Originally Posted by
jspauld2
Hi Guys,
In regards to the new smaller RCExl ignition versus the older style RCExl ignition: there should be no difference in the operation or the internals that would cause the issues you are experiencing. The ignition itself should use NO MORE than 500 mAh at wide open throttle. You should easily be able to run a 2000 mA battery for 1.5 hours powering just the ignition (I'm not sure about how much current draw the ibec demands). From the above post, it seems like it draws quite a bit of current.
I have also heard about a lot of guys running the ibec with no issues, maybe some of them can speak to what they are doing to be successful?
Marty H. if you haven't sent your engine in yet, I can confirm that they only need the engine. If they give you any problems with that let me know and I can straighten it out.
Thanks,
Jimmy
I had problems with the new RCEXL ignitions on a 4 Cell NiMi battery pack WITH the IBEC. The problem is that the new RCEXL ignitions, ones that will work on voltages above 4.8 volts (such as the one for the EVO and the DLE-35 for example) draw a little more current at the start of the capacitor charge cycle. The overall current draw is about the same. The problem is that the new ignition modules will start misfiring if the voltage drops below about 4.1 volts. The old, 4.8 volt only, ignition modules would work with the 4 Cell pack and IBEC combination because the current draw was not as heavy at the start of the capacitor charge cycle, so the voltage did not drop below about 4.2 volts with a fully charged battery pack. Also, the 4.8 volt only, ignition modules would work at a voltage below 4.1 volts. I never did the testing to see what the minimum voltage was that would cause the ignition to start cutting out, but I suspect it would work with an input voltage as low as 3.5 volts.
The problem is not with the "current draw" of the IBEC; it is negligible. The problem is the "voltage drop"; it will drop about 1.2 volts from the battery input voltage. To look at another way, if the battery voltage INPUT to the IBEC is 5.3 volts, the OUTPUT to the ignition module will be 4.1 volts and the new ignition modules will start cutting out.
FYI - If the IBEC ignition regulation voltage is set to 5.2 volts, the input voltage from the battery will need to be above 6.4 volts to maintain the 5.3 volt output. A lower battery input voltage to the IBEC will result in a lower voltage (by 1.2 volts) to the ignition module.
Another problem is that the voltmeters, used by most of us to monitor battery voltage, will not be able to display the "spikes" in the voltage that are caused during the ignition module charge and discharge. Your voltmeter may indicate 5 volts, but the voltage spike may actually be as low as 4.5 volts and that is the voltage that matters to enable the ignition module to work properly.
I know this may be TMI for a lot of you, but the bottom line is that if you use an ignition module that is designed for more than 4.8 volts, with any battery, AND an IBEC, and you want to be safe, don't fly if the battery voltage is below 5.5 volts. The good news is that if your ignition module starts cutting out, you can idle down the engine and still have enough current to run your receiver/servos and land your plane.