Connect with us

Adding accessories to component systems

Discussion in 'General Electronics Discussion' started by tedstruk, Aug 22, 2017.

Scroll to continue with content
  1. tedstruk


    Jan 7, 2012
    motorcycle accessories are all the rave....
    so here is my final workup on the overpower tail light problem I have created for myself...

    Alternator puts out 14v 20amps @ 5000rpm to charge a 12v/20ah battery

    if I run an accessory of 5 - 27.5w bulbs, which totals to 137.5watts
    My alternator puts out 280watts at 5000 rpm....
    but I have a 4 amp regulator, which reduces the power capability substantially--
    280w / 4a = 70v which is about 68v short of what I need.
    assuming this same equasion with the actual watts instead of alternator watts at 5000rpm
    137.5w / 4a = 34.375v still way too high.

    60w headlamp
    8w x2 = 16w tail
    27w x2 = 64w brakes (intermittent mostly off)
    27w x 4 = 108w signals(intermittent mostly off, 64w normal max flash)
    3.8 x2 = 72w plate light
    control board
    3.4w x9 = 30.6w indicators
    8w x2 =16w running lights
    366.6w total standard wattage
    137.5w of accessories
    504.1w required

    a 20ah, 12v battery delivers 240watts.
    504.1w required - 240w available = 264.1w
    because 264.1w is larger than 240w
    we could say we have a 504.1w drain of 24.1w
    We can't build a speciallized 504.1w system, because we are using 24.1w too many...
    because the system has intermittent usage of the turn signals and the brake lights and the control board,
    the system is working ok.... but it can't deliver the 4a that is nessesary to charge the battery
    24.1w / 12v = 2amps
    So if I can create a direct input generator that delivers 2amps into my fancy accesory it should allow the regulator to charge the battery... as it is, the regulator is taxed 2amps by the accessory, leaving only 2amps of charging power to charge the battery...

    so I would need to isolate the original system, make a secondary set of controls-add a battery-and generate 137.5w @12v
    and the 11.46a that this produces could trickle spare charging power in, if needed. Like 20ma for 16hrs with a drain shunt to the main battery when the engine is off. caveat- the battery that I add will have to be larger than the one the system already has in it.
    Whoo whoo was that a train?
  2. Bluejets


    Oct 5, 2014
    Loads in automotive run in parallel. Your assumptions and calculations are incorrect to arrive at a final outcome.
  3. tedstruk


    Jan 7, 2012
    reprisal by rote...
    When you generate current, you are creating more problems. more resistance, more amperage, more more more..
    this problem is a real pain because it jumps back and forth between more and less, and I guess that's the only way to do it right.
    But all I really need is that extra 11.46 amps, and to me that is do-able....
    Amplifiers increase current and in my mind an 11.46 amplifier is better than a battery,regulator rectifier and gobos lights all around....
    So what if I tapped into the AC generator before it goes into the rectifier regulator, and just add what I need to power the accessory?
  4. duke37


    Jan 9, 2011
    A 20Ah battery does not deliver 240W, it will deliver what the load needs within reason. A car starter motor takes about 3000W for a few seconds with a battery not much bigger than yours.

    Add up the current of all the devices. Compare this to the 20A alternator. You will see if there is a lot spare.
    The high voltages you calculate are rubbish, they do not occur. Everything runs on 12 to 14V.

    Taking three phase AC direct from the alternator windings will not help and will add complications.
    The 20A alternator is rated at 5000rpm, it will give less current at lower speed.

    I do not understand why there is a 4A regulator to control 20A.

    What is a gobos light?
  5. kellys_eye


    Jun 25, 2010
    @duke37 - I admire you wading in to comment...... I read the OP and just 'walked aways shaking my head....'
    davenn and (*steve*) like this.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day