A little improvement

Discussion in 'Electric Bicycles' started by Borromeo, Nov 9, 2009.

  1. Borromeo

    Borromeo New Member

    Dear people, I have thought a little improvement for my SLA batteries: Connect in parallel with them a large-capacity electrolytic capacitor, let's say 5000 uf x 80 V, the purpose is to improve the peak current to the motor, What do you think?

  2. spad4me

    spad4me Member

    You are thinking of a boost capacitor .
    Used in an automobile audio system where the alternator is too small to carry the load.
    They are placed before the load .
    They are usually expensive.
    If you have to buy them.
    I would recommend buying better batteries like lipo4 .
    If you already have them give them a try .
  3. Borromeo

    Borromeo New Member

    For now I can't buy those lipo4 batts but I've some capacitors for a try...
  4. safe

    safe Active Member

    This idea is correct. In fact there have been SLA batteries built with capacitor plates built into them in order to "pre stage" energy before release.

    One thing you will discover is that when you connect your wires together from controller to battery that with added capacitors you will get a bigger spark. When the connection is made the capacitors need to charge up and that sucks currents really fast.

    Controllers already provide a pretty large capacitor reservoir... but adding to it would be good. You could simply take the controller apart and "upgrade" to larger capacitors. That way you don't really invent anything but just add to what is there.

    You might want to upgrade to these: (1000µF)



    ...for many of the chinese controllers this should be about right.

    The stock capacitors on mine are 470µF.


    However... I wouldn't get too excited about the idea. When you start to demand more power from the battery these capacitors will give a "sugar high" of temporary power, but eventually the underlying sluggishness of SLA will dominate. You would need to build the capacitor into the battery in order to really do this right.

    But I'd like to see it done... :thinking:


    What I've done with my old bike is to place a set of NiCads at 24 volts in series with SLA's also providing 24 volts because I put the SLA's into series - parallel. (four SLA's, 2x2) The result is that the SLA's are allowed to be sluggish and drain slowly (good) while the NiCads are able to deliver their current really fast. This means that most of the harder work goes to the NiCads which love it. The NiCads are sized so that they run out first and this tends to protect the SLA's even more.

    You can also place the NiCads in parallel at 24 volts and this tends to level out things because when the SLA's "sag" the NiCads pitch in to help. The negative is that when the NiCads run out then you get a very sudden drop off in power. (you can lose several volts in seconds when at full throttle) It kind of depends on what battery performance curve you prefer...
    Last edited by a moderator: Dec 18, 2015
  5. AussieJester

    AussieJester Member