Creating an efficient IPhone charger for 150cc scooter

Thread Starter

USarepo

Joined Sep 19, 2021
8
Hi all, new to the forum and am hoping maybe there is a cool way to do this. I’ll give a little background to my project. I’m in the process of finishing a ‘from the ground up’ rebuild of a 150cc scooter. The scooter originally used AC voltage directly from the stator/magneto to power the lights and the AC powered CDI(capacitor discharge ignition) but, I have changed that and am now running a setup where everything is powered from an 8ah powersports battery. So, new and fewer LED lights and a DC CDI. So, here is where my interest for an efficient phone charger comes into play. I plan on using this scooter for food delivery as well as a bit of travel where I’ll be using Google maps constantly on my phone. Because I’ll need my phone constantly charged and working all the time for deliveries, I’d prefer to use the 2 amp charging current available in the 5v cigarette port chargers and the likes.
Now, Im only half crazy and the other part reasonable and I’d not like the crazy part to ruin a longer trip by killing my battery in the middle of nowhere by just winging it and seeing what happens. I would use a bigger battery but, Im trying to keep the weight down being Im already over 200lbs and some of the larger batteries are over 15 lbs (cost more) and then there’s all my gear, tools, delivery items, constant starting etc.
What Im wondering is - is there some form of buck converter setup or a way to take a tiny current from my battery and boost it up to a higher voltage/current? Am I just dreaming? I have no idea how those cigarette chargers drop 12v to 5v and whether that would be better or worse for my electricity needs but, I’m all for learning. The one mysterious component of my setup is the DC CDI. I just can’t find info on the net anywhere for how much current it draws throughout the rpm range. I’ve heard someone say 2 or more amps and others say no where near that. But, that plus a phone charger, starting and all my lights means I might have to step up the battery which I’m trying to avoid. I will however step up the battery if I have too. Any help would be greatly appreciated.
 

dl324

Joined Mar 30, 2015
13,277
Welcome to AAC!
I have no idea how those cigarette chargers drop 12v to 5v and whether that would be better or worse for my electricity needs but, I’m all for learning.
I don't think it'll be worth the bother to build your own. You'll have to put it in a case, and since it can be exposed to moisture, you'll want something appropriate.

This one has the added advantage that it will monitor your battery voltage.
1632066079659.png

If you really want to build your own, there are a large number of commercially available buck regulators. Getting 2A will probably require an external pass transistor.
 

Irving

Joined Jan 30, 2016
2,173
Weird, I've never seen an AC powered CDI, normally theres a voltage regulator to create DC from the AC magneto/alternator. How are you charging the battery?

AFAIK the iPhone will only charge at 0.5A max unless you provide an intelligent charger that negotiates a higher voltage/current. So there's no point in creating a 5v 2A supply, it won't use more than 0.5A.
 

Thread Starter

USarepo

Joined Sep 19, 2021
8
That device will be perfect if it ends up I can’t build a circuit. I was thinking about adding a volt meter so, that would kill two birds with one stone. I had to read up about the pass transistor so, obviously I have to do a lot more research to figure out how to come up with something. I’m all for building something usable with a case as I have some CAD experience and my local library has a 3D printer. I was wondering if I might run something by you. Being that stepping down to 5v from a buck converter to use one of those usb chargers would probably kill my voltage because of the resistors inside the charger - what if I stepped down to a lower voltage with a buck and then stepped back up with a buck to 12v to use one of those chargers?

Welcome to AAC!

I don't think it'll be worth the bother to build your own. You'll have to put it in a case, and since it can be exposed to moisture, you'll want something appropriate.

This one has the added advantage that it will monitor your battery voltage.
View attachment 248333

If you really want to build your own, there are a large number of commercially available buck regulators. Getting 2A will probably require an external pass transistor.
 

Thread Starter

USarepo

Joined Sep 19, 2021
8
You’re absolutely right. Originally, a line went directly from the magneto right to the CDI and then there was another line that went to all the lights but, that line dipped into the regulator/rectifier on its path to the lights (to give them a stable 12v opposed to the higher charging voltage, I think) and then there was a third line from the magneto going right to the regulator/rectifier that turned the AC from the magneto into DC in order to charge the battery. So, now instead of all that, all of the power lines coming from the magneto go right to the regulator/rectifier (I had to get a 3 phase magneto and matching rectifier) and then there are positive and negative leads coming out of the rectifier to charge the battery. I’m not sure how other CDI’s work outside of the scooter world but, in my research with scooters, it was the other way around I.e. more AC powered CDI’s and less DC CDI’s so, I had to study a bit to figure this all out. However, I believe once the voltage passes into the discharge capacitor in the CDI whether it’s an AC or DC CDI, it’s direct current that gets shot into the ignition coil to the spark plug.
Weird, I've never seen an AC powered CDI, normally theres a voltage regulator to create DC from the AC magneto/alternator. How are you charging the battery?

AFAIK the iPhone will only charge at 0.5A max unless you provide an intelligent charger that negotiates a higher voltage/current. So there's no point in creating a 5v 2A supply, it won't use more than 0.5A.
 
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dl324

Joined Mar 30, 2015
13,277
Being that stepping down to 5v from a buck converter to use one of those usb chargers would probably kill my voltage because of the resistors inside the charger - what if I stepped down to a lower voltage with a buck and then stepped back up with a buck to 12v to use one of those chargers?
I don't follow your reasoning. The USB chargers that take 12V input should be using buck regulators. No credible designer would use a voltage divider to provide 5V @ 2A from a 12V source.

If the commercial device used a linear regulator, that would have an efficiency penalty. It's more likely that they used a switching regulator so they don't have to worry about power dissipation. A linear regulator would dissipate 15W and that would require a heat sink and, possibly, an external pass transistor.
 

Thread Starter

USarepo

Joined Sep 19, 2021
8
It’s funny that you immediately brought up buck converters inside because I’d deleted a whole section where I questioned whether they use either resistance to step down or voltage regulators (but, wasn’t sure if you knew) and then went on to ask - if it was a step down with a voltage regulator inside, wouldn’t I need a minimum higher voltage than the 5v output in order to have the usb device work? I played it safe because I wasn’t sure exactly what circuitry they used inside and was hoping you’d see where I wasn’t sure. That and the fact that I have had those fail on me quickly in the past was my reasoning. But, if I do need a minimum voltage and can’t tell what minimum voltage I need without tearing the charger apart, would it just be a matter of trial and error stepping down with whatever buck converter I choose until I step down to a voltage that works with the charger? Would you happen to know off the top of your head what minimum voltage I might need to make one of those chargers work? I’m also not opposed to creating a pcb with a USB port to eliminate the manufactured charger so I can just go from buck converter to usb charging port. I know the circuit would probably be more complicated than that but, I’m just fishing for ideas here.

I don't follow your reasoning. The USB chargers that take 12V input should be using buck regulators. No credible designer would use a voltage divider to provide 5V @ 2A from a 12V source.

If the commercial device used a linear regulator, that would have an efficiency penalty. It's more likely that they used a switching regulator so they don't have to worry about power dissipation. A linear regulator would dissipate 15W and that would require a heat sink and, possibly, an external pass transistor.
 
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Thread Starter

USarepo

Joined Sep 19, 2021
8
Maybe the circuit inside doesn’t need a minimum voltage? I don’t know. Like I said, I’m open to figuring it out.
 

Irving

Joined Jan 30, 2016
2,173
However, I believe once the voltage passes into the discharge capacitor in the CDI whether it’s an AC or DC CDI, it’s direct current that gets shot into the ignition coil to the spark plug.
Yes, there would be a rectifier inside the CDI unit. The reason for powering with AC is, I suspect, is for timing. The magneto is coupled to the crankshaft so the polarity/phase of the AC would represent the position of the crank. On DC CDI there's a separate line from a pickup in the magneto housing.

Maybe the circuit inside doesn’t need a minimum voltage? I don’t know. Like I said, I’m open to figuring it out.
A buck converter from 12v to 5v will usually work down below 9v which is below minimum battery volts (typically around 10v @ fully discharged)
 

dl324

Joined Mar 30, 2015
13,277
But, if I do need a minimum voltage
Why do you need to know the minimum allowed input voltage? It will work over a range of voltages, but why do you care? Presumably you have a battery, which I'm assuming to be 12V. The battery voltage will vary between 10-12.6V (for lead acid); maybe higher if you have the USB charger attached while you're charging the battery. If you're not constantly charging the battery, you don't want to be using it to charge USB devices when it's low.
can’t tell what minimum voltage I need without tearing the charger apart, would it just be a matter of trial and error stepping down with whatever buck converter I choose until I step down to a voltage that works with the charger?
You don't need to take the device apart. Just vary the input voltage and note when it stops providing 5V. You should do this test with a load on the charger.

If you wanted a charger that allowed a larger input voltage range, you could use a buck-boost topology.
I’m also not opposed to creating a pcb with a USB port to eliminate the manufactured charger so I can just go from buck converter to usb charging port. I know the circuit would probably be more complicated than that but, I’m just fishing for ideas here.
You're not going to be able to make anything smaller or more professional looking than something you buy.
 

LowQCab

Joined Nov 6, 2012
1,183
You're over-thinking this.
The Automotive, Panel-Mount, Volt-Meter/USB-Charger is all You need,
and is very efficient.

A larger Battery is always a bonus, but probably not necessary.

Having all LED-Lights effectively increases the charging Current to the Battery.

Minimize Engine Stop-re-Starts any time You can.
.
.
.
 

Thread Starter

USarepo

Joined Sep 19, 2021
8
Why do you need to know the minimum allowed input voltage? It will work over a range of voltages, but why do you care? Presumably you have a battery, which I'm assuming to be 12V
What do you mean why and why do I care? Why not? Why anything? Who cares why I’d want the lowest possible working voltage of a converter? Also here - no shit I have a 12 volt battery on a 150cc scooter that carries a voltage.

You don't need to take the device apart. Just vary the input voltage and note when it stops providing 5V.
Again, here - I don’t want to take the goddamn thing apart. You don’t seem to have the slightest introspective reasoning toward giving a constructive answer at all. OBVIOUSLY I know to tune the buck to a workable voltage or I wouldn’t have said it.

You're not going to be able to make anything smaller or more professional looking than something you buy.
What a pessimist. You obviously have no skills toward anything creative or you’d understand the outside world is capable of doing whatever the fuck it wants.
It’s not hard to create simple plastic case for any small electric device you come up with and make it look nice. It happens all the time and you should know that and not just assume that everyone is as incapable as you. You are so dense[/QUOTE]
 

Thread Starter

USarepo

Joined Sep 19, 2021
8
That’s a fascinating idea about coupling AC polarities with crankshaft position. I know on this scooter the AC CDI worked just the same as the DC. They both use a magnetic pulse from the flywheel passing a magnet, sending a pulse to the CDI for discharge. I’m interested to learn what vehicles use polarity to signal the discharge.
Yes, there would be a rectifier inside the CDI unit. The reason for powering with AC is, I suspect, is for timing. The magneto is coupled to the crankshaft so the polarity/phase of the AC would represent the position of the crank. On DC CDI there's a separate line from a pickup in the magneto housing.


A buck converter from 12v to 5v will usually work down below 9v which is below minimum battery volts (typically around 10v @ fully discharged)
 

Thread Starter

USarepo

Joined Sep 19, 2021
8
Thanks for the replies guys. I’ll come up with something and hopefully come back to post my resolution. Take care.
 

dl324

Joined Mar 30, 2015
13,277
Thanks for the replies guys.
You obviously have a problem with constructive criticism... You can dish it, but can't take it...

I don’t want to take the goddamn thing apart. You don’t seem to have the slightest introspective reasoning toward giving a constructive answer at all. OBVIOUSLY
You obviously have no skills toward anything creative or you’d understand the outside world is capable of doing whatever the fuck it wants.
 
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