Kickstart-only Battery Delete capacitor vs tiny Ballistic/Shorai Li-Iron battery

[Chuck78]

I'm needing to replace my dead battery now, and I've been hung up on kickstart engines quite a lot since I got into motorcycles, for the rider to machine connection, potential weight savings, nostalgia, etc. I dropped my '77 GS750 from 552 lbs wet weight now to 500lbs, & more weight savings would nicely offset the hefty crankcase contents of these overbuilt engines. 16-17 lbs weight savings deleting the battery, starter, and starter gears on my dieting large-cc corner carving machine would be excellent!

http://www.oregonmotorcycleparts.com/BEC.html Oregon Motorcycle Parts says that much less than a 22,000uf capacitor is no good for trying to smooth out the gaps in the stator pulses on ignition startup & idle on a smaller or 2 cylinder engine., & are working on a 40-60,000uF cap kit for 4 cylinder bikes.

I see very large 22,000uf and larger caps in the 35 to 70 volt current handling capability for $10-$40 on ebay, and I thought about running two of those in parallel in order to have more power and have 2 in case one blew, so for $30-$80 I could have 40,000+uF of electrical ignition assist in kickstarting, and keeping the lights from flickering at idle (plus no battery/starter weight).

Downside I hear is that the caps (maybe just smaller ones?) are bad at soaking up high revving voltage surges from your charging system at it's peak output, and you blow light bulbs much more often. The other downside to this is that if I run out of gas (or the bike breaks down) at night in the hills or in low lit areas where there may be traffic, I am totally without lights as soon as I pull in the clutch or the bike comes to a stop. I go camping with the bike, so lights with the battery off would be nice.




Ballistic and Shorai have been making Lithium-Iron Phosphate batteries (similar to Li-Ion) for motorcycles that cost quite a lot, are a little smaller, and weigh SUBSTANTIALLY LESS. Comparison: http://www.webbikeworld.com/motorcyc...le-battery.htm
How much power/amp-hours do I really need to adequately power the Dyna-S ignition and one or two indicator lamp bulbs when kickstarting?
I am looking at tiny 4 cell Ballistic batteries, with no starter motor draw, how small can I go? A 50cc-scooter-spec 4 cell battery should do it, right? May be able to afford one of those, and have some quick headlight power still after the engine is off.



Ballistic 4 cell battery, this thing might be the ticket for a kickstart only, what do you guys think?:

http://www.ballisticparts.com/products/batteries/4cell.php

Ballistic 100-009 $58 ebay shipped (2"x2"x3.25"), or the slightly larger Ballistic 100-010 (2.5"x2.5"x4.25" 2.3 amp/hours) $87 shipped.



CAPACITOR(S):
+slightly lighter than LiFePO4 battery
+much cheaper (~$30-60 ebay)
+substantially smaller than lead acid battery
-may burn out light bulbs more frequently on higher rev's (inability to act as a large cushion for charging system spikes)
-no lights when engine off, no lights when bike dies from no gas or mechanical issues (danger in traffic)

SMALL LIGHTWEIGHT LI-IRON-PHOS BATTERY:
-substantially more cost, $100+
-does not tolerate charging more than 14.4 volts, will fail
-does not tolerate running it dead below 9 volts, battery is shot if you discharge it less than 6 volts +smaller to much smaller than lead acid battery
+lights still work when engine is not running (safer if bike dies, handy when parked in the dark)
+probably makes starts and idling better/smoother than caps


Any users of very large capacitors on here to comment on the downfalls of them (reliability, light bulbs blowing, etc)? Also, just how small can I go on the battery and still have enough voltage spike cushion, as well as electrical capacity to easily start up my 4 cylinder Dyna-S ignition powered bike??

[Chuck78]

As far as power for the size and weight, the Antigravity Batteries' smallest 1lb and 4.25" x 1.25" x 3.75" 6amp/hour offering is the best, but $108 best deal, $119 retail. Seems better for sure. Shorai didn't stack up for my needs. Caps or Ballistic are closer to my over-extended (total engine rebuild!) budget...

http://shop.antigravitybatteries.com/antigravity-batteries-ag401/

[850 Combat]

With Points, you can get away with a capacitor. With electronic ignition, I think you need a solid 10 volts to make them fire reliably. I've gone with a dead battery for years at a stretch on a British bike, then I put on an electronic ignition and needed a good battery. These new ones are powerful and dense, but I've heard of them getting ruined by incorrect charging. Its a pretty cool idea though.

[Chuck78]

With Points, you can get away with a capacitor. With electronic ignition, I think you need a solid 10 volts to make them fire reliably.

YES, I could not get my bike to start today at all, battery had barely enough voltage to light the oil&neutral indicators, headlight would not even light up at all... Got one backfire, but otherwise no ignition.

With a big enough cap, I bet the dyna would fire up alright enough. I guess you woyld be limited to the voltage that the speed of a single kick could provide the engine/stator.

[tkent02]

With points ignition and a good flick of the wrist on the kickstarter, my bike will start with a 9 Volt transistor radio battery. With electric ignition, not do much.