BATTERY CURRENT FOR EDIS

[BRUCEROE]

I ran a curve to see what the battery current would be. With an efficient electronic dwell, its pretty much proportional to number of ignition coils driven times rpm. There is a base current of around .12 amp with the engine not running, which increases to maximum of .22 amp by 1000 rpm. Each coil adds to this, an amount proportional to rpm. However, the current seems to peak at 3000 rpm, then decrease somewhat as the dwell starts to decrease.

The current formula here is 0.12 amp + 0.00023(number of coils)(rpm)amp. This peaks out about 2.9 amp for a V8 (4 coils), or 1.5 amp for a 4 cylinder. This helps an engine like mine, which has minimal alternator output at low rpm. MJLJ-V4 here, Bruce Roe

[alhbln]

Do you want to measure the average or peak current? 220 mA sounds quite low for 1000 RPM, i would have expected at least 1-2A. Have you measured the current with a digital multimeter or a scope with a current clamp?
The coil's primary current spikes are quite fast (1-4 ms, depending on dwell with an inductive ignition), so a multimeter would not show the current spikes but kind of an average current, depending on its sample speed.

[BRUCEROE]

alhbln, Thanks for the comment. My objective here was to find out how much DC current my wimp alternator must supply to keep up. This was a new load on a rather small source, 'cause the old ign ran off flywheel magnets, no battery. I put a pretty heavy filter on the input to smooth the spikes, and measured current with a digital voltmeter & a 0.01 ohm shunt. Ampere current spikes are certainly there, but I didn't measure them. A 4ms current ramp peak of 2A would average 1A, 1A X 1000 per minute X 4ms, all divided by 60,000 ms per minute gives about .066 A average. Multiply that by the number of coils, increase proportional to rpm, sounds like the right ballpark. The EDIS control draws some 1/8 A additional, independent of rpm. Bruce Roe

[BRUCEROE]

Guess I should have said, this was run on the bench using my trigger wheel emulator circuit. And up to 4 coils/8 spark plugs. That makes it easy to get any coil config desired, no hot screaming engine. Bruce Roe