The new 18650-format cells that are just now becoming available are an exciting milestone that changes everything in the high-performance E-bike world. Back in 2013, we wrote about the trend of E-bikes using 18650 cells with the NMC and NCA chemistry. In 2014, we wrote about the recent availability of high-current cells (so you didn’t have to use LiPo for high performance). Well, now…in 2015, the story to know is about medium and high-current 18650 cells from a variety of sources, that have a higher capacity.
18650 = 18mm in diameter, 65mm long.
What about LiPo?
Batteries have been the biggest performance hold-up in the electric bike world…until now! Before I get started, I know some of you will think I am forgetting about LiPo. I’ve used LiPo before, I own LiPo right now, and trust me when I say…LiPo will never catch on with the general public. LiPo is for high performance enthusiasts, but…the charging systems are too cluttered and complex, and although many LiPo users can assemble a pack together cheaper than a pack made from 18650 cells, a LiPo pack that is used daily to a full discharge/charge cycle will likely only last for one years riding season.
If you want to argue that you have managed to get a couple years out of a LiPo pack, I am happy for you, but…just try to sell a LiPo pack that is one year old. Nobody wants it. What Battery Management System (BMS) did you use? (if the pack even has a BMS). LiPo packs use soft-sided flat foil cells, so anyone who wants to “save money” by using LiPo has to build a protective housing.
For every E-bike enthusiast who assembles a LiPo pack and charging system, there are hundreds who will never go to the effort of building one, and they just want to buy a battery and a simple charger. I can’t find anyone I trust who is selling complete 12S / 15-Ah LiPo packs and charging systems with a cell-balancing capability.
LiPo is here to stay (for racing), but…once you factor in how a quality 18650-cell pack will last for several years of daily use, any cost benefit you thought LiPo had…it just doesn’t pan out.
Side note: for those jobs where you still want to use LiPo for an E-bike, the large-format Hobby King Multistar brand is popular right now.
The Samsung 25R cell
Last summer, in 2014, Samsung made a real splash in the E-bike DIY world when they began selling the 20R cell. It is rated as a 22A cell, so if you made a pack out of parallel strings that each use five cells (5P), that pack could put out 110A! This was the turning point when garage builders had a real choice between LiPo or something else. The 20R cell got a lot of garage builders to buy a spot welder.
Of course, there was a downside. The “20” in the name 20R meant that this cell only had 2000-mAh of range. When you series a group of paralleled cell-strings, it raises the voltage of the pack, but…everything you need to know about a battery packs range and total amp-producing capability is in the parallel sub-packs.
A 5P string of 20R cells (capable of 110A peaks) would make a pack that only had 10-Ah of range. For a common 12S pack (around 44V), that would mean you’d only need 60 of the 18650 cells. As you can imagine, 60 of the 18650 cells are not hard to fit onto just about any bicycle frame, but…having only 10-Ah of range is not enough for most riders.
All of this is an issue because E-bikes don’t have a lot of space to mount battery packs. When thinking about compromises, should you sacrifice range to get high amps?…or do you sacrifice high performance to be able to get a decent amount of range?
E-bikers who are happy with a simple commuter using 36V are not the kind of people who spend time reading articles about the cells in the battery pack…they just want something that they can plug it in and it works when they want to take it out for a spin. This article is focused at DIY kit builders who want to use between 12S to 18S system voltages (44V-72V), but they want to avoid using LiPo on their daily driver E-bike.
This year is the turning point for E-bikers who want an easy and reliable battery pack with good performance, long life, and still have decent range. Samsung (in S. Korea) is one of the top players in the 18650 cell world. They decided to release a cell that had 20% more range than the 20R cell, but only had to give up a small amount of its ability to crank out the amps.
The 25R cell has 2500-mAh of range, but still is able to produce 20A of current. This means a 5P string can produce peaks of 100A (more than enough for the E-bikers I am writing for), and!…a 60-cell 12S / 5P pack will have 12.5-Ah of range. That doesn’t sound like a huge improvement, but with mid-drive systems getting very good range per watt-hour (WH), an extra 2.5 Amp-hours (Ah) in the pack can go a long way.
E-bike battery packs made from the 25R cell are available right now. If I was buying a battery pack for a hot rod ebike today, this is what I’d get.
So, following this logic…meaning that if we give up a little bit of the max current to get more range, how far can we take that? Samsung has already answered that question for those of you who might be curious.
Right now (summer of 2015) you can buy loose/individual (New In Box/NIB) Samsung 30Q cells, but there are no E-bike battery packs from these…yet (but they are coming soon). Like the name implies, these cells have 3000-mAh per cell, so a 5P string provides an impressive 15-Ah, and you can get that from a very small 60-cell pack if it is configured for 12S. If you wanted to go up to 18S (around 72V when fully charged), you would need to fit 90 cells into a pack somewhere on your bike.
So…how much current do we have to give up to get 15-Ah from a small 60-cell pack? the Samsung 30Q cell is rated for 15A per cell, so a 5P string still provides 75A peaks. In my humble opinion, this is the turning point for E-bike batteries. There will still be some users who want more amps or more range, but there have been a lot of potential E-bike buyers who have been holding off due to low performance, short range, and high prices.
Prices will come down in time, but when it comes to a plug-and-play battery pack that has both high performance and long range in a small package (plus it will last for years)…the tipping point is here right now. Here’s a peek: The upcoming Samsung 35E cell has 3500-mAh and we feel it safely provides 9A per cell. Our theoretical 60-cell 12S / 5P pack made from the 35E would give you 45A with 17.5-Ah of range!
What about Panasonic?
Now that I’ve made a case for 18650 cells that can provide at least 10A per cell, and still have at least 3000-mAh of range, what has Panasonic and LG been doing? Sitting around scratching their heads?
Last year when Samsungs newest high performance cell made its debut (the 25R), Panasonic introduced more range instead of more current. They developed their now-famous “B” cell (3400-mAh Panasonic NCR18650B), which was the result of Panasonics relationship with the Tesla electric car company.
What about Sony?
For a high performance E-bike pack, the expensive and well-known Sony VTC family has been the cell of choice in the past for several years, but…now?
The VTC3 was a 30A cell with 1600-mAh, and that was the “safe” alternative to LiPo five years ago. They then came out with the VTC4, which boosted their range to 2100-mAh per cell (this is when I started to see more E-bike battery packs made from Sony “Konion” cells). Recently they introduced the VTC5 cell, which has 2500-mAh of range, but even though many places list them as a 30A cell, they actually get very hot at 30A, and they only perform well at 20A per cell. That would put them in the same general performance class as the Samsung 25R, and even though they are very expensive (compared to the other choices), the real problem with Sony cells is something completely unexpected…
Authentic Sony VTC4 “Konion” cells had been highly respected, and years ago were first harvested out of Makita cordless tool battery packs, in order to assemble together an E-bike battery pack (and later purchased as new individual cells). However, in March of 2011…disaster struck.
A huge earthquake rocked northern Japan, which led to a very destructive Tsunami (tidal wave), and directly led to the Fukushima nuclear power plant disaster. All of this damaged Sony’s nearby main VTC cell factory (and restricted electrical use for the region). At that time, there were millions of authentic VTC cells in warehouses across the globe, with many of them contracted to go into Makita cordless tools.
In order to continue to service their existing supply contracts, Sony began having their VTC cells made in the Philippines and China. The problem right now is…a shockingly high percentage of Sony VTC cells are being found to be counterfeits.
What happened to Sanyo?
Sanyo is actually one of the largest battery makers in the world, due to all of the consumer products that they directly or indirectly make. Cordless phones, cell phones, cordless tools, laptop computer batteries, etc
For whatever reason, Panasonic purchased control over Sanyo’s 18650 cell operations. Every Sanyo product that is using 18650 cells is being upgraded to new versions, even if only to make the products run longer (at the same number of amps). Sanyo products that used 18650’s will now be upgraded to the appropriate Panasonic cell, except…Sanyo had one new model of cell in particular that is exceptional (all the named manufacturers are constantly experimenting and patenting improved batteries). That cell is now called the Panasonic-Sanyo 18650GA, 3400-mAh, 10A (more on this cell below)…
Current vs Capacity
The developments over the last year have resulted in products that are a real milestone for electric bikes. Look carefully at these three Samsung cells, and the capacity along with the current they can put out safely, and see the relationship between the two:
New technology has dramatically increased the capacity of these 18650 format cells, but the more current you want, the less capacity they can hold. The three cells listed here are all from the same company, using the same chemistry.
There has been such a huge explosion of cell varieties in the common-performance types, that there’s not enough room to list them here. Plus, I’m not interested in them. There are hundreds of retailers selling common-performance battery packs in 5P that provide 20A (4A per cell), and they compete on lowest price.
I am going to list several models of 18650 cells below that I think will soon become available to build battery packs from, and that I believe will become the most desirable cells to use on an E-bike.
The first group I want to tell you about has three models, and they are all are from South Korea.
I’m not mentioning price because…prices on new products are high, the prices will come down in time, and prices vary from one supplier to another.
That being said…these cells are the current replacement for LiPo in high performance E-bikes. All three are rated for 20A continuous per cell (and some web-sites list their temporary peak capabilities at around 35A!). I am reluctant to list peak amps, because…the few places that do that do not agree on the amount, and they don’t list for how long the “peak” amp-draw is, or what temperatures they reached before they stopped raising the amp-draws.
With either of these cells, a tiny 5P pack (only 60 cells if configured for 12S/44V) can put out 100A! If you are only drawing 60A as a peak during acceleration, and maybe 20A during a cruise-phase…a pack like this will not even get warm, and should last a very long time.
[The new Sony VTC6 has 3100-mAh of capacity, and provides 30A, but…the market has been flooded with counterfeits. If you want these, you have to go back to gutting authentic Makita cordless drill packs]
3000-mAh, ICR18650HG2, LG-Chem
2500-mAh, INR1865025R, Samsung
2500-mAh, ICR18650HE4, LG-Chem
High Current with More Capacity
In the example above, a 60-cell 12S/5P pack of 2500-mAh cells would have 12.5-Ah of range. But…what if you wanted more range than that, and you didn’t need 100A of acceleration? The cell choice in this category is the Samsung-SDI 30Q cell. It has 20% more capacity, and yet it still puts out 15A per cell. A battery pack that is a 12S / 5P would have a useful 15-Ah of range, but still put out 75A continuous.
The Samsung 30Q is an exciting cell, but…I think most hot-rodders can be happy with even fewer amps if it means even more range in a tiny battery pack.
3000-mAh, INR1865030Q, Samsung
MAX Capacity that still has Great Current
There are several new cells in this category that will just plain transform what builders understand about what is possible in a tiny high-performance battery pack. With 10A of current per cell, a 5P pack can provide 50A continuous, but at a higher capacity. It would be reasonable to expect temporary 75A peaks from a 50A continuous pack, as long as there were frequent cruise-phases when you were only drawing 20A to maintain your top speed, so the pack could cool down.
The 10A per cell options are:
3500-mAh, NCR18650GA, Panasonic-Sanyo
3500-mAh, INR18650MJ1, LG-Chem
3200-mAh, NCR18650BD, Panasonic
3200-mAh, INR18650MH1, LG-Chem
2900-mAh, NCR18650PF, Panasonic
(out of the 10A cells listed, the PF is turning out to be the most affordable choice from most suppliers. Plus, this last year it has proven to truly perform well at an actual 10A per cell)
I’m listing the Panasonic-Sanyo “GA” cell first, because it has performed so well for a variety of trusted sources. When drawing a continuous 10A, the cell didn’t even get warm, so it may actually be an 11A/12A cell.
EDIT, a 2016 re-evaluation of a couple of these cells
3500-mAh, INR1865035E, Samsung
All the information I had available in 2015 indicated this was a 10A cell. It has a higher capacity, but for long life, I am now calling this a 6A cell. Its a good cell, just not able to put out 10A continuous without getting hot.
3400-mAh, NCR18650B, Panasonic
Same story here. This is a great cell, but for long life and the battery not getting too hot? Limit it to 6A per cell. This is the cell used by the Tesla car company in 2015.
If you can fit a large battery pack in your frame, you don’t need to pay top dollar for the high-current 25R, HE4, HG2, or 30Q cells to get high amps out of the pack. As an example, if you increase the parallel strings from 5P to 6P, and you use the high capacity 3500-mAh GA cell, a 12S / 44V pack at 6P will give you an incredible 21-Ah of range, and it will do that with only 72 cells! A 6P pack of GA cells at 11A per cell would be 66A continuous, and peaks at roughly 90A.
You can take that same 72-cell volume of GA cells, and if configured for an 18S (72V) pack, it will have a 4P arrangement that still provides 14-Ah of range. Not bad!
In the pic above, these 100 cells are being “dry fit” to ensure they will all work in this small frame (before spot-welding the nickel strips to form series/parallel groups). If configured for 5P with the GA 10A cells, it would have 17.5-Ah of range, 55A continuous (70A peak?), but the real news is…100 cells would also get a pack at 20S. That means 82V when fully charged.
Or…96 cells can mean a 12S / 44V pack, with an incredible 8P, which would result in a 28-Ah ‘s of range and 88A of continuous current (120A peak?)
Be aware, when I say the GA cell is a 3500-mAh cell that provides 11A, you can have one or the other. This goes for all the cells listed above. If you calculate the range you need so you can build the smallest possible pack, and then you hit the throttle hard and often to get max amps, the pack will not deliver the full rated range. The rated capacities of all of these cells are tested in a lab at a 2A per cell drain.
Here is a video of disassembling an 18650 shell that has a very tiny 4.2V battery inside. Counterfeits are everywhere these days!
If you begin shopping for loose individual 18650 cells, and you find advertisements for 4200-mAh cells that put out 30A per cell…they are lying (Trustfire, Ultrafire, etc). An authentic Ultrafire cell is not horrible, but again, there are lots of counterfeits.
Buy some samples of the cell you think you want to use. Set-up a current-drain pulling the same watts that the cell is rated for, and…if it is too hot to hold in your hand after 5 minutes, its a fake. It may even look exactly like an authentic Samsung, Panasonic, or LG cell. Once you find a trusted vendor, only buy cells from them.
Once the test-sample cells are drained to 3.0V, charge it with 1A on a data-logging charger like the Soshine, and once the cell reaches 4.2V, the charger will tell you how many mAh went into it. It won’t be close, because either it will provide the rated capacity, or it will be way off.
edit: ES member Thomas Luptak reminded me that there can be significant resistance and voltage drop in the bus-strips that connect the individual cells to the battery packs output cable. Whether you build or buy, you should use or spec low-resistance nickel strips, and realize that the actual pack output can have more voltage sag than the paralleled cell specs may suggest on paper.
This is just another reason to use authentic name-brand cells from a trusted vendor, and to use cells that can comfortably provide more amps than you actually need.
Best of luck!
Written by Ron/spinningmagnets, July 2015