I got a retro-fit kit for my bike for a few hundred dollars and upgraded the batteries with a 500 Watt-hour LiFePO4 battery pack I had (plus the original kit battery as a spare). I love it. As my knees get older this gives me the boost I need to get up hills without seeing the Physical Therapist for the next eight weeks. Got one for my spouse as well.
Simple control, press a button on my handlebar and it adds torque to the front wheel. (I tried a couple of those “torque multipliers” controllers that boost your torque by 2x, 3x or more, found the complexity unnecessary.)
For the less lazy and willing to re-spoke a wheel you can get hub motors for less than a hundred bucks, (I like 8fun motors), another $25 or so will get you a controller, and add the battery size to suit your needs.
I don’t know about where you live, but around here catching teenagers on delimited scooters is a stereotypical cop activity. Cops not being engineers won’t do you much good once they are convinced that you are implausibly fast.
Oh man, I completely forgot about recumbents. I’ve ridden all kinds: short wheel-base (SWB), long-wheel base (LWB), high-bottom bracket SWBs (which are really just for racing), and trikes. My personal favorite is the underseat-steering (USS) LWB. Those ride like magic carpets.
Assuming you don’t feel any stigma riding one (and most recumbent riders I’ve met are just that damn cool and/or married), the biggest adaptation curve to recumbents isn’t mental, but physical. Compared to uprights, recumbent cycling demands a lot more from your gluteal muscles and other dorsal muscle groups in the leg. If you have knee trouble, stick to models whose bottom bracket is only below the hip, rather than at-level or above.
Seattle too. It’s called the rainy city, but a large portion of the year it’s just soakingly ■■■■■ and rain means a constant off and on sprinkle or misting.
I gotta do this. I have a Currie e-Trailz that, once upon a time, was a heck of an electric moped. As the NiCad batteries have aged, it’s no longer reliable. And riding a dead 100+ lb bike up a hill isn’t a lot of fun. I’ve seen Li-Fe batteries that will fit it, but rigging up a charger for them would be somewhat problematic.
They sell cells and battery packs, too, and protection circuits.
Be sure the charger matches the chemistry. LiFePO4 cells have lower voltage than more common lithium chemisteries. A bit lower energy density as well, but thousands of charge cycles and 10 year battery life I think is an advantage for applications like this.
There are chargers out there. If you don’t need cell balancing (which is admittedly a Good Thing), it is fairly easy; and if you get a generic circuit where you can set the current and voltage limit and the charging cutoff, it will work with more or less anything.
All the pre-made battery packs I’ve seen have cell balance & protection circuits built in.
I also have a charger that will charge just about anything up to 25 volts or so at up to 6 amp and can balance cells and exercise (go through multiple discharge/charge cycles) as well. It helps restore old batteries of certain chemistries. An older sibling of this…
Yeah, it shouldn’t be a big deal. They actually make kits to convert the bike from NiCd to Li tech. They’re hugely expensive, though-- like $500 for the battery pack and the charger.
I may have to break down and buy one of them. I usually prefer a DIY solution to these kind of problems, though. My maker spirit runs strong even when I know very little about what I’m doing!
I hear you, but these are BIG lithium cells we’re talking about (though LiFePO4 is much safer). Millivolts matter. Timing matters. Temperature matters. Battery charging should not be taken lightly. Where I work we use a lot of modest sized 18650 lithium cells (as seen in many laptop computers) in our designs. Our design protocol has three independent fail-safe layers, and we still worry if something could go wrong.
Take, for example, those “hover-boards” which are so popular these days. Any charger that recommends disconnecting it when it’s done charging is poorly designed in my book. Red flag.
One or two small cells and you can get a chip that, with a proper design, can safely charge and monitor a battery pretty easily. Put 3 or more in series at 5, 10 or more amp-hours and you’ve got some serious designing to do.
I saw a 12 volt 3-cell series Li-poly battery that had a separate battery protection chip for each of the cells. A crude cheap Chinese workaround but better than nothing.
I would actually prefer this solution, but I haven’t been able to find the parts to build a medium-to-large array of 18650s. I’ve heard that the Tesla cars and home battery use 18650s, so I figured a big array would be available from my Chinese sources but so far I haven’t found one. (I use a Chinese manufacturer to make ABS parts for my wastewater-treatment company but my contact there hasn’t been able to find me anything. Yet. Sooner or later someone will contract it out, and then it’ll be available from 20 different suppliers the next day.)
