best rear wheel rear-hub conversion kit?

[indianajo]

What nobody mentioned here is that with GMAC or a DD hub motor, you use electricity all the time or drag the motor with your feet. My DD hub motor dragged like being in 2 higher sprockets (of 8) than I really was. I ride the bike unpowered 80% of the time, using electricity mostly for days like yesterday with a 20 mph headwind gusting to 33 mph. 30 miles of that wind unpowered is 6 hours. My commute doesn't shorten because the headwind is bad. I do intend concert/festival trips where I pedal unpowered out 50 miles and motor back at midnight. As soon as I find a seat I can sit on for 5 hours.
DD 1000 W motor was much slower accelerating across intersections. That is something I use the geared hub motor for even on windless days, as most traffic lights will not turn green for a bicycle. If they do turn green they turn yellow in 6 seconds unless I went 40' out of my way to push the pedestrian cross button. I use throttle for crossing in gaps in traffic in minimum time. DD motor also used a third more watthours on my hilly commute than the ebikeling 48 v 1300 w motor. Both would red light & drop power on the last hills of the 27 miles with a 17.5 AH battery. The Mac12t I'm using now uses about a fourth less than that. 52-48 v in 30 miles with >80 hills. The plastic gear in the ebikeling motor wore out in ~4500 miles. It was rideable unpowered even with the gear locked up because of the one way clutch. I rode it locked up 7 miles out to summer camp then 27 miles home for replacement without drag. The Mac12t will go about 23 mph on the flat, fast enough without a suspension on a cargo bike. I carry up to 80 lb cargo with it on up to 15% grades. I peak at 35 mph frequently on the downhills before blasting up the next at 10.
Advantage of a conversion, generic battery can be replaced by something even cheaper as the generic prices go down. Mount is a box of aluminum angle & plastic foam, can be customized to fit whatever shape is on sale. The 20 screws has baffled at least two wannabe thieves. Elastic stop nuts you torque every turn of 20 to 40.

 

[stw]

Pedal assist from Grin is IMHO about the best around. It's the way the Cycle Analyst handles the sensor and ramps up the power as you spin. The physical parts (sensor and it's mounting) are dead simple. The alternative is to delve into a torque monitoring BB (the torque sensor options). The upside is an even more natural feel to adding power, the downside is that these specialized BBs can require drilling the BB mounting on the bike and/or require unique crank arms. If you're like me and picky about your crank arm length and such you may be better off staying away from the torque sensor and using only the PAS as this will give you more options in your choice of crankset and crankarms.

Thanks for all the information, mclewis and other responders. I studied what I learned on this thread over the week since I posted and I ordered a Grin GMAC kit 10T wind motor (still trying to figure out how wind works), with their 52V 14.5 Ah battery with Panasonic NCR21700A Cells, 40A BMS, their Phaserunner controller and V3 CycleAnalyst. Since I like pedal assist riding, and enjoy the natural pedaling feeling on a Bosch mid-drive, what you said about how Grin's Cycle Analyst above is a plus.

For natural pedaling feel, I'm going to use their regular PAS for now I guess. I might prefer a torque sensing BB but will need to find one in 68x107mm or so, square taper. Like you, I have crank preferences and didn't want to use one of the torque sensors/crank combination. It is hard to tell on Grin's site, but I think you can't just use the torque sensing BB and install your own crank on it--the crank is part of the sensor pick-up?

Grin describes the GMAC as 600-1200 watts motor, and I'm wondering how that will compare to the power/torque of the mid-drive Bosch Active Line Plus, 50nm (500Wh Bosch battery pack) I'm used to. I'm guessing the GMAC is overall more powerful.

One thing I've learned this week in comparing what everyone says about hub drive vs mid-drive, is that there are several things I may really like about hub drives, and at this early point in my e-bike learning, I would not be satisfied to not explore how a good hub drive works and feels for my conversion. Even if I end up preferring mid-drive later on, I would want that to be after trying a good hub. I considered a cheaper hub set-up but decided I should compare like to like and get a good one.

No problem not having brake sensors. Some folks prefer them, some don't (I don't ride with them). I think they become more important from a safety point of view if you are running higher power (kw class and up) motors. With the Grin kits there's usually a small multifunction switch setup that has a nice simple red power on/off switch on top. So if you ever did experience a sticky throttle (didn't shut off) then just pressing the little red button beside your thumb removes any problems. The real "need" for brake cut out sensors is on mid drive bikes that may not have a shift sensor installed. This way the motor's power can be briefly cut off while you shift (unloading the gears). With a hub motor this isn't a concern at all since the human is the only one putting pressure on the gears.

I'm going to try Grin's pull type battery sensors because the GMAC has re-gen braking. On Grin's site it sounds like I can tap the sensor-ed brake and go right into re-gen on descents.

The GMAC kit also has Grin's freewheel simulator controller function where a little power goes to the wheel when not pedaling to simulate how a freewheel/clutch geared hub feels when it coasts. That sounds fine too, but I assume I have to choose between re-gen braking or this freewheel simulator feel. If so, I wonder how I choose and can I easily toggle between them while riding? I'm guessing on flat or slightly rolling terrain I'd like the freewheel simulator going so it doesn't feel like resistance when I stop pedaling. But on a descent (I live in canyons so lots of descents) I'd want re-gen braking.

Your battery choice will be a balance between what you want for distance vs. weight, and there are a lot of variables that will affect the choice. As mentioned already you'll find it helpful to go down the rabbit hole of running Grin's motor simulator and trying out various battery capacities and voltages against various motors. This will show you what kind of range you can expect. You likely won't want to be carrying a lot of excess battery capacity. Also as mentioned above the Grin controllers (BaseRunner or PhaseRunner) can run any of the popular voltages so you have lots of choices.

I would recommend a standard wind motor and a 52v battery. This will give you a higher top speed vs. the often seen fast wind motors combined with cheap 36v batteries. If you choose a downtube style battery with a nice road frame you'll want to have a mounting plate under the battery base. This will do two things, first it gives you more flexibility in the position of the battery with respect to where your water bottle mounting bolts are (so you can alter the position of the battery up and down the downtube a bit), and second it offers a flat base to attach the battery base to. This prevents rocking which can destroy the water bottle nuts in the frame when a big heavy battery starts torquing on them sideways. These mounting plates are just the same as (and in many cases are the original) the water bottle mount extension products. I know this will sound like a broken record but Grin makes (IMHO) the best version of these mounting plates, the BOB.

Thanks for this advise on the motor wind + 52v battery, and the BOB mounting plate.

Now I haven't mentioned a particular motor. This is going to be quite a personal choice that will depend on a bunch of options but primarily just how much power you want. Given what I assume is pretty reasonable power output on your part I think you'd be fine with a motor in the 500w class but I'll leave that conversation to the smarter folks around here. As always there is the inevitable trade off, in this case it's weight vs. power. All things being equal a bigger geared hub motor obviously gives you more torque (the voltage and wind speed will with the wheel diameter determine top speed) and the additional weight from the mass of the motor assembly dissipates more heat so they would take longer to overheat, if at all. Many motors now come with a temperature sensor so if things are all wired up correctly you can monitor the temp of the motor. The idea is to prevent it from overheating on long climbs and such. Grin's Cycle Analyst does this and will automatically start to roll back the power if the motor starts to overheat. This has an interesting effect of allowing you to run a slightly smaller (and lighter) motor that performs well and won't destroy itself if you push it too hard.

OK, that's probably TMI in one post, but you did ask ... lol.

 

[stw]

What nobody mentioned here is that with GMAC or a DD hub motor, you use electricity all the time or drag the motor with your feet. My DD hub motor dragged like being in 2 higher sprockets (of 8) than I really was. I ride the bike unpowered 80% of the time, using electricity mostly for days like yesterday with a 20 mph headwind gusting to 33 mph...

Thanks for this. I considered motor-drag for the GMAC conversion and went with it anyway. I'm new to e-biking and I've noticed my riding habits using my Bosch mid-drive have evolved in just a few weeks toward using power all the time on the flat and I'm using Eco less and Tour more on the flat, so I'm using power more often and a little more of it. That suggests to me that I'll likely ride the GMAC conversion with some pedal assist most of the time unless I'm descending.

The Bosch mid-drive I've been riding rolls/pedals easily power-off or zero-assist, and there is no sensation of drag--surprising but even this iZip fat bike rolls easily power off. At first I was riding it no assist a lot on the flat like a regular bike, and thinking of power assist as valuable for hills or inclines. I think that was a noobie habit coming from an cyclist background, and now I see little reason not to use some level of power, and more than the minimum, all the time unless I'm coasting down hills.

Also the Grin site rates the drag of the no-clutch GMAC as lower than the drag of a DD hub motor. I probably won't know for myself the difference between a GMAC and DD, unless I happen to ride a DD bike some time.

 

[RunForTheHills]

You can install your own square taper crank on a torque sensing bottom bracket. That is what I did. I bought the Sempu before they had the Erider BB's, so I did have to drill a hole in my bottom bracket shell. I used an IRD Defiant Double crankset. I would recommend getting a torque sensor over PAS.

MTA: The Sempu BB was available in different widths and I ended up with a good chainline.

 

[stw]

You can install your own square taper crank on a torque sensing bottom bracket. That is what I did. I bought the Sempu before they had the Erider BB's, so I did have to drill a hole in my bottom bracket shell. I used an IRD Defiant Double crankset. I would recommend getting a torque sensor over PAS.

MTA: The Sempu BB was available in different widths and I ended up with a good chainline.

Hmm, good to know. I may find a BB and amend my Grin order.

 

[mclewis1]

Hmm, good to know. I may find a BB and amend my Grin order.

I'd keep the PAS on the order. It's inexpensive and it may keep you riding if you end up having a delay in putting together or troubleshooting a particular BB, crank arm and chainring configuration.

 

[kmccune]

As RunForTheHills mentioned, Grin makes excellent products, but they are on the pricy side. Then-again, you usually get what you pay for. They are also very knowledgeable.

Justin loves hub motors.

 

[kmccune]

My take you can do it for under$600 and learn a heck of a lot along the way, get a 1000 watt bafang geared motor add the rim and width you want you still have to round up the rest of the kit controller etc, a PAS is easy add that,if you do not want cutoffs fine( beware of the hazard though and a pretty good battery is not that hard to find.
Now for the easy get a 1000-1500 Viomart kit and a hailong battery, easy peasy just make sure your dropouts are wide enough, some of these Guys must have pretty nice bank accounts, however it holds true you get what you pay for and do not diss the 36 volt TZD bb kits a lot of bang for the buck( includes torque sensor) consider this if you are going to really put some money into this operation look for an ebike already pre assembled for a fast taste of ebike satifaction( you will probably never go back"acoustic")

 

[kmccune]

I understand and didn't mean to demean your build. 6 years of thousands of support emails and phone calls have alarmed me to the pitfalls of cheap battery packs.

I've done business with Dillenger and have no issues. Yugo or Camry. They both get you to where you need to go. What I am alarmed about are lowball-priced batteries. I've been into these packs and believe me they are sub-par. In my opinion all good if you understand what you bought. I've had batteries like theirs that lasted a few months and a couple that gave me reasonable service for 2-3 years.

I think it's important to point out the weak spot in budget kits. Any n00bs reading these threads should be aware of the risk of cheap batteries.

Kits with 15A controllers and like-sized controllers do much better with these batteries.

Above all have fun! The building is a great alternative. Most DIY builders think theirs is the best. Likewise with brand name eBikes. But there's a 100 ways forward and they all make me grin like a hippy on LSD.

Ride it like you stole!

As always YMMV,

I think you nailed that side of the argument,if you demand little from the lower end these may just be a win for the average person( such as Moi')