Diablo-RCU

My Feedback: (1)

I picked up a used 3W twin with a "blue dot" on the ignition. The ignition
is labeled 4.8 Volts. I tried using a 4-cell 2700mAH nickel metal hydride
battery and I get 2 flights before it loses spark. If I don't quick charge
(and peak) the battery, it won't restart. The battery shows good voltage
(over 5.0) under a 500 mA load even when the ignition won't spark. The same
type of pack works just fine on my other 3W twin that doesn't have the "blue
dot" ignition. Is this normal behavior for the "blue dot" ignition?
Do the "blue dot" ignitions require a 5-cell pack? Can you run a 5-cell pack
without a regulator?

ZAGNUT

My Feedback: (1)

my blue-dot single ignitions work just fine with a 4 cell 600mAh ni-cd for at least a half hour. i can't imagine the twin needing that much more current.


dave

rc bugman

My Feedback: (30)

Diablo

It sounds like you have a faulty battery pack. Have you tried cycling it to check capacity?

In my research planes, I use 1600-1800 4 cell nicads with no problem. They power the ignition for two plus hours running the engine at full rpms (max draw) with no need to recharge before the day is over. I also stay with nicads because they tolerate the abuse of vibration and discharge better than Ni-mih. The weight savings is not that significant in the context of the entire plane.

Elson

Diablo-RCU

My Feedback: (1)

I agree that it may be a faulty pack. Puzzling though that it tests well using a 500 mA load. I understand that the ignition draws about 800mA, so perhaps the pack just can't delivery the current. I think NiMH packs are here to stay, Nicads will be gone in the future because of the EPA and their cadmium concerns. I'm going to try a 5-cell pack today. I hope the smoke doesn't leak out of the ignition.....

ChickenStick Rick

My Feedback: (674)

I thought the blue dot meant it was a 6.0 volt ignition

tony_kilwein

I have blue dot and run on 4.8v with no problem, the previous owner also ran on 4.8v no problem.
3w150ts

Hope this helps.
Tony

Diablo-RCU

My Feedback: (1)

Well the 5-cell pack worked for a couple of flights, then the ignition quit completely. I swapped in an old ignition and it fired right up using the original 4-cell pack. The blue dot ignition was a little weak on spark and gave difficult starting since I got it - finally it gave up the ghost. I talked to Cactus Aviation and they will help me out on the ignition.

ram3500-RCU

My Feedback: (221)

The way i understand it, the older ignitions, although intended to be capable of handleing 6v, had a component on the board that could overheat at that voltage. The "blue dot" ignitions have a replacement to that componant that will not overheat and thus are good for 4.8 or 6v without failure from overheating. Please correct me if i'm wrong, because i intend on using 4.8v 1800ma battery on mine.

Kris^

My Feedback: (1)

According to Gerhad at Aircraft International, the "Blue Dot" ignitions are designed to work best with 5-cell/6volt power to them, though they will work okay with 4-cell/4.8 volt power if that is what you desire. I just got back from a IMAC Meet at Trenton SC this weekend, whree I flew my heavier Composite-Arf using a 3w150-TOC and canisters in competition( VERY windy. . put the BME powered plane in the van and left it there) I run a 2150 ma NiMH 5-cell pack on ignition, and the engine performed flawlessly all weekend long. I saw one DA ignition lose a cylinder, a 3W got something lodged on top of the piston and started making noises so it was put away, and my own BME suffered a leaking gasket on the carb block (got another one coming already. . 300 flights or so and I've had that carburetor off one too many times it seems )


You will get a substantially hotter spark with 6V instead of 4.8 volts. Personally, I'd advise using the larger battery pack. That is what the ignition is designed for . why not take advantage of it?

ram3500-RCU

My Feedback: (221)

Thanks for the good feedback on ignitions Kris. I will take your advice.