I’m a newbie here, and seeing these terms used quite a bit… and not sure how it relates to what I need. I assume protected means there’s ovld protection built in to the batteries, unprotected- none. Button tops… flat tops…. I assume differences in length’s for these different types, how do I determine what I should use- what will fit- and which will be the best choice for me??
Thanks!
Wes
Anyone who is new to li-ion should definitely get quality protected cells imho. Really anyone would do well to stick to quality protected cells unless they had a reason to want unprotected. Some like to really overdrive LEDs & push their cells.
Best price for quality Protected NCR18650B 3400mAh
Trustfire / _any_fire are junk. Clear wrapped “Protected” cells like these NCR18650B (protection added by a mystery company) tend to use junk protection. 3 out of 4 of those clear wrapped protected cells failed in one report.
If you search for flashlight reviews on here they should mention if the light has any issues fitting protected.
If you don’t know answer to title question get the protected button top and you will be fine 
There, problem solved 
Only problem with protected cells is its size.
Not all flashlights designs are made to accommodate the extra length.
Protected button tops like the ncr18650b are the way to go.
You are sure to get lots of conflicting advice around here but there are some general tips that you could take heed of.
Try to buy quality cells and stay away from crapfire brands.
Always use protected cells if you are planning on running more than one of them in series.
Invest in a good quality charger and never leave Li-Ion cells charging unattended or on a flammable surface.
Try to understand that not all cells meet the exact dimensions they are supposed to. Protected cells can be longer or wider than you would expect and this can cause some fitment problems in smaller lights.
Flat-topped cells may have trouble making contact in lights with physical reverse polarity protection. A light that has a spring on the positive contact will be able to use a wide range of cell tops.
A cell which is too long can damage either the light or the cell if you tighten the tailcap too much. It is also possible if the tailcap doesn't screw down properly that you may compromise your waterproofing.
Spend some time reading and researching here (or even CPF if you like) and you will find a wealth of info. Look up member HKJ for detailed tests on cells and chargers - heaps of great info on his site as well.
Thanks so much for the inputs… I really appreciate the comments. Yes, I know I may get conflicting information, but it’s not hard- given different/varying inputs- to make a choice for myself. I should have a better understanding of batteries, being an electronics tech- but I don’t work with/use batteries in my work really, and the past little experience in batteries used in R/C systems is old and out of date.
I know chargers are an important part of the equation, and intend to ensure the chargers I get are top quality. Doesn’t make any sense to scrimp on either the batteries or the charger :bigsmile: I just bought some Tenergy Centura C/D cells for my 2 MagLights, and got their matching charger, their best model. I have 3 other lights coming, I know at least a couple use 18650’s, so I’m going to be looking for a quality charger for them as well. 1- a SupFire Cree X5-T6- comes with a charger, but I’m sure it’s a cheap, generic charger, and am looking for a better one.
Wes
Really interested with these NCR18650B protected batteries. It looks the same as Mountain Elect version.
http://www.aliexpress.com/item/10pcs-lot-free-shipping-18650-protected-li-ion-battey-ncr18650b-3400mah-for-LED-Lighting/699995461.html
You probably need to get more sets to reduce the shipping price. Wish someone is staying near my area to share the deal.