21700 Batteries i bought are 77mm long not 70 why ?

buckyball

Newly Enlightened
Joined
Mar 18, 2014
Messages
79
Location
England UK
just bought 4x Keeppower branded 21700 batteries in england uk £11.49 each but when i tried to put them in my charger that says it can do 21700 batteries they wouldnt fit ! so i measured them and i make them approx 77mm long, i though 21700 were always 70mm ? what is going on ? i ordered a new jetpower torch to put these in ( due in a few days ) if they dont fit i will have to return them to the seller

keeppower is a brand i heard about on this forum and they have good 18650 batteries
if i do decide to keep them what charger would 77mm long bateries fit in ?
thanks
update 8december 2023
keeppower replied to my email :
We have
https://www.keeppower.com.cn/products_detail.php?id=599
lenght: 75mm,
need charge by PD2 https://www.keeppower.com.cn/products_class2.php?bid=21&sid=61
and
https://www.keeppower.com.cn/products_detail.php?id=662
Lenght: 76.7mm,
it can be charge by a TYPE-C cable or charge by PD2 https://www.keeppower.com.cn/products_class2.php?bid=21&sid=61
PD2 charger please buy from: website: www.akkuteile.de
Thanks and best regards.

Allen Li/KeepPower Supports Manager
KEEPPOWER TECHNOLOGY CO., LIMITED
ADD: Bld 4, Yongfa Hi-Tech Park, 113 Jiaoping Avenue, Tangxia, Dongguan 523710, China
TEL: +86-769 8295 3418
Mobile: +86 139 2371 1713
Email: [email protected]
Website: www.keeppower.com.cn
 
Last edited:

F89

Flashlight Enthusiast
Joined
Mar 15, 2014
Messages
1,420
I just measured a protected 21700 (the only one I have) and it measures about 74mm.
I would expect that all protected 21700 batteries would be more than 70mm, although 77mm sounds like it's going to be longer than most?
 

aznsx

Flashlight Enthusiast
Joined
Apr 24, 2015
Messages
1,682
Location
Phoenix, AZ USA
just bought 4x Keeppower branded 21700 batteries in england uk £11.49 each but when i tried to put them in my charger that says it can do 21700 batteries they wouldnt fit ! so i measured them and i make them approx 77mm long, i though 21700 were always 70mm ? what is going on ? i ordered a new jetpower torch to put these in ( due in a few days ) if they dont fit i will have to return them to the seller

keeppower is a brand i heard about on this forum and they have good 18650 batteries
if i do decide to keep them what charger would 77mm long bateries fit in ?
thanks

Firstly - I don't know the answer; however I believe others have reported that the latest version Vapcell S4+ charger accommodates their protected 21700 cells. The web page mentions that it accepts "21700 w/ button top and PCB", although it also lists max length at 75mm.

If it does work for cells like yours and you decide to go with it, you should set it for 'manual' rather than 'auto' charge current selection, as an earlier version HKJ tested reported erroneous internal resistance results ("The internal resistance calculation is wrong"), and that's used to determine charge current in 'auto' mode. That may or may not have been fixed since that test of the earlier model, but just thought I'd mention it. There might be a more recent test / review somewhere which addresses that.

Again, I have no 21700 cells, and have never used the Vapcell S4 - just thought it might be one to look at.

Here's the web page for the S4:

...and here's the referenced test of the earlier version:
 

aznsx

Flashlight Enthusiast
Joined
Apr 24, 2015
Messages
1,682
Location
Phoenix, AZ USA
I was just at the Malkoff site, and recalled they sell a similar cell, so I checked theirs and they list it at 75.0 mm(?).
Maybe you got the 'XL' version;-)

 
Last edited:

Mike G

Newly Enlightened
Joined
Jan 25, 2022
Messages
57
Location
Canada
so i measured them and i make them approx 77mm long, i though 21700 were always 70mm ? what is going on ? i ordered a new jetpower torch to put these in ( due in a few days ) if they dont fit i will have to return them to the seller
70mm is just the length of the "core", the actual electrochemical cell itself - protection circuits and button terminals are considered an optional extra for Li-ion cells and don't need to conform to the 70mm core envelope.

Keeppowers are indeed pretty good by most accounts. Don't return them - you ain't gonna find a protected button-terminal cell that fits in the "just barely" 21700 chargers (sometimes they're nice enough to put an asterisk next to the spec that says "unprotected flat-top only" or somesuch).

Here's a convenient review repository: https://lygte-info.dk/info/roundCellChargerIndex UK.html
Each parameter is sortable, so you can sort by battery length and only consider chargers that will fit your cells. Most chargers that will fit a cell that long are good, though some are better than others. Many options. The Vapcell S4 is listed there as a 76mm but that's rounded down, the actual measurement is 76.9 so it will fit a 77mm. I'd reckon most 76mm chargers will have enough fudge room to fit a 77mm.
 
Last edited:

Guitar Guy

Enlightened
Joined
Oct 23, 2016
Messages
590
Location
West Virginia
I don't know if this will help, but you may give it a try.

My Fenix charger also does 21700, but most of my cells are a little too long for the charger slots. However, I am able to insert them into the slot, negative end first, and push the positive end down far enough for the lower edge of the button to make contact and charge with no problem. I'm able to get all 4 cells in and charging, even though the positive ends are riding a little higher than the negative ends. They don't necessarily have to be snapped all the way down to where they are flat level, as long as they contact the charger terminal.

I don't know if you've tried this, but it may work, unless your slots are just way too short. Good luck.
 

buckyball

Newly Enlightened
Joined
Mar 18, 2014
Messages
79
Location
England UK
I just measured a protected 21700 (the only one I have) and it measures about 74mm.
I would expect that all protected 21700 batteries would be more than 70mm, although 77mm sounds like it's going to be longer than most?
keeppower replied to me :
We have
https://www.keeppower.com.cn/products_detail.php?id=599
lenght: 75mm,
need charge by PD2 https://www.keeppower.com.cn/products_class2.php?bid=21&sid=61
and
https://www.keeppower.com.cn/products_detail.php?id=662
Lenght: 76.7mm,
it can be charge by a TYPE-C cable or charge by PD2 https://www.keeppower.com.cn/products_class2.php?bid=21&sid=61
PD2 charger please buy from: website: www.akkuteile.de
Thanks and best regards.

Allen Li/KeepPower Supports Manager
KEEPPOWER TECHNOLOGY CO., LIMITED
ADD: Bld 4, Yongfa Hi-Tech Park, 113 Jiaoping Avenue, Tangxia, Dongguan 523710, China
TEL: +86-769 8295 3418
Mobile: +86 139 2371 1713
Email: [email protected]
Website: www.keeppower.com.cn
 

buckyball

Newly Enlightened
Joined
Mar 18, 2014
Messages
79
Location
England UK
70mm is just the length of the "core", the actual electrochemical cell itself - protection circuits and button terminals are considered an optional extra for Li-ion cells and don't need to conform to the 70mm core envelope.

Keeppowers are indeed pretty good by most accounts. Don't return them - you ain't gonna find a protected button-terminal cell that fits in the "just barely" 21700 chargers (sometimes they're nice enough to put an asterisk next to the spec that says "unprotected flat-top only" or somesuch).

Here's a convenient review repository: https://lygte-info.dk/info/roundCellChargerIndex UK.html
Each parameter is sortable, so you can sort by battery length and only consider chargers that will fit your cells. Most chargers that will fit a cell that long are good, though some are better than others. Many options. The Vapcell S4 is listed there as a 76mm but that's rounded down, the actual measurement is 76.9 so it will fit a 77mm. I'd reckon most 76mm chargers will have enough fudge room to fit a 77mm.
thanks Mike i will look into chargers once the torch i intend to fit them into arrives, if they will fit ok in the torch i will keep them and sort out a new charger
 

buckyball

Newly Enlightened
Joined
Mar 18, 2014
Messages
79
Location
England UK
I was just at the Malkoff site, and recalled they sell a similar cell, so I checked theirs and they list it at 75.0 mm(?).
Maybe you got the 'XL' version;-)

keeppower told me :
We have
https://www.keeppower.com.cn/products_detail.php?id=599
lenght: 75mm,
need charge by PD2 https://www.keeppower.com.cn/products_class2.php?bid=21&sid=61
and
https://www.keeppower.com.cn/products_detail.php?id=662
Lenght: 76.7mm,
it can be charge by a TYPE-C cable or charge by PD2 https://www.keeppower.com.cn/products_class2.php?bid=21&sid=61
PD2 charger please buy from: website: www.akkuteile.de
Thanks and best regards.

Allen Li/KeepPower Supports Manager
KEEPPOWER TECHNOLOGY CO., LIMITED
ADD: Bld 4, Yongfa Hi-Tech Park, 113 Jiaoping Avenue, Tangxia, Dongguan 523710, China
TEL: +86-769 8295 3418
Mobile: +86 139 2371 1713
Email: [email protected]
Website: www.keeppower.com.cn
 

buckyball

Newly Enlightened
Joined
Mar 18, 2014
Messages
79
Location
England UK
Does it have a USB port in it?
yes they do so i can charge them that way but i would also like to be able to charge them in a charger as that would be 1 plug i would need not 4 seperate plugs if charging 4 at a time eg if on holiday
 

Chicken Drumstick

Flashlight Enthusiast
Joined
Dec 9, 2011
Messages
1,651
Location
UK
just bought 4x Keeppower branded 21700 batteries in england uk £11.49 each but when i tried to put them in my charger that says it can do 21700 batteries they wouldnt fit ! so i measured them and i make them approx 77mm long, i though 21700 were always 70mm ? what is going on ? i ordered a new jetpower torch to put these in ( due in a few days ) if they dont fit i will have to return them to the seller

keeppower is a brand i heard about on this forum and they have good 18650 batteries
if i do decide to keep them what charger would 77mm long bateries fit in ?
thanks
update 8december 2023
keeppower replied to my email :
We have
https://www.keeppower.com.cn/products_detail.php?id=599
lenght: 75mm,
need charge by PD2 https://www.keeppower.com.cn/products_class2.php?bid=21&sid=61
and
https://www.keeppower.com.cn/products_detail.php?id=662
Lenght: 76.7mm,
it can be charge by a TYPE-C cable or charge by PD2 https://www.keeppower.com.cn/products_class2.php?bid=21&sid=61
PD2 charger please buy from: website: www.akkuteile.de
Thanks and best regards.

Allen Li/KeepPower Supports Manager
KEEPPOWER TECHNOLOGY CO., LIMITED
ADD: Bld 4, Yongfa Hi-Tech Park, 113 Jiaoping Avenue, Tangxia, Dongguan 523710, China
TEL: +86-769 8295 3418
Mobile: +86 139 2371 1713
Email: [email protected]
Website: www.keeppower.com.cn
If the battery has a protection circuit or USB socket on it, it'll be longer.

There are lots of options for batteries. Generally Samsung or Sony are good. However I can recommend these from this seller:

Good performance runtimes and will fit your charger.
 
Top