Current limiter setting question - is it set too low on an off-the-shelf ebike?

[romandesign]

Hi, I just bought my first ebike: Whelspeed Taurus, an inexpensive Chinese fat bike with a 500W rear hub motor, 14.5Ah battery and S830 display. Of course, I found the unlock code and removed the speed limiter. But going through the settings, I discovered that the factory Current Limiter settings are set to 12A. Now I'm puzzled. It seems too low according to the specs. Am I missing anything? Should I increase the limiter to the lowest of the rated controller / battery / motor rating?

1. The best I could do to identify the white-label motor is MXUS GDR-15-FAT - which according to the chart can draw 24.5A on max power at 904W, and it's ~21A at max torque and max efficiency peaks.
2. My battery is 48V 14.5Ah/696Wh with maximum discharge current of 25A
3. My controller current limit is listed as 18A

So it seems that the lowest denominator is the controller, and logically, the S830 current limiter setting should be set to 18A. Or maybe add some safety margin and do 16A or 17A. It should significantly increase the acceleration, I'd guess, and maybe the top speed. But the default 12A seems too low. Is there a reason for this? Should I raise it?

With the speed limiter removed, if the wheel is suspended in the air it gets to 49km/h on a freshly charged battery. I only tried it once on the road, and I was too scared to accelerate past about 37km/h but it still wanted to accelerate, so maybe it can get to 49 km/h if I let it. The default was limited to 32 km/h. One thing I noticed on the motor specs page is that it's rated for speeds of "25 - 40 km/h", so maybe that would be the reason, so it doesn't spin too fast? But if the speed is the issue, I can set the speed limiter to 40km/h and enjoy the improved acceleration, right? Also, I don't think occasional speed peaks should matter much.

The bike product page says the motor is "500W with up to 800W output". 800W / 48V equals 16.6A draw, which makes sense. So isn't 16A a proper setting to use then?

I'd appreciate some advice...

Here are my component's photos:

 

[romandesign]

Update: I have a suspicion that I found out why, thanks to this forum. Though my battery has a maximum discharge rating of 25A, it doesn't list the continuous discharge rating, and that may be the limiting factor. I googled and it seems that most similar batteries have a continuous discharge current that is roughly half of the peak discharge current. So for my 25A max battery, it would be ~12.5A, which would make my battery the limiting factor. That also matches the 12A current limiter settings. Then it makes sense.

 

[docw009]

12A is close enough to 750W. That's the main reason. The bike was designed to meet the Canadian and US power limits.

Does the S830 show current or wattage, so that you can tell if the current settings work out in real life? I would just set it at 18A, since you cannot get more than what the controller is designed for, and just ride like an adult. If you can't see the current, sneak a glance at the volts under acceleration. The amount of sag in voltage on full throttle is a good guide to the health of your battery. A four volt drop at full throttle is typical for a generic chinese battery.

Don't overthink all this power stuff. Bottom line is if you make a habit of climbing long hills while lugging the motor, something will melt or break.

 

[romandesign]

Does the S830 show current or wattage, so that you can tell if the current settings work out in real life?

I can see voltage and current (amps). Not wattage.

 

[From-A-To-B]

I appreciate Docw009’s comments. All things considered, ebike parts are pretty cheap (for lots of people, but not everyone.) So if you melt a controller, it’s $50 and you’re back on the road. The expensive or hard to come by bit is figuring out how to fix things when they break. In my experience, the cheaper electric vehicles are much harder or more tedious to fix than their higher quality, more expensive counterparts.

Personally, I run my 25A-capable ebike at 18A max. I like the head room. I like to think that my 40A-max battery is being treating nicely and maybe it will be a friend to me a little longer because I don’t beat on it. But that’s just me.

So it depends on what you expect this bike to do for you and how bummed you’ll be if something breaks. It’s all about getting around safely and having fun. Glad you’re learning about your new wheels.

 

[romandesign]

I like to think that my 40A-max battery is being treating nicely and maybe it will be a friend to me a little longer because I don’t beat on it. But that’s just me.

Makes sense. I think I'll leave the limiter at 12A. I only tested it once on the street, I'm sick now so can't continue testing, because it's cold outside. But the acceleration felt quite nice, not sluggish at all, and with the speed limit removed, I chickened out at 35-37 km/h - it was just too scary, I need to get used to the speed. It wanted to keep accelerating, so it would probably get to at least 40 km/h if not more, which is definitely enough. So if the top speed is OK and the acceleration is acceptable, there is no real reason to try to squeeze more juice out of it, I guess. It's relatively flat where I live, and some slopes may pose a problem, but I don't mind pedalling when needed.

 

[gromike]

Always best to use less power, and 40kph is 25mph in my world. So that is about as fast as you would want to go on a bicycle, though I like the power to achieve 48kph when I need to escape danger.

 

[From-A-To-B]

Always best to use less power, and 40kph is 25mph in my world. So that is about as fast as you would want to go on a bicycle, though I like the power to achieve 48kph when I need to escape danger.

Here here — I do most of my riding between 16 and 22 mph. Any faster is just too fast for me. The potholes come quickly at those speeds. I do appreciate the ability to ride at 25mph when pushing through tricky intersections.

I don’t feel like rapid acceleration would keep me any safer on my ebike. Defensive riding and taking the space I need in the lane is my key to staying upright — quickly darting around in traffic wouldn’t help me much. But maybe others’ traffic situations are different than mine are.

 

[Chalo]

In my experience, the cheaper electric vehicles are much harder or more tedious to fix than their higher quality, more expensive counterparts.

It's not clear what cheaper vs. more expensive bikes you're talking about, but my experience is the opposite. Generic no-name bikes are simple and modular, easy to diagnose, and easy to repair or replace components. Closed systems like Bosch and Shimano are resistant to everything it takes to keep them running, including understanding what's going on.

I think it's fair to characterize cheap e-bikes as needing more work, and being likely to cascade into a Russian doll of nested problems due to cheap construction (just like cheap department store pedal bikes). But in my experience it's usually the name brand ones that get donated to my community bike shop that strongly refuse to be repaired, or even salvaged for (electrical) parts.

 

[From-A-To-B]

It's not clear what cheaper vs. more expensive bikes you're talking about, but my experience is the opposite. Generic no-name bikes are simple and modular, easy to diagnose, and easy to repair or replace components. Closed systems like Bosch and Shimano are resistant to everything it takes to keep them running, including understanding what's going on.

I think it's fair to characterize cheap e-bikes as needing more work, and being likely to cascade into a Russian doll of nested problems due to cheap construction (just like cheap department store pedal bikes). But in my experience it's usually the name brand ones that get donated to my community bike shop that strongly refuse to be repaired, or even salvaged for (electrical) parts.

Ahhhhhh- word. Chalo, I agree with you. I’ve never laid hands on a Tern or Reise and Mueller caliber ebike. Now that I realize my blind spot, I think you’re right. You’re working with these bikes day after day, and I don’t have your depth or breadth of experience.

I’ve had a much better time working on broken Radpower bikes or Juiced bikes, for instance, than bikes people buy from Amazon for three, four, five hundred bucks. The connectors on the more pricey bikes are higher quality and more likely to be water resistant. The wheel builds don’t completely suck. I’ve found that controllers on higher priced bikes tend to be bolted down in their own little place, rather than shoved into a hole with double sided tape or silicone, which makes removal for tinkering easier.

And that’s not even starting on the batteries. Juiced batteries, for instance, I have found to be very serviceable. Batteries off of cheaper bikes are just a mess and are hard to access for repair.

So aaaaanyway- I agree with you. Cheaper bikes are fiddly, $1-2000 bikes have been easier for me to service, and it sounds like the really schazzy ones are impenetrable black boxes.

 

[Chalo]

I’ve had a much better time working on broken Radpower bikes or Juiced bikes, for instance, than bikes people buy from Amazon for three, four, five hundred bucks. The connectors on the more pricey bikes are higher quality and more likely to be water resistant. The wheel builds don’t completely suck. I’ve found that controllers on higher priced bikes tend to be bolted down in their own little place, rather than shoved into a hole with double sided tape or silicone, which makes removal for tinkering easier.

Man, I hear that. Just yesterday I put a Juiced Crosscurrent in Mad Max-ish but sellable condition with a Lectric downtube battery strapped in. That bike was donated without a battery by a kind but deranged person who apparently thought almost any problem with it could be addressed with various colored duct tape and stickers. The seatpost had been secured by drilling through the clamp, seat tube, and post and installing a sheet metal screw. It was caked with greasy gritty filth, and I felt almost sure it would only be worth gleaning for components.

But when I bodged one of my batteries to the plug in the frame, it just worked. Couple Anderson plugs, a second life e-bike battery, and tons of cleaning and tune-up, and it was good to go. I only replaced the chain and damaged seatpost parts; everything else was well worth keeping. A really fun, capable e-bike returns to the road for $75 worth of battery, charger, and connectors.

If it had been an Ancheer, Heybike, Eahora, etc, the same amount of previous use would have clapped it out completely (if it had even been possible at all).