Something that has been bugging me lately:
The highest capacity 18650s available today are ~3100mAh but the best 17670 I could find was rated at 1800mAh.
The volume of a 17670 is 15213.78...cubic millimeters and an 18650 is 16547.14... cubic millimeters which isn't that big of a difference. Certainly not 1300mAh difference.
What's the deal? Is it just an uncommon and unimproved battery size?
exactly correct. the 18650 gets all the R&D money because it's very popular and common. Look at the physical volume of a 26650 or 32650, and you'll see that they too suffer from a lack of mAh / mm3
PPtk
18650 is the most technologically advanced. They use it in the Prius and stuff like that. Next year we'll have 3400mAh, and then 2 years later 4000mAh. By Panasonic, not AW/Redilast (rebranders)
And let's not forget that an Ultrafire 1800mAh cell will almost certainly not have a genuine 1800mAh capacity.....
Sanyo do produce a 16650 cell rated to 2100mAh minimum, 2200mAh typical, but getting hold of them in anything other than bulk quantities is difficult at this time.
Even this capacity, despite being much better than the 1600mAh best genuine capacity that we are accustomed to, still seems low in comparison to 18650s, even after accounting for the reduced volume, but it's a big step in the right direction. Having said that, some of this increased capacity is achieved by having a higher charging termination voltage.
Indeed!
We won't get 2200 out of it, this is the 4.3 Charge Volt type. But it's nominal voltage is 3.7.
Thinking of the normal 4.2V : 4.2V - 100%, 4.0V - 80%
So I'm guessing that for the 4.3V batts : 4.3V - 100% , 4.2V - 90%
We probably get 1950mAh-2000mAh if the cell would be charged to 4.2V with a standard charger.
It is a simple case of supply and demand, there are millions of these batteries out there. The very fact that most laptop computers use 18650 packs is the reason we have such great 18650s. The big computer companies invest millions of dollars into battery technology to increase the run time of there laptops because it is such an important selling feature.
The automotive industry has starting to pump money into R and D with Tesla using them, both Ford and Volkswagen are experimenting with 18650 cell packs. The Tesla uses Panasonic 18650s and runs 11 packs of 69 batteries in parallel.
The Prius actually uses D cell size batteries. The Chevy Volt and the Nissan Leaf use lion batteries but not 18650 size which was probably a mistake. I can see all electric cars using 18650 packs in the future.
A little off topic but can you imagine what 700 18650 cells exploding in a crash would be like.
Yep, as per my last paragraph, these do have a higher termination voltage - 4.3v as you stated.
Some hobby chargers (the iCharger range certainly, but most likely other higher end hobby chargers as well) allow the option to adjust the CC/CV peak voltage up to 4.30V, so it would actually be possible to use the full voltage range of these cells if you had one of these chargers.
I believe that Cottonpicker's charger can also be ordered set to provide a higher voltage - this would normally be 4.35v, but he may be able to set one to 4.30v.
Thank you for your input. I will be sure to check out the Louis Vuitton 17670 cells. I hope they have the LV monogram on the wrapper.
EDIT - This was a response to some spam. That spam is gone. Which means this post makes me look really retarded. Disregard please.
And then imagine what almost 7,000 18650 cells exploding in a crash would be like! That's actually how many cells the Tesla Roadster uses. Those 11 packs are actually "sheets" and there are 9 bricks of 69 cells in each sheet. When I first found out I had a hard time believing that was the real amount. That's crazy!
Also - I imagine the battery walls of 18650s and 17670s are of similar thickness. That means a greater % of the total volume is not actually energy-storage in the 17670.
R&D aside - look at AA & AAA batteries. AAA should have less - but not *as* much less as they do, the explanation is that the cell wall doesn't get proportionally thinner as battery sizes shrink.
This is true, 'scaling' the capacities of the cells in direct correlation with diameter is not going to give an accurate indication of the capacity of the cell. Internal components are also likely to be the same as those found in 18650 cells, losing even more volume. However, with reference to the more common 1600mAh capacity, rather than the 2200mAh Sanyos, you still wouldn't expect a 1mm reduction in cell diameter to lead to an almost 50% reduction in capacity (compared to Panasonic's 3100mAh 18650 cells).
I was looking at a thread regarding an i4 style charger that another member had found (confusingly, located in the 18650 light forum, rather than in the charger forum.....), and saw that in one of the posts, someone had posted a screenshot of a site listing this charger. I have an i4, so that didn't interest me.
Something else caught my eye though.....
http://www.intl-outdoor.com/sanyo-ur16650zt-lion-battery-p-214.html
High-cap Sanyo 16650s being sold individually, for a decent enough price (assuming the real deal), free shipping if you buy three or more, and with the option to add a protection circuit (for an additional charge).
Sanyo's own documentation shows that these cells tend to sag a fair amount with high current draw, but these may be of interest to some people depending on their light's power characteristics.
Damn, 4.3 volt cells. I would have to buy another charger for those.
I wonder what the capacity would be if charged to 4.2 volts...
I've ordered three - minimum number for free shipping, and just what I need for my triple XM-L tri-bored Mag, or tri-bored Mag85 (though the current draw on that may be too high). Meant to be here in approximately three weeks. Hopefully I can do some testing at both 4.3 and 4.2v and so what the real difference in capacity ends up being.