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Thread: Sachs xtc 125 conversion

  1. #121
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    Jun 2017
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    Long term- well medium term update

    Hi all,
    now have a little more than 1000km on the xtc (620 ish miles)
    weather was not too favourable to ride lately.

    bike has performed flawlessly so far, using self locking or locktided screws exclusively nothing has come off or got loose.
    So basically the bike is near maintenance free to use.

    Making the most out of the rainy weather i have replaced the back wheels bearings like i already did on the front.
    Now the power consumption at 100kph on a flat is down to about 6,4Kw - the previous mentioned 6,3 have been a typo and should have been 7,3 ish KW.
    Quite a difference and a recomendation to everyone trying to get some more miles out of their ev - look after the bearings as well.
    Total cost of two sets of skf bearings .. aprox 10 Euro - savings in power consumption at 100kph (62mi) aprox 1,2kw . Well worth it -if not for money spend- at least for range gained.

    Talking about range:
    Reprogrammed the kelly`s cutt off down to 3.2 V per cell so it powers down at aprox 3.35 under load i finally performed a real range test yesturday.
    To get you all facts: my single cell monitors alarm start at 3.45 V per cell
    and i have - for the first time the since the charger arrived ballanced the pack- went from 0,04v difference down to 0,04V difference.
    That only proves two things:
    cells had not drifted in those aprox 12-15 charges and the cells simply "sit" at slightly different voltages.

    Back to the range test:
    first 45km i spend simply hooligan the bike around as much as to stay at least not too far off the legal side of traffic. accellerating fully to say 110kph and staying there, I knew i would get at least that range...
    I then opted to "loop " around my village in a more civilised manner - lets call it commuting style in order to find out how much more there really was. Still accellerating full but keeping it between 85-90, no overtaking...
    Well At exactly 75km (42mi) the weekest cell hit 3,45 Volts causing alarm while speeding up so from than on i rode it more cruizing style to see whats still left in it. Speed was sitll kept at about 85kph..
    80km into the ride (49 ish mi) the Cycle Analyst showed exactly 50Amphrs consumed and Cells showed about 3,49 volts at cruizing load..so i turned home.

    84km , 52 Amphr i stopped at home. cells would still read 3,47V average at cruize and cell voltage jumped up to 3,53 av. at standstill. perfect comparison to my calculations and user profile predifined for the cells.
    I am sure if ridden in a tame manner and somewhat slow i could get another 8-10 km out of the cells - while it may cause some voltage alarms while doing so each cell would surely stay safe above 3.3V at load.
    I wasn`t about to test that for simply not wanting to take chances and maybe even damage the pack for no need at all...

    mostly flat, a few smallish hills in between , hardly any wind and temp about 17-18 deg. C.

    I can savely asume to get about 75 to 80 km per ride, with another 10km or so reserve to "drag me home" at reasonable/slow speed and mild accelleration. If i want to extend my range that is... much more fun to spend it all on say 50-55 km rides

    Power consumption on this ride comes to

    0,61 Amphr/km or exactly 1 Amphr per mile
    asuming average 82Volt (90Volts charged, 77 depleted)
    that translates to
    about 50 whr/ km or aprox 80 whr/mile

    seems quite efficient to me so if one thinks about a conversion maybe consider a light, low and fully faired bike for maximum range.
    Might be of intrest as well:
    Total capacity (charged to 4,2V) would be 90Aphrs /8,1KWh
    as used (4,1V down to 3,45 nominal) slightly above 52 Amphrs - might get 57 out if driven slowly (at 62 nominal)

    so calculate enough extra to actually achive your range..


    Last edited by flo; 23 August 2019 at 0401. Reason: spelling

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  3. #122
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    Jun 2017
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    End of season

    Hi all,
    a few days ago i drove the xtc to my friends workshop - where it will spend the winter without freezing temps.
    Through the quite short season ( late June to mid Nov) i managed to ride it just short of 1950 km without a single hick-up.
    Quite pleased with it so far.
    Basically all systems performed as estimated, only range or rather amp-hrs lacking a little.
    AS is, i cannot safely reach the twisties in the mountains near me without even a charge on the way to. Well i ain`t going to split a 2 hrs round-trip into 3 legs with 1,5 hrs charge in between each.
    Getting the bike onto a truck or suchlike would be simply stupid considering the distance.
    Apart from that minor drawback i really enjoyed the rides and it certainly has enough range for all those little tasks usually done by car. On a normal day i do not really miss the range at all.
    Just so easy to hop off, plug in and 2 hrs later take off again. Of course i enjoyed passing the gas stations most.
    Did some short rides with friends and all of them wanted to try it for sure. Each commented positive and most were impressed by the acceleration it gets. Even more so after telling them how few KW it has.
    Few bikers on the road realised it was electric, but the ones that did gave me a thumbs up. Same with pedestrians, mostly childs were quite exited. Actually feels quite rewarding to get so much positive feedback for ones work.

    The cells have drifted a little more now sitting at about 0,06 volts apart- even after balancing. This may cut into range even more next season - we will see. For now it rests at about 3,75 Volts for the winter.

    Hopefully comes Jan i will be swapping to a 14 tooth front sprocket so i am exited not only if the bats will last but also how this will affect power consumption and acceleration.



  4. #123
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    Jun 2017
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    Hi all,
    as i just commented in another topic i guess i could update on the sachs.
    Got it out of its winter place about 10 days ago but only had the opportunity to ride it 3 times since then, by now weather turned winterly again and for corona we are not allowed to leave our homes.
    Anyway, got hold of a lump of tool-steel for the 14 tooth sprocket but in winter my buddy could not fabricate the new adapter and now he is housbound as well. Further mods will just have to wait i am afraid.
    On those 3 trips the little bike performed awfully and reliable as ever, range it seems has not dropped and there is still not noticeable more voltage drop during acceleration than last season.
    I have not bothered to balance the pack after hibernation, just wanted to take a few rides, there has been a little drift which i did not bother before storage but it has not worsened..0,8mV between all cells max (time to balance actually) - just like it was in november. Guess i have more than enough time on hand now to do it..
    I am still not happy with its front beams, the led lights do not help confidence to drive in the dark, supposedly these are 2000lm but perform more like a "day light".
    So i have to look into that again..
    Taking care about chain oscillation at a certain speed has been posponed until i have tried the 14 tooth sprocket so no news about that either..

    Hope you all out there still healthy and stay that way!
    All the best


  5. #124
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    Jun 2017
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    3000 km / 1900mile Update

    Hi all,
    just hit 3000 km last weekend so i guess its worth an update.
    Took off fairing this week to inspect.
    As before all conversion components perform flawless, using lock nuts or locktited screws exclusively nothing has come loose, only maintenance so far being chain lubricant. Back wheel brake doesnt work too good anymore but thats nothing electric related.. will have to source a new one i guess..
    Bats hold up fine, i do not see any degrading, and under power they still show only 0.1V dip per cell across the board.
    Speaking of bats:
    I had previously mentioned the cells "sitting" at slightly different voltages, as it seems i have been wrong.
    Some of you might remember that i manually balance my pack (split into sub packs) using an rc charger.
    A couple of weeks ago i bought a new balance charger, Model ISDT-8T, simply as it would balance up to 2 amps per cell/ channel and does active balancing while charging. As it is possible to calibrate the charger i went to my buddy Robert and we calibrated it using his high quality equipment.

    Surprise, surprise, my cell monitors in the sachs cockpit still show 0,06 Volts difference after balancing. So actually the pack is just fine, only my monitoring is worth crap.
    Need to find out if these can be calibrated as well...

    Anyway getting the cells into balance is now greatly more convenient, i can get all 4 sub-packs done within 20 or so hrs. easy. As this is needed only every two weeks or so thats fine with me.

    Oh - actually rode it in the rain this week too for the first time, without getting electrocuted- so i guess i must have gotten it right.

    Stay save and healthy


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  6. #125
    Senior Member Stevo's Avatar
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    Nov 2014
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    Hi Flo. Nice to see things have woke from winter sleep A-OK!
    Are you running with a BMS installed? The one I am using from Thunderstruck is doing great... no more manual balancing for me anymore.
    The convenience and peace of mind is worth the $$$ in my humble opinion.
    I just put new tires on and reduced my drive sprocket down to a 13 tooth.... I forgot how fast this beast goes now but I'm still only getting about 42-45 (about 70 km) miles per charge. I really only use it for goofing around and riding to work, which is only a few miles ( I could walk ) so one charge lasts me all week!
    Hopefully I can get 5 years of use out of these batts so some new battery tech can come our way! This thing keeps getting better and better!!
    Like a good bottle of Rotwein... better with age!
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: eVOR.v3.4

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