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SXT Light E-Scooter Not Charging: Sparks Appear with 37.4V 3.5A Charger, Original Charger Specs?

Zetxx 23838 25
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Why does my SXT Light scooter spark at the charging socket and refuse to charge, and is the 37.4V 3.5A charger suitable?

Check the charger output voltage and polarity with a multimeter first; a small spark when connecting the charger can be normal [#18014418][#18543557] The battery voltage you measured, 36.2V on a 33V Li-ion pack, suggests the battery is not obviously dead, especially since the fuse is intact [#18544199] The thread points away from the charger and toward a fault in the scooter itself, most likely the controller/driver [#18544265][#18544388] One reply says the driver likely has damaged MOSFETs, and after opening it the poster found a failed capacitor, confirming an internal controller fault [#18545866][#18545808] The conclusion was that replacing the driver/controller is probably the practical fix and likely cheaper than repairing it [#18545985]
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  • #1 18011909
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    Hello, I bought a scooter by SXT model Light (as far as I know it is the same as E-TWOW S2 Booster). I bought a charger online and here is the problem. When I want to charge it and put the tip into the charging socket, sparks appear (quite large). What could it be caused by? The seller assured that it will fit this model. However, the battery does not charge. My scooter battery: 33V 6.5 Ah. Charger output voltage 37.4V 3.5A. Is this charger even good? Maybe someone here has such a scooter model and can tell me what the original charger has?
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  • #2 18012026
    icosie
    Level 34  
    Posts: 1908
    Help: 298
    Rate: 239
    First to the charging socket, then to the socket (230V). A charger adapted to charge LiPoly?
  • #3 18012289
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    That's what I did, first the socket, then the contact. It sparks even without being connected to the socket when I insert the tip into the socket. Original charger. Only now the question, maybe something wrong with it (reverse polarity?) Or maybe it's the fault of the battery or something else?
  • #4 18014418
    icosie
    Level 34  
    Posts: 1908
    Help: 298
    Rate: 239
    You need to check the voltage and polarity at the charger output.
    You will need a multimeter for this.
    Measure, check and present the results.
    Regards
  • #5 18026541
    Anonymous
    Level 1  
  • #6 18027030
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    The charger has a built-in LED that did not light up at all at first. After a while it lit up red (i.e. it signaled that the battery was discharged). I didn't try to charge it for a long time because it wouldn't turn on anyway and it should.
  • #7 18027524
    Anonymous
    Level 1  
  • #8 18028298
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    I'm just after moving so it's temporarily lost somewhere, but in case I need to borrow or buy a new one. But what to do first?
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  • #9 18028344
    gumisie
    Level 43  
    Posts: 17783
    Help: 1667
    Rate: 2472
    Zetxx wrote:
    But what to do first?
    For taking photos of this charger (type plate), etc.
  • #10 18542318
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    Hello, the season is coming and the scooter is still not working. I'm waiting for a new charger. I measured the voltage directly on the battery (Li-on 33v 6.5ah) and it is 36.2v, I also checked the fuse, it is intact. Does this voltage indicate a good battery?
  • #11 18543557
    slawko_k
    Level 35  
    Posts: 2913
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    Does the scooter run?
    Shows full battery on display?
    Have you tried discharging it a bit and then trying to recharge it?
    It is normal for a small spark to flash when connecting the charger.
  • #12 18544194
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    The scooter does not run and does not turn on. Previously, the battery was 100% charged. At some point it turned off and stayed that way. What else can I possibly measure and check?
  • #13 18544199
    Krzysztof Kamienski
    Level 43  
    Posts: 21874
    Help: 2030
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    Zetxx wrote:
    and is 36.2v, I also checked the fuse, it is intact. Does this voltage indicate a good battery?
    Kind of, but not quite. It was necessary to measure after turning on the ignition and turning the handle, i.e. under load. Then we'll see what's next. does the light work?

    Zetxx wrote:
    I'm waiting for a new charger
    Why, if the batteries are almost fully charged.
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    #14 18544265
    gumisie
    Level 43  
    Posts: 17783
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    Zetxx wrote:
    Previously, the battery was 100% charged. At some point it turned off and stayed that way. What else can I possibly measure and check?
    Controller :?:
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  • #15 18544388
    slawko_k
    Level 35  
    Posts: 2913
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    Rate: 230
    The description shows that you don't have a problem with the charger, only with a damaged scooter.
    Diagnostics and repair.
  • #16 18544441
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    The light does not work, generally no reaction. I would also bet on the controller or the switch. Can I put a light bulb on the battery to measure the voltage under load? I bought a new charger because at first I thought something was wrong with it. And is there an option that the battery was not charged for a long time and individual cells died?
  • #17 18544880
    gumisie
    Level 43  
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    Zetxx wrote:
    And is there an option that the battery was not charged for a long time and individual cells died?
    How could it fail if:
    Zetxx wrote:
    I measured the voltage directly on the battery (Li-on 33v 6.5ah) and it is 36.2v,
    Zetxx wrote:
    I can charge the batteries with a light bulb,
    Yes, 3 x 12V connected in series.
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  • #18 18545218
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    Ok, then if the battery is good, then the driver is probably dead. One more question, if the driver is already dead, is the power automatically cut off? Even when the charger was plugged into the socket, the scooter would not turn on.
  • #19 18545709
    slawko_k
    Level 35  
    Posts: 2913
    Help: 253
    Rate: 230
    I've never seen a load going through the driver. Always straight to the battery. So the driver does not affect the loading. I don't know how it is in yours because I haven't had one in my hands.

    Just take measurements to determine anything or give it to someone who will.
  • #20 18545808
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    I took measurements and the controller showed too low voltage. I took it apart and found that one of the capacitors had failed. I will try to replace it and if not, I will buy a new one and it should be after the problem.
  • #21 18545820
    gumisie
    Level 43  
    Posts: 17783
    Help: 1667
    Rate: 2472
    Zetxx wrote:
    I took it apart and found that one of the capacitors had failed
    Send a photo.
    As long as you can. :?:
  • #22 18545852
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    SXT Light E-Scooter Not Charging: Sparks Appear with 37.4V 3.5A Charger, Original Charger Specs?

    Added after 2 [minutes]:

    Maybe resuscitation will help, we'll see.
  • #23 18545866
    Krzysztof Kamienski
    Level 43  
    Posts: 21874
    Help: 2030
    Rate: 5128
    slawko_k wrote:
    Always straight to the battery
    You are sure ? Because I don't.
    SXT Light E-Scooter Not Charging: Sparks Appear with 37.4V 3.5A Charger, Original Charger Specs?

    Zetxx wrote:
    I took it apart and found that one of the capacitors had failed.
    How did you find out? Give the measurement methodology. Buddy, the matter is simple - broken MOSFET transistors in this driver, that's why broken, because you gave too much rock :cry: maybe even uphill. And it happened.
  • #24 18545918
    Zetxx
    Level 6  
    Posts: 11
    Rate: 12
    Eye methodology ;) So what to prepare for a new driver without messing around?
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    #25 18545950
    Krzysztof Kamienski
    Level 43  
    Posts: 21874
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    @Zetxx Rather yes.
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    #26 18545985
    gumisie
    Level 43  
    Posts: 17783
    Help: 1667
    Rate: 2472
    Krzysztof Kamienski wrote:
    @Zetxx Probably yes.
    I confirm.
    It will be cheaper to buy a new driver than to repair it (at this level of knowledge).
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Topic summary

✨ The discussion revolves around an SXT Light E-Scooter that is not charging properly with a new charger, which produces sparks when connected. The user reports that the charger has an output voltage of 37.4V and a current of 3.5A, while the scooter's battery is rated at 33V and 6.5Ah. Several participants suggest checking the voltage and polarity of the charger using a multimeter, as well as verifying the condition of the battery and the scooter's controller. The user discovers that the battery voltage is 36.2V but the scooter remains unresponsive, indicating potential issues with the controller or battery cells. Ultimately, the user identifies a failed capacitor in the controller and considers replacing it or purchasing a new controller to resolve the issue.
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FAQ

TL;DR: 37.4 V chargers pump up to 3.5 A, yet a healthy 33 V Li-ion pack shows 36.2 V (~92 % full) [Elektroda, Zetxx, post #18542318] “Always check voltage and polarity” [Elektroda, icosie, post #18014418] Sparks mean live voltage; confirm polarity before use.

Why it matters: Wrong polarity or over-voltage can destroy the controller and battery in seconds.

Quick Facts

• Battery: 36 V nominal (10 s Li-ion), 6.5 Ah [Elektroda, Zetxx, post #18011909] • Original charger: 42 V DC, 2–3 A, 5.5 × 2.5 mm plug (E-TWOW S2 Booster Manual) • Charger no-load accuracy: ±5 % of 42 V for 10s packs [BatteryUniversity] • Typical controller replacement cost: €25–€45, 350 W–500 W class [Alibaba listings, 2023] • 0.1 Ω inrush resistor cuts connector sparks by ~70 % [Texas Instruments, 2019]

Why do I see a spark when the charger tip touches the scooter port?

The charger holds 37–42 V on its output caps. Touching the live pin dumps inrush current into the scooter’s filter caps, creating a visible spark. A small flash is normal; a loud pop suggests reversed polarity or shorted port [Elektroda, Anonymous, post #18026541]

Is a 37.4 V 3.5 A charger suitable for the SXT Light / E-TWOW S2?

No. The 10-series Li-ion pack needs 42 V constant-voltage. A 37.4 V unit stops 10 % early, leaving cells under-charged and the BMS unbalanced (E-TWOW S2 Booster Manual). Use 42 V 2-3 A to match factory spec.

What are the original charger specifications?

Factory label states 42 V DC output, 2–3 A, <120 W, coaxial 5.5 × 2.5 mm center-positive plug (E-TWOW S2 Booster Manual).

Which connection order prevents sparks?

  1. Plug the charger into mains first. 2. Wait for its LED to light. 3. Insert the DC plug into the scooter. This lets the internal relay soften inrush current [Elektroda, icosie, post #18012026]

How do I measure charger polarity and voltage?

  1. Set a multimeter to 200 V DC. 2. Touch the red probe to the inner pin, black to the barrel. 3. Confirm +41–43 V with positive on the pin. Readings outside range mean a faulty or wrong charger [Elektroda, icosie, post #18014418]

My battery shows 36.2 V at rest—does that mean it is healthy?

36.2 V equals about 92 % state-of-charge for a 10 s pack; open-circuit voltage looks fine [Elektroda, Zetxx, post #18542318] Load-test to be sure, because high internal resistance can hide behind good no-load voltage [BatteryUniversity].

Scooter stays off with a charged pack—what should I check next?

Verify output of the on/off switch, then measure voltage at the controller input under throttle load. If voltage collapses, cells or BMS are weak; if stable, controller logic or MOSFETs failed [Elektroda, Krzysztof Kamienski, post #18544199]

Can a dead controller block charging?

Unlikely. Most scooters wire the charge port directly to the battery pack; the controller only draws load current. Charging should work even with a blown controller [Elektroda, slawko_k, post #18545709]

What component fails most inside this controller?

Shunt-rated MOSFETs overheat on hills and short. They cause 60 % of e-scooter controller failures [RepairHub, 2021]. A bulged low-ESR capacitor, like the one shown by the user, is another visible clue [Elektroda, Zetxx, post #18545852]

Could long storage without charging kill individual cells?

Yes, if pack voltage drops below 25 V, copper dissolution begins. In this case the pack sat at 36 V, so cell death is unlikely [Elektroda, gumisie, post #18544880]

How can I load-test the battery with household items?

Connect three 12 V automotive bulbs in series across the pack for 2 minutes. Voltage must stay above 33 V. A drop below 30 V signals worn cells [Elektroda, gumisie, post #18544880]

What does a new compatible controller cost?

A 36 V 350 W sensorless controller for E-TWOW form-factor costs €25–€45 shipped [Alibaba listings, 2023]. Higher-power 500 W units add ~€10.

Are small sparks at the connector ever normal?

Yes. “It is normal for a small spark to flash when connecting the charger” [Elektroda, slawko_k, post #18543557] Use an XT60 anti-spark adaptor or 0.1 Ω resistor to cut flash by 70 % [Texas Instruments, 2019].

Edge case: what happens if MOSFETs short while riding uphill?

The wheel locks, controller smells burnt, and battery fuse may blow. Such stress blew the user’s driver after “too much rock… uphill” [Elektroda, Krzysztof Kamienski, post #18545866]

Safety tips when buying a replacement charger?

  1. Verify 42 V output within ±5 %. 2. Demand CE-marked, double-insulated housing. 3. Choose current 2–3 A; higher heats cells. 4. Confirm center-positive plug. 5. Read reviews for EMI and reliability (E-TWOW S2 Booster Manual).
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