First ride on The Electric Mahuna - pedal vibration

[rifraf650]

Did my first commute in today on my newly converted 29" Mahuna. Overall, the BBS02 performed very well and operates very smoothly. However, I noticed a vibration coming from my pedal that seemed unusual. I have my PAS set at a max of 3, and never exceeded 3 for the ride (most of the ride on 1 and 2). Is this normal?

Where I live is quite hilly, and after 6 miles the battery seems to have plenty of juice, it still indicates "full". The bike is HEAVY, and so am I. I'm guessing I'm at about 275 lbs total weight me and the bike. The ride back has far more up hill sections, so I am interested to see how the battery is after the round trip. I have a 48V 12Ah battery.

Pics of the new setup.

 

[rifraf650]

The return ride went great. I kept PAS at 3 most of the ride each way, but used PAS 6 for the fun of it for the ride up the big hill at the end to my house. Total ride round trip is about 750' total ascent and descent, and 12 miles. The battery only registered one bar from full during the PAS 6 ascent on the final hill (200' over 1 mile) and went back to full once I let up. Feeling pretty good about the capacity. Tomorrow I plan to attempt using higher PAS to decrease my travel time and see how that effects battery capacity. As far as the vibration, I think it mainly happens when I am close to the speed cutoff, which is 40 km/h. Perhaps it's modulating there? I'll see if that makes it go away. I am also working on gear selection. My feet want lower gears, but I think the motor wants higher gears, which makes it hard for me to have pedal resistance at a given speed. I'm also considering ditching the throttle. Not sure when I'll ever use it.

 

[Ann M.]

Excellent observations, rifraf650! It's normal for the battery gauge to show almost nothing under load and show true level when on the flats or stopped. You can add a simple 'watts up' style console that gives you the true battery capacity and display watts consumed.

 

[flymeaway]

I am close to the speed cutoff, which is 40 km/h. Perhaps it's modulating there?

When the motor is under extreme load, and you are at higher PAS levels the drive may seem to pulse. Never thought too much about the cause, but my guess is the controller reaches it's max amp output and cycles off and on creating the pulsing. I learned to avoid putting the motor under high loads in upper PAS.

Court J.

 

[Ann M.]

Very likely cause, the BionX system I ride does the same when the max speed is hit; however, as soon as I drop below the max it's back on and it can feel like a little surge with hard pedaling or on hills when in top PAS level.

 

[rifraf650]

The vibration is definitely electrical. It ceases when I hit the e-brake button. Setting the speed governor higher also seems to have helped make it happen less. I'm less concerned about it.

Yesterday, I changed my PAS from 1-6 to 1-4, and that is much preferable to my ride. I also took slightly longer route and used PAS 2-3 most of the ride (with PAS 4 for the last big climb up, for fun!). I checked the battery voltage before the ride (54.3V, nearly 100%, and an hour after the ride it was 50.7V (about 3.9V per S), which I cross reference on the 18650 cells to about 60%. So, I have PLENTY of juice, even for using more PAS or a longer ride. The display on the C961 still reads 100% (read 80% under load at the end), but it supports the battery indicator being not very accurate.

I have a watt meter like you suggest (for my RC planes) with the same connectors I used, but the problem is location. My battery connection is down by the bottom bracket, so I think I'd have to fabricate some extensions to be able to locate it higher to be able to see. May not be a priority if I am able to determine that my typical ride has plenty of capacity remaining.

 

[George S.]

A few discharge cycles and most people have a good idea of how the battery works. It's great when people figure out they have more battery than they will likely ever need. The main thing to grasp is that speed kills the battery because the aero drag goes up 4x if the speed doubles, and that drag is most of what a motor works to overcome.

You can use the accumulating watt meter tucked away somewhere, and just note the total amp hours used at the end. The other way to know what was used is to determine the amps into the battery, from the charger. It's often 2 amps or 3 amps. Figure the total hours needed to charge, like 1.4, and multiply times the charge rate. Chargers slow down at the end.

The charging stuff for LiPo RC stuff is more refined, actually. It's too bad they don't give more battery info on ebikes, but you can add it to your kit easily.

Those kits impress me. Take a nice bike and you end up with a really nice ebike, just the look. The performance pleases most people, of course. Where did you get the kit, if you don't mind saying?

 

[rifraf650]

I think there's pluses and minuses with RC gear compared to eBike. One thing that attracts me to the 18650 based packs vs. a soft pack, is the added safety of the hard casing around each cell and the on-board BMS. With an RC lipo, the charging circuitry is well refined, but once you disconnect the pack and are using it, there is no protection other than the LVD in the motor controller. However, the use of those batteries is entirely different - you typically are only charging/discharging them in supervised fashion (or you SHOULD be). I feel comfortable with the low amp charger of the eBike pack not to over charge the pack, or become unbalanced during charging. Far less risk.

I bought the mid-drive kit from em3ev (http://em3ev.com/store/index.php?route=product/product&path=36&product_id=166). I was highly impressed with the service and how quickly it arrived to the US. For the battery, I ordered the 48V 12Ah (probably 11.6) from AliExpress (http://www.aliexpress.com/item/Free...y-with-BMS-Board-and-Charger/32344393587.html), which took about 2.5 weeks to arrive. I saved a few bucks on the battery than if I had ordered from em3ev, and got a couple more Ah in it than if I bought one from the US.

 

[rifraf650]

Just a little update - I broke 100 miles today on the Electric Mahuna. I've been playing with different PA settings to see what kind of life I can get from my batteries, so far, I'm very impressed. Up until today, I could keep my PA level at 3 of 4 for the entire ride (12 miles round trip), and constantly put 4Ah charge back in (I have a watt meter on the charger). Today, I changed the PA max level to 5, and kept it at 4 the whole ride. Wow, a very significant difference compared to 3 of 4. I hauled a**!

The charge just completed at 4.5Ah. That's about 240Wh round trip, average 360W rate of consumption for the ride. With electricity at $0.12/kWh, I calculate the cost of my commute at 4.3 cents round trip - we can round to a nickle to account for the efficiency of the charger. Works for me.