The Fat Unicyclist Posted November 20, 2016 Share Posted November 20, 2016 I'm not sure of the best place to put this post, so I am going with the IPS section, and will link it back to other relevant places... So today I rode my Lhotz from a full charge, directly uphill to check how it handled (while monitoring the stats). Leg 1 - Uphill Starting elevation: 100m Starting charge: 100% Starting temperature: 16°C Starting load: 115kg Finishing elevation: 250m Finishing charge: ~70% Finishing temperature: 49.5°C Distance travelled: 2000m So I wheeled hard on the uphill, while watching the stats. I wanted to see what the point of failure was... And while I expected my wheel to beep me (requesting a rest) I expected it to be due to the temperature - but the reality when I got the warning was that the app was showing the battery status as <15% but the temperature was still less than 50°C. But after stopping, and allowing the wheel to recover, the status ramped back up to around the 70% mark - so after a 30 second stop I was good to go. Now I should point out that this was 1800m (at pace) into the trip, and I did not let up at all along the way (though I may have slowed down a little as I passed the bakery to check out my options for the second leg). Previously I wasn't sure whether I needed to stop due to temperature or battery drain, but this is now confirmed. I am expecting to take some flak for this, but my statement now is that, "For a heavier rider going uphil, the battery drain can be more significant than the temperature." And in my case, the load became the limiting factor well before the temperature was an issue. Interestingly, it wasn't a torque issue, as the wheel still had a lot of pull in it, but it just didn't have enough stored energy available to draw on to power through? Is this a limitation of the battery technology? Leg 2 - Downhill This was a bit more experimental... The IPS app kept crashing (and I don't think I can use WheelLog) - It seemed to crash particularly when I was on the steeper downhill sections. I wonder if this was when the motor power was a negative value (regenerating) and it didn't understand how to present that? But what I did notice is that while the app showed power usage around 15-20% (while travelling ~10km/h) I did end up at the finish line with the battery charged to around 80% . Overall, my observations (and feeling) makes me think that on the "shallow" downhill, I am still using power to actively drive, but on the steeper sections, power is flowing back into the battery as one would expect. My conclusion is that, at slower speeds with a heavier load, it requires a steeper gradient to achieve regenerative power - and a percentage is actually used on the shallower gradients to maintain a constant (slower) speed. And continuing on that thought - I was interested to note the "stopped" effort - on the flat, I can hold onto something and the motor power to keep me upright is 1-3%. But on a good hill, it is 10-15% Okay, that is me - everyone feel free to shred my comments with science - I am more than happy to be wrong, I just want to understand all of this more! Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted November 20, 2016 Share Posted November 20, 2016 It could be that the app is basing it's battery charge level on the voltage reading so under heavy load up a hill it likely isn't accurate. Going up the hill draws a lot of power so the voltage drop under load at one point makes the app think there is only 15% battery level left triggering the warning? Imagine attaching a flashlight lightbulb to an AA cell. Add another light bulb in series. Measure the voltage drop. Keep adding bulbs and remeasure. At one point everything will be pretty dim and the voltage reading likely will be well below 1.5 volts. Disconnect all bulbs except for one and see how long it burns for. As long as you do this experiment quickly and not too long at each bulb addition, there should still be a fair bit of life left in the battery. It is just the increasing demand draw that reduces the voltage at each interval. Riding uphill places a larger demand on the battery so the voltage drop will be greater over time. When you stop and take a reading it gives you a better estimate of the battery charge remaining. With a larger capacity battery those extra amps are able to reduce the voltage drop I think so you can ride up and down more hills without any warnings but with an increase in MOSFET temperature as a consequence. If the wheel doesn't have a temperature overheat warning in the firmware, that could lead to increasing MOSFET temperatures without warning the rider. Does anyone know if the Gotways will warn you of a high temperature situation and tiltback? Or do they only tiltback on low voltage detection? Future controller designs should have temperture sensors at the MOSFET to keep track of these critical components. I bet that temperature overload may have occurred to @ImpulseZeo9201. If you had a 1200 wh battery you likely could go zooming up and down hills endlessly or until you overheated the MOSFET to the point of failure without triggering a low voltage alarm. Disclaimer: I could be totally wrong as I'm just theorizing all this. I don't own a Gotway or IPS so yep I may be out to lunch here. It won't be the first time I've been wrong. I conjure the almighty @esaj to help comment and dispel any errors in my logic! Link to comment Share on other sites More sharing options...
Xima Lhotz Posted November 20, 2016 Share Posted November 20, 2016 I can confirm the battery vs heat situation and the regenative breaking observations. I own the Lhotz 340wh and it's always the battery that gives up and never a heat issue. I can always push uphill and when the battery goes low it forces me to stop, fully charged or not, in hot 25 degrees C (for Sweden anyhow) or minus 15 C. 2-3 quick hard breaking maneuvers removes the alarm so I can keep going so I don't have to stop. Feels really safe. Im 75 kg. And for regenerative braking, I have the same feeling, as steady as possible, constant "harder then light" braking seems to work best for me. As soon as the wheel needs to correct for anything but a breaking motion or the hill gets less gradient the regenative breaking works less well. Might be obvious :-) Link to comment Share on other sites More sharing options...
esaj Posted November 20, 2016 Share Posted November 20, 2016 5 hours ago, Hunka Hunka Burning Love said: It could be that the app is basing it's battery charge level on the voltage reading so under heavy load up a hill it likely isn't accurate. Going up the hill draws a lot of power so the voltage drop under load at one point makes the app think there is only 15% battery level left triggering the warning? Imagine attaching a flashlight lightbulb to an AA cell. Add another light bulb in series. Measure the voltage drop. Keep adding bulbs and remeasure. At one point everything will be pretty dim and the voltage reading likely will be well below 1.5 volts. Disconnect all bulbs except for one and see how long it burns for. As long as you do this experiment quickly and not too long at each bulb addition, there should still be a fair bit of life left in the battery. It is just the increasing demand draw that reduces the voltage at each interval. The bulbs would be needed to be added in parallel for this to work as intended. Putting them in series, yes, the bulbs will get dimmer, but that's not only because of the voltage drops of each bulb but also because the total resistance of the circuit goes up, leading to less current flowing through. That way, the battery actually puts out HIGHER voltage, as there's less current draw and thus less internal voltage drop in the battery itself. But as there's more bulbs "sharing" the voltage, they each get a "smaller share" of the the total voltage and as the current also goes down, so does the power per bulb. Placing them in parallel, the total resistance of the circuit goes down, as there are more "paths" for the current to travel, each path having the resistance of a single bulb, and thus the total current from the battery will go up. Adding "enough" bulbs in parallel, at some point the battery won't be capable of pushing as much current through them all because the internal resistance of the battery will drop the voltage coming out from it (ie. a larger part of the energy gets burned off by the battery itself, heating it up). Quote Riding uphill places a larger demand on the battery so the voltage drop will be greater over time. When you stop and take a reading it gives you a better estimate of the battery charge remaining. The battery voltage (seemingly) dropping during high current draw is because of the internal resistance of the battery/batteries. Let's say that the total internal resistance of a single pack is 100 milliohms (0.1 ohms) and the open circuit voltage is 60V. If you pull 1 ampere (1A) of current draw out from the battery, you will see a battery voltage of: 60V - (0.1ohm * 1A) = 59.9V Now, if you pull out 10A, the voltage will be 60V - (0.1ohm * 10A) = 59.0V On top of that, the battery voltage goes down as the "state of charge" (abbreviated as SOC in many articles) goes down, ie. as the battery is being depleted. Also, the "wasted" power from the internal voltage drop caused by the internal resistance will also heat up the battery/cells, and as the battery heats up, the internal resistance also goes up. There's probably some other electrochemical stuff going, as the voltage might take a while to get back up to "normal" after the high current draw ends (ie. after stopping). This might be also caused at least partially by the heated cells, the measured voltage should also go up as the battery cools down. More battery packs in parallel lowers the total resistance of the circuit, and smaller amount of current per pack is needed for the total current output. This is why you see smaller voltage drops with more batteries in parallel. From this, one could claim it's always better to have multiple (smaller) packs in parallel than smaller amount of large packs. In theory, it's actually possible to get more mileage out from, say, 3 x 132Wh (396Wh in total) packs than 2 x 210Wh (410Wh in total), as the larger amount of packs in parallel should waste less power through internal resistance. Of course there's more to it in reality (cell ratings/quality etc). Quote With a larger capacity battery those extra amps are able to reduce the voltage drop I think so you can ride up and down more hills without any warnings but with an increase in MOSFET temperature as a consequence. Sounds about right in theory, although it's not the extra maximum amps, but the lower internal resistance, so it's not as much up to the battery capacity than the cell internal resistances (cells meant for large current draw typically have lower internal resistance). Of course large total capacity usually indicates more parallel packs, so in that sense large capacity and less voltage drop goes pretty much hand-in-hand. The MOSFETs also have internal resistance, which causes again power loss in them and heats them up. Smaller internal resistance mosfets will heat up less, but again there are also other factors at play (like switching losses if the gate driver cannot supply/sink high enough current to switch the mosfet on and off fast). Quote If the wheel doesn't have a temperature overheat warning in the firmware, that could lead to increasing MOSFET temperatures without warning the rider. Does anyone know if the Gotways will warn you of a high temperature situation and tiltback? Or do they only tiltback on low voltage detection? Future controller designs should have temperture sensors at the MOSFET to keep track of these critical components. I bet that temperature overload may have occurred to @ImpulseZeo9201. If you had a 1200 wh battery you likely could go zooming up and down hills endlessly or until you overheated the MOSFET to the point of failure without triggering a low voltage alarm. Don't know about Gotways, I think at least the older models didn't have temperature warnings, but could be wrong. At least they did put out the temperature data in the protocol, but it seemed that it possibly comes from the internal temperature sensor of the gyro (MPU-6050, the way to calculate the celsius-value from the protocol data was the same as with the gyro itself). Link to comment Share on other sites More sharing options...
The Fat Unicyclist Posted November 20, 2016 Author Share Posted November 20, 2016 4 hours ago, Xima Lhotz said: 2-3 quick hard breaking maneuvers removes the alarm so I can keep going so I don't have to stop. Feels really safe. Yes, I've found that too - just a few seconds where the wheel isn't drawing too much power, and all is good. But I have also found that if I push on (without breaking or cycling the wheel) for too long, the wheel will reach a point that it rocks backward and forward - even when not moving... Odd... Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted November 20, 2016 Share Posted November 20, 2016 7 hours ago, esaj said: Hunka, basically you're right but not really. Well, the condensed version of it. <Dude, you're supposed to be my electronics guru wingman! Don't voltage block me! How am I supposed to impress all the hot chix on the board who are into electronics?> Link to comment Share on other sites More sharing options...
MaxLinux Posted November 21, 2016 Share Posted November 21, 2016 18 hours ago, The Fat Unicyclist said: the load became the limiting factor well before the temperature was an issue. I'm sure the battery is the primary factor, but I have become convinced that better heat dissipation does improve hill climbing. I noticed a difference when summer ended and outdoor temperatures around here became cooler. Hills that I had to carefully coax the wheel to climb during the summer, now the wheel seems to climb noticeably easier. Since the only thing that changed was the ambient temperature, I speculated that the wheel was able to release heat better and therefore was functioning better. Link to comment Share on other sites More sharing options...
Rehab1 Posted November 21, 2016 Share Posted November 21, 2016 3 hours ago, Hunka Hunka Burning Love said: Well, the condensed version of it. <Dude, you're supposed to be my electronics guru wingman! Don't voltage block me! How am I supposed to impress all the hot chix on the board who are into electronics?> Link to comment Share on other sites More sharing options...
The Fat Unicyclist Posted November 21, 2016 Author Share Posted November 21, 2016 Whoever said, "Thread hijacking is dead." Doesn't know what they're talking about! Link to comment Share on other sites More sharing options...
steve454 Posted July 2, 2017 Share Posted July 2, 2017 @The Fat Unicyclist just found this thread, been reading some reviews of the LHotz, Someone said it performed near the same as the MSuper, just with less range, and people always say the IPS wheels have about the best climbing ability. I just watched @MaxLinux's video review of the 121, he climbed some long, steep hills on it. I didn't know they could go 30kmh either. That was an interesting test you did. Link to comment Share on other sites More sharing options...
The Fat Unicyclist Posted July 3, 2017 Author Share Posted July 3, 2017 4 hours ago, steve454 said: @The Fat Unicyclist just found this thread, been reading some reviews of the LHotz, Someone said it performed near the same as the MSuper, just with less range, and people always say the IPS wheels have about the best climbing ability. I just watched @MaxLinux's video review of the 121, he climbed some long, steep hills on it. I didn't know they could go 30kmh either. That was an interesting test you did. I'm hoping to ride an MSuper this coming weekend... it will be interesting to compare. Link to comment Share on other sites More sharing options...
Carlos E Rodriguez Posted July 3, 2017 Share Posted July 3, 2017 On 11/20/2016 at 7:24 PM, Rehab1 said: I think @Hunka Hunka Burning Love MOSFETS just blue up! Link to comment Share on other sites More sharing options...
MaxLinux Posted July 3, 2017 Share Posted July 3, 2017 8 hours ago, steve454 said: people always say the IPS wheels have about the best climbing ability. IPS 121 and 191 (Lhotz), both of which I ride regularly, are great hill climbers. I live in a very hilly area, so hill performance is very important to me. I've been very pleased with the hill capabilities of my IPS wheels. My latest wheel is a Gotway MSuper 2. It's better on hills, not by a very large margin, but enough to be noticeable. The extra power of the MSuper 2 adds confidence and makes hilly riding more relaxing. I'm saying MSuper 2 is definitely superior on hills to IPS 121 and 191, but not so superior that it makes me say "Wow, that's amazing!" I'll be interested to see what The Fat Unicyclist thinks of the comparison with MSuper 3. I'm assuming the margin of superiority will be larger. Link to comment Share on other sites More sharing options...
Slaughthammer Posted July 3, 2017 Share Posted July 3, 2017 16 hours ago, steve454 said: been reading some reviews of the LHotz, Someone said it performed near the same as the MSuper, just with less range, and people always say the IPS wheels have about the best climbing ability. So, just to make this clear, the Lhotz does in no way perform similar to the MSuper V3, except for tire width. While riding a Lhotz, at my 80 kg you always need to be careful to stay within the power limits of the wheel. On an MSV3 (not the s+, just the regular 67V version) when coming from riding the Lhotz, you won't even come near the power limitations of the wheel. Even when you're trying to. I won't say the Lhotz is a bad wheel, but it's just a 1000W P_max wheel, whereas the MSV3 is a 1500W cont. wheel, that can easily output up to 3500W P_max. Thats like comparing a 50 HP car with a 200 HP car. They will perform similarly as long as you don't exceed a power consumption of 50 HP. I still think the Lhotz is a good wheel for what it is, but it has it's limitations. Link to comment Share on other sites More sharing options...
Carlos E Rodriguez Posted July 4, 2017 Share Posted July 4, 2017 18 hours ago, MaxLinux said: IPS 121 and 191 (Lhotz), both of which I ride regularly, are great hill climbers. I live in a very hilly area, so hill performance is very important to me. I've been very pleased with the hill capabilities of my IPS wheels. My latest wheel is a Gotway MSuper 2. It's better on hills, not by a very large margin, but enough to be noticeable. The extra power of the MSuper 2 adds confidence and makes hilly riding more relaxing. I'm saying MSuper 2 is definitely superior on hills to IPS 121 and 191, but not so superior that it makes me say "Wow, that's amazing!" I'll be interested to see what The Fat Unicyclist thinks of the comparison with MSuper 3. I'm assuming the margin of superiority will be larger. He did! The. Soldered connectors melted causing a cutoff Link to comment Share on other sites More sharing options...
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