Eric’s 72v battery is pretty amazing. When I took off with it the first time I actually felt a sinking feeling in the pit of my stomach, like the fear you get when you crest on a roller coaster and are facing the downhill section. I haven’t felt that way for a long time on an ebike.
So I want you to keep in mind, this is coming from someone who has done nothing but sell ebikes for over 2 years and gave up his car over 5 years ago to go ebike-only. I told him I would be right down to confirm his suspicions that this new battery might actually kick ass. I showed up at his shop and he let me take his 5-year-old Extracycle extended ebike for a spin around the block. This bike had an ancient Crystalyte motor that was completely corroded from 5 years of constant usage in the rain, sun and snow. I had used plenty of Direct Drive (DD) motors over the years and to be frank, they all sucked. This article is about how I began to realize that maybe DD motors had some potential for commuters after all … at the right power levels.
When Eric from Luna bought thousands of non-crappy variable voltage chargers from China (The Lunagizer) he knew that 60v and 72v batteries were going to be the future of ebikes so he thought ahead and had those chargers built as well. Unless you are using a variable voltage charger like the Cycle Satiator or a Hobby King charger, you’re going to have a hard time finding 72v chargers that work well without blowing up in your face.
When Larry handed over his ebike I didn’t even waste any time figuring out how to shift the gears because I knew I wouldn’t need it. With an old Grin tech 40 Amp sensor less controller the Cycle Analyst was consistently showing a solid 3000 watts which is four times the legal limit. I didn’t really feel like I was riding an electric bike anymore, it was more of a scooter. The Crystalyte did not have the wheelie power of the 3000W Tangent Ascent, but the acceleration was comparable to a 1500W peak BBSHD mid drive. I have never actually experienced a DD that was comparable to a decent mid drive so for me it was quite a surprise. Normally with a mid drive you have to cut power to shift, but from a standstill to 40mph the power just kept coming out of the old faithful Crystalyte motor. These 72v packs might make a DD believer out of me yet.
I headed out into traffic and headed for the nearest steep hill that was over a 10 degree grade. I expected the DD motor to quickly get bogged down, overheat and just stop working on me. This model of Crystalyte is not supposed to be fed over 2000W for any real length of time. Luckily the hall sensors had been fried a long time ago and Larry has more than got his milage out of this particular motor. The case was badly corroded and starting to warp at the seams. I think secretly he wanted me to kill it for him so he could buy something even more powerful for himself.
When it comes to going fast on a DD motor the way to do it is with voltage not amps. When you run a higher voltage through the hub you have less of a chance of overheating and melting down the phase wires or the windings. When you start dumping massive amps into a DD you run the risk of destroying the hub faster. Remember amps give you torque and voltage is going to give you higher top speed. With a 72v pack this ebike easily made it to 40mph. Larry had been using this ebike for many years with an 18650 52v battery. Although we both had experimented with Hobby King Lipos in our wild and crazy youth, we don’t really talk about that anymore. You can’t run an ebike business selling batteries that explode and burn down people’s houses when you look at them funny.
If you’re currently running a 72v setup with Lipos, I would highly recommend you consider switching to the 11.6 Ah 18650 pf pack from Lunacycle. Although I only tried it once it was a real hoot and it will make you get exceedingly annoyed at how slow all the damn cars are. Now that Luna has both the charger and the BMS figured out for these batteries lets hope we see a lot more options for 72v packs in the future.