(Continued from Part 2.)
Battery Drain
While I briefly mentioned battery drain earlier it’s worth going into a bit more detail. Drain rate describes how fast a device uses power when a device is in operation. Examples of high-drain devices include things like digital cameras, GPS devices, portable gaming consoles, high-lumen LED flashlights, radios (when transmitting) and motorized devices like power tools. Some low-drain devices include television remote controls, wall clocks, smoke detectors, and red dot sights. Rapidly draining a battery’s charge can significantly shorten its life, so choosing the right type of battery for each type of device is critical.
How fast a battery can provide power to a device is called its Continuous Discharge Rating (CDR) and is measured in amps (A). A related measurement is a ‘C-rate’, which is calculated as discharge current (CDR in amps) divided by the battery’s rated capacity (in amp-hours). C-rate consists of a number followed by a ‘C’ – ‘1C’ means the battery can discharge it’s entire capacity in one hour, .5C means it can fully discharge in two hours, 2C means it can fully discharge in 30 minutes, etc. The higher the C-rate the faster the battery can provide power.
Using a low-drain battery in a high-drain device can cause the battery to seriously overheat, which can damage the device and significantly reduce the battery’s life. High-drain devices work best with high-drain alkaline, lithium, or high-capacity rechargeable NiMH – standard alkaline or lithium batteries are the best option for low-drain devices. High-drain Lithium chemistries include LiFePO4 and most LiPo batteries – any other type of chemistry is generally meant for low-drain applications. If you’re going to use something like an 18650 battery in a high-drain device you should also make sure it’s protected, which means it has a built-in circuit to prevent the device from drawing more power than the battery can provide.
With all of that said, one significant problem is that many manufacturers don’t provide information such as chemistry, CDR or C-rate for their batteries so you’ll have to search for the manufacturer’s data sheet (if you can find one). Some web sites I highly recommend that do provide a good amount of information are IMR batteries [1] and the 18650 Battery Store [2] – they provide details such as discharge rate for pretty much every battery they sell.
Temperature Impact
Another area worth examining in more detail is the impact temperatures will have on mobile battery performance. If you live anywhere that’s subject to hot or cold temperature extremes it’s important to understand how that will impact the batteries in your mobile device. Different battery chemistries are impacted differently by temperature extremes:
Cold:
- Li-ion rechargeable – Capacity is reduced and internal resistance starts to increase as temperatures start to drop below 50F or so, and capacity is reduced to less than 50% at around -4F (-20C). Depending on how long the battery was exposed to the cold, warming it up can partially or fully restore its capacity. Charging Li-ion batteries in temperatures below 40F can cause something called lithium plating, which can damage the battery and permanently reduce its capacity. The ideal charging and operating range for Li-ion batteries is around 60F.
- LiPo – LiPo’s tend to to do better at lower temperatures than Li-ion, with a relatively reliable operating range of 32F-95F and around 50% capacity at around -4F. As with Li-ion batteries LiPos should never be charged in temperatures below 40F.
- Li-ion Primary – These are some of the best generally available batteries to use at low temperatures. They maintain up to 80% of their capacity at -40°F and are ideal for outdoor, high-drain devices like trail cameras, flashlights, or emergency gear. Energizer Ultimate Lithium is one example.
- Nickel-based (NiCd and NiMH) – These tend to perform poorly in cold temperatures, with a rapid drop in capacity at around 32F. As with Li-ion and LiPo batteries they should never be charged in temperatures below 40F.
- Alkaline – As with nickel-based batteries, alkalines perform poorly in cold temperatures with a rapid power drop-off as temperatures drop below freezing. They can lose up to 75% of their capacity at 0°F.
In general, no mobile batteries should ever be stored in temperatures below freezing for any significant period of time as this will potentially cause permanent damage. If you’re mobile outside in cold weather you should carry your batteries and mobile electronic devices with batteries inside your outer insulating layer to protect them, or wrap them inside some insulation like your sleeping bag.
Note that there are some companies that make specialized batteries such as 18650s that are specifically designed to operate in lower temperatures. Some examples include Molicel P30B [3]/P45B [4], Nitecore NL1835LTHP [5] and Sunpower New Energy’s Low-Temperature 18650 [6], which can maintain around 85% of their capacity at temperatures down to -40F.
Heat:
Heat is the single biggest enemy for all battery chemistries – operating in temperatures above 85F or so for a long period of time will cause most chemistries to begin deteriorating, and getting above 100F can cause permanent damage or explosions. Keep in mind that batteries produce their own heat when the internal chemical process is running (including during recharging) which is added to the external temperature, so even though it might only be 70F outside a high-drain device’s battery could be well over 90F internally. This makes operating mobile electronics in high-temperature environments like deserts a significant challenge. Some recommendations to mitigate the impact of heat are to swap batteries frequently if the device is in constant use to allow them to cool down, and store/carry batteries where they’re insulated from the worst of the heat.
Battery Management Systems
Since how a battery is recharged and discharged is so critical to its safe operation and lifetime, many manufacturers include a battery management system (BMS) in their batteries, devices and charging systems. These range from simple circuits built directly into the battery to prevent things like overcharging, over-discharging, short-circuiting, and extreme temperatures (a protected battery) to the super smart systems built into modern mobile phones that continuously measure and control battery charging, temperature and usage to maximize battery life. Batteries with built-in USB charging [7] have a simple BMS that ensures the battery isn’t overcharged and display a red/green LED to show the charging status. Some devices can use removable rechargeable batteries but also have a USB charging circuit built into the device so you don’t have to carry a separate charger, but these vary in quality. For example, my older Uniden BCD325P2 radio can use rechargeable AA batteries and has an (ancient) mini-USB port built-in for charging the batteries from USB power, but it doesn’t have any kind of cutoff to stop charging when they’re full – the manual just says to unplug it when the batteries are fully charged. Caution – if a device has a built-in battery charger you should never use it to recharge batteries that also have a built-in USB charging capability – many such batteries can be fried if you try to push power into them using the terminals instead of the USB port.
Most dedicated battery chargers have a BMS built in, including basic features such as overcharging protection and shutting of charging when a battery is full. Higher-end ones have many more advanced charging features such as automatic battery type detection, selectable charging modes, etc. This is one area wehere you shouldn’t skimp out and buy cheap battery chargers – a quality charger with a good BMS can significantly increase the life and safety of your batteries. Some examples of quality charger manufacturers include:
- Nitecore – https://nitecorestore.com/collections/chargers [8]
- LiitoKala – https://liitokala.com.cn/charger/LiitoKala-Charger/list_101_2/ [9]
- Fenix – https://www.fenixlighting.com/collections/batteries-chargers [10]
- Tenergy – https://www.tenergy.com/Chargers-Category [11]
The ones I’m currently using include several LiitoKala Lii-S12 and Lii-M4S models, Nitecore New i4 and UMS2 models and a Fenix ARE-A4. I also have several specialized chargers for unique batteries such as my drone batteries, NP-BX1 for my Sony pocket camera, small chargers for LIR2032 batteries, etc. For charging LiPo battery packs used in various devices like drones and RC vehicles I have a Tenergy TB6B [12]. I like to have a combination of larger chargers that use an AC power supply for ‘normal’ home use and smaller chargers such as the Lii-M4S and UMS2 that use USB-C Power Deliver (PD) for input power, since getting access to USB-C power after a disaster will probably be easier than AC power (refer to my previous article on ‘Compact Power to Go [13]’). The USB-powered chargers can also be useful for charging batteries when you’re mobile.
EMP and Batteries
Since the core of batteries consists of a chemical reaction, the general consensus is that batteries themselves shouldn’t be impacted by an Electromagnetic Pulse (EMP). However, what is less clear is whether or not small charging circuits such as a built-in USB charger or protection circuits such as those found in some 18650 batteries would be impacted. Some of the arguments against them being impacted are that they are extremely small circuits and shouldn’t absorb any measurable amount of energy, and that the metal casing could act as a Faraday cage to protect the battery’s internals. The ‘Dumb’ batteries without any built-in electronics shouldn’t be impacted at all by EMP.
If the battery is installed in a device or plugged into a charger it may be a different story – if the device absorbs any significant amount of energy it could be passed through the battery, which could impact the chemicals in the battery. Also, battery support devices such as voltage testers and battery chargers tend to have pretty sophisticated electronics, which would more likely be impacted by an EMP.
(To be concluded tomorrow, in Part 4.)