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Capacitor to help with staring? 07 Apr 2021 09:03 #846329

  • DOHC
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Hemmek post=846311
​I must clarify one thing thou, I didn't intend to replace the battery :p 
Just helping out with the voltage drop during the starting event. 

I realize I didn't actually answer your question directly. I was really just curious myself to work out how a capacitor compared to a battery in terms of energy storage. 

You're not alone in thinking that super caps can be used to supplement lead-acid batteries.  This is one that I found that is advertised for exactly that purpose.


Of course this one is $1217, so maybe not really practical at this point.  But the idea is sound enough.

However, a normal AGM battery in good shape should start your bike without any help.  The other day I started a '74 Z1 with ~1250cc  and ~12:1 compression with a 1/2 size battery because that's all I happen to have handy.  I did maybe 6 starts before it noticed it start to slow down.

If you're having trouble with slow starting, you either need a new battery, to check your charging system, or do some work on your harness.  
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Last edit: by DOHC.

Capacitor to help with staring? 07 Apr 2021 11:36 #846343

  • F64
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I'm kind of a fan of the K.I.S.S. method (keep it simple stupid).

Inserting another device in the path is just another thing to go wrong.
I'm a fan but my electrics tend to be more rube goldberg.
I've had relays go bad when I could have just increased the wire size and not had the issue.

I would increase your wire size first. I think my starter pulls 80amps at 12V.
With that amperage...12V  4ft.  A 1% voltage drop requires 4awg.
The stock bike is not 4awg. It may be closer to 12awg which is a 6% drop.
Size your wires correctly then add the supercap if you need it.
Your ground wire to the frame should be 4awg as well.

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Last edit: by F64.

Capacitor to help with staring? 08 Apr 2021 14:37 #846401

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A super capacitor is already a sort of hybrid between capacitor and battery.  I would think it much easier to just put in a bigger battery, possibly lithium, if you are going to make room for a super capacitor.  Like F64 said, why complicate it.

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