Current draw from glo plug?
 

I want to run an on-board glo plug igniter on my inverted moki 2.1. I was wondering what the current draw is for a typical glo plug - I am using an OS "F" plug. I plan on using two 2000 Mah NiMH bateries wired in parallel. My installation will work via an on/off switch and not be influenced by a throttle setting.

Thanks for any input,
ScaleME

RE: Current draw from glo plug?
 

The typ number is 1.25 A to 2.2 Amps so 1.5 A is good number to go by. They vary from glow plug type to temperature it is at. Start high current and amps drop as it heats up.

RE: Current draw from glo plug?
 

Well I did a test and determined that the plug was lit for approximately 45 minutes and tapered off quickly thereafter. When I charged the battery I could only get it to 1.39 volts - I was expecting around 1.5. So I am not sure if the battery is really getting its max capacity. If my assumption is right, theoretically I should be able to get around 2 hours of glow with the 4000 Mah battery (2 2000 Mah in parallel) if the plug draws around 2 Amps.

RE: Current draw from glo plug?
 

http://www.rcuniverse.com/forum/m_5734666/tm.htm

RE: Current draw from glo plug?
 

Greg, thanks for the link. Per that link, they were siting 3-4 amps draw for on OS f plug. That would validate my test better than the 1.5-2.2 amp draw assumption.

With this knowledge I think what I will do is make two of these battery packs and use one pack for 2-3 flights then drop in the other for more flights while the other is charging. After 4-5 flights I am pretty much done for the day anyway.
ScaleME

RE: Current draw from glo plug?
 

Here is a reference table of mine, I thought I would share and might be of some help.

RE: Current draw from glo plug?
 

Thanks Jetpack. The list is useful, however, I am not familiar with the plug discriptions. Were would the OS F plug be on this list?
ScaleME

RE: Current draw from glo plug?
 

I don't believe there is any type of cross-reference between manufacture's in existence. What I think might be helpful is the wire diameters vs. amperage. This does not take in account the number of turns on a coil which is unknown however, but it does give a slight picture of what goes on with wire size and amperage between one manufacturer's plugs.

RE: Current draw from glo plug?
 

ScaleME,


A Nickel-Cadmium battery and a Nickel Metal-Hydride battery have a nominal voltage of only 1.2V. When they are fully charged, their actual, no load voltage is 1.38-1.46V. Their internal resistance is very low, resulting in pretty high voltage falling on the glow element.

This no-load number becomes lower under load, so expecting 1.5 V is like waiting for a train that never comes in...

Normal carbon-zinc dry cells, or alkaline cells do have a higher nominal voltage (1.5V) and when new show 1.65-1.68V with no load, but they have a high internal impedance/resistance, so the rechargeables are preferable, giving more voltage and current to the glow element.

RE: Current draw from glo plug?
 

Well said DZ.

ScaleME you should really look into getting an on-board glow driver that is controlled off your throttle setting. This allows a much smaller battery cell to be used, saving weight.

See link below as example:

http://www.southhertsmodels.co.uk/IGs.htm

Cheers

RE: Current draw from glo plug?
 

I think glow plug wear is ingreased if you have battery connected all the time. Platinium coil resistance will ingrease when it heats up, either by current or catalystic reaction of methanol. So constant voltage is better and simple principle.

Years ago during nitro shortage I installed small microswitch next to the throttle servo and used round servo wheel which I filed "bumpy" so it made contact around 1/3 from idle. Just one 1200mAh NiCd and I was able to even start engine with sysem first two flights. Then changed the cell or sometimes quick charged between flights. About 80 gram sacrifce for reliable idle.

RE: Current draw from glo plug?
 

Thank you for the information guys - it helped
ScaleME