educate me on batteries

In another thread I was looking for a specific light for drone search and rescue. Im trying a few but one light uses 21700 batteries. I can find them in 4000 mAh and 4800 and 5000. Im confused as to battery specs and these terms. Can somebody point me in the right direction?

Think of mAh as the size of the batteries gas tank.
The larger the number, the longer the battery can produce a given output. IE. Longer Run time for the light.
As long as the voltage remains constant.
Another factor is the amount of current a battery can supply at a given time.
Some batteries are only rated for a few amps current draw, while others can safely put out many amps without any issues.
The design of the flashlight determines the current draw at different brightness levels. You want a battery that can keep up with your desired light output current draw.
Hope this Helps,
All the Best,

Meant to add, that “usually” higher current draw cells often have lower capacities - Lower mAh ratings.
But many 21700 cells can produce plenty of current for all but the most demanding lights.

Thanks for that. The light I bought is a sofirn sp35 and when I bought it I had the option of buying it with 4000 or 5000 mAh so I opted for the 5000, since Im dumb I figured that since that option was a little more money it must be better.

If it’s a Sofirn branded battery, you did good. Every Sofirn I’ve tested has always met or exceeded its mAh rating.
Just be aware that there are many batteries that claim outrageous outputs. For example a 18650 with a 9800mAr rating.
These are bogus cells that are at best just a crappy battery, at worst a fire waiting to happen.
You can find out way more info over in the battery forum. A member, HKJ, has a vast amount of battery tests there.
All the Best,


You could have taken either cell they offered with this light - both are fine. The 4000mAh is a Lishen LS2170SA and the 5000mAh is a Lishen LR2170SD battery. Both batteries perform quite similar up to 10A current. The little extra money for the 5000mAh battery will result in a little bit more runtime. Be careful with the SP35, though. This flashlight has no thermal regulation (yet), i.e. it will not step down its brightness on turbo but gets really really hot (> 80°C). Step down manually once the lights gets too warm in your hands. ;-)

Im buying because of the lack of step down. I want the max lumens 100% of the time since this light (actually 2 of them) will be fan cooled and only used outdoors . They will be mounted on a search and rescue drone right under the front rotors so the downwash from the props will really blow a lot of night air over them. They wont be held by hand.

More questions from a newb. I got 2 chargers. The larger one from nitecore when I bought the ec11 lights and the small came with the drone for the signal booster batteries. will these work with the 21700’s. I dont think these chargers will work with 21700’s

What are the active buttons for “C” and “V” Id expect them to mean current and voltage but why would I press either

Lastly, what is the best and most reliable and dependable brands I should be looking for in batteries???

The best brands are the big names: LG, Panasonic, Samsung, Sony/Murata, Molicel. I’ve not tried any of the Vapcell ones from aliexpress but people say they’re decent.

For high capacity, relatively low discharge rate 21700 batteries I have some Molicel M50A. For maximum discharge rate I have Molicel P42A.

Lastly, the chemistry of the battery can make them slightly safer. Someone correct me if I’m wrong but from what I remember the INR chemistry is the safest (though slightly lower performance).

The C and V buttons may be for charging at constant current/constant voltage? I’m not so sure about this though

If the charger supports 18650 and you can fit a 21700 in there it will charge it just fine

Additional info for OP : Maybe add in Sanyo as some are still sold in the name of Sanyo. Even buying from these big brands, as they are BIG BRANDS, a lot of fake cells in the market. BEWARE! It will take some time to understand about batteries. Here are 2 posts that might help if you have time.

As for rewrap cell, I will trust Vapcell a bit more than the other few popular around.

would I want protected or unprotected batteries for this light?

An SST40 LED putting out 2000 lumens will draw about 6 amps, so as long as the cell protection doesn’t kick in before that you’ll be fine with either. Lots of protected cells have a 10A max so you should be fine. It’s a constant current driver though, so a high current battery won’t make it any brighter.

Unprotected Samsung INR21700-40T would be my recommendation.

You should be reading up about battery safety if you’re new to lithium cells

If misused they can explode, so it’s important to have a read.

Make sure you run a test before launching your drone with the SP35 set on Turbo, you don’t want an exploding drone. Worst case I read ages ago on here was a SkyRay King flashlight exploding, the shrapnel shattered his windows, thankfully he wasn’t in the room or holding the thing.

good question

the site says:

“Low voltage protection: yes”

“using one Protected 21700”

so, by my reading, they claim LVP, but they also say they use a Protected LiIon

so if It was me, I would use Protected LiIon

unless someone knows for a fact (and can provide a link confirming) that the driver (not the battery) has built in LVP

I reviewed this model and can confirm 2.80v cut off.

Use unprotected since it’s harder to find chargers that’ll fit a protected 21700. From the pics above it looks as if an external charger will be used.

Don’t pay any attention to the runtime specs since there’s no temp regulation on this batch.