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BU-808: How to Prolong Lithium-based Batteries

Battery research is focusing on lithium chemistries so much that one could imagine that the battery future lies solely in lithium. There are good reasons to be optimistic as lithium-ion is, in many ways, superior to other chemistries. Applications are growing and are encroaching into markets that previously were solidly held by lead acid, such as standby and load leveling. Many satellites are also powered by Li-ion.

Lithium-ion has not yet fully matured and is still improving. Notable advancements have been made in longevity and safety while the capacity is increasing incrementally. Today, Li-ion meets the expectations of most consumer devices but applications for the EV need further development before this power source will become the accepted norm.

As battery care-giver, you have choices in how to prolong battery life. Each battery system has unique needs in terms of charging speed, depth of discharge, loading and exposure to adverse temperature. Check what causes capacity loss, how does rising internal resistance affect performance, what does elevated self-discharge do and how low can a battery be discharged? You may also be interested in the fundamentals of battery testing.

What Causes Lithium-ion to Age?

The lithium-ion battery works on ion movement between the positive and negative electrodes. In theory such a mechanism should work forever, but cycling, elevated temperature and aging decrease the performance over time. Manufacturers take a conservative approach and specify the life of Li-ion in most consumer products as being between 300 and 500 discharge/charge cycles.

Evaluating battery life on counting cycles is not conclusive because a discharge may vary in depth and there are no clearly defined standards of what constitutes a cycle(See BU-501: Basics About Discharging). In lieu of cycle count, some device manufacturers suggest battery replacement on a date stamp, but this method does not take usage into account. A battery may fail within the allotted time due to heavy use or unfavorable temperature conditions; however, most packs last considerably longer than what the stamp indicates.

The performance of a battery is measured in capacity, a leading health indicator. Internal resistance and self-discharge also play roles, but these are less significant in predicting the end of battery life with modern Li-ion.

Figure 1 illustrates the capacity drop of 11 Li-polymer batteries that have been cycled at a Cadex laboratory. The 1,500mAh pouch cells for mobile phones were first charged at a current of 1,500mA (1C) to 4.20V/cell and then allowed to saturate to 0.05C (75mA) as part of the full charge saturation. The batteries were then discharged at 1,500mA to 3.0V/cell, and the cycle was repeated. The expected capacity loss of Li-ion batteries was uniform over the delivered 250 cycles and the batteries performed as expected.

Eleven new Li-ion were tested on a Cadex C7400 battery analyzer. All packs started at a capacity of 88–94% and decreased to 73–84% after 250 full discharge cycles. The 1500mAh pouch packs are used in mobile phones.

Although a battery should deliver 100 percent capacity during the first year of service, it is common to see lower than specified capacities, and shelf life may contribute to this loss. In addition, manufacturers tend to overrate their batteries, knowing that very few users will do spot-checks and complain if low. Not having to match single cells in mobile phones and tablets, as is required in multi-cell packs, opens the floodgates for a much broader performance acceptance. Cells with lower capacities may slip through cracks without the consumer knowing.

Similar to a mechanical device that wears out faster with heavy use, the depth of discharge (DoD) determines the cycle count of the battery. The smaller the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine. There is no memory and the battery does not need periodic full discharge cycles to prolong life. The exception may be a periodic calibration of the fuel gauge on a Smart battery or intelligent device(See BU-603: How to Calibrate a “Smart” Battery)

The following tables indicate stress related capacity losses on cobalt-based lithium-ion. The voltages of lithium iron phosphate and lithium titanate are lower and do not apply to the voltage references given.

Table 2 estimates the number of discharge/charge cycles Li-ion can deliver at various DoD levels before the battery capacity drops to 70 percent. DoD constitutes a full charge followed by a discharge to the indicated state-of-charge (SoC) level in the table.

100% DoD is a full cycle; 10% is very brief. Cycling in mid-state-of-charge would have best longevity.

Lithium-ion suffers from stress when exposed to heat, so does keeping a cell at a high charge voltage. A battery dwelling above 30°C (86°F) is considered elevated temperature and for most Li-ion a voltage above 4.10V/cell is deemed as high voltage. Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling. Table 3 demonstrates capacity loss as a function of temperature and SoC.

What Can the User Do?

Environmental conditions, not cycling alone, govern the longevity of lithium-ion batteries. The worst situation is keeping a fully charged battery at elevated temperatures. Battery packs do not die suddenly, but the runtime gradually shortens as the capacity fades.

Lower charge voltages prolong battery life and electric vehicles and satellites take advantage of this. Similar provisions could also be made for consumer devices, but these are seldom offered; planned obsolescence takes care of this.

A laptop battery could be prolonged by lowering the charge voltage when connected to the AC grid. To make this feature user-friendly, a device should feature a “Long Life” mode that keeps the battery at 4.05V/cell and offers a SoC of about 80 percent. One hour before traveling, the user requests the “Full Capacity” mode to bring the charge to 4.20V/cell.

The question is asked, “Should I disconnect my laptop from the power grid when not in use?” Under normal circumstances this should not be necessary because charging stops when the Li-ion battery is full. A topping charge is only applied when the battery voltage drops to a certain level. Most users do not remove the AC power, and this practice is safe.

Modern laptops run cooler than older models and reported fires are fewer. Always keep the airflow unobstructed when running electric devices with air-cooling on a bed or pillow. A cool laptop extends battery life and safeguards the internal components. Energy Cells, which most consumer products have, should be charged at 1C or less. Avoid so-called ultra-fast chargers that claim to fully charge Li-ion in less than one hour.


[1] Courtesy of Cadex [2] Source: Choi et al. (2002) [3] B. Xu, A. Oudalov, A. Ulbig, G. Andersson and D. Kirschen, Modeling of Lithium-Ion Battery Degradation for Cell Life Assessment, June 2016. [Online]. Available: [4] Source: Technische Universität München (TUM) [5] With permission to use. Interpolation/extrapolation by OriginLab.

The material on Battery University is based on the indispensable new 4th edition of Batteries in a Portable World. A Handbook on Rechargeable Batteries for Non-Engineers which is available for order through

The Goods

The iron arrived well-packaged in a Smart cardboard container that was well up to the task of protecting it through international air mail. Nestled in foam were the iron handle, a single combined element and bit, and an envelope containing a short instruction leaflet and a click-seal bag with an Allen key and a spare screw to secure the bit. There was no power supply, you supply your own 12 to 24 V DC to power it.

The handle is a plastic wand containing the temperature control electronics about 100 mm (4″) long, and similar in girth to a chunky fountain pen. At its rear is a barrel socket for the DC supply alongside a micro-USB socket for firmware and configuration, on its top are a small OLED display and a couple of buttons, and at its front is a receptacle for the element unit. Meanwhile the element unit is about 105 mm (3.15″) long, with an exposed length to the end of the bit of about 70 mm (2.75″).

Assembling the iron is simple enough, the element slots into the receptacle and an Allen screw is tightened to hold it in place. The whole assembled unit weighs 30 g, or a shade over an ounce, and has a balance point almost at its centre.

We hadn’t ordered a power supply with our TS100, but you will doubtless be able to buy one if you don’t have one of the right power level and polarity to hand. We used a 19.5 V netbook supply which was far more than capable of delivering the 40 W the instruction leaflet claims for the iron at 19 V. Maximum power is given as 65 W when supplied with 24 V, while minimum is 17 W with 12 V.

In the hand, the iron is light and easy on the fingers. On its own it is similar in weight and feel to holding a fountain pen, and it is easy to see where comparisons with more expensive irons from the likes of Weller come from. However the iron itself is not the whole story, because your choice of power supply and in particular its lead will make a huge difference to how it feels in practice. The Weller will come fitted with an extra-flexible silicone lead probably designed to work at higher temperatures, by comparison the lead on a cheap power supply is likely to be a stiffer and cheaper affair. Our netbook supply had a right-angled plug, and though it wasn’t a nice flexible silicone cable it turned out not to be a significant burden once it was ensured to be out of range of the hot end.

Heating up, the TS100 may not be as quick as some irons, but it’s no slouch. It’s quoted as 15 seconds to 300 Celsius at 19 volts in its instruction leaflet, and our iron certainly didn’t disappoint. Setting the temperature is a simple case of using the buttons to move the temperature up and down on the OLED display, and once it remains at a particular temperature it stores that setting in its non-volatile memory.

In Test

To test the iron we assembled a little radio kit, a surface mount design intended for first-time surface mount solderers and thus using fairly substantial 1206 components and SOICs rather than SOPs or smaller integrated circuits. We found the iron perfectly easy to use, but with one caveat: the stock bit is a pencil tip, type “B2” that is fine for the larger surface mount devices but which would in our opinion probably be a little unwieldy for anything smaller than an 0805. Fortunately there is a large range of other bits of all shapes and sizes for the iron, including one with a finer point that surface-mount wizards may want to look at.

One of the features of the TS100 is that its firmware can be easily upgraded over USB, and to that end it is easy to download the latest version and install it. Simply hold down one of the buttons on live USB plug-in to enter firmware upgrade mode, and when it appears as a drive on the computer into which you’ve plugged it, copy the firmware file to the drive and it upgrades itself.

Unfortunately, in our case the curse of the firmware upgrade struck us, and after downloading and unpacking the file we were unable to make our iron accept it. We can confirm that the process failed for us on Ubuntu, Windows, and MacOS computers, so maybe it just wasn’t our lucky day. Fortunately the TS100 is not one of those devices that is easily bricked by a failed firmware upgrade, so we were simply presented with an error file rather than a dead iron. A soldering iron is in essence a hardware device not a software one, and the shipped firmware version is fine for soldering, so that’s what we’re reviewing.

It’s worth pointing out here that the TS100 firmware is billed as open-source, and that the code and schematics are available from the link above. We say billed as open-source though, because while the code is officially freely available it does not seem to be accompanied by any form of open-source licence. This may be of more concern to software libre purists than many readers, but still, it is worth mentioning.

We’re told that the latest versions of the firmware provide adjustment of the iron parameters other than temperature through a menu system on the device itself, but on our model the older firmware requires the editing of a text file that appears in a drive when you plug the iron’s USB port into a computer without holding a button down to enter firmware upgrade mode. In the file you can find settings for the different temperatures and timings, and adjust them to your taste.

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The Bottom Line

After having the TS100 for a few weeks, what’s our verdict? Is it a good iron, does it give those expensive irons a run for their money, and would we recommend that you consider one?

It’s important to consider the soldering iron market as a whole when answering those questions. If you spend a four-figure sum on a soldering station, you will find yourself with an iron that is lighter than the TS100, it will have a shorter reach, a quicker warm-up time, better software control, more available bits, in fact it will beat the TS100 in every way possible. You’ll be using that soldering station hard every day for a decade, and it will still deliver the goods.

If however you spend a low three-figure sum on a soldering station from a quality manufacturer, you’ll get something closer. It’ll probably have a similar choice of bits and a nice extra-flexible silicone cable, and it will probably last longer, but in soldering terms it will be a surprisingly similar experience. Even having to spend a few more dollars on a power supply, a decent soldering station in this range will still cost you over twice as much as the TS100.

At the same price range or lower as the TS100 it’s likely that soldering stations will start to decrease in quality, be from anonymous manufacturers with no replacement bit support, and not have quite such a good user experience. Perhaps an all-in-one iron for a similar price such as the Antex TCS50 we reviewed earlier in the year is a better comparison, and at this point we start to see how the TS100 is redefining this sector. The Antex is a good iron for everyday soldering, it is the same weight as the TS100 and has the same reach. It’s mains-powered and comes with an extra-flexible silicone cable, but when you compare the irons side-by-side it becomes obvious that the Antex is being left behind. Its handle is huge by comparison, and its temperature control is limited to a very basic up/down setting with no configurability.

So if you are a high-end professional user looking for an iron to work with every day, the TS100 is probably not a choice that will displace your top-of-the-range model. But if you are a regular solderer or serious electronics hobbyist who is looking for the best bang for buck, you should definitely consider one as an alternative to a low-end soldering station. And if you are buying at the bottom of the temperature-controlled iron food chain then you should really give the TS100 a serious look. Returning to our point at the start of this review, it’s cheap, lightweight, and certainly good enough.

Meanwhile if you manufacture soldering irons, this one will probably have you worried. We look forward to seeing what the models produced to compete with it have to offer.

The Miniware TS100 soldering iron, along with associated bits and power supplies, can be found online from all the usual vendors of Chinese electronics.

Posted in Featured, Reviews, Slider, Tool Hacks Tagged soldering, soldering iron, temperature controlled soldering iron, ts100

True or False. you should fully discharge Li-Ion Batteries in order to maintain capacity?

False. While it’s true that NiCd and NiMh batteries need to be fully discharged to keep their optimum condition. The opposite is true for Lithium-Ion batteries which should NOT be left to fully discharge. This can actually damage the battery. Li-Ion also doesn’t suffer from Memory Effect and so can you can charge these at any point.

As soon as the performance of the battery decreases and you feel a loss of power, get the battery on charge. It doesn’t matter if the battery isn’t at 100% before using it again. As long as some extra charge is put in, it’s ok to part charge these. Bosch’s wireless batteries work on this principle so you can simply top up as you work without straining the battery.

Never let the battery run all the way down. For example, if you’ve got one last screw to turn and then the battery is depleting, don’t force it over the final furlong. You shouldn’t keep your finger on the trigger and keep turning to try and drive the screw. Let it rest and put the battery on charge. Forcing it is a definite way to damage the battery. You can always top it up briefly and then come back to finish.

Who has absolute power?

Each manufacturer’s power tool batteries have their own distinct advantages. It’s up to you to decide which best suits your needs.

Makita‘s unique position with its 18V battery is that it has the world’s largest range of compatible cordless tools. Over 100 of Makita’s tools can be powered by their 18V Lithium-Ion battery. This gives you a huge selection to work with. They also have some of the fastest charging times. Charging a 3Ah battery takes 22 minutes, 4Ah ready in 36 minutes and the 5Ah complete in just 45 minutes.

By comparison, Bosch has some of the smallest and lightest batteries on the market. This can make a real difference especially when doing a lot of overhead work. They also have a robust construction, having been tested to withstand being dropped from 3 metres. Inside, each battery comes with Electronic Cell Protection (ECP) which protects the battery against total discharge, overloading and overheating. See the results of their heat test here.

Festool’s new AIRSTREAM battery again comes with leading battery technology and the company highlights the cell balancing that goes into its units. This involves carefully selecting equally matched cells, resulting in proportionate charging and discharging cycles which prolong battery life. The new AIRSTREAM battery also has a cooling system in combination with the SCA 8 charger, which draws air over the battery to cool it. As a result this reduces charging times by up to 65% so you can get back to work faster.

Interestingly, Festool and FEIN are so confident in the quality of their batteries that they have a 3 year guarantee on Lithium ion batteries and chargers.

Axminster’s battery for the Makita 18V Li-Ion cordless tools, however, uses Samsung SDI cells. Analysing the battery cell market, Samsung SDI is the market leader in small size rechargeable batteries producing 315 million cells a year. As a result they know what they’re talking about when it comes to batteries. There are many cheaper replica batteries out there using inferior quality cells and that’s when you have problems with the batteries failing after a few cycles.

New power tool battery technology

One of the most recent developments to the market is DeWALT’s new FLEXVOLT battery. The batteries are fully compatible with existing DeWALT 18V XR tools and when fitted to the new DeWALT XR FLEXVOLT tools the voltage then surges to an unparalleled 54V. FLEXVOLT is a world first with this new 18/54V battery platform and the aim as DeWALT state is to give you: the power of corded, freedom of cordless.

Bosch has developed a world first with their wireless charging system. This is able to charge the wireless battery without having to take it out of the tool as with the GSB 18-12-LI Plus Combi Drill. If time is of the essence, as it invariably is, this is perfect in repetitive situations where you need to pick up and put down the tool over long periods. The battery continually tops up without interrupting your work.

With all these advances to battery power, there is now some interesting technology that can utilise this power, not only for your tools but also your mobile device.

Over time the power of batteries is surely set to increase with higher ampere-hour (Ah) and longer run times. If you look after your power tool batteries, this will help to prolong their life to give you even greater value for money. Here are the optimum conditions for maintaining batteries and some further specifications to help you differentiate between manufacturers.

The Best Cordless Stick Vacuum

After testing 25 new models, we now recommend the lithe, nimble Dyson V12 Detect Slim and the sturdy, extra-strong Ryobi 18V One HP Cordless Pet Stick Vac Kit with Dual-Roller Bar as the best cordless stick vacuums.

If you deal with frequent small messes, or if you hate lugging out your full-size, plug-in vacuum cleaner, a cordless stick vacuum could be your dream cleaning partner. But like a good marriage, using a cordless stick vacuum requires you to make some compromises. We’ve tested dozens of them, and the perfect model just doesn’t exist.

Depending on your priorities, we recommend the Dyson V12 Detect Slim and the Ryobi 18V One HP Cordless Pet Stick Vac Kit with Dual-Roller Bar. If you’re on a tight budget (and willing to overlook some red flags), consider the Kenmore Elite CSV Max Cordless Stick Vacuum DS4095.

How we picked

We’ve tested hundreds of vacuums since 2014, most recently evaluating 25 cordless stick models priced from 100 to 450,000.

makita, batteries, explained

We measured how much baking soda, cereal, birdseed, glitter, and hair each vac pulled from four types of rugs and bare floors.

We looked for cordless stick vacuums with at least a two-year warranty, as well as a replaceable battery—a major plus.

We considered how easy and comfortable it was to maneuver each vacuum, and whether its attachments fit their purpose.

Buying Options

The Dyson V12 Detect Slim comes closer to an ideal stick vac than any model we’ve tested. It’s light and nimble around furniture and on stairs, and it even works on shelves, walls, and ceilings.

The V12 Detect Slim rivals more expensive vacuums (such as the Dyson V15) in suction, airflow, and cleaning power, and it comes with multiple brushes and attachments, including a motorized brush for pet hair. It runs for 45 minutes on a single charge, longer than most of the other vacuums we’ve tested.

It has high-tech features that make it almost fun to use, including a sensor that automatically adjusts suction, a laser headlight that illuminates dust in dim corners, and an LCD screen with a battery countdown and other information. It’s also one of the quietest models we’ve tested.

The biggest downside of the V12 Detect Slim is its tiny, 12-ounce dustbin, which requires frequent emptying. You also have to swap between two different brushes depending on whether you use it on carpet or bare floor.

It takes four hours to recharge—longer than most other models—and doesn’t stand up on its own. Dyson covers it with a two-year warranty.

Who can use this cordless drill?

Professional woodworkers, carpenters, and plumbers who engage in both large-scale and small-scale projects will enjoy this tool. The instructions on how to use and maintain the equipment are easy to follow making it an ideal tool for both DIYers and hobbyists.

Shortcomings of this impact drill

One of the biggest shortcomings of this drill is the tendency of its chuck to loosen after an extended period of use. Other than that, the Makita 18v cordless drill is still a fantastic tool.

How it compares to other compact drills

Both units have an 18-volt lithium-powered battery. However, Makita’s star-powered technology gives it an edge in both charging times and battery life.

makita, batteries, explained

Makita vs. DeWALT

The major difference between these two manufacturers lies in the voltage. DeWALT’s cordless drills pack 20 volts compared to Makita’s 18 volts. A 3-year warranty is standard in both models.

What user’s day about the unit

A majority of users are impressed by the unit’s compact design and lightweight nature. The devices superb battery performance coupled with its LED lighting have endeared it to many professionals. All in all, reviewers seem to consider the Makita 18V cordless drill a capable handyman tool.

Final thoughts

If you are looking for a best-in-class cordless drill that is capable of driving, drilling and fastening in tight spaces then the Makita 18-Volt cordless drill might be the tool for you. I would recommend it to anyone.

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