Jump to content
Sign in to follow this  

Capacitor install instead of battery, have to discharge cap to get lights to work

Recommended Posts

Got have capacitor in place of the battery on my '83 xr200.  Runs 35W headlight, LED tail/stop and horn works, but the only problem is that if I shut the motor down and start it again the lights will not work...well, they will if I discharge the capacitor.

 

My 6V lighting stator put out 50watts @ 5000rpm and is internally grounded (so, only two wires from stator).  I run the blue wire (lighting coil) up to a 12V rec/reg to one of the yellow wires on the rec/reg, and the other yellow wire is grounded to the frame.  Other two wires run to the pos(+) and neg(-) of the capacitor.  All the DC neg(-) are isolated from the frame and terminate back to the neg(-) side of the cap.  The capacitor is rated at 18000uf @ 36V.

 

Is it because I do not have a floated ground at the lighting coil why the capacitor has to be discharged for the lights to work again?

 

On a side note, if I take the neg(-) off the capacitor and put it to a frame ground, while the motor is running the lights go out.  If I pull the pos(+) off the capacitor while the neg(-) is still grounded to the frame, the lights come back on.

 

Learning as I go...

 

Kirk

Share this post


Link to post
Share on other sites

I eliminated the battery on a quad some years ago.  I seem to recall the capacitor not being the only part needed.  I needed a resistor in line to keep everything operating properly.  Not sure that helps, but maybe something to check in to.

 

Share this post


Link to post
Share on other sites

Seems like I need a bleed resistor in series with the capacitor.  Basically hook the resistor between the two terminals.  Now how to figure what size resistor...any electrical gurus out there to point me in the right direction? 

 

50watts @ 5000rpm

12V rec/reg

18000uf @ 25V capacitor

35watt headlamp with LED tail/stop/license

 

I know the resistor uses up some energy and there is a time constant (discharge time?) to think about.  So I want to get it right and not use up too much of that power I got.

 

Appreciate any help or suggestions,

 

Kirk 

Share this post


Link to post
Share on other sites

Got have capacitor in place of the battery on my '83 xr200.  Runs 35W headlight, LED tail/stop and horn works, but the only problem is that if I shut the motor down and start it again the lights will not work...well, they will if I discharge the capacitor.

 

My 6V lighting stator put out 50watts @ 5000rpm and is internally grounded (so, only two wires from stator).  I run the blue wire (lighting coil) up to a 12V rec/reg to one of the yellow wires on the rec/reg, and the other yellow wire is grounded to the frame.  Other two wires run to the pos(+) and neg(-) of the capacitor.  All the DC neg(-) are isolated from the frame and terminate back to the neg(-) side of the cap.  The capacitor is rated at 18000uf @ 36V.

 

Is it because I do not have a floated ground at the lighting coil why the capacitor has to be discharged for the lights to work again?

 

On a side note, if I take the neg(-) off the capacitor and put it to a frame ground, while the motor is running the lights go out.  If I pull the pos(+) off the capacitor while the neg(-) is still grounded to the frame, the lights come back on.

 

Learning as I go...

 

Kirk

 

I did that to an 83 XR200R but I used a late model alternator with floating ground because of it larger capacity.

IMO your system should work but I don't have much knowledge of the internal wiring of Honda alternators so more information would help. What is needed is a response from someone who has done a similar conversion. More info would also help.

What rect/reg are you using?

Does it provide instructions for use with an internally grounded alternator?

 

For DC charging systems Honda floats the ground. Add an unknown rect and I can imagine potential problems.

 

You could do a test by disconnecting the rect outputs and use a volt ohm meter and check the voltage out of the rectifier to the chassis ground to verify polarity. 

In the absence of knowing how your reg will work with an internally grounded alternator try reversing the two yellow input wires. 

 

There was a recent post in another thread, don't remember forum or subject, where the member isolated  the ground (floated) on the DC side to make his system work.

Share this post


Link to post
Share on other sites

The term "bleed resistor" would normally refer to a resistor directly across the cap.   Could you put a resistor across the terminals of the cap. that would discharge it when it wasn't running?  Of course it would be a tiny bit more load on the stator because it's always draining current so you'd have to compromise in choosing a resistor value that first,  won't put too much extra load on the stator AND will discharge the cap. in a reasonable amount of time after you shut it off.

BTW-for choosing the resistor value, Google "R/C time constant".

Edited by motoxvet

Share this post


Link to post
Share on other sites

I did that to an 83 XR200R but I used a late model alternator with floating ground because of it larger capacity.

IMO your system should work but I don't have much knowledge of the internal wiring of Honda alternators so more information would help. What is needed is a response from someone who has done a similar conversion. More info would also help.

What rect/reg are you using?

Does it provide instructions for use with an internally grounded alternator?

 

 

Chuck, I am using the BajaDesigns rec/reg and, yes they do have a diagram how to hook up with a internally grounded stator coil.  One yellow to the stator output and the other to ground (frame), but you have to isolate all your DC neg(-).

 

Kirk

Share this post


Link to post
Share on other sites

Man I need a electrical book for dummys to simplify all this stuff.

 

All those equations to use, but got it down to a few that come close.

 

Looks like I need a resistor in the value of 470ohms to 820ohms, that also depends on what wattage they are, too.

 

An example I found: a 820ohm resistor with @ 12V running thru it would only dissipate (lose energy as heat) 0.176mW (milli-watts), so a 0.25 watt can be used (got that from this equation P = U^2/R, where P is power in watts, U is voltage across resistor, and R is resistance in ohms).

 

How I got to the actual resistor size to use I was still working on that, and then found this example, so I am going to start there.  Headed to the electrical store tomorrow...

 

Kirk

Edited by kirkallen143

Share this post


Link to post
Share on other sites

P=E (squared) over R (in ohms) so that's 144 over 820 = .176 WATTS, not milliwatts.

Share this post


Link to post
Share on other sites

P=E (squared) over R (in ohms) so that's 144 over 820 = .176 WATTS, not milliwatts.

Yes sir your are correct, and thanks for the heads-up.  I should have not put the decimal there in front.  Thanks.

 

Kirk          

Share this post


Link to post
Share on other sites

All right, the verdict...the 820 ohm 1/2 watt resistor just robbed power from the lights at upper rpms (the only one I tried so far).  And, it still did not bleed the capacitor, I thought until I put a meter on it, 0.0 volts DC after @ 30sec. So, started the bike up again and still no lights, darnit!  Well, out frustration I revved the engine up and lights came on.  Well I'll be?  So for kicks I took the resistor off, started the bike, and no lights, revved the engine and presto...LIGHTS!

 

Looks like this 6V stator to make 12V capable you got to get those rpms up a little...go figure (where is my head in situations like this, is fluoride in the water or something?).

 

This is the first time I did put a meter on the bike to check the capacitor, should of done that in the first place.  Now having bothered you fine fellers, I feel like an ass. 

 

I do have a capacitor question (oh great here we go again), should I go up or down in capacitance to get the lights to come on earlier in the revs?

 

Kirk

Share this post


Link to post
Share on other sites

All right, the verdict...the 820 ohm 1/2 watt resistor just robbed power from the lights at upper rpms (the only one I tried so far).  And, it still did not bleed the capacitor, I thought until I put a meter on it, 0.0 volts DC after @ 30sec. So, started the bike up again and still no lights, darnit!  Well, out frustration I revved the engine up and lights came on.  Well I'll be?  So for kicks I took the resistor off, started the bike, and no lights, revved the engine and presto...LIGHTS!

 

Looks like this 6V stator to make 12V capable you got to get those rpms up a little...go figure (where is my head in situations like this, is fluoride in the water or something?).

 

This is the first time I did put a meter on the bike to check the capacitor, should of done that in the first place.  Now having bothered you fine fellers, I feel like an ass. 

 

I do have a capacitor question (oh great here we go again), should I go up or down in capacitance to get the lights to come on earlier in the revs?

 

Kirk

If that really is the situation like you describe, a smaller value of capacitor will charge faster....

Share this post


Link to post
Share on other sites

If that really is the situation like you describe, a smaller value of capacitor will charge faster....

 

So, I could relatively just half the capacitance value I have now (from 18000uf to 9000uf), is that in the smaller direction?  Or would it be from 18000uf to 36000uf?  I had the same problem with resistance values, could tell which value was larger.

 

Kirk

 

I got it finally, I just put the values into an equation and found which is larger/smaller...9000uf.

Edited by kirkallen143
  • Like 1

Share this post


Link to post
Share on other sites

I used a capacitor in the past to help control load.  IE keep the volts from climbing too high and frying my bulbs.  The battery would normally have been the balance in the system to do this.  

Share this post


Link to post
Share on other sites

Why are you using a capacitor? What is its specific purpose?

To smooth the ripple in the DC current from the rec/reg, to replace the battery, and because I got tired of always having to charge that small sealed lead acid battery.

Share this post


Link to post
Share on other sites

Been away awhile, and forgot to give the results.  I ended up just getting a smaller value capacitor (6600uf @ 25V) and all works well now.  I do get a little tail light flicker with the LED's in the rear at idle, but goes away when idled up or riding.  I guess my 35watt headlight bulb put a max on this stator (rated 45-50 watts @ 5000rpm).  Everything is running on DC as of the moment, if I ran the headlight AC only would that help the tail light at idle?

 

Now that starts my question, if I wanted to run the headlight strictly off AC straight from the stator, but keep the horn and tail light DC, how could I when I only have one wire out of the stator for lights?

I have a separate regulator and rectifier for my system (not a combined unit), could I just tee off the existing wire going to the regulator (which is before the rectifier) and run it to the headlight?  Then ground the headlight directly to the frame?  So I guess my real question is, would it have any effect on the rectifier output, because its the same wire?  Is this where the diodes in the rectifier would stop that from happening?

 

Appreciate it,

Kirk

Share this post


Link to post
Share on other sites
I have a separate regulator and rectifier for my system (not a combined unit), could I just tee off the existing wire going to the regulator (which is before the rectifier) and run it to the headlight?  Then ground the headlight directly to the frame?  So I guess my real question is, would it have any effect on the rectifier output, because its the same wire?  Is this where the diodes in the rectifier would stop that from happening?

 

Yes, tee into the alternator output

Yes, ground the headlite to the frame

 

That makes the regulator and rectifier an add on to the stock AC wiring. 

 

As a side note I have a LED tail/brake lights on my X and I run it on the headlite AC circuit so I can turn it off with the handle bar Hi/Lo/Off switch. That means the voltage polarity is wrong half the time but it seems bright enough for my use, but might not be bright enough for street use.

 

I don't know enough about the actual voltage the regulator is set to,   I say that because all of these devices have a nominal rating of 12 volts but 12 volts AC has peak voltages of about 16 volts, and rectifiers have 1/2-1 volt loss. And batteries need 14+ volts for charging.   I suggest measuring the regulated AC voltage and the DC voltage with a good RMS voltmeter, that may provide an answer to the dimming question other than alternator capacity. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...