Portable Solar Electronics and Gear

Buying Tips - Solar Energy Storage | Battery Capacity and Amperage Ratings

June 05, 2015

In a previous Buying Tips post (Buying Tips - Solar Energy Storage...Your Battery), we touched on some basic battery specifications you need to think about when purchasing a solar panel, solar powered device or rechargeable battery. Whether you have an internally integrated battery with a solar panel or electronic device, or an independent recharger, battery capacity is one of the key considerations you need to become familiar. And one of the more technical topics you will need to focus on is the battery capacity rating.

Battery capacity rating is the specification that tells you how much charge the battery can store for later use. How much energy do you need to operate a camp light plugged into your battery pack...and how long will it last? If you have a weather radio with an internal rechargeable battery, how long will it take to manually charge the battery? If you have a portable battery pack and you want to recharge a phone, camera or GPS device, how many charges can you make with the battery you have before you need to recharge the battery pack? All of these questions are easily answered when you understand the storage capacity of your battery and/or by comparing the storage capacity of the battery provided with your portable electronic device.

We learned before that storage capacity unit of measure is typically the milliamp hours (mAh) or Amp hours (Ah). For larger batteries, the storage capacity unit of measure you may see is the Watt hours (Wh).

Capacity ratings are typically presented as milliamp hours (mAh), or 1/1000th of an amp/hour. The mAh number indicates how many amps or the amount of current a battery can supply over a set period of time. Think of it like having two lawn mowers with identical engines...with one mower having a 2 gallon tank of fuel and the other mower having a 5 gallon tank of fuel. The larger the tank mower will deliver a longer performance, while the other mower will perform the same, but need a refill 5 times to every two times for the other mower. This is the same for battery capacity in that the higher the number, the more likely the battery will deliver prolonged performance

As you can imagine, larger devices, like tablets, have much higher-capacity batteries built in because they often draw more power. An iPad3, for example, has a massive 11,666 mAh battery, whereas the iPhone 5 uses a 1,440 mAh battery. In terms of solar rechargers, the SiiG Portable Solar Battery Charger offers a small Lithium Ion boost charger at the 800 mAh capacity, while the on board lithium polymer battery on the mPowerpad 2 Pro Solar Charger as a capacity of 6,600 mAh...and with the additional mPowerpack 50 power pack adds an additional 5,000 mAh of portable capacity (total over 11,000 mAh capacity)

   

Using some basic calculations it is possible for you to estimate how practical a portable battery charger is going to be for your device or devices. For example, a battery pack with 5,600 mAh worth of storage capacity should be enough to charge the iPhone 5 from dead to fully charged almost four times over (5600 mAh / 1440 mAh =3.89 recharges). However, if you used the same portable battery pack to charge a tablet, the same battery will likely only take the tablet from 0 – 48 percent (5600 mAh / 11,666 mAh = 0.48 charges). The Siig recharge would never be a recommended product for tablet charging or boosting, but for a small smart phone, it would be ideal for a portable boost charger.

Whatever the capacity estimate you find listed on the devices, please keep in mind that these are only estimates. During the transfer of electricity and based on the internal electronics of the recharger and phone or electronic device you with to charge, there typically is energy loss...which is normal and means estimates rarely play out in reality. Keep your expectations realistic and be careful fully relying the on the manufacturer's claims.

What about the amperage rating?

Along with the estimated capacity of the recharger, it is also important to recognize and compare the amperage ratings. The amperage rating, or Ampacity, is defined as the maximum amount of electrical current a device can carry before sustaining immediate or progressive deterioration. The amperage rating is often dependent on several technical conditions, such as insulation rating, resistance, conductor material. These conditions can influence resistance and the flow of electricity. When manufacturers are designing portable solar electronics and other devices, they will be considering this flow between devices and how the wires, circuits, fuses and other internal electronic components are working in the system.

   

If you have ever plugged in a tablet or iPad into one of the USB ports on your office PC, you may have been told that it is “plugged in, but not charging” The reason for this is that because the amperage of that USB out port is too low to charge the device with any kind of reasonable speed. The amperage coming out of the USB port is not providing enough energy through the wire to you tablet. The tablet may require more energy for the screen, wifi, and operating system then the battery or, in this case, the USB out port can provide. With this in mind, you need to make sure your amperage out is properly matched with the device you would like to charge.

The best portable solar rechargers and independent battery rechargers will use a simple integrated circuit to manage power output. Most portable battery charger manufacturers will disclose how many amps they can deliver, which is usually 0.5 A, 1.0 A, or 2.0 A. Amperage is important, because it tells you how quickly a battery pack can charge up your device. For example the Solpro Helios portable solar recharger has two USB output ports (See image above). The dual USB Output Ports let you charge multiple devices at the same time. One of the USB ports is rated at 1.0 Amps and the other is rated at 2.1 Amps.

Again, this is important because most tablets require a 2 A charge output in order for their batteries to be replenished with any kind of speed. With a 2A charger, a tablet can be used while charging and still gain some capacity. Using a tablet while on a 1A charger, however, means that if you choose to use the device while “charging,” you’re just operating on the other battery’s power and not replenishing the tablet battery.

Please keep these points in mind when your are considering your portable solar recharger and thinking about the devices you will be using and or recharging. If you ever have any questions or comments, please let our support team know and we will get back to you.




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