DC CDI

[MickYork]

Is anyone using a battery powered CDI/Coil and if so what make and where from ?

Thanks

[missing lynx]

cdi's are nether dc or ac it's the regulator that you need to be ac or dc depending on your set up

[MickYork]

cdi's are nether dc or ac it's the regulator that you need to be ac or dc depending on your set up

Hmm maybe......but....the normal voltage to the cdi from the LT coil is 100v ac increasing to over 300v when the rev's pick up. If it's just powered from the battery it will be 12v ....and no more regardless of rev's. The other factor is that the low tension coil produces AC which can be transformed, DC volts has to be "altered" to increase the voltage. I think (not 100%) that DC CDI's have a built in inverter, or similar, to allow the voltage to be increased. If you do a search you will see CDI's advertised as either AC or DC.

............................but I may be wrong !!

[missing lynx]

the cdi gets it's power from the low tension coil the power for the lights and charging circuit are supplied by the other coils via a voltage regulator I use a Wassel one for full dc. I'm a bit stumped as to what you mean battery powered as the cdi is powered by the the flywheel spinning round the stator plate

[Adam_Winstone]

Readspeed are releasing / have recently released a CDI that can be run directly off the lighting circuit, which is a massive help if you find that your LT coil fails on a rally. You may wish to speak with them to find out more.

Adam

[MickYork]

the cdi gets it's power from the high tension coil he power for the lights and charging circuit are supplied by the low tension coil via a voltage regulator I use a Wassel one for full dc. I'm a bit stumped as to what you mean battery powered as the cdi is powered by the the flywheel spinning round the stator plate

On more modern bikes the CDI is powered from the battery, which is a constant voltage and gives better performance at lower rev's.

I think your confused with the phrasings for the Low Tension coil, Lighting coils and CDI (which incorporates the HT coil, with the HT lead coming out to the spark plug).

I'm hoping to do away with the LT coil and supply the CDI direct rom the battery. As I mentioned before the "DC CDI" is different from the standard Lambretta AC CDI.

hoping to fit one like this: http://www.electrexworld.co.uk/acatalog ... --DCP.html

[MickYork]

Readspeed are releasing / have recently released a CDI that can be run directly off the lighting circuit, which is a massive help if you find that your LT coil fails on a rally. You may wish to speak with them to find out more.

Adam

Thanks, will give them a call

[missing lynx]

will a std lambretta stator produce enough power to keep a battery charged enough to power it and will it work on a single cylinder machine without an engine managment system? looking at their site they do cdi's

[dickie]

.the normal voltage to the cdi from the LT coil is 100v ac increasing to over 300v when the rev's pick up. If it's just powered from the battery it will be 12v ....and no more regardless of rev's. The other factor is that the low tension coil produces AC which can be transformed, DC volts has to be "altered" to increase the voltage. I think (not 100%) that DC CDI's have a built in inverter, or similar, to allow the voltage to be increased. If you do a search you will see CDI's advertised as either AC or DC.

............................but I may be wrong !!

No, you're not wrong. Most (possibly all) modern bikes connect the cdi directly to the 12v circuit. I've been thinking of trying it myself but it seems a waste of the power available from the low tension coil.

[MickYork]

will a std lambretta stator produce enough power to keep a battery charged enough to power it and will it work on a single cylinder machine without an engine managment system? looking at their site they do cdi's

If you've got full DC (120w of power) I don't think there's a problem. The CDI I showed on the link looks a tad expensive compared to some others but I'm not 100% which types will work and wont (some are pre-mapped and have rev limiters).

[Knowledge]

Back in 1980's when did a bit of racing, I had luminition electronic ignition. The scooter had a battery and a big HT coil. The Luminition system was also DC, as there was no AC supply.

Now I appreciate that this is different from what Mick is asking, but it does prove in the very simplest way, that you can have a DC ignition system.

Anthony Tambs supplies is CDI that is separate form the coil, so there are clearly several ways of doing this spark-lark and it is good to see Mick looking at alternative solution.

Good luck, Mick.

[dickie]

I've been nosing around as I'm bored on a train and I think a honda c90 cdi is a good candidate. You'd need a separate coil between the cdi and spark plug though.

The reasons I think that may be suitable are: no advance built in; cheap; readily available.

I'm going full dc on my current build so I may give it a go.

[coaster]

I'm keeping a eye on this but my concern would be that although it would be perfectly feasible, in practice there isn't enough power to give decent lights, let alone the additional current required to operate a DC ignition system. Perhaps Martin can give an indication of how long his 'total loss' ignition worked between charges? My only experience is with car systems which take in the region of 5 amps at low speeds but that increases in relation to revs.
I think that this would be a fantastic idea where a 3 phase system is fitted such as the Electrex system or Richards Taylor's

[Knowledge]

On a standard six pole stator, you could take the LT coil off the stator and fit another coil for the DC charging.

You could fit an external pick-up and replace the internal pick-up and fit a sixth charging coil.

Just trying to think outside the box

[dickie]

On a standard six pole stator, you could take the LT coil off the stator and fit another coil for the DC charging.

You could fit an external pick-up and replace the internal pick-up and fit a sixth charging coil.

Just trying to think outside the box

I like that. Quite a lot. I've got to have a go now. Unfortunately I don't anticipate trying to start the motor this side of Christmas. Plus i don't fancy messing about with a brand new bgm stator. I have an old points stator I could fit a load of coils too though. Can anyone see any flaw in that?

[Fast n Furious]

Most old 4 and 6 pole magneto type generators suffer from the same typical problems. Namely, they don't produce enough steady power at tickover and produce too bloody much at full chat. We see this as flickering lights on tickover and this is simply resolved by going DC and fitting a battery like 99.99% of all other road going vehicles!
They produce too much voltage at the higher revs and this excess has to be dumped to earth via the regulator, which is released in the form of heat. Too much voltage overloads the regulator and then it fails. You probably won't notice this until you need your lights. Chances are the regulator has blown open circuit so the excess voltage blows all your bulbs. Not good if your dashing for that all important ferry in the dark.

Fitting an extra coil on the redundant LT pole, wired in series with the other lighting coils, will exacerbate the "too much voltage" scenario, making it even more likely that you will blow your "questionable quality" regulator when day riding.
Technically, an improvement could be made by dumping the original coils and the pickup and using an alternative method to trigger your spark.
Fully populate all 6 poles with coils wound to the optimum value. (good luck with that) This would improve the flicky lights on tickover on AC machines but it wouldn't eliminate it. Yes. You would get more power without frying the regulator but why do you need this extra electrical power? What would you do with it?
By design, the Electrix kit looks good if you want good AC lights with a dc supply for the CDI. Bit pricey though!

I've commented in another thread on how to optimise the use of a points stator for DC CDI.

[coaster]

If you were to utilise the all 6 poles on the stator then wire them to give a 3 phase output you would then have a system similar to most motorcycles and cars as you would then have an alternator rather than a magneto. I believe Anthony Tambs has this idea in his 'things to do list'

In answer to Fast N Furious question, the extra power would supply a DC ignition and give enough power for decent lights without having to resort to HID/LED options.

[dickie]

If you were to utilise the all 6 poles on the stator then wire them to give a 3 phase output you would then have a system similar to most motorcycles and cars as you would then have an alternator rather than a magneto. I believe Anthony Tambs has this idea in his 'things to do list'

In answer to Fast N Furious question, the extra power would supply a DC ignition and give enough power for decent lights without having to resort to HID/LED options.

Yes i agree and have been mulling it over at work today. If we wire the six poles in delta, the voltage will be slightly lower than what we get at present (around 60% if my maths is right).

The best regulator rectifiers are the mosfet type that some cbr600s and zx6r use. Fh008 I think. These are essentially the same as a switch mode power supply so create very little heat.

Mrs dickie is going out tonight so I'm going to play in the garage. I should probably get my series 3 running properly and finish building that winter model first.

[Fast n Furious]

If you were to utilise the all 6 poles on the stator then wire them to give a 3 phase output you would then have a system similar to most motorcycles and cars as you would then have an alternator rather than a magneto. I believe Anthony Tambs has this idea in his 'things to do list'

In answer to Fast N Furious question, the extra power would supply a DC ignition and give enough power for decent lights without having to resort to HID/LED options.

Well a DC CDi uses a few hundred millamps of current. CDI's dont pull current like inductive ignitions do.
An HID or incandescent lamp greater than 35w is impractical.
6W max for the tail light.
We can ignore the intermittent use of the horn and brake light.
Say 50W as a constant demand. This would be no problem if the scoot was at cruising speed all night long. Your standard 80-90W stator even has enough left to charge the near flat battery you started out with.
The problem would be for the boy who only uses his scoot for a tootle into town and back in the dark regularly. Not enough revs to provide enough constant power to recharge the battery that is being discharged by the lights every night. This is probably a bit extreme but demonstrates the point. The 3 phase solution is the ultimate way, with a standard plate, to providing more power at lower revs where it's needed. It would also help reduce the working voltage span of the generator which plagues single phase geny's. This then makes the regulator design simple and cost effective to make. One from a Japanese bike would probably do nicely.
In reality though, if the battery capacity is sufficient, 5AHrs or more, it wouldn't be a problem unless you really like to sit at red lights ticking over for most of the night.
If contemplating an HID lamp conversion, it needs to be realised that if the DC line voltage of your scoot falls below around 9V the front headlamp will just shutdown. No warning. No dimming down. These conversions, as good as they are, need a good size healthy battery if your light is to be reliable and blinding around town during the dark months.

[coaster]

I agree about the 9v issue with an HID, I have had bad battery connections on mine where the light went out completely at tickover. Doesn't need many revs for it to work though but would be better not to have to rely on the battery. Interesting about the CDI current consumption, I have only noted the current drawn through a car ignition (non CDI) which is around 5 amps with the ignition off