USB" and that they come with the header pins! Also, some minor soldering is usually required. The item you are looking for looks like this:
+{{ :kit:micro_usb_pinboard.jpg?nolink&256 |}}
 ===== Choosing a power bank =====
-Due to the enormous popularity of smartphones, tablets and other devices which are recharged through a USB cable, portable batteries with USB ports (USB power banks) are also extremely common and relatively inexpensive. As long as you choose a USB power bank that meets the requirements listed below, you will find it to be an effective and easy-to-use power source.
+Due to the enormous popularity of smartphones, tablets and other devices which are recharged through a USB cable, portable batteries with USB ports (USB power banks) are also extremely common and relatively inexpensive. USB power is 5 volts, the same as our CrowBox, which is very convenient for us.
+There are a couple of important features you must look for in a power bank and we'll go over those after a discussion on energy capacity.
 ==== Power Bank Capacity ====
-USB Power Bank capacity is expressed in milliamp-hours, or mAh. For our application, 5000 mAh is the minimum you should consider. High-capacity power banks may provide 30,000 mAh or more.
+USB Power Bank capacity describes how much energy the power bank holds when fully charged and is expressed in milliamp-hours, or mAh. For our application, 5000 mAh is the minimum you should consider. High-capacity power banks may provide 30,000 mAh or more.
-Capacity matters because it determines how long your CrowBox can run off of the power bank before the power bank must be removed and recharged. Here's how you figure out how long a CrowBox will run on a given power bank:
+Capacity matters because it determines how long your CrowBox should run off the power bank before the power bank must be removed and recharged. Here's how you figure out how long a CrowBox should run on a given power bank:
   [Hours of continuous operation] = [power bank capacity in mAh] / 50
-This computation assumes the CrowBox is idle most of the time. Depending on the level of activity, particularly how many times the sliding lid is opened and closed each day, the power bank may need to be recharged sooner.
+This computation assumes the CrowBox is idle most of the time. Depending on the level of activity, particularly how many times the sliding lid is opened and closed each day, more energy will be used and the power bank may need to be removed and recharged sooner.
+This computation also ignores power that may be consumed by the power bank itself. Power banks contain voltage regulation circuitry and many of them use one or more LED's to indicate power or status. These items consume some of the power bank's battery power during use. To compensate for these unknown factors in our power consumption it's a good idea to be conservative and recharge the power bank sooner than this formula would suggest. Let's look at some examples:
+If you are considering a 5000 mAh power bank, our formula says that a CrowBox should run for 100 hours before the power bank is dead. (5000 / 50 = 100 hours). This works out to 4.16 days (100 hours / 24 hours = 4.16 days).
+A high-capacity power bank providing 30,000 mAh **should** be able to power a CrowBox for around three weeks!
-There are some things we don't yet know about the true capacity of USB power banks and it's reasonable to assume that all power banks vary. For instance, we don't know for sure how much power is consumed by the power bank itself- Power banks contain circuitry for voltage regulation and most of them use LED indicators to show that the power bank is on, and some of them use multiple LED's to show how much power is remaining.
+**However!** These computations assume ideal conditions and must be made more realistic. To figure out how long you should actually try to run a CrowBox from a power bank before recharging, use a modified version of our formula which attempts to take into account the extra power consumed by the power bank itself:
-As you no doubt realize, power banks are mainly designed to provide a lot of power quickly (quickly charge a phone or tablet) and then be recharged. This may mean that they are not always designed to be very efficient for long-term use as a battery- the internal circuitry and the indicator LEDs may use more power than we think, which can reduce the amount of time that the power bank will run a CrowBox.
+  [practical hours of operation] = [power bank capacity in mAh] / 75
+Using this updated formula, here's how long you should actually expect to run a CrowBox off of a given power bank before stopping to recharge the power bank:
-So- If you are considering a 5000 mAh power bank, a CrowBox should run for about 100 hours on a full charge (5000/50 = 100 hours). 100 hours divided by 24 comes out to about 4.166 days of operation on a single charge. To be safe, it would be best to recharge the battery about every three days. This should account for the additional power consumed by the CrowBox opening and closing several times a day as well as trace power consumed by the internal circuitry of the power bank as well as any indicator lights the power bank may have.
+  * 5,000 mAh - 66.6 hours or 2.77 days
+  * 10,000 mAh - 133.33 hours or 5.3 days
+  * 22,000 mAh - 293.3 hours or 12.2 days
+  * 30,000 mAh - 400 hours or 16.6 days
-A high-capacity power bank providing 30,000 mAh **should** be able to power a CrowBox for around three weeks. The math works out to 25 days but it's probably a good idea to plan on recharging the battery sooner.