Could I connect a capacitor in paralell to the battery?

[stinkwheel]

My bullet is kick-start only and has quite a small bettery. On a few occasions, the ignition has been left switched on, as happened today when it was in for the MOT and if the points are closed, it'll flatten the battery in a couple of hours.

I do have a large capacitor which will start and run the bike instead of the battery. I'm going to leave this in the battery box in case of emergency but it occurred to me that I might be able to leave it connected all the time which would give me a dead-start facility without having to fuck about with wiring?

I'm pretty sure it's safe to leave the cap and battery in paralell without damaging the cap but will this flatten the battery when parked up? I can't see why it would if there's no circuit for it to discharge into but do capacitors discharge over time anyway?

I considered fitting it to the switched side but then realised the bike would keep running with the ignition off.

Or maybe connect the capacitor using a battery isolator switch?
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Nobby the Bastard]

The problem is that the capacitor will just discharge just like the battery if you leave the ignition turned on.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[stinkwheel]

Yes, but it will charge the capacitor with a couple of kicks then start. I did originally have the bike running with the capacitor only but you have no lights with the engine off and it struggled with the horn which is an old solex one that draws a lot of amps.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Islander]

I stuck a reply on the 'What grinds my gears thread'

[WD Forte]

[WD Forte]

If we're talking large electrolytic then yes they will self discharge
as will any battery but much faster and the rate depends on various factors.
Super capacitors have much better/slower leakage current rates then electrolytics but like a battery they too will self discharge over time.

In your case I'd say the simplest solution is just make sure you turn the fecker off when not running and if left for extended periods stick the battery on a tender
____________________
bikers smell of wee

[Islander]

[stinkwheel]

[Nobby the Bastard]

Okay, whats to stop the kickstarter from trying to charge the battery rather the capacitor.

The capacitor shouldn't really flatten the battery unless it's knackered and is leaking power.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[stinkwheel]

Nothing, which is what I was concerned about.

Of course, someone elsewhere just suggested using a changeover switch so you can change from battery to capacitor, which seems like it ought to work. You could probably even flick back onto battery once it's running and the rev speed is up.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[The Shaggy D.A.]

[The Shaggy D.A.]

Page 6 of the Manual from '85 :-

https://3.bp.blogspot.com/-9AJGa4uvxkI/UWl_ckW2TiI/AAAAAAAAAIQ/DQsGBF7WwH4/s1600/Picture+006.jpg

https://oldraremotorcycles.blogspot.com/p/bullet-350-1985_13.html
____________________
Chances are quite high you are not in my Monkeysphere, and I don't care about you. Don't take it personally.
Currently : Royal Enfield 350 Meteor
Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[The Shaggy D.A.]

https://2.bp.blogspot.com/-vX_WN6ZWkUU/UWl_lfanUEI/AAAAAAAAAJw/yUQLlM4aKo4/s1600/Picture+018.jpg
____________________
Chances are quite high you are not in my Monkeysphere, and I don't care about you. Don't take it personally.
Currently : Royal Enfield 350 Meteor
Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[The Shaggy D.A.]

And a mention from the G2 workshop manual :-

https://www.team-bhp.com/forum/attachments/motorbikes/2164339d1622923094t-royal-enfield-g2-bullet-story-screenshot_2021060601062965.jpg
____________________
Chances are quite high you are not in my Monkeysphere, and I don't care about you. Don't take it personally.
Currently : Royal Enfield 350 Meteor
Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[The Shaggy D.A.]

...and a final breakdown of the switch contacts
____________________
Chances are quite high you are not in my Monkeysphere, and I don't care about you. Don't take it personally.
Currently : Royal Enfield 350 Meteor
Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[The Shaggy D.A.]

Seemed to remember that when using the EMG position, the bike would start, but run lumpy as fuck, but was good enough to get to a point where it could be switched over and the bike kept running.
____________________
Chances are quite high you are not in my Monkeysphere, and I don't care about you. Don't take it personally.
Currently : Royal Enfield 350 Meteor
Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[stinkwheel]

That's interesting and now makes me wonder if the bike would start if I just disconnected the battery which in theory would allow the reg/rec to directly feed the points. I only have a single phase alternator so it's a different setup to the one you've shown.

I suppose the main issue would be getting it spinning enough on a single kick to produce enough charge. Whereas with the capacitor, you can kick it over a few times to store some charge). Not convinced it'd do it on the kicker unless you held in the decompressor and spun it with the kicker then dumped the decompressor which could result in something of a hey-ho-rumbelow. Probably work for a bump start, although I find bullets a total sod to bump even with a charged battery. I'll try it tomorrow (not the spinning over thing, just see if it'll fire up with the battery disconnected)

Of course, as I've long maintained, the ideal setup would be to retro-fit a magneto to the distributor for power supply and use a crank mounted, self-exciting electronic ignition. I'm too tight to buy a lucas replica mag though, especially since it would need to be lightly butchered to fit because RE used a non-standard mag housing.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Robby]

This whole thing is looking like a rather complex solution for a problem that shouldn't happen. Which would suggest that in the unlikely event it does happen, the solution doesn't need to be as simple as flicking a switch.

That said, can you run the ignition system off a 9v battery? It could be neater to have a 9v battery terminal hidden away somewhere, and a battery to use with it velcroed close by. Advantage is that they hold their charge for years. Similar idea to carrying a spare spark plug.

[WD Forte]

This reminds me of my torch
I modded it with a cheapo power pack and DC-DC convertor PCB to run a 12v MR16 led
that I could recharge from a mini USB phone plug
5v in 12v out

Did this a few years ago and it still works too

https://imgur.com/II7P2tV.jpg
____________________
bikers smell of wee

[stinkwheel]

I do suspect, as above I'm over-engineering this idea and potentially introducing an additional point of failure with a switch and additional connectors.

I think the best/simplest thing would be to just fit double connectors on the battery leads and mount the capacitor in the battery box with flying leads. Then if I get a flat battery, disconnect the battery, connect the capacitor and start it. Once it's running, connect the battery back up again leaving the cap in place until I get wherever I'm going to smooth the current delivery.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[jeffyjeff]

How big is the capacitor? Depending on size, it might be worth considering a battery connected in parallel with the stock battery. A lithium iron battery could be mounted in any orientation and would not take up much space. No isolation required; extra capacity on hand all the time. just a thought.
____________________
History shows again and again how nature points out the folly of men - BOC

[stinkwheel]

[WD Forte]

You recall the Mobylette I converted to 12v with AC CDI and led lights?
it didn't even have a battery and started so much easier than before
the guy used to have to pedal like buggery to get it started
I could start it with one downward kick.
the magneto windings were pathetically tiny and the lights wouldn't light up the sky but
were far better than the appallingly poor 6v bulbs
I could have fitted a small battery but kept it as simple as possible for him
but did fit a capacitor in parallel which helped give a better and more consistent light output.

The ignition and lights were independant of each other stator wise
The 4 pin rectifier for the lights and cdi box were easily sourced and cheap as chips
probably 20-25 quid for the pair as I recall.

I'd do a similar mod to the Enfield if it were mine, I wouldn't entertain 6v pos earth
and Lucas 'prince of darkness' lights
you could even keep the points and just use them as a trigger source so no burn out due to arcing.

My two pennorth

More Moby
https://www.bikechatforums.com/viewtopic.php?t=334589
____________________
bikers smell of wee

[stinkwheel]

[stinkwheel]

An update on this.

I have confirmed my bike will start and run with a 4700 microfarhad, 50V capacitor connected in place of the battery. Lights are sketchy but the engine runs fine.

I have also confirmed there is zero measurable current leakage when the ignition is off and the capacitor and battery are connected in paralell. By zero i mean less than 0.1 microamps which is the limit of my gear (and that's enough to measure the current generated by moving the meter cables about in the earths magnetic field).

That in itself is unusual and I think a function of the Enfields having the reg/rec output upstream of the ignition switch to allow the ammeter to function. There's normally a tiny amount of current leakage on any motorbike which i think is mostly back-leakage through the reg/rec diodes.

Upshot. I can safely leave the capacitor connected in paralell with the battery all the time.

What I haven't checked is if a near totally flat battery will immediately pull down any current generated by a kick preventing it starting. A knowledgeable friend has suggested if this was to happen, connecting a power resistor in the battery positive should allow the cap to charge first but still allow some charge to get into the battery once running.

So the current plan is to leave the capacitor fitted and put a flasher ballast resistor in the toolbox with flying leads attached so if I find myself with a flat battery and it turns out not to start, I can connect this in for the next leg of the journey. If that doesn't work, the engine will run on the capacitor alone if I simply disconnect the battery.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.