battery after 3 week vacation

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rickmaz

Active member
Joined
Aug 23, 2011
Messages
42
Just for everyone's interest... just got back from a three week vacation, and left the car with 14 bars of charge, which were still all there when I got back. Over 5000 miles on the car so far and still LOVING it!!!

Note for the two other 'i' owners in Hilo: the Hilo Airport has two charging stations just makai of the paybooth, and they don't charge for electric car parking according to the attendant!

Aloha everyone!

Rick
 
rickmaz said:
Just for everyone's interest... just got back from a three week vacation, and left the car with 14 bars of charge, which were still all there when I got back.
I am guessing that the battery charge level gauge calculates the charge level by measuring current flows in and out of the battery pack. If true, the self-discharge that occurs when the battery pack isn't being used won't be reflected by the charge level gauge. I.e., whatever charge level the gauge reported when you parked your car won't change no matter how long your car is parked even though the battery pack will have discharged somewhat. The gauge will likely recalibrate either when you fully charge or discharge it, but it won't accurately reflect the real charge level before this recalibration occurs.

This is all speculation on my part based on my experience with the charge level gauge on my Honda Insight hybrid. If someone knows that the i charge level gauge functions differently, please correct my misconception.
 
alohart said:
I am guessing that the battery charge level gauge calculates the charge level by measuring current flows in and out of the battery pack. If true, the self-discharge that occurs when the battery pack isn't being used won't be reflected by the charge level gauge. I.e., whatever charge level the gauge reported when you parked your car won't change no matter how long your car is parked even though the battery pack will have discharged somewhat. The gauge will likely recalibrate either when you fully charge or discharge it, but it won't accurately reflect the real charge level before this recalibration occurs.

This is all speculation on my part based on my experience with the charge level gauge on my Honda Insight hybrid. If someone knows that the i charge level gauge functions differently, please correct my misconception.
Probably as good a guess as any. I think the RR meter takes all that into account, but I'm not sure the less accurate 'gas gauge' indicator does - I *think* it's primarily based on reading the packs voltage, which isn't the most accurate way to do it for Lithiums. I guess we'd have to park a car for 6 months or so to find out for sure

An interesting discussion on determining the SOC can be found here - http://www.mpoweruk.com/soc.htm

In Rick's case, the 14 bars showing when he left and when he returned were probably about as accurate as looking at the gauge any other time - The indicator isn't accurate within 5% or so under the best of conditions, and the battery pack self discharges at less than 3% per month . . . . and he was only gone 3 weeks - Hard to 'measure' a percentage point or two of capacity loss with a meter less accurate than 5%

Self Discharge Rate

Another reason why all the energy put into the battery is not available to come out again is the self discharge of the cells. Self discharge of Lithium batteries is typically less than 3% per month so for periods of a day or so the effect is very small but it becomes more significant the longer the periods between charging and can be the source of accumulating errors unless the battery monitoring circuit is regularly reset or calibrated.


Don
 
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