Archive for the ‘Useful Battery Articles’ Category

Power banks are quite useful gadgets nowadays with so many battery powered devices we use in our everyday life, not only our smartphone or tabled, but a number of other gadgets like a smartwatch, hands-free, wireless headphones and many more. When all of these cool and useful battery powered gadgets do come with a rechargeable Lithium battery and can be charged over USB you need a power bank with you to be on the safe side when you are in need of some extra power and are on the move. Carrying a USB charged is also a good idea, however you not always have access to a power outlet, especially when you are traveling around or even just on the move to go somewhere like school or work. Getting the right power bank for your specific needs however can be a bit challenging and power bank manufacturers usually do not help you that much to ease your choice. There are already a lot, really a lot of brands with different forms and shapes, capacities and features you can find available and with a different price range, so how to choose he right power bank and what to look for? We are going to try to help not only with our tests of various power banks, but also with some tips to have in mind when choosing a power bank…

The capacity of a power bank is usually the fits thing people look for, the higher – the better, however there is a catch here and you need to know a few things. First and most important one is that the capacity stated for a power bank is not the actual capacity you can get out of the device, the capacity on the package is the capacity of the battery that is used inside the power bank. The actual usable capacity that comes out from the output USB port for charging devices is usually in the range of about 60-70% and there is a really simple reason for that.

Power banks use Lithium-based rechargeable batteries that are rated at 3.6V-3.7V (when fully charged they reach 4.1V-4.2V), but the device needs to output 5V to charge USB devices. In order to have 5V output you need a step-up voltage converter that increases the input voltage to the desired value, however during this power conversion there is loss. The efficiency of conversion is better in the beginning when the Lithium battery is fully charged with lets say 4.2V, but as it gets discharged the voltage drops and the efficiency gets worse.

Here is an example with a power bank that is being advertised as 10000 mAh capacity, the maximum actual output from the USB port for charging devices will very likely be somewhere in between 6500 and 7500 mAh when you take into account the efficiency of the power conversion into account.

Time to Charge the Power Bank

You need to read the specifications of a power bank carefully and pay attention not only to the capacity, but also to what is the input voltage and current that is needed to charge the power bank itself. The input voltage is normally 5V, so that you can easily use a standard USB charger to charge the power bank, however the more important number is the input current in Amps. Smaller power banks do come with 1.0A input current and larger capacity normally come with 2.0A input current as this is pretty this is standard for power banks that use mini or micro USB ports for charing the internal battery. There are some higher capacity models that come wit USB type-C connectors for charging the power bank and these can actually have support for higher input voltage and curent. But why are these numbers actually important? Well, the input voltage and current are crucial to the time it takes for your power bank to get charged after you use it to charge other devices and it needs recharging.

If we have a 10000 mAh capacity power bank that has 5V and 1.0A input, then it would mean that that time needed for a full charge of the battery inside the power bank could as well be around 10 hours or even a bit more. That also depends on the source of power you are using to charge the power bank as power banks are normally being sold without charges and only a USB cable by default. If the input voltage is 5V and the current is 2.0A the charge time will be cut in half, so around 5 hours for a full charge of the same 10 Ah battery.

If you use the USB 2.0 port of your laptop for example to charge a power bank the time needed for a full charge may be even longer with the standard 0.5A output for these and for USB 3.0 the standard maximum output current is 0.9A, so a bit better. It is recommended to use an external charger with higher current output if your power bank supports it and you should look for higher capacity models that do support higher input currents and maybe even voltages as well in order to have the power bank charge itself faster.

Time to Charge a Device

The output voltage and current specifications are as important as the input ones as they relate to how quickly you will be able to charge your smartphone especially as with most other devices things are not that important. The latest generation of smartphones come with big screens and larger batteries and they implement new faster charging technologies in order to ensure that the device can be recharged faster when plugged in. Most power banks, especially the more affordable models do not yet support faster charging technologies, so you are normally limited to 1.0A or 2.0A/2.1A maximum. If the primary use of the power bank is to charge your smartphone and it supports any of the fast charging technologies you may look for a power bank that supports higher output voltages and currents to match the smartphone. There are a few technologies like that available, so make sure to match the one of the smartphone with the power bank.

In order to get a better idea on how fast is your smartphone or tablet charging you can use a helpful software application for Android such as Ampere for example available for free from Google’s Play store. It will give you a real time information about the battery type, capacity, voltage and charging current and other information. This is important to know as sometimes you may just think that your smartphone is charging with higher current than it actually is due to some incompatibility with a specific power bank resulting in improper detection of the supported charging parameters.


So far we have been testing and reporting the Amp-Hours (Ah) of the various batteries we have tested with the reason being that they are usually being rated in Ah regarding their capacity. But there is another unit that may actually give a better idea about the capacity of a battery and it is Watt-hours (Wh) when talking about batteries. This is precisely the reason why we have decided to also include not only the measured Ah in our battery tests, but also the Wh values – the good thing is that we actually should have all of these for the batteries we’ve tested so far and we are going to include the Wh results for all tests already done.

With each battery we usually have two important ratings, though both are usually revealed by the manufacturer only for rechargeable batteries – Voltage and Amp-Hours (usually written in mAh). Different batteries may have different voltages and capacities and normally you should do some math to know what you can expect from a battery if you know the power requirements of the device you need the battery for. Here is an example: an AA type of NiMH rechargeable battery that has a typical voltage of 1.2V and is rated at 2000 mAh (2 Ah) should be able to power a device requiring 2 Amps for 1 hour, or a device requiring 1 Amp for 2 hours and so on. However when measuring the actual battery performance life in our tests you can clearly see that the starting voltage of a fully charger NiMH battery is higher than the official 1.2V rating and when the battery is considered discharged it is lets say at 1V. So by switching from the Ah to Wh we can take into account the changing voltage of the battery while it is being discharged and get even better idea about its actual energy capacity, even though the Amp-Hours ratings usually do a good job for comparing batteries.

To get an estimate about the Watt-Hours rating of a battery you need to multiply the Amp-Hours by the Volt rating of the battery. So for the above example with 1.2V NiMH battery with 2 Ah capacity we are going to get 2.4 Wh, meaning that this battery can power a device with power consumption of 2.4 Watts for 1 hour, or for 2 hours if it uses 1.2 Watts and so on. But this is just an estimate, because as we’ve already said the voltage of the battery will vary while it is being discharged, so we need to do a thorough test measuring the full discharge cycle to get more accurate value. If you look at the discharge graph and the Amp-Hours in our battery tests with different loads you will see how the voltage is different at different load levels and this will also affect the Watt-Hour ratings as well.

Another thing that we are going to be adding soon are tables that will make it easier for you to compare the performance of all of the batteries that we have tested, of course the tabled results will be divided by battery type. This should allow you to quickly get an idea what could be the best choice for your particular needs for a battery…

If you are using various kinds of rechargeable batteries you might have trouble keeping them all in shape and maximizing their performance and life, the more the batteries, the harder it is and we are not talking only about NiMH batteries, but LiPo, PB as well as other various kinds. For example if you only use a couple of NiMH batteries, then probably a simple and slow charger could do a good job, but if you are using many batteries and not only NiMH, but also Lithium-based rechargeable ones you might want to get a more serious charger or even multiple charger in order to properly maintain and take full advantage of the rechargeability of your batteries. You probably have seen that rechargeable NiMH batteries offer up to 1000 recharge cycles and Li-Ion and LiPo batteries can go from anywhere between 100 and 500 cycles if properly used and maintained. But in reality most people literally kill their rechargeable batteries in just about few dozens of recharge cycles due to improper maintenance and it is very often due to a problem with forgetting to recharge or overcharging or discharging them. In order to fully utilize the potential of the rechargeable batteries and also do what they are supposed to – help nature by avoiding the use of so many primary batteries like Alkaline for example or even worse Carbon-Zinc ones, you need to pay some attention and use better chargers in order to maintain and use the batteries as they are intended to be…


We are starting with the MAHA Powerex MH‑C9000 WizardOne Charger-Analyzer, probably the single best charger for NiMH batteries out there. But this is more than just a charger for AA and AAA size NiMH and NiCD batteris, because it can not only Charge but also Refresh and Analyze, Break-In, Discharge and Cycle the batteries in order to maintain them in the best possible shape. The device has four independent channels, one for each battery, thus allowing you to have a different function for each of the battery you have there or just to work with a single or more batteries at the same time. The standard charging current is user selectable from 0.2-2.0A (200-2000mA) and the discharging currents can be between 0.1-1.0A (100-1000mA) in increments of 0.1A and you can of course have different current for each channel. Thanks to the extra functions besides the standard charge and discharge you can use this to always maintain the health of your NiMH/NiCD batteries, even if they are not used for a while or they were not properly charged or discharged for some time. The charger is great both in terms of functionality, reliability and quality and the only better thing than getting one Powerex MH‑C9000 is to get two in order to be able to have 8 slots and nit just 4 with a single one – that is especially useful if you have and use a lot of AA and AAA size rechargeable batteries. In fact we are using one of these chargers as a part of our test equipment and are planning to get a second one in the near future. If you manage to find the Memorex Pro Genux 1 charger you could have a chance to get the Powerex MH‑C9000 for less as this is a rebranded version of the MH‑C9000, so grab a better deal if you can with the rebranded model.


Now, if you need a good charger that can quickly properly charge and maintain a larger number of AA and AAA size NiMh/NiCD batteries the Powerex MH‑C9000 might not be the best choice with its only 4 channels per device. Yes, it does have more extras, but with the significant increase in the number of batteries having a more functions with menus and options could turn out to be a problem and a distraction, so MAHA has some other chargers that might be more interesting in such situations. MAHA Powerex MH‑C800S and MAHA Powerex MH‑C801D which are AA and AAA NiMH/NiCD battery chargers with 8 independent channels for charging batteries and the only difference between the two is the charging current. The Powerex MH‑C800S has a Rapid Charging Mode with 1.0А and Soft Charging Mode with 0.5A per channel and the Powerex MH‑C801D is with 2.0A and 1.0A respectively and both these also have a Conditioning Mode intended to help revive batteries that are not performing optimally.


If you need similar chargers to the 8-channel Powerex models with lower charging current and similar simpler use and good quality you might also want to check out the chargers made by the Japanese company Tensai. They have the very nice 8-channel Tensai TI-800L, 12-channel Tensai TI-1200L and even 16-channel Tensai TI-1600L chargers for AA and AAA NiMH/NiCD batteries with independent channels for each battery. The charge rate per channel here is fixed at 0.5A for AA batteries and 0.25A for AAA, so higher capacity batteries might need more time to be charged, but in other hand if you don’t need very fast charging, but you need charging of a lot of batteries a single 16-channel charger can be quite useful for some. These chargers also have a Conditioning Mode for maintenance of batteries that are not giving their best.


Another good option are the LaCrosse Technology chargers such as the 4-channel chargers LaCrosse BC-700 (RS-700), LaCrosse BC-1000 (RS‑1000) and the many other names that these go rebranded under. The smaller LaCrosse RS-700 does have a bit more limited functionality giving you the ability to use only 200/500/700 mA per channel (independently set) and the better LaCrosse RS‑1000 supports 200/500/700/1000 mA per channel (up to 1500/1800 mA if charging only two batteries). Both of these chargers also support battery Refresh and Test modes aside from the standard Charge and Discharge modes and are good and more affordable option as compared to the MAHA MH‑C9000, though not as powerful and feature rich. The good thing is that these can probably be easily found, even if rebranded under another name in some countries, unlike the MAHA chargers that may be harder to be found in some places.


So far we have covered some of the best chargers for AA and AAA size rechargeable batteries, but what if you need a more universal charger that can charge pretty much all of the more common battery chemistries? For example both MAHA and Tensai are also making specialized chargers for 9V NiMH batteries (8.4V NiMH), but they are not as powerful as their models designed for the more common AA/AAA batteries, and the same goes for other battery types such as the C or D size NiMH batteries. If we want to add LiPo, LiIon or LiFe batteries or even Pb batteries along with the NiCD/NiMH models and have them in a single device we need to look elsewhere. A good and very popular choice is the SkyRC IMAX brand of chargers and one of their most popular model the IMAX B6AC, the model we are using this in our test setup for Lithium-based rechargeable batteries. The SkyRC IMAX B6AC is designed to charge NiMH and NiCD batteries in packs of multiple cells (it can still charge single cells), so it is probably not the best choice for such cells, but it can be used for 9V NiMHs (though it is limited to minimum 0.1A charging current). Regarding Li-xx batteries, you can charge 1 cell up to 6 cell batteries with a charge current between 0.1-5.0A (up to 50W) and discharge them with between 0.1-1.0A (up to 5W), there is also a built-in balancing functionality to make sure that all of the individual cells are charged properly. You can also charge PB batteries with a voltage between 2-20V. The B6AC charger can be powered by either AC input (100-240V) or DC input (11-18V), there is a B6 only version that does not include a built in adapter for AC input. What you should be very careful with these chargers is when buying to make sure they are genuine and really made by SkyRC and not a cheaper fake copy as they have a lot of copies, also have in mind that SkyRC has these chargers rebranded for some companies such as Team Orion for example. SkyRC also makes more advanced and powerful models that are based around the base functionality of the B6, but even a B6AC should be enough for most. If you however use LiPo batteries with more than 6 cells for example or even 3S-4S batteries with higher capacities you might want to look for more powerful models. There are of course a lot of other Li-xx chargers out there that are more powerful or offer extra functionality, but the B6AC should be more than Ok for most of you that need to have a good charger and don’t want to go doing things like advanced testing batteries for example.