Kickstart Only

[cqyqte]

If as the Title suggests, I am only going to have kickstart only, what minimum size battery can I get away with to provide adequate voltage for the ignition system and lights on a 1971 CB450 Twin? Would a small 3 AH maintaince free battery work well?

 

[cqyqte]

I am hoping to be able to tuck the battery away under the cafe seat or above the front fender support under the seat.

 

[Tim]

You should be able to use a small battery - first figure out where you want to put it and what the dimensions of the battery need to be.

I run a relatively small battery in my XS650 - I'd have to get the dimensions, but it's a 7ah battery I think. Kick only and no problems. I have it in the hump of my seat.

 

[Tim]

I've since swapped out the battery - was a lower capacity but found a higher cap battery the same size.

 

[skatetheame]

I ran a 3.2ah batt on my 360 and it was fried after about 7 months. I'm running a 5ah now and it runs a lot better.

 

[Tim]

Yeah - I don't know much about charging, but I seemed to be 'over charging' my last battery - the one in the pics. It boiled over, acid out of it etc. even though it was sealed. Ran through 2 of them.

Then got a newer better AGM battery of higher capacity and no probs since.

 

[crazypj]

You can measure the actual charge of bike with an amp meter.
Smallest battery you 'should' use is 10x larger than average charge current.
e.g. 0.5a at idle, 1.5a at 6,000 rpm = 2a total
Average 1a x10 = 10A/hr
Using a smaller A/hr battery will 'cook' it
Personally,I wouldn't go 'smaller' than 7.5 A/hr as that gives best life/cost/capacity.
Using 3a/hr will work but may only last 3~6months, plus, it could explode/catch fire

 

[StrtLegal]

I'm also doing a kick only on my cb750. I bought a 4 cell from Antigravity Batteries. It is rediculously small. I'll see if I can snap some pictures for you next to my stock battery.

 

[crazypj]

I'm also doing a kick only on my cb750. I bought a 4 cell from Antigravity Batteries. It is rediculously small. I'll see if I can snap some pictures for you next to my stock battery.

Not sure which CB750 you have but your going to have to upgrade your charging system
I'm not sure if it was TwoTiired or Hondaman on SOHC4.net who posted explanation but link is in the exploding Shoria battery thread

 

[StrtLegal]

Already did!

 

[Finnigan]

Does "upgrade the charging system" mean getting a modern rectifier/regulator from DCC?

 

[mydlyfkryzis]

the real problem with a permanent magnet alternator is that the system is voltage regulated only, not current regulated. The alternator ALWAYS puts out the maximum current it can. the regulator only shorts to ground when the voltage is over 14.5v to 15.5v depending on the regulator.

A field excited regulator actually has the output of the alternator regulated, so as the load goes down, so does thevoltage and available current.

So when you strip all the lights off your Cafe Racer, (go LED Say) your PM alternator actually has excess capacity. If the load from the battery charging keeps the voltage below 14.5, the entire excess current goes to the battery. So an 11 amp system, with 5 amps going to lights, maybe 3 amps to ignition, has 4 amps available for battery charging. And as long as the voltage stays below 14.5, all the current is absorbed by the battery. A 3.5 AH battery should receive, at best 0.4 amps of charging, not 4 amps . So if your battery is a little low, the PM Alternator is charging at 3-4 amps until the battery voltage is higher. this high rate charging quickly deteriorates the battery.

This is why the Original system had either 2 sets of coils, so it wouldn't overcharge if the lights were off, or they increased the light load to be fairly constant and allowed foil coil pairs on all the time.

The permanent Magnet Alternator is in a balanced system. Output is designed to be almost exactly load. So if you jump the coil pairs together, then reduce the load, you have heavily unbalanced the system on the excess capacity side, which is then absorbed by the battery most of the time.

 

[AgentX]

Theoretical question:

What if you ran a permanent-magnet alternator with a much higher output than your normal power consumption, but without a battery...using a combined reg/rect/capactior style battery eliminator, in my case?

I've got a Boyer powerbox. Would it get fried?

(Am re-wiring using a new alternator designed for equivalent electric-start bikes on my kick-only bike...and I don't use my headlight in the daytime, as I'm not in the US and it causes massive confusion and garners a ton of unwanted attention as people desperately try to get you to turn it off. Currently running a 12v 5AH sealed battery but once I get the system back up and running, was thinking of yanking the fuse out of the battery line and seeing if I could run satisfactorily without the battery at all. It starts and runs decently as-is without the battery except that it tends to die at idle. Was hoping the new alternator and clean, new wiring would clear that up, but I also don't mind running a battery, especially a small one.)

 

[mydlyfkryzis]

Hard to say. A cap will charge to a higher voltage. A good regulator will keep the voltage in check. There is always a chance of spiking the system though. A battery is large capacity voltage sink. A cap less so, depending on size. On a pm system, all electronic devices are at risk due to the large variance in voltage. So it also depends on the robustness of the device and its components.


Sent from planet Earth using mysterious electronic devices and Tapatalk

 

[Finnigan]

the real problem with a permanent magnet alternator is that the system is voltage regulated only, not current regulated. The alternator ALWAYS puts out the maximum current it can. the regulator only shorts to ground when the voltage is over 14.5v to 15.5v depending on the regulator.

A field excited regulator actually has the output of the alternator regulated, so as the load goes down, so does thevoltage and available current.

So when you strip all the lights off your Cafe Racer, (go LED Say) your PM alternator actually has excess capacity. If the load from the battery charging keeps the voltage below 14.5, the entire excess current goes to the battery. So an 11 amp system, with 5 amps going to lights, maybe 3 amps to ignition, has 4 amps available for battery charging. And as long as the voltage stays below 14.5, all the current is absorbed by the battery. A 3.5 AH battery should receive, at best 0.4 amps of charging, not 4 amps . So if your battery is a little low, the PM Alternator is charging at 3-4 amps until the battery voltage is higher. this high rate charging quickly deteriorates the battery.

This is why the Original system had either 2 sets of coils, so it wouldn't overcharge if the lights were off, or they increased the light load to be fairly constant and allowed foil coil pairs on all the time.

The permanent Magnet Alternator is in a balanced system. Output is designed to be almost exactly load. So if you jump the coil pairs together, then reduce the load, you have heavily unbalanced the system on the excess capacity side, which is then absorbed by the battery most of the time.

This is a great explanation, I can understand how batteries may get fried more often on old bikes! But my question still remains the same. Will getting a "modern" regulator/rectifier that is grounded to the frame of the bike "fix" the overcharging problem for a battery with a smaller Amp rating?

 

[Sonreir]

Not on a permanent magnet system. You still want a battery with a higher A/h rating. A newer regulator will let you use a battery that is more voltage-sensitive, though (such as Lithium Ion), so you can get a reduction in battery size through that method.

 

[crazypj]

Basically, it comes down to this, do you know what your doing?
If not, forget about what you want and do what your told (sucks but that's life)
Use the largest amp/hour battery you can fit in position you want it.

 

[Sonreir]

Basically, it comes down to this, do you know what your doing?
If not, forget about what you want and do what your told (sucks but that's life)

That might have to go in the sig line on my profile...

 

[crazypj]

;D LOL ;D

 

[RustyRivets]

I got myself one of these for my kick-start bike. (slowly coming together) Ebay listing said it was rated for my bike. >Hoping I don't have to upgrade anything.