Putting a 48V Silverfish Battery in a 36V Bike

tunzafun001 on 17/02/2025 - 00:52

Got an older 36v Ryder Ebike.

Has a 200w bafang rear hub (not the 250w) with a silverfish 36v 10Ah battery.

Has the old school 3 coloured G,Y,R battery lights on the throttle (not an adjustable screen).

Live on a steep hill and it struggles. Got some sag (sits on 35v under load).

Tried a friend's new 36v battery pack. Not much better. 40v under load at least, but still struggles to get up the hill.

Hub always cold though. Even after long hill climbs.

I need a new battery anyway, so was thinking of getting a 48v 30Ah silverfish battery (same price as 36v).

What's the chance it will run with the 48v pack (which would be 52v charged).

Surely standard 63v rates caps inside? Maybe 50v caps. What do you think? Bit of a pain to get the inbuilt controller out to look inside.

Alternatively, I could reduce the pack from a 13s5p to a 11s5p.

Anyone tried simply putting a 48V on a 36v silverfish bike?

Cheers

Electrical & Electronics Battery

Comments

  • oscargamer on 17/02/2025 - 07:03
    +3

    You could pedal?

    • JIMB0 on 17/02/2025 - 10:14

      Manual labor to get yourself around is highly unpopular these days.

    • tunzafun001 on 17/02/2025 - 10:51

      Oh I definitely need to pedal.
      Especially when my daughter is on the back.

  • nizzkid on 17/02/2025 - 07:22
    +3

    Find the controller and see what it's rated for.

    • tunzafun001 on 17/02/2025 - 10:53

      It's inside the hub. Not marked. I'll have to disconnect everything and open it up.
      But you are right, it's the safest way.

      Was just hoping someone had already done it.

      This type of cheap ebike is everywhere.

    • tunzafun001 on 17/02/2025 - 12:42

      Yielded and got it out. No go!!!

      Tiny controller (8cm x 5cm x 3cm).
      6amp Nom (makes sense for 200w@36v). 12A max (so the hub should take 400w+ no probs)

      6 MOSFETs, BUT…caps only rated to 50V.

      48v pack fully charged is something like 53v.

      They are tip toeing the line at 36v (42v charged)..

      Might get away with a 11S pack, but that's about it.

      I guess adding just one extra pack in series should give 10% more power…but then there is the BMS cut out etc.

      Might see if I can find an acctual 42v pack, or get a 48v controller and be done.

      Any ideas if the Bafang rear hubs are all brushless? Looks like all the controllers are brushless.

      • bargaino on 17/02/2025 - 14:49

        At low speed, torque will be proportional to voltage, yes,
        As will the current be. Do you have a current/power meter? Your 200W nominal motor is probably already drawing close to 12A on a climb.
        So at 48V, I'd want at least a 16A rated controller.

        You could get a new controller - they are very cheap compared to the battery. Can you use a generic controller on a Bafang?

        Then you have to worry about wear and over-heating on the motor though. If your bike is road-legal, and power cuts out at 25km/h or so, you are probably fine.
        But start cruising at your new max RPM, and the motor might not last.

        • tunzafun001 on 17/02/2025 - 22:25

          @bargaino

          Looking at one of these generic 36-48v controllers.
          It's identical in wires/ appearance and size specs as mine.

          I'll bet my left nut it's exactly the same, except with 63v rated caps.

          Tempted to just upgrade mine (I already have the caps, mosfets should be ok), but technically my bike is illegal as it doesn't have a speedo. I just have 3 battery lights.on the throttle, and that's it. Apparently you need a speedo now.

          Also,.my bike has flat out only pedal assist. Which is so horrible I disconnected it entirely. Going up hill the battery cuts out with max throttle. But with half throttle I can climb our hills twice per charge.

          • Note - I tried a brand new 36v battery to see if any better. It wasn't any better…other than not cutting out. Did give me a chance to flog it for a big climb and the hub was stone cold at the end. Online suggests the Bafang will take 63v…as long as you don't go full throttle from a stand still.

          So for $35, it's worth it to get adjustable pedal assist, max power out, speedo etc.

          Be good if they provided the controller amp specs though. I'll find them through Ali or Temu..all same price.

          https://www.amazon.com.au/Controller-Electric-Brushless-Moto…?

  • Marty156 on 17/02/2025 - 07:49
    +3

    Check house insurance for fire is paid up!

    • tunzafun001 on 17/02/2025 - 10:54

      That's more about the BMS failing on charging.

      I'd never plug it in and walk away. Only charge for 1hr at a time.

  • Russell Dupsumtucka on 17/02/2025 - 08:04
    +1

    You will let out all the smoke.

    • tunzafun001 on 17/02/2025 - 10:55

      Maybe…controllers are like $30. So risk is not huge.

    • tunzafun001 on 17/02/2025 - 12:34

      Well..it would. 50v caps inside.

      Full charged 48v nominal is over 50v.

  • Protractor on 17/02/2025 - 10:17

    Just do it.
    Looking fwd to the license laws in the wings. Although the videos of morons doing DIY skin grafts on bitumen is one of my favourite film genres.

    • tunzafun001 on 17/02/2025 - 10:55

      Yeah, I don't want speed. I just need grunt.

      • Protractor on 17/02/2025 - 11:14

        Is there a prevailing wind?

        • tunzafun001 on 17/02/2025 - 12:43

          No matter where you go..it's always a head wind!

  • tunzafun001 on 17/02/2025 - 12:44
    +1

    Wrapping up in case it helps others.

    If you have an old school 200w rear hub silverfish battery bike .. don't go above 42v pack.

    Components inside aren't rated for any higher.

    • GordonD on 17/02/2025 - 12:55

      Gee, what a surprise, something built as cheap as possible is only just able to do the job required, and very little more. Who'd a thunk it.

      • tunzafun001 on 17/02/2025 - 13:07

        There is that, but there is also the "build one model for all sizes" economies of scale.

        Hence modern controllers are pretty universal.. they spent an extra 3cents per 100v cap…but saved 6 cents by making 10 000.

  • lgacb08 on 18/02/2025 - 15:03

    It's just not about the voltage but more so of current, there's reason it's only 200w with the thin wiring and abysmal number of mosfet. Raising voltage doesn't solve the problem because many of the components are just stock standard and can only sustain few amp. You're looking at a couple more or higher rated mosfet, thicker wires and other thing to sustain 10amp. So no they didn't skimp on capacitor but something else.

    • tunzafun001 on 18/02/2025 - 17:17

      Yeah, the stock controller is 6A nominal, 12A max. It has 6 mosfets.

      The cheapo 34/48v controller doesn't actually have an amperage rating, but I can read 13A max on one of the pics from buyer feedback
      It's exactly the same form factor (box is an identical 8x5x3 cm),and it has identical screw positions for the mosfet heatsinks. So going to assume its a very similar amperage, just 48v components, marginally higher mosfets etc…maybe.

      One thing that I have no idea about, this part of the instructions (below)…What on Earth is a booster?

      "Note:
      1. The product power factory setting is 8, the basic general market most of the split booster, if the customer uses an integrated booster, set it to 12.
      2. P13 on the manual is to set the product power, in the case of incompatible booster, the customer needs to adjust to 8 or 12"

      Wha????

      • bargaino on 19/02/2025 - 01:40

        In this context, booster likely refers to the PAS (Pedal Assist Sensor) system used to detect pedaling and control motor assistance. There are generally two types of PAS sensors in e-bikes:

        Split Booster (Separate PAS Sensor) – This typically consists of a separate magnet ring and sensor installed near the crank. The controller is set to 8 to work correctly with this setup.
        Integrated Booster (Built-in PAS Sensor) – Some e-bike motors or bottom brackets have an integrated PAS sensor. For these systems, the controller should be set to 12.
        The setting (8 or 12) likely adjusts the number of PAS signal pulses the controller expects per crank revolution. If the controller is set incorrectly, the PAS may not function properly, causing erratic pedal assist behavior.

        If you're configuring the controller for your e-bike, you'd need to determine which PAS type you have and adjust the setting accordingly.

        —- ChatGPT

        • tunzafun001 on 19/02/2025 - 01:48
          -1

          Thakyou sir.. and thankyou AI…

          i would have never guessed that (a bit scary).

          Never done the ChatGPT thing.

          Slightly off tangent, but what does it come up with if you ask 'what is the best predicted Australian shares for total yield in 2026'?, or maybe something like 'what is the best return you could get on a $200 000 investment in 2025'.

          Thanks again.

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