More miles on GOM After 12v Battery Failure

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CWO4Mann

Well-known member
Leaf Supporting Member
Joined
Jul 28, 2011
Messages
476
Location
Brentwood, TN
My LEAF has been in garage for several days; cold snap last night down to 25 deg F. This morning attempt to start indicated zero miles and lots of flashing lights on dash display. Figured the 12v battery was dead. It was. Charged the little battery up and car started right up. Now for my surprise. Last trip out, about 4 days ago. GOM showed 45 miles when I got home. Today, after 12v battery was recharged and display came back up, GOM reading was 78 miles. Drove up to Kroger for flue shot, distance of 2.1 miles. GOM reading was 43 miles arriving at store.

Wondering if the loss of the 12v battery reset something in the GOM's brain?
 
Probably so. The memory used for the GOM could be either in flash or DRAM. Flash memory keeps its data without power but DRAM loses everything when the power is removed. More importantly, flash can only be written a limited number of times before it 'wears out' so variables that are used frequently are best kept in DRAM.

My guess is that some of the recent driving history used to generate the GOM is saved in DRAM that is powered all the time from the 12V battery whether the car is on or off. It would be a tiny load and would remove the need to update flash variables constantly.
 
Hi,

I have noticed this too.

GOM is always more optimistic when freshly charged 12v battery is reconnected. Last night I had a funny one though.

As mentioned in my first two posts car has killed another battery (a cheapie off a well known auction site). I charged the car and unpugged EVSE. Thirtysix hours later I went to go out and car would not start. Dashboard lit up 3 bars on GOM and "Switch Off" on instrument cluster. On checking battery was down to 8.6v so put on charge. Ninety minutes later car started (with battery charger still connected) but GOM showed 33 miles. Over the next 22 miles and 1 1/2 hours GOM krept up to 61 miles which is about right for the distance driven with the heater on. I might add I did not switch off the car at my destination... Left it standing with the lights and heater switched off.

I don't understand why the GOM was initially so far out bearing in mind that the traction battery was fully charged and that the battery was not disconnected.

KR, Emma
 
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