Chriull Posted June 2, 2017 Share Posted June 2, 2017 Since i did not find the thread with the latest discussions about regenerative and non regenerative braking here a new one. (Was the last discussion in http://forum.electricunicycle.org/topic/6022-breaking-crash-analysis/ ?) Anyhow - Since i had a very nice ride again yesterday with logs i just looked a bit through them and found the following: (keep in mind that my KS16C with firmware 1.25 transmits current data only as postive values no matter in which direction it flows! ) Between 3m00.00 and 3m05.00 is a nice braking maneuver from ~23 km/h until standstill. from ~18 km/h on there is an average current of almost 35A flowing while the voltage is constantly reduces! So definitely a non regenerative braking. Same again at around 3m45.00... Between 2m40.00 and 3m00.00 some regenerative braking seems to occur - the voltage rises some volts... Or one more "impressive" log for regenerative braking: imho the peaks at ~1m41 and 1m59 could only be from regenerative braking. The trip: Link to comment Share on other sites More sharing options...
meepmeepmayer Posted June 2, 2017 Share Posted June 2, 2017 I thought "nonregenerative braking" was an euphemism for falling -- Maybe you meant this thread? Result was a collective shrug of "dunno for sure" and "well we'll have to look at actual logs" (incidentally from you) so you're going in the right direction. Logs logs logs logs logs (and systematic experiments)[or not caring]. What's the best Android logging app? (I can't seem to get the wheellog logs from my phone to my PC, they don't show). Link to comment Share on other sites More sharing options...
Chriull Posted June 2, 2017 Author Share Posted June 2, 2017 7 minutes ago, meepmeepmayer said: What's the best Android logging app? (I can't seem to get the wheellog logs from my phone to my PC, they don't show). I just know of the wheellog app for android - when i used it last year i just let it upload the data to my google drive. I can't remember any probs - but i also cant't give any hints... it's too long ago to remember any details... thanks for the link! Link to comment Share on other sites More sharing options...
lizardmech Posted June 3, 2017 Share Posted June 3, 2017 The voltage might sag due to the cells heating up because they can't charge at 30A. Link to comment Share on other sites More sharing options...
Mono Posted June 3, 2017 Share Posted June 3, 2017 @ChriullThanks for the graphs! We can get more and more confident that there are (at least) two types of braking. What puzzles me a little bit is the voltage rise between 2m38 and 3m48. It may be just the recovery from a previous voltage dip. Link to comment Share on other sites More sharing options...
Chriull Posted June 4, 2017 Author Share Posted June 4, 2017 On 3.6.2017 at 10:58 AM, lizardmech said: The voltage might sag due to the cells heating up because they can't charge at 30A. The amperage reported by KS/GW was imho always known to be strongly exaggerated (by the factor ~1.5?) Regenerative braking is imho also very inefficient, from what i have seen at some studies with other electronic vehicles (?something between 15-25%?). I agree with you, that pushing 30A (or maybe just 20A) "into" the battery pack will mainly result in a voltage drop at the internal resistance of the cells, heat them up and not really charge the cells. This graphs where mainly intended to show (?again?), that the wheels firmware definitely uses the battery to brake the wheel (regenerative braking - also in this case the efficiency in regard to recharging could be neglectable) Just took a look at the datasheets of the inr 18650 MJ1 batteries (imho my KS16 has 4 of them in parallel - 840(828)Wh modell from einradwerkstatt): https://www.nkon.nl/sk/k/Specification INR18650MJ1 22.08.2014.pdf Standard Charge current: 0,5C Max Charge Current: 1,0C (3400 mA) So depending on the exaggeration of the wheels current values that would be "just" a factor of about ~1,5-2,2 of overburdening the cells while charging. Definitely not a measure to prolong battery life ;( 23 hours ago, Mono said: @ChriullThanks for the graphs! We can get more and more confident that there are (at least) two types of braking. What puzzles me a little bit is the voltage rise between 2m38 and 3m48. It may be just the recovery from a previous voltage dip. Yes - that also came into my mind. After i found the impressive upward spikes in voltage while braking in the second graph i linked i thougt of removing this not as clear/secure example of regenerative breaking again. But there is quite some current flowing - around almost 5A in the first part (2:40-2:50) and the voltage is still rising slowly. For my "gut feeling" too much for the battery beeing able to recover. Then there is a small voltage sag with a current spike at around 2:50 when i braked from ~27 to 23 km/h with then again a slightly rising voltage while going at about constant speed and ~15A of current. All of this additionally happening while going down a decline (red line showing height divided by five). So all together i tend way more to interpret this as regenerative braking then just a recovery. But anyhow - this was just intended to definitely show that for braking both "current directions" are used. Don't know if much more could be read from this data - values are quite unprecise, it's not definetely known which spike is positive or negative, and the sampling rate is not too overwhelming. Link to comment Share on other sites More sharing options...
Mono Posted June 4, 2017 Share Posted June 4, 2017 26 minutes ago, Chriull said: All of this additionally happening while going down a decline (red line showing height divided by five). oups, I missed this information, that of course can well explain the voltage rise. BTW, do you have an explanation for these bumps in the temperature graph? Link to comment Share on other sites More sharing options...
Chriull Posted June 4, 2017 Author Share Posted June 4, 2017 30 minutes ago, Mono said: BTW, do you have an explanation for these bumps in the temperature graph? Temperature just has a resolution of one degree. Link to comment Share on other sites More sharing options...
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