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M84 and 4s Lipo

PostPosted: Wed May 15, 2019 4:51 am
by acca
Hello
I use a Motec M84 for a monocylinder Shell eco marathon engine (25cc)
Everything works fine with a 12v Ni-cd battery
I'd like to use a 4s Lipo battery in order to reduce weight and to obtain more stable voltages when cranking

This lipo (4s 5A 90C) give 16.5v when fully charged
My engine starts but stops randomly when accelerating

My injector dead times have been calculated for this voltage.

I don't know why it doesn't works, any idea please ?

Re: M84 and 4s Lipo

PostPosted: Wed May 15, 2019 8:59 am
by SDean
Do you have any logging showing the engine stopping during a run, especially one that shows the ECU voltage?

What coil and injector are you using? they may be pulling more current out of the battery than the battery can supply thus dropping the voltage down to a point that the ECU stops (~8V) The peak voltage isn't an issue with the M84, they can run at a higher voltage than that.

Re: M84 and 4s Lipo

PostPosted: Wed May 15, 2019 4:55 pm
by acca
Hello
The coil is a Denso coil :
https://www.ebay.fr/itm/Blueprint-ADG01 ... 1430262115
The injector is a 50cc injector (measured resistance 23 ohms)
The voltage falls to 15.4 volts at cranking and is then stable