Topic: Battery delete?

[Cormac]

Is it possible to get rid of the battery on a K3? Without using a magneto?
Had an oakie friend, years ago, who claimed he used a standard little 9 volt battery to kick it over... 'Course I did mention he was an oakie...

[Duke McDukiedook]

K3 what?

Oakie? From Oakland?

[bryanj]

Not really, might just fire but run---doubt it

[Spanner 1]

Might work for 2 to 5 mins. with the headlight and tail-light disconnected. Strictly kickstart only. One touch of the starter button and it's all over!
Almost forgot, alternator would need to be un-plugged too.

[Bodi]

Fantasy.
The ignition coils would take close to 2 amps each at 9V. 4A is unlikely from a 9V battery, and would drain it in a minute anyway. To make electricity the alternator needs field coil power too - maybe 5 amps or so.
This idea of ditching the battery comes up often. You need to install a different alternator/generator with permanent magnets if you want lights, or a magneto if you don't. Using a small AGM or gel cell battery and removing the electric starter is about the closest you can easily get.
There are constant loss ignitions available for racing use with a gel cell or other battery and good for an hour or so of operation. Not much good for a street bike.

[Cormac]

From arkansas, '73 CB750.
So the regulator can't just use alternator out-put for the field signal? Don't know about bikes, but every automotive system I've ever had dealings with, once the system is running, the battery can be removed and the system is self sustaining. God help you if you stall out though.
Where would you source an agm, and how much how big?

[bryanj]

wont work on the honda charging system, its different as there is no residual magnetism as in a car generator

[wannabridin]

you can get an AGM at a batteries plus, or interstate batteries.  i picked one up from there, they have a great selection for size if you know what you want. 

Rob (Voxonda, voxonda.com) sells some REALLY trick solid state batteries that are tiny and powerful, but i imagine a tad pricey.  i'm going to look into one of these bad boys for my k6 rebuild, as i'm going to mount the battery under the seat cowl.  just my $.02

[MJL]

From arkansas, '73 CB750.
So the regulator can't just use alternator out-put for the field signal? Don't know about bikes, but every automotive system I've ever had dealings with, once the system is running, the battery can be removed and the system is self sustaining. God help you if you stall out though.
Where would you source an agm, and how much how big?

Maybe, but the alternator requires power in to make power out.  Without a battery, and with a stock alternato, you are just exercising your kickstart leg.

You could buy an alternator that has permanent magnets and go battery delete, but it is also starter delete as well.

[Cormac]

Understood that you have to have power to start with, hence the battery. Thanks for the tip on the agm and dry-cell.
Also, just found (on cycle X) the pm alternator.
Who needs a starter anyway? 'course it is like 15 degrees out right now...

[wannabridin]

i'd like to run starterless, even on my simple rebuild, as it will save weight and allow faster revs because you have less mass on the end of your crank. 

[TwoTired]

Alternators, motors and generators all function because a magnetic field is present in which to spin coils of wire, which induces electrical flow within the wires.

The Honda SOHC4 uses an electromagnet to generate this magnetic field, and is powered by the battery on the bike.  The alternator makes no power, no matter how fast it spins, if there is no magnetic field present inside the alternator.   Most of the SOHC4s have a 5 ohm field coil to create the magnetic field, the 750's coil is about 6.8 ohms.  The power that the electromagnet draws is voltage dependent.  A 5 ohm electromagnet will draw 2.4 amps or 28.8 watts @ 12 V and 1.8 amps or 16.2 watts at 9V.  A 6.8 ohm electromagnet will draw 1.8 amps or 21.2 watts @ 12 V and 1.3 amps or 11.9 watts at 9V.  

But wait, there is more..
The coils draw, on average 16.2 Watts (1.8 amps) each during the starting phase.  And, if you are lucky, only one of them will be "on" when you first apply the 9v battery to the bike. ( 9 v is a marginal level to allow the coils enough energy to spark the plugs.)

So, in the best case (750 with only one coil and one alternator field powered), you will need 11.9 Watts Plus 16.2 watts or 28.1 watts for each second the 9v battery is connected and powering those two devices (no lighting is allowed).
However, it is very doubtful that a 9v battery can maintain any voltage level with that sort of load (3.1 amps).  They are nominally rated 9v at .625 amps (5.6 watts).  

Curious, I unwrapped a brand new 9v battery, and put my meter on the terminals.  It read 9.85 V open circuit/no load.  I happened to have a bank of resistors which are wired to present a 13 ohm load to the battery.  When I connected these to the 9v battery terminals the voltage almost immediately dropped to 6V and 5-10 seconds later the voltage read 2.5 V, where I disconnected the resistor load.

I question the possibility of reliable spark plug firing at 6v, even 9v is marginal and produces a very weak spark.  But, maybe, just maybe, if you can connect the battery and get the bike to kick start within 3 seconds, you could start a specially wired 750 with a 9v battery.   I also note the possibility of a pig being able to sustain flight if it had wings stapled to it (it may be airborne right after the staples are inserted, but it is unlikely to remain so).

I'm asserting that your oakie friend has more power in his imagination and the breath of his speech than what is available in a 9v battery.  He'd be more likely to start the engine if he just puffed into the engine intake, IMO.

[Cormac]

You will note that I very specifically stated that he claimed, not that I believed... But I really do appreciate your breakdown of all the specific loads involved, nothing like proof.

Thank you all for your imput, found an AGM, $70ish, couldn't get on Voxonda's site, and didn't find any dry-cells in my brief searches... The quest continues.

[Queeg]

my buddy and i found an old gelcell battery and hid it in the place where the starter was. plugged the starter hole with a expanding plug. been fine for about 9 months now

[754]

 We performed a test a couple months ago, and started the warm motor at under 7 volts...this was with neutral light fairly brightly lit.

 In the morning cold, the light is barely visible, yet the bike still starts. When it gets under freezing it gets harder, a lot more kicks. I am thinking though, every kick puts a bit more juice into the battery.

[BLUE71TURBO]

  Okie + Moonshine =  BULLSH!T   

[Cormac]

Nah, he was famous for cherry bilge-wine. Not sure where he stashed his brewing bottles, but our chief never found out... Stuff wasn't bad though.

[MattFreeman]

my buddy and i found an old gelcell battery and hid it in the place where the starter was. plugged the starter hole with a expanding plug. been fine for about 9 months now

Where do you run the wires? Got a photo? Sounds like a cool idea!

MF

[TwoTired]

my buddy and i found an old gelcell battery and hid it in the place where the starter was. plugged the starter hole with a expanding plug. been fine for about 9 months now

Where do you run the wires? Got a photo? Sounds like a cool idea!

MF

Quite the opposite of cool, actually.  The starter compartment gets to engine temperatures (180 F  -ish).  Heating a battery, even a gel cell is not a great idea, IMO.

[Queeg]

my buddy and i found an old gelcell battery and hid it in the place where the starter was. plugged the starter hole with a expanding plug. been fine for about 9 months now

Where do you run the wires? Got a photo? Sounds like a cool idea!

MF

we ran new smaller wires. along the frame then into the housing like the starter wire would run. (not having the starter draw) ill see if i can snap a pic this weekend if i can get over to my buddies house. it basically fallows the old giant starter wire routing!