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-   -   Common voltage drop during cranking (https://www.miataturbo.net/megasquirt-18/common-voltage-drop-during-cranking-100385/)

wherestheboost 06-11-2019 07:31 PM

Common voltage drop during cranking
 
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From an old topic started earlier in the year, I was having cranking issues. tl;dr, I killed the battery from the repeated failed tests earlier in my megasquirt experiences. Battery is replaced, and car hasn't needed a jump start since then. Regardless, it does feel like my car takes "longer" to start. It "feels" like it might not start at some point. Regardless, I've seen other datalogs posted here, and the voltage drop I get doesn't seem to be all that common (see attached).

Battery typically is sitting at ~12.5V, and when I crank, it drops down to 9.2-9.5V. Is this normal? If not, where should I start looking? Battery and starter terminals look good.

DNMakinson 06-12-2019 06:44 AM

Those voltages, if measured at / by the ECU, sound normal. I have never measured at the battery terminals.

Goingnowherefast 06-12-2019 11:03 AM


Originally Posted by wherestheboost (Post 1538225)
From an old topic started earlier in the year, I was having cranking issues. tl;dr, I killed the battery from the repeated failed tests earlier in my megasquirt experiences. Battery is replaced, and car hasn't needed a jump start since then. Regardless, it does feel like my car takes "longer" to start. It "feels" like it might not start at some point. Regardless, I've seen other datalogs posted here, and the voltage drop I get doesn't seem to be all that common (see attached).

Battery typically is sitting at ~12.5V, and when I crank, it drops down to 9.2-9.5V. Is this normal? If not, where should I start looking? Battery and starter terminals look good.

According my my brothers datalog, those are exactly what we are seeing at the ECU with a new'ish battery. I'd say those are normal.

wherestheboost 06-13-2019 05:44 PM

Well..then - alrighty. Thanks!


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