One of my favorite ebikes has gone through an evolution of battery pack changes in its five year life, which is a good illustration of ebike battery technology changes and the different ways to mount battery packs. (read our story on mounting ebike battery packs)
The technology for the ebike motor and controller has not changed much…the direct drive Crystalyte hub motor is still one of the most reliable and convenient motors you can buy at the 1500 watt level…and the controller is still a common 35-amp standard ebike controller. It is sad, but the technology on ebike motors and controllers hasn’t improved much.
Batteries (on the other hand) are a different story, since ebike battery evolution has benefited from big advances in automobile and other industries that use standard 18650 cells for power packs. Four years ago only high-end ebike pioneer Optibke was building packs out of name-brand 18650 cells. Now, many other ebike companies are following suit. In the pic above, you can see a Tesla Battery constructed out of thousands of Panasonic 18650’s that were spot-welded together…many ebike packs these days now use the same technology.
Mounting the battery pack is among the most challenging parts of designing an ebike…whether it be a commercial bike or a DIY ebike build. Space is our most precious commodity when designing an ebike. We all want long range on our bike, but we also want our bikes to be lightweight and feel and look as much like a regular bicycle as possible.
Things to consider when mounting a pack:
- Distribution of front and rear weight…the more in the center the better
- The lower the better. Low-mounted weight really keeps the bike grounded.
- Is the pack safe from being damaged or knocked around?
- Safety is king…a pack with physical damage can be a safety/fire risk
- Air cooled…if your pack runs hot it might need some cooling, because frequently running hot will drastically reduce your batteries life cycle.
Fortunately, battery technology is improving quickly and affordable ebike packs that are energy dense and safe are becoming available. The latest greatest in ebike battery pack technology is 18650 lithium ion cells. There is a huge difference in the quality of 18650 cells, and getting good name-brand cells that are not fakes is the key. Thanks to the new Ebike Store Lunacycle.com you are able to get these packs with guaranteed authentic name brand cells at an affordable price right from the USA. (Lunacycles is a sister website of electricbike.com).
Here is the first configuration of my ebike back in 2009. Notice that I was building fat tire electric bikes way before any commercial bike makers thought of how awesome they are. Back then, the best affordable packs available were LiPo packs strewn together with Hobby King RC cells. No triangle bags for batteries were available at the time.
Birth of my Titanium Fat Bike Rear Mount Pack
I decided to mount the bulky and heavy pack in the rear cargo rack bag. I am running a high power Crystalyte hub motor and made the decision to mount the hub motor in the front wheel for better weight distribution. This is a titanium bike, and when using titanium its a bit risky to use a powerful hubmotor in the front fork, so I used beefy torque arms as a mandatory safety device. Powerful hub motors have the capacity to snap a front fork. which is one of the most dangerous things that can happen on a DIY ebike.
Putting the motor in the front made this bike an effective AWD, and allowed me to keep my Nexus 8 internal gear hub (transmission is built into the rear hub). This bike with its fat tires does not have enough chain clearance for a standard derailleur. The AWD makes this bike actually rideable in soft sand.
I did not like the look or the feel of the rear bag battery pack. I started with a 10-Ah 48-volt pack but did not get the range I wanted, so upgraded to 20-Ah. The weight of my 20-Ah battery was very high, and I would really feel that whenever I leaned the bike over, to get on it.
Triangle Bag Upgrade
Triangle bags were invented by some industrious ebike dealers, and I bought this bag from Falcon EV for $80 and was able to stuff my batteries in the triangle.
I didn’t like the Velcro straps and thought they really detracted from the look of the bike, and I eventually changed them out to black zip-ties which are stronger than velcro and look much better.
Today you can get velco strap bags or my favorite zip tie mount bags for $35 on Lunacycles.com making them an even more affordable mounting option than your typical rear rack and bag.
I really liked the look of the triangle mounted battery, and I thought it really improved the balance of the bike. I did not like the look of the velcro straps and later designed my own zip tie triangle bag to eliminate the nuisance of thick straps. The problem I had is the fact my battery was so large (48V 20-Ah Hobby King configuration), and it was rectangular shaped, plus it would require a lot of padding to keep the pack from being dented and destroyed by rubbing against the frame.
Also the pack was so bulky that my pedals would rub against the ebike triangle bag. So, I decided to go with a much smaller 10-Ah battery, which cut my range in half. To compensate, I would ride with an extra 48V 10-Ah ebike battery in my back pack when I did longer rides.
Triangle Pack added to Triangle Bag
The next innovation came in 2013 thanks to Paul at EM3ev.com who decided a triangle shaped battery pack would be much better suited than a rectangle battery to fit in a triangle shaped hole.
Paul is based in China and is able to assemble his own packs using 18650’s in any shape. So he made a triangle shaped pack, designed to fit in a triangle shaped bag. This made it possible to not only fit more amp hours in a the bag, but he was also able to pad the pack in just the right places so it does not need to be padded as much by the DIY customer (extra padding is still recommended).
I bought one of these batteries and installed it on my bike, which made it so that I was able to have a 20-Ah battery mounted on the bike, which is a much better solution for me than multiple 10-Ah packs.
One thing to remember is that…even if you are not using all the available amp-hours in your pack, the larger the pack is, the less strain you are putting on the pack when you run it hard, plus…the longer life expectancy you will get out of it.
Paul offers awesome triangle battery packs with good customer support. The drawback is that even though he is an English-speaking European, he still is in China and runs a China company. This means you have to pay for air shipping a lithium battery from China which is expensive and borderline illegal. And air shipping a battery back to China is prohibitively expensive and for sure illegal so you might as well forget about the warranty.
In 2015, I started Luna Cycles, which builds its own triangle batteries and fits perfectly into its own triangle bags. These packs use premium 18650 cells from Japan and South Korea, and ship to our customers from the USA and sold by a USA seller, so you are supporting a new USA company when you buy from Luna Cycles.
I was able to put an LG HG2 triangle pack inside the bike which fit wonderfully, and is the best power to weight triangle pack yet on this bike. Luna Cycles routinely uses cutting edge cells such as the Samsung 30Q, the LG HG2, and the Panasonic 3400 NCR-B to get the ultimate performance to size ratio.
Luna Cycle Bottle Battery Pack Added
As Luna Cycles added more and more packs to its line up, we started experimenting with using quality Chinese made hard cases, and packing them with premium top shelf name brand cells. I really love the Panasonic 3400 NCR-B for ebike applications that do not require ultra high amperage.
But, if you run a pack with these cells with too much amperage for too long? it will get hot, which will shorten the lifespan of the pack. Luna Cycles dealt with this by using a BMS (Battery Management System) with a high temperature cut off. If you push the pack too hard and the pack gets too warm…it will shut itself off and will not turn back on until its cooled down to a safe level.
I have had this ebike a long time, and have used the same 35-amp ebike controller which would be a pain in the ass to rewire. I wanted to squeeze some more power out of my bike without going through the hassle of rewiring a new model of controller. So upgrading from 48 to 52 volts was the key…getting me 10 percent more power without changing anything else. (read more about the benefits of 52 volt battery)
I did decide to mount the controller under the bike which is a convenient way to hide it and its wiring. Luna Cycles builds many of their sexy bottle batteries and dolphin packs in 52 volts to increase power for most 48 volt systems.
Because our bottle battery pack can be bought with 52 volts, and uses the sexy Panasonic 3400 NCR-B cell, it is able to hold 13.5-Ah which is a whopping 700 watt hours in this sexy and easy to mount bottle pack. To calculate the watt hours for this pack you times the voltage by the amp hours (13.5-Ah) to get the total watt hours.
700 watt hours is more power and range than 90 percent of commercially available ebikes, and Luna Cycles sells the 52 volt bottle battery pack for only $459 with charger. I really liked this bottle battery pack because it really brought my bike together visually and has perfect function.
The mount screwed right into the standard water bottle mounting holes, and holds the battery more securely than ever. For the first time I think I could ride this ebike off-road on brutal single track conditions, and not worry a bit about damaging the pack.
The bottle battery pack has a convenient ON/OFF switch which none of the packs above have (read my rant about the lack of on/off switches on DIY products). It also has a key lock, which effectively locks it to the bike to keep my $400 investment safe if the bike is locked to a post or something.
Also, the battery quickly pops out of the mount, if I want to take the battery inside to charge or if I want to swap for a freshly charged pack.
When it comes to Bottle batteries, its fun to have an extra one because they are easy to swap and are easy to carry in a back pack as an auxiliary battery. Because of the hard shell they are more protected and safer than carrying soft packs.
Written by Eric Hicks, November 2015