18650 panasonic 3400mah 1Rechargeable lithium ion 18650 batteries are common power source choice for many electric and electronic devices often found on small and large fishing or leisure boats and even kayaks. Since their characteristics degrade over time, they must be occasionally replaced - and choosing right replacement can be a nightmare, but it shouldn't be! Also, after replacing with new batteries, old batteries should be recycled!

18650 batteries are commonly found in diving, tactical, EDC and other flashlights, in battery packs powering cordless electric tools, marine electronics, trolling motors etc.

Before buying new 18650 batteries, there are many things to consider.

18650 Batteries - Features

Dimensions - official physical dimensions of 18650 rechargeable batteries are (diameter x length) 18.6 × 65.2 mm (0.73 x 2.56 inches). When these values are rounded, they are 18 mm diameter, 65 mm length, hence the name '18650' battery.

But, these dimensions differ slightly from model to model, but in most situations, these small variations are not so important.

Other very similar batteries are:

- 16650 battery - same length, but slightly narrower batteries. Some devices accept both 16650 and 18650 batteries, just be aware that 16650 batteries often have lower capacity and come unprotected (no protective electronics in the battery),

- 19670 battery - slightly larger battery than 18650 battery. 19670 batteries commonly come with protective electronics (protect the battery from short circuit, overcharging, prevent overheating and similar), and are known as 'protected 18650 batteries'. But there are also unprotected 19650 batteries, often offering really large capacities, especially when compared with high-drain, protected 18650 batteries.

- CR123A battery - this is primary (non-rechargeable) 3 V lithium battery, 17 mm diameter, 34.5 mm in length. Some devices accept both 18650 battery or two CR123A batteries for one 18650 battery. Main advantage of CR123A batteries is their extra long shelf life - up to or even more than 10 years. For example, some EDC flashlights for occasional use recommend CR123A batteries and for regular use they recommend 18650 batteries. Of course, there are also rechargeable CR123A batteries, offering 3.6-3.7 V per cell, slightly smaller capacity than primary CR123A - such batteries are often designated as 16340 batteries.

- 17670 battery has twice the length of standard CR123A battery and often can be used instead of 18650 (if additional 2 mm are not problem).

Note: having an option to replace 18650 battery with another battery sounds great, but the best replacement battery for 18650 battery is another 18650 battery :)

Protected battery - protected lithium ion batteries come with a protective electronic circuitry which monitors parameters of the battery and protect the battery from overcharging, over-discharging, high charging/discharging currents, prevent overheating etc. Since lithium ion batteries pack lot of energy in small packages, having protective circuitry is recommended. On the other hand, this circuitry decreases capacity of the battery. IMHO, for small devices like flashlights and similar, where current drain is rarely above 1-2 Amps, protective electronics in batteries is overkill, especially since many modern flashlights already comes with smart electronic controllers which also monitor the status of the battery.

18650 button flat type

Button or flat type - some models come with button top side (positive), while some batteries come with flat top side. Before purchasing new 18650 batteries, be sure to check your old batteries - most devices and chargers accept both models, but better safe than sorry. Photo above batteries - on the right is positive (top) side of 'flat top' battery and on the left side is positive (top) side of 'button top' battery.

Soldering tabs or not? When building a battery pack, soldering tabs help significantly. However, be very careful when building custom 18650 battery pack - be sure that all of the batteries come from the same manufacturer, that they are of the same model and preferably the same batch! 

ohmash 18650 40aConnecting in parallel or in series - connecting lithium ion batteries in parallel can be done using special circuitry. Reason is that even the slightest variations in capacity and chemistry can lead to over-discharging or overcharging some cells, which can lead to overheating and possible fire hazard. Connecting lithium batteries in series is relatively safe, when protected cells from the same manufacturer are used. When individual cell is, for example over-discharged, it will shut off and whole pack will stop to provide energy. If more such packs are connected in parallel, this can lead to over-stressing remaining 'sub-packs'.

When connecting 18650 batteries in series, they provide:

- two 18650 cells produce 7.2V,

- three 18650 cells produce 11.1V,

- four 18650 cells produce 14.4V,

- five 18650 cells produce 18.5V,

- six 18650 cells produce 22.2V,

- seven 18650 cells produce 25.9V, etc.

High capacity vs. high current 18650 batteries - some batteries are optimized for capacity, some batteries are optimized for high discharge currents. High capacity 18650 batteries come with stated capacities of 5000 or even 6000 mAh, but their continuous discharge currents are rarely larger than, for example, 10 Amps. Some batteries can safely provide 30 A, continuously, but such batteries rarely have capacity of more than 2000-2500 mAh. Newer lithium ion manganese oxide batteries improve maximum stated continuous currents, while having 'decent' capacity.

Choosing the right battery depends on your application - if it is flashlight or electronic device, requiring just few Amps, go for high capacity models. For high power devices, go for high current batteries.

Note: if you need lightweight fishfinder or even trolling lithium battery, consider purchasing finished lithium battery pack - some manufacturers even offer lithium packs with built-in protective circuitry allowing such packs to be charged using lead-acid battery chargers. On the other hand, such battery packs cost much more than lead-acid fishfinder or trolling motor batteries.

 Rewrapped batteries or not? Battery brand is very important, since large brands like Samsung, Sony, Panasonic or LG thoroughly test their batteries and discard bad ones.

However, there are many companies that buy finished cells and wrap them with their own markings. Such wrapped batteries can come from reputable manufacturers and can be quite good batteries, but there are also cheep knockouts which are simply not good. And NOT safe.

So, when buying 18650 batteries, be sure to get batteries from reputable sellers/manufacturers and the batteries with good reviews.

Following table lists few high quality 18650 batteries:

Model Capacity Max. Continuous Current Comment Amazon Link
LG HD2 2000 mAh 30 A - LG HD2
LG HE4 2500 mAh 20 A - LG HE4
LG HB6 1500 mAh 30+ A Very powerful battery -
LG HG2 3000 mAh 20 A - LG HG2
Panasonic NCR18650B 3400 mAh 6.8 A (12 A, 5 sec) For low current devices. NCR18650B
Samsung 25R 2500 mAh 20 A Great sturdy battery. Samsung 25R
Samsung 30Q 3000 mAh 15 A Can go up to 20A, but ... Samsung 30Q
Sony VTC4 2100 mAh 30 A - Sony VTC4
Sony VTC5 2600 mAh 20 A - Sony VTC5

Note: Amazon affiliate links in the table open in the new windows.

Although there are many other 18650 batteries on the market (with higher claimed capacities, very low self-discharge rates, high dicharge currents), if you need general, sturdy and tough battery, go for Samsung 25R - it is very popular battery with good maximum current and 'decent' capacity. We say 'decent', but this battery can withstand many charge/discharge cycles, it is reliable and is very often used as a 'standard battery' for evaluating other batteries. Also, LG HG2 is very good battery with nice balance between capacity and maximum continous current.

If you need good and reliable, high capacity battery, go for Panasonic NCR18650B 3400 mAh battery. There are 18650 batteries on the market with larger capacity, even with good reviews, but ... Last thing than a fishermen or outdoor enthusiasts need is failed equipment because of the cheap, unreliable batteries. Never go cheap with batteries and similar equipment - one day, your life can depend on it!

Note: author of this article has Masters degree in electronics and he still uses dual purpose AGM lead acid battery as the main boat battery and he does NOT plan on moving to lithium ion batteries as the main boat battery any time soon - actually, probably not for next few decades. However, his main flashlights are powered via rechargeable 18650 batteries AND non-rechargeable CR123A (with few new CR123A as spare batteries), just to be sure :)

What Does IMR, IFR, ICR, INR Stand For?

 Often, one can see letters IMR, IFR and ICR as part of battery labels.

These letters describe battery chemistry:

- IMR batteries are based on LiMn204 (Lithium Manganese Oxide) chemistry, their nominal voltage is 3.6 - 3.7 V, maximum recommended charging voltage is 4.2 V. IMR batteries commonly has smaller capacity, but are capable of delivering stronger currents.

- IFR batteries are based on LiFePO4 (Lithium Iron Phosphate) chemistry, their nominal voltage is 3.2 - 3.3 V per cell, maximum recommended charging voltage is 3.5 - 3.6 V.

- ICR batteries are based on LiCoO2 (Lithium Cobalt Oxide) chemistry, their nominal voltage is 3.6 - 3.7 V, with maximum recommended charging voltage 4.2 V. They commonly have higher capacities, but maximum allowed currents are limited to just few C, if even that.

- INR batteries are based on LiNiMnCoO2 (Lithium Manganese Nickel) chemistry. Very similar to IMR batteries, they can provide plenty of currents, with slightly lower capacity.

Note: unprotected ICR batteries vent out easily, but other chemistry batteries must be treated with respect, too! Also, there are other technologies, including hybrid technologies like: Lithium Nickel Cobalt Oxide (LiNiCoO2), Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2), etc.

Best 18650 Battery Chargers

When buying good 18650 battery charger, there are few things to consider, like:

- number of battery slots,

- safety features (reverse polarity, overcharging, charging modes etc.),

- maximum charging current,

- charging of all 18650 battery types, regardless of their chemistry,

- optional charging of other batteries, not just 18650 batteries,

- charging of different batteries at the same time, etc.

Big brands like Sony, LG, Samsung and Panasonic have very good chargers, but there also chargers from other companies that perform exceptionally well.

Following table lists some of the most popular, high quality, 18650 battery chargers (alphabetic order):

Charger Number/Types of Batteries Notes Amazon Link
18650 ebl charger t
EBL Smart Battery Charger

2 slots

18650, 26650, 22650, 17670, 18490, 16340 (RCR123), 14500, 10440 Li-ion cylindrical and AA, AAA, C Ni-MH Ni-CD batteries

 Small and portable - power input: 100-240V AC 50/60Hz DC: 12V 8W;
charging current up to 500 mA, three charging modes, overheat-detection to prevent over-charging, automatically stop charging when the batteries are fully charged
EBL Smart Battery Charger
18650 efest luc v4 t
Efest LUC V4 LCD Universal Battery Charger

4 slots

10440, 18350, 14500, 18500, 16650, 18650, 26650 

Protects batteries from over-discharging, over-voltage, short-circuit and reverse polarity; USB output for charging cell phones; functions as a portable power bank; 4 fully independent charging channels; automatic stop; max charging current 2 Amps;  26650 batteries only in middle slots; Efest LUC V4 LCD
18650 foxnovo f 4s t
Foxnovo F-4S LCD Battery Charger

4 slots

26650, 22650, 18650, 18500, 18490, 17670, 17650, 17500, 16340, 14500, 10440 and Ni-MH /Ni-CD: A, AA, AAA, C, SC 

 4 independent charging channels; automatic stop; max charging current 1 Amp; reverse polarity protection, short-circuit protection; input - 110V AC and 12V DC (car) Foxnovo F-4S
18650 digicharger d4 t
NiteCore DigiCharger D4 

D4 - 4 slots; D2 - 2 slots

Li-ion: 26650, 22650, 18650, 17670, 18490, 17500, 18350, 16340 (RCR123), 14500, 10440;
Ni-MH/Ni-Cd: AA, AAA, AAAA, C 

4 independent charging channels; input - AC 100-240V 50/60Hz 0.35A, DC 12V 1A; output voltage - 4.2V ±1% / 3.7V ±1% / 1.48V ±1%; output current - 375mA x 4 / 750mA x 2; overcharge and overheat protection, automatic stop 

NiteCore-D4

NiteCore-D2

18650 nitecore intellicharge i4 t
NiteCore i4 Intellicharge Universal Smart Battery Charger 

4 slots

Li-ion: 26650, 22650, 18650, 17670, 18490, 17500, 18350, 16340 (RCR123), 14500, 10440;
Ni-MH/Ni-Cd: AA, AAA, AAAA, C 

4 independent charging channels; three charging modes; overcharge, overheat, reverse polarity protection, automatic stop  NiteCore i4
18650 xtar vp4 t
XTAR VP4 

4 slots

four Li-ion: 10440, 16340, 14500, 14650, 17670, 18350, 18490, 18500, 18650, 18700;
two Li-ion: 22650/25500/26650 

 4 independent charging channels, each with 3 stage charging; 3 current level selections; low voltage, over-load, reverse-polarity and over-heat protection; XTAR VP4

Note: Amazon affiliate links in the table open in the new window.

Obviously, there are many more 18650 battery chargers, but these chargers are very popular for their features and are often considered 'the best' on the market.

But which one is really 'the best'? Well, it depends on many things, but IMHO, if you are not 100% sure, be sure to check NiteCore DigiCharger D4 Amazon link.

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