Samsung
Samsung INR18650-25R – High-drain lithium-ion battery (2500 mAh)
The Samsung INR18650-25R (often simply called "Samsung 25R") is one of the best-known and most proven high-current batteries on the market. Recognisable by its typical green cover, it is regarded as the "all-rounder" for power-hungry applications. With a capacity of 2500 mAh and an enormous constant discharge current of 20 amps, it bridges the gap between pure high-capacity batteries and extreme high-drain cells. It is the standard choice for power tools, powerful e-cigarettes and bright torches.Highlights at a glanceHigh current load capacity (High Drain): This battery delivers a constant 20 amps without overheating. Short-term (pulse) even up to 100A is possible. This makes it ideal for devices that need "power", such as cordless screwdrivers or sub-ohm vapers.Safe INR chemistry: The lithium nickel manganese cobalt oxide chemistry used (LiNiMnCoO2) is considered more thermally stable and safer than conventional Li-Co cells (ICR), which is vital at high currents.Good balance: With 2500 mAh it offers a solid compromise. It lasts longer than pure power cells (which often only have 1500-2000 mAh), but the voltage does not sag as much under load as cells with 3000+ mAh.Low internal resistance: This keeps the battery relatively cool even under high loads and the voltage remains stable ("low voltage drop"), ensuring consistent performance.Industry standard: As this battery is used millions of times in powertools (e.g. Bosch, Makita battery packs), it is extremely reliable, cycle-resistant and usually very attractively priced.Unprotected construction: It is a Flat-Top cell without protection electronics (PCB). This allows for high current flow, but requires responsible handling and suitable chargers.The favourite for "vapers" and power toolsWhile the Samsung 30B (from your previous enquiry) is a long-distance runner, the 25R is the sprinter. When you pull the trigger of your cordless screwdriver or activate the turbo mode of a torch, high currents flow instantly. A normal battery would immediately collapse here (voltage drop). The 25R delivers the energy effortlessly in such cases. Features ModelSamsung INR18650-25R ApplicationPower tools, e-cigarettes, vacuum cleaners, high-drain lamps Nominal capacity2500 mAh Nominal voltage3.6 V (Standard Li-Ion) End-of-charge voltage4.2 V (compatible with all standard chargers) Max. discharge current**20 A** (constant) / up to 100 A (pulse < 1s) Protection circuit (PCB)No (unprotected / flat top) - be careful when handling! ChemistryLiNiMnCoO2 (INR) - thermally very stable & safe Internal resistanceVery low (< 18 mOhm), therefore ideal for heavy loads Dimensions (Ø x L in mm)18.4 x 65.0 (Standard 18650) Weight (g)approx. 45 FAQs about the Samsung INR18650-25RIs this battery suitable for e-cigarettes?Yes, absolutely. The 25R is one of the most popular batteries among vapers. With 20A continuous load, it is safely suitable for almost all regulated battery mods and many mechanical mods (within reasonable resistance range).What is the difference to the Samsung 30Q?The Samsung 30Q (pink) is the modern successor in spirit.25R (Green): 2500 mAh, gets less hot under extreme loads, very robust.30Q (Pink): 3000 mAh, lasts longer under moderate load. For absolute high-current safety, many still go for the 25R; for longer runtimes, choose the 30Q.Do I need a special charger?No. Unlike the 30B (4.35V), the 25R is a standard battery with 4.2 volt end-of-charge voltage. Any normal Li-ion charger (Nitecore, Xtar, etc.) works perfectly.Can I use it in torches?Yes, for powerful lamps. Many modern LED lamps with over 2000 lumens require such high-drain batteries to reach the turbo mode. Note: As it is a Flat Top (flat positive terminal), it may not work mechanically in some lamps if they require a protruding positive terminal (Button Top). Please check this beforehand.
Samsung INR18650-30Q – The "Pink" Power All-Rounder (3000 mAh)
The Samsung INR18650-30Q (recognisable by the distinctive pink-coloured cover) is one of the most popular 18650 batteries worldwide. It is considered the direct competitor to the LG HG2 ("Chocolate") and solves the classic dilemma between capacity and current. With 3000 mAh it offers a very high capacity, but at the same time delivers stable 15 amperes continuous current (and considerably more for short periods). This makes it the first choice for applications that require long runtimes and a lot of power.Highlights at a glancePerfect balance: Usually you have to choose: High capacity (but low current) OR high current (but low capacity). The 30Q offers both: A lot of energy (3000 mAh) and enough power for almost all applications.High current output (15A+): Officially specified for 15 amperes continuous load. However, independent tests and practical use often show that it can safely deliver up to 20A (with temperature monitoring) as well. This is ideal for power-hungry devices.Stable voltage: The battery does not sag in voltage as quickly under load ("Low Voltage Sag"). This means your torch will stay brighter for longer or your e-bike motor will still pull strongly even uphill.Safe chemistry (INR): Uses safe nickel-manganese-cobalt chemistry. It is thermally stable and is less prone to "thermal runaway" on overloading than older ICR batteries.Versatile: The standard battery for e-cigarettes (vapers), high-performance torches, robot vacuum cleaners and cell replacement in Dyson battery packs.The successor to the 25RMany users ask themselves: Should I get the green 25R or the pink 30Q? The 30Q is essentially the upgrade. It offers about 20% more runtime at similar load capacity. Only if you operate the device at its very limit (permanently above 20 amperes) is the old 25R slightly more robust. For 95% of all users, the 30Q is the better choice today. Features ModelSamsung INR18650-30Q ApplicationHigh-end torches, e-cigarettes, robot vacuum cleaners, e-bikes (high power) Nominal Capacity3000 mAh Nominal Voltage3.6 V End-of-Charge Voltage4.2 V (Standard CC/CV charge) Max. Discharge Current**15 A** (continuous load) / 20 A (with temperature monitoring < 75°C) Protection Circuit (PCB)No (Unprotected / Flat Top) - Beware of short circuits! ChemistryINR / NMC (Lithium-Nickel-Manganese-Cobalt) Internal ResistanceLow (approx. 22-26 mOhm) - Low heating under load Dimensions (Ø x L in mm)18.4 x 65.0 (Standard) Weight (g)approx. 46 FAQs about the Samsung 30QIs this battery good for vapers (e-cigarettes)? Yes, one of the best. It is the standard for regulated battery holders up to approx. 45–50 watts per cell. It lasts noticeably longer than a pure high-current battery, but still delivers enough "punch".Will it fit in my torch? If your torch accepts unprotected flat-top 18650s: Yes. It is excellent for torches such as the Emisar D4V2, Lumintop FW3A or bright Olight/Fenix/Nitecore models (as long as they do not require special batteries or button-tops), as it can power the turbo mode for a long period.Can I use it as a replacement for my vacuum battery? Yes, the 30Q is very often used to re-cell Dyson battery packs (V6, V7, V8). It provides enough power for the vacuum motor and often increases the runtime compared to the original cells.Are there counterfeits? Unfortunately yes, as the 30Q is very popular. Make sure you buy from trusted specialist dealers. Original Samsung cells have a lightly printed code under the shrink sleeve, which can be seen against the light.
Samsung INR18650-29E7 – The endurance specialist (2900 mAh)
The Samsung INR18650-29E7 (version 7 of the popular 29E series) is a lithium-ion cell that is specially designed for Longevity and Endurance was developed. In contrast to the "sprinter" Samsung 25R, this battery is a "marathon runner". With a capacity of 2900 mAh and a very high cycle stability, it is the industry standard for e-bike batteries, pedelecs and large energy storage devices (powerwalls). The "E7" version is the latest iteration of this cell and offers an even more stable voltage curve than its predecessor (E6).Highlights at a glanceFocus on service life: This cell is optimised to be charged and discharged over many years. It can withstand many charging cycles (often over 500-1000 with gentle use) before the capacity noticeably decreases.Ideal capacity: With 2900 mAh offers around 15-20% more runtime than the standard 2500 mAh cells, without being as sensitive or expensive as the absolute high-end cells (3500 mAh). It hits the "sweet spot" of price and performance.Medium current output (middle drain): It delivers up to 8.25 amps (approx. 3C). This is perfect for e-bikes (where many cells are connected in parallel) or normal torches, but not enough for high-performance vaping or extreme tools.Safe INR chemistry: Uses lithium nickel manganese cobalt oxide. This chemistry is considered very safe and thermally stable.E-bike standard: If you were to open a high-quality battery for your Bosch, Yamaha or DIY e-bike, you would most likely find exactly this type of cell in it.The centrepiece for e-mobilityThe Samsung 29E7 is often underestimated because it does not deliver extreme amperage figures. But in a battery pack (e.g. 4 cells in parallel), the current adds up to over 30 amps, which is enough for almost any electric motor. Its strength is the UniformityThe cells hardly drift apart (balancing) and keep the voltage stable for a very long time. Features ModelSamsung INR18650-29E (Version 7) ApplicationE-bike batteries, power banks, storage solutions, laptop cells Nominal capacity2850 mAh (min.) / 2900 mAh (typ.) Rated voltage3.65 V (ideal for 36V/48V packs) End-of-charge voltage4.2 V (standard CC/CV charge) Max. Discharge current**8.25 A** (continuous load) / approx. 13 A (short term) Protective circuit (PCB)No (Unprotected / Flat Top) - Spot welding recommended ChemistryNMC (Nickel Manganese Cobalt) - Balanced mixture Special featureOutstanding "cost-per-cycle" balance (price-performance winner) Dimensions (Ø x L in mm)18.4 x 65.0 (standard) Weight (g)approx. 45 FAQs about the Samsung INR18650-29E7What does "E7" mean? This is the revision number. There used to be the 29E (version 6). The Version 7 (E7) is the improved new edition. It has a slightly more linear discharge curve, which makes it easier for the battery display on the e-bike to calculate the exact charge level ("remaining range").Can I use it to repair my cordless screwdriver? Conditional. For small screwdrivers (Ikea, Bosch IXO) yes. For large professional machines (Makita 18V, Hilti) that drive thick screws into wood, this cell is not suitable. too weak (only 8A). It would overheat here. It is better to use the Samsung 25R (20A).Is it suitable for vapers (e-cigarettes)? Only for "back-end vapers" (MTL) at low wattages (up to approx. 20-25 watts per battery). The current flow is not sufficient for sub-ohm or high wattages.Why do some data sheets only state 2750 mAh? This is the Guaranteed minimum capacity with a discharge up to 2.5V. In normal use (typical), however, fresh cells reach the advertised ~2850-2900 mAh.Can I mix these cells (e.g. with 29E6)?In a series connection (battery pack) you should use the avoid. Always use cells of the same charge and version, as slight differences in internal resistance will otherwise result in the pack becoming unbalanced and ageing more quickly.
Samsung INR21700-30T – The undisputed high-current king
The Samsung INR21700-30T (short "Samsung 30T") is a legend among lithium-ion cells. It utilises the modern 21700 format (slightly thicker and longer than the classic 18650 cell) and is uncompromisingly designed for maximum performance. With a constant discharge rate of 35 ampere (and with temperature monitoring, even significantly more), this is the cell of choice when you absolutely do not want to compromise on power. It is extremely popular worldwide among users of mechanical e-cigarettes ("mech mods") and extremely high-performance torches, as the voltage hardly drops at all, even under brutal load.Highlights at a glanceExtreme current load capacity (High Drain): The 30T delivers continuous 35 ampere. This is an immense value that easily powers even the most demanding motors or heating coils. It is considered one of the "toughest" cells on the market (minimal voltage drop).Hard Hitting Performance: While other batteries drop the voltage under heavy load (the device seems "tired"), the 30T keeps the voltage up. The result: motors spin faster, lamps shine brighter, vapour is more intense.21700 Format: This cell is larger than a 18650 (21mm diameter vs. 18mm). It only fits in devices that are explicitly intended for 21700. This format is the new standard for high-performance electronics (e.g. in Tesla Model 3 battery packs or professional tools).3000 mAh capacity: To enable this enormous performance, the cell sacrifices some capacity. 3000 mAh is solid, but less than models geared toward endurance (like the Samsung 50E with 5000 mAh). The focus here is purely on "power".Safe chemistry: Uses robust INR chemistry (lithium-nickel-manganese-cobalt), which is very thermally stable – a basic requirement for currents of this size.Unprotected industrial cell: This is a Flat-Top cell without integrated protection circuit (PCB). This is necessary to allow high currents to flow freely but requires expertise in use.30T vs. 40T – Which is the right one?Samsung offers two top models in this class: the 30T and the 40T.Samsung 40T (4000 mAh): The all-rounder. Offers more runtime, but under extreme loads (over 25-30A), the voltage drops a bit earlier.Samsung 30T (3000 mAh): The sprinter. Has less runtime, but still delivers relentless performance at 35A or 40A. Conclusion: If you need the absolute maximum power (e.g. for competitions, drag racing with RC cars, or mechanical vaping at the limit), choose the 30T. For everyday use, the 40T is often more practical. Features ModelSamsung INR21700-30T ApplicationExtreme torches, mech mods (vaping), high performance tools Nominal capacity3000 mAh (Relatively little for 21700, in favour of power) Nominal voltage3.6 V End-of-charge voltage4.2 V (Standard CC/CV charge) Max. discharge current**35 A** (Continuous load without temp limit) / **40A+** (with 80°C cut-off) Internal resistanceExtremely low (under 10 mOhm AC), therefore hardly any voltage drop ("Voltage Sag") Protection circuit (PCB)No (Unprotected / Flat Top) – Always use transport cases! ChemistryNMC (Nickel Manganese Cobalt) High-Power Mix Dimensions (Ø x L in mm)21.1 x 70.3 (Significantly thicker and longer than 18650) Weight (g)approx. 67 FAQs about the Samsung 30TWill this battery fit in my 18650 charger?Often not. The cell is 70 mm long and 21 mm thick. Many older chargers are too narrow or the slider doesn't go far enough. Check whether your charger is explicitly "21700 compatible". If the battery only goes in by force, you will damage the shrink sleeve (risk of short circuit!).Can I use it in a torch?Yes, if the torch is built for 21700s (e.g. Olight Seeker 2/3/4, Acebeam, Imalent). For torches with extreme turbo modes (5000+ lumens), the 30T is often the best choice to achieve maximum brightness. Please note, however, that the 30T is a Flat Top – some torches require button tops or magnets.Is it safe for e-cigarettes (Mech Mods)?Yes, it is the gold standard. There is hardly a safer cell for mechanical vaping. Even with coils at 0.10 Ohm, the 30T stays "cool" and delivers stable power.What happens if I put it in an 18650 device?It does not fit mechanically (too thick). Never try to insert it without a case or by force.
Samsung INR21700-40T – The perfect all-rounder (4000 mAh)
The Samsung INR21700-40T (short "Samsung 40T") is perhaps the most versatile battery in the modern 21700 format. It solves the problem that users often have: The decision between maximum runtime or maximum performance. With 4000 mAh it offers an enormous capacity (33% more than a 30T), but still delivers impressive 35 amps (with temperature monitoring) or a stable 25 amps in continuous operation without cooling. This makes it the "egg-laying wool-milk sow" for almost all high-performance applications.Highlights at a glanceThe "sweet spot" of battery technology: The 40T combines the power of a high-current cell with the endurance of a high-capacity cell. It is the ideal compromise for users who do not need extreme competitive performance (as with the 30T) but want to work significantly longer.High capacity (4000 mAh): Offers significantly more energy reserve than classic 18650s (usually max. 3000 mAh at high current) or the Samsung 30T. This means longer evenings with the torch or more puffs on the e-cigarette before charging is required.Powerful power output: Even if it doesn't quite come close to the 30T, the 25-35 amps more than enough for 95% of all applications, including powerful e-bikes, hoovers and torches in turbo mode.Future-proof format: The 21700 format (21mm diameter, 70mm length) physically offers more volume for the chemistry than 18650s, which makes these performance data possible in the first place.Market-leading quality: Samsung SDI cells are known for their consistency. If you buy 10, all 10 will behave almost identically – important for battery packs.40T vs. 30T vs. 50E/50STo categorise the 40T, a comparison with its "siblings" helps:Samsung 50E (5000 mAh): Maximum runtime, but weak on the chest (only 10A). Suitable for e-bike "cruising" or normal lamps.Samsung 30T (3000 mAh): Maximum power (35A+), but battery drains quickly. Only for extreme peak loads.Samsung 40T (4000 mAh): The golden mean. Lots of power AND lots of runtime. It is therefore usually the best choice for everyday use. Features ModelSamsung INR21700-40T (Often referred to as 40T3) ApplicationPowerful torches, e-mobility (skateboards), professional tools Nominal capacity4000 mAh (The perfect compromise) Rated voltage3.6 V End-of-charge voltage4.2 V (standard CC/CV charge) Max. Discharge current**30 A** (continuous load) / **35 A** (temperature monitored < 80°C) / 45A (peak) Internal resistanceVery low (approx. 12 mOhm AC) - Low waste heat Protective circuit (PCB)No (Unprotected / Flat Top) - Caution during transport! ChemistryNMC (Nickel Manganese Cobalt) Dimensions (Ø x L in mm)21.1 x 70.3 (Does not fit into 18650 slots!) Weight (g)approx. 70 FAQs about the Samsung 40TWill the battery fit in my device, which previously had 20700 batteries?Yes in 99% of cases. 20700 and 21700 are almost the same length (70mm). The 21700 is only 1 millimetre thicker. Most battery compartments have enough clearance ("rattle") so that the 40T fits and is an excellent upgrade.Is it suitable for e-cigarettes?Yes, excellent. It is the standard for regulated 21700 battery carriers. You can easily vape up to 70-80 watts per cell and still have a very good runtime. Only for extremely low-resistance mechanical mods (under 0.12 Ohm) do professionals tend to use the 30T.Can I use it as a replacement for 18650?Only if the device is compatible. The 40T is thicker and longer. It does not fit into a pure 18650 tube. However, some devices are supplied with adapters and can take both sizes. Check the instructions.What does "T3" or "T4" mean on the battery?These are internal revisions (40T3, 40T4). This makes little difference to the end user as the performance data is almost identical.
Samsung INR21700-50E – The capacity
The Samsung INR21700-50E (often simply "Samsung 50E") is a top-class lithium-ion cell when it comes to maximum energy density. With a whopping 5000 mAh this battery offers the technically achievable upper limit in capacity for commercially available 21700 cells. It is the exact counterpart to the Samsung 30T: While the 30T is designed for raw power (amperes), the 50E is purely optimised for runtime and endurance.Highlights at a glanceMaximum energy reserve: With 5000 mAh this cell offers almost double the runtime of an average 18650 battery (2600 mAh). It is ideal for applications that need to run for days without being recharged.Low-drain characteristic: This battery is not built for high-current applications. It delivers a maximum of 9.8 to 10 amps of continuous current. This is sufficient for normal torches (up to around 1500 lumens), power banks or e-bike motors (in combination), but not for high-performance tools.The standard for e-mobility: Due to the enormous range possible with these cells, they are found in the highest quality battery packs for e-bikes (e.g. Bosch PowerTube), e-scooters and electric cars (Tesla used similar chemistry).High cycle stability: The 50E is known for being very durable. With correct handling (charging/discharging in the medium range) it survives hundreds of charge cycles with only minor capacity loss.Ideal for "Powerwalls": Because of its good price-per-mAh ratio and durability, this is the most popular cell for DIY home storage (solar power storage).50E vs. 40T vs. 30T – The decisionIt is crucial to understand the difference to avoid disappointment:Samsung 30T: A racing car. Extremely fast (35A), but the tank is quickly empty (3000 mAh).Samsung 40T: A sports car. Fast (35A) and good tank (4000 mAh).Samsung 50E: A long-haul lorry. Not very fast (10A), but goes extremely far (5000 mAh). Important: Do not use the 50E in an e-cigarette at high wattages or an ultra-bright tactical torch in turbo mode. The voltage would drop immediately. Features ModelSamsung INR21700-50E (Often also 50E2 or 50G) ApplicationE-bike batteries (range!), energy storage, moderate torches Nominal capacity**5000 mAh** (typ.) / 4900 mAh (min.) Nominal voltage3.6 V End-of-charge voltage4.2 V (standard CC/CV charging) Max. Discharge current**9.8 A** (constant) / 14.7 A (pulse) - Do not overload! Internal resistanceMedium (approx. 25-30 mOhm) – Becomes warm under heavy load Protection circuit (PCB)No (Unprotected / Flat Top) ChemistryINR / NMC (Optimised for energy density) Dimensions (Ø x L in mm)21.1 x 70.7 (Standard 21700) Weight (g)approx. 69 FAQs about the Samsung 50EWhat is the difference to the Samsung 50S?The Samsung 50S is the newer, significantly more expensive development.50E: 5000 mAh, max. 10A current. (endurance)50S: 5000 mAh, max. 25A current. (endurance + power) If you need a lot of capacity AND a lot of current (e.g. for a very powerful lamp), the 50S is the better (but more expensive) choice. For normal applications, the 50E is perfectly sufficient.How long does charging take?As 5000 mAh is a lot of energy, charging takes longer. With a standard charger (1 ampere) it takes approx. 5 to 6 hours. However, the cell can also handle a charging current of 2 amperes, which reduces the charging time to around 3 hours. Use a high-quality charger (e.g. from Xtar or Nitecore).Will it fit in my Olight Seeker / Warrior?Mechanically yes (21700 format). Electrically it depends: most Olight torches use special 21700 batteries with both poles on one side ("Customised Battery"). A standard Samsung 50E does not work in these torches and cannot be charged there either.Is it suitable for MTL vaping?Yes. If you vape "mouth-to-lung" at low power (10 to 20 watts), the current flow is low enough (under 10A). With a 50E battery you will achieve phenomenal runtime of several days.
Samsung ICR18650-30B – Lithium-ion battery (3000 mAh, 4.35V)
The Samsung ICR18650-30B is a high-quality lithium-ion round cell in 18650 format. It was primarily developed as an industrial cell for laptop batteries and energy storage. The special feature of this cell is its chemistry, which has a final charge voltage of 4.35 Volt (instead of the usual 4.20 volts). Only when charged to this voltage does it reach its full capacity of 3000 mAh. It is an "Energy Cell" (designed for endurance) and not a "Power Cell" (not for extremely high currents).Highlights at a glanceHigh energy density: With nominal 3000 mAh this cell offers a very long runtime for applications with moderate power consumption, such as normal LED torches (under 1000 lumens), power banks or laptop battery packs.High-voltage technology (4.35V): This cell is designed for a higher end-of-charge voltage of 4,35V designed. This enables a higher energy yield compared to standard cells, but requires a compatible charger for full power.Unprotected industrial cell: This is a Flat-top Battery without integrated protection circuit (PCB). This makes the cell shorter (65 mm) and ideal for battery packs, but requires caution when handling (no short-circuit protection!).Moderate power output: The maximum discharge current is approx. 5.9 amps (2C). This is sufficient for standard applications, but not suitable for e-cigarettes (vaping) or high-performance torches in turbo mode.Brand quality from Samsung: Samsung SDI cells are characterised by very low series dispersion, high cycle stability and safety when handled correctly.Important note on charging voltageThe ICR18650-30B is a 4.35V cell.Standard charger (4.2V): You can safely charge the cell in a standard Li-ion charger. However, the charger stops at 4.2 volts. The cell is then only charged to approx. 90% full (approx. 2700 mAh).Special charger (4.35V): To utilise the full 3000 mAh, you need a charger that can be switched to 4.35V (e.g. certain models from Xtar). Features ModelSamsung ICR18650-30B (High Voltage) ApplicationLaptop batteries, torches (with HV driver), industry Nominal capacity3000 mAh (with 4.35V charge) Rated voltage3.78 V (higher than standard 3.6V) End-of-charge voltage**4.35 V** ± 0.05 V (Attention: special charger required!) Final discharge voltage2,75 V Max. Discharge currentapprox. 5.9 A (2C) - Not a high-current cell! Protective circuit (PCB)No (Unprotected / Flat Top) ChemistryLi-Ion ICR (Lithium Cobalt Oxide) Dimensions (Ø x L in mm)18.4 x 65.0 (standard 18650) Weight (g)approx. 48 FAQs about the Samsung ICR18650-30BCan I use this battery in my e-cigarette?No, better not. With a maximum discharge current of just under 6 amps, this battery is too weak for most modern vaporisers. If overloaded, the battery will become hot and, in the worst case scenario, will burn out. Use high-current cells (such as Samsung 25R or 30Q) for this purpose.Will it fit in my torch?Mechanically mostly yes (18650 format). Electrically only if the torch draws less than 6 amps (which is usually the case for torches up to approx. 1000 lumens). As it is a Flat top battery, some lamps require a small magnet on the positive pole or a spring in the lamp head to make contact.What does "ICR" mean?The identifier usually stands for a cathode from Lithium cobalt oxide. This chemistry offers a high capacity, but is somewhat more thermally sensitive than manganese (IMR) or hybrid (INR) cells. ICR cells should therefore never be overloaded.Is it dangerous to use without a protective circuit?If you know what you're doing, no. But: The battery switches itself off in the event of a short circuit or deep discharge not itself.Do not leave it loose in your trouser pocket with keys (risk of short circuit!).Do not discharge it below 2.75 volts, otherwise it will break.