26650 vs 18650 amps

[jmc1980]

sorry if this has been asked before. it seems that 30 amp 18650 cells are nothing new. the lg hb2, hb4, and hb6 are all good 30 amp 18650's. however, the ijoy inr 26650 40 amp cell is the only 26650 that is rated by mooch at 30 amps. it seems all the other 26650 cells are below 30 amps. all the 30 amp lg's i mentioned are 1500 mah. the ijoy 26650 is 4200 mah. it surprises me that the 26650 cells don't have more amps because they are so much larger, although the higher mah makes sense. thank you to anyone who can explain why these cells perform this way.

 

[Shawn Hoefer]

sorry if this has been asked before. it seems that 30 amp 18650 cells are nothing new. the lg hb2, hb4, and hb6 are all good 30 amp 18650's. however, the ijoy inr 26650 40 amp cell is the only 26650 that is rated by mooch at 30 amps. it seems all the other 26650 cells are below 30 amps. all the 30 amp lg's i mentioned are 1500 mah. the ijoy 26650 is 4200 mah. it surprises me that the 26650 cells don't have more amps because they are so much larger, although the higher mah makes sense. thank you to anyone who can explain why these cells perform this way.

It's the size, popularity, and chemistry... the 18650 cells have been so popular, the manufacturers have focused on getting them better, and most of the 26650 cells are using 2014 tech or older. The size is a contributing factor as all that mass leads to increased internal resistance which leads to heat when discharging, reducing the CDR.

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[Barkuti]

Besides the relative amount of involved R&D, there's an additional factor which needs to be understood, and this is energy density. At comparable values of internal resistance and format, power cells with higher levels of energy density will have lower continuous ratings because these need to be adjusted to meet thermal limits. One of the main reasons LG HBx type cells have 30A ratings is their low capacity; Sony VTC5As can't have such continuous rating because they would overheat before end of discharge, not because of comparatively sub-par internal resistance.
26650 cells have not been developed by the big f̶o̶u̶r̶ three (Panasonic-Sanyo, Sony -soon Murata- or LG). Their internal resistance is comparatively “high”. There are, however, some nice cells, like the IJOY INR26650 4200mAh, and I'll also mention here the latest units from PLB (LiitoKala 26650-50A and Shockli IMR26650 5500mAh) because of their advances in energy density (Shockli IMR26650 5500mAh has proven to deliver almost 5600mAh down to 2.8V at 20A!).
A123's LiFePO4 ANR26650M1-B can do 60A continuous hitting ≈80°, but this in part is because of its low energy density (effective capacity above 2500mAh down to 2V).

Cheers