Hi, i have a KE125 from 1978 (mint condition). The problem is that it is a 6v system and the points setup is a nightmare (yes for this model it is really bad, the stator plate cannot be adjusted etc). Anyway - i decided to upgrade to a Solid state 12v system from powerdynamo. Looks very simple to fit etc, no problems.

The 12v battery I have (needs to fit compartment for bike) - Absorbent Glass Mat (AGM) states that the charger should not exceed 1.5 amps and I have a 12v desktop trickle charger that is perfect.

Now the conversion has a diagram (Picture 1) - if you look you will notice that the regulator output goes directly into the battery (a lot more that 1.5amps). So what I want to do is convert is to Picture 2.

It is a kickstart bike and will run without a battery (UK law requires a battery for lights for road use - parking at night etc), so the feed into the battery only needs a top up trickle charge)

Questions:
1) How do I restrict to 1.5 amps for a trickle charge
2) Will a simple 15 - 20 amp diode stop feed into the battery from the regulator after the trickle unit or will i need something a bit more sophisticated?

thanks
Rimmel

 

Note to admins: I tried editing the post to send me instant email notifications but it won't let me - saying the content is probably spam?!?!?

Yet I haven't changed the content (it is already posted) just wanted to add instant notification. /Strange

 

You're better to regulate the output from the generator rather than trying to drop the output from the regulator, or modify the regulator with an optional switch to give a trickle charge mode.

 

You're better to regulate the output from the generator rather than trying to drop the output from the regulator, or modify the regulator with an optional switch to give a trickle charge mode.

Thanks for the reply:

As well as trickle charging the ouput from the regulator has to power the lights, horn etc on the bike. So I thought this was the easiest way - basically it is treating the battery as another component and charging it. When the regulator isn't being used (bike not turning over) then the battery powers the lights.

Also The generator and regulator are sealed units or modification would break any warranty.

thanks
Rimel

 

You might look into battery-tending ICs (e.g. Texas Instruments has a line, as I supposed the other chip makers do). These are intended to do exactly this task, to keep the battery charged according to whatever scheme is best for the battery, while supplying power as needed to the load. This is if you want to build something.

I don't care for the diode idea you've shown, because a diode introduces a voltage drop of 0.4-0.7V or more, depending on the diode. That means your lights will always be hair dimmer than they should be, and the diode will be burning off as waste heat 0.6V/12V = 5% of the power used by the lights. Your bulbs may last longer, but it just doesn't seem like a good idea. It would work, though.

 

I don't really see the concern being many motorcycles, ATV, and similar machines use AGM batteries with electrical systems that also supply the currents you are implying you have.

Typically on a starting battery the charging amp rate limit is for long term charging or constant current variable voltage not short term constant voltage charging like what their systems operate with.
However, if you are using the wrong type of battery for the intended job you are better off finding the right one rather than trying to hack the system to make it work.

Simply put, just because your motorcycle may not have a electric starter on it doesn't mean it's not an application where a starting battery best suits the job.

 

You might look into battery-tending ICs (e.g. Texas Instruments has a line, as I supposed the other chip makers do). These are intended to do exactly this task, to keep the battery charged according to whatever scheme is best for the battery, while supplying power as needed to the load. This is if you want to build something.

I don't care for the diode idea you've shown, because a diode introduces a voltage drop of 0.4-0.7V or more, depending on the diode. That means your lights will always be hair dimmer than they should be, and the diode will be burning off as waste heat 0.6V/12V = 5% of the power used by the lights. Your bulbs may last longer, but it just doesn't seem like a good idea. It would work, though.

Thanks for the reply - I will look at the battery tending IC's. I also see your point about the diodes - I guess a simple relay could be used e.g. powered by the regulator, when the regulator is OFF (bike not running) then the relay will route the power from the battery, but when the regulator is ON then the relay with cut off the battery power and route through the regulator power. ??

thanks again

 

Hi, i have a KE125 from 1978 (mint condition). The problem is that it is a 6v system and the points setup is a nightmare (yes for this model it is really bad, the stator plate cannot be adjusted etc). Anyway - i decided to upgrade to a Solid state 12v system from powerdynamo. Looks very simple to fit etc, no problems.

The 12v battery I have (needs to fit compartment for bike) - Absorbent Glass Mat (AGM) states that the charger should not exceed 1.5 amps and I have a 12v desktop trickle charger that is perfect.

Now the conversion has a diagram (Picture 1) - if you look you will notice that the regulator output goes directly into the battery (a lot more that 1.5amps). So what I want to do is convert is to Picture 2.

It is a kickstart bike and will run without a battery (UK law requires a battery for lights for road use - parking at night etc), so the feed into the battery only needs a top up trickle charge)

Questions:
1) How do I restrict to 1.5 amps for a trickle charge
2) Will a simple 15 - 20 amp diode stop feed into the battery from the regulator after the trickle unit or will i need something a bit more sophisticated?

thanks
Rimmel

View attachment 128192 View attachment 128193

If you are not using it, AGM batteries are great at holding their charge vs other lead and many lithium batteries.

Also, a commercial trickle charger has built in safety features to shutdown, restart and check for shorts or reverse battery connection. I recommend a commercial unit.

 

If you are not using it, AGM batteries are great at holding their charge vs other lead and many lithium batteries.

Also, a commercial trickle charger has built in safety features to shutdown, restart and check for shorts or reverse battery connection. I recommend a commercial unit.

Hi I would love to use a commercial version - however I am hard pushed to find a 12v (14.4v) version. All seem to be 240v AC to 12v. I need 12v (from regulator feed) to 12v.

thanks

 

Thanks for the reply - I will look at the battery tending IC's. I also see your point about the diodes - I guess a simple relay could be used e.g. powered by the regulator, when the regulator is OFF (bike not running) then the relay will route the power from the battery, but when the regulator is ON then the relay with cut off the battery power and route through the regulator power. ??

thanks again

I don't see what a battery charge control IC will do for you without some sort of additional extra circuitry to provide the higher input voltage than what your base 12 volt system will provide being a 12 volt AGM would require a power source with a the capacity to go above 15 volts during constant current charging whereas your motorcycles own systems are limited to ~ 14.4 volts making a constant voltage source overcharging event impossible to begin with being that range of voltage your motorcycle's system work at is the normal stage 2 voltage level range the constant voltage phase of a 3 stage charger works at any way.

Also given you need the capacity for the lighting system to stay even if the engine quits that adds more complexity to the overall system requirements.

I can follow the need for the higher end smart charging requirements for a AGM battery that is in an application where it is connected to a power source 24/7 like ina UPS standby unit or such application but on a motorcycle the typical run times are only a few hours at best and most far less than that.

As I have mentioned before I just don't follow the want for such a complicated system when its not used in common other mobile applications that use the same type of batteries.

 

I don't see what a battery charge control IC will do for you without some sort of additional extra circuitry to provide the higher input voltage than what your base 12 volt system will provide ...

I was assuming his 12V nominal was actually much higher when running, before regulation. I guess we don't know that? But anyway a charge controller such as one meant for solar could include a buck-boost module to accept almost any voltage and still tend the battery and load properly.

 

You may not need to limit the charge current, since the current will drop as the battery reaches full charge.

If you really need it then you could just put a small value resistor in series with the battery in place of the red box shown in the schematic.
You can experimentally determine the value to give the desired maximum charge current, probably an ohm or less.

The diode should be a Schottky type for low voltage drop and dissipation, but will likely still need to be mounted on a heat sink.

To reduce the drop to a negligible value and eliminate the heat sink you could use an ideal diode circuit.

 

I was assuming his 12V nominal was actually much higher when running, before regulation. I guess we don't know that? But anyway a charge controller such as one meant for solar could include a buck-boost module to accept almost any voltage and still tend the battery and load properly.

From the given circuit the battery is on the output side of the regulation system where a optional battery can be placed so it would make sense that it's on a voltage limited circuit.

You may not need to limit the charge current, since the current will drop as the battery reaches full charge.

If you really need it then you could just put a small value resistor in series with the battery in place of the red box shown in the schematic.
You can experimentally determine the value to give the desired maximum charge current, probably an ohm or less.

That's what I was thinking. Don't worry about meeting theoretical 'what if's" requirements until they prove to be real problematic issues.