JoeS wrote:Does anyone remember if we have measured what the quiescent current draw is by the i-MiEV when it's parked and either locked (with/without key fob) or unlocked? I'm just curious as I'd like to calculate how many days the i-MiEV can remain parked with this 7.8Ah battery.
To answer my own question I ran the following test: attached an external 12v battery through a precision resistor to the Anderson connector I have attached to my i-MiEV battery and simply lifted the negative terminal on the car's battery (to disconnect it) and measured the voltage drop across that resistor.
1) What shocked me is that it made no difference whether the car was locked or unlocked, whether locked manually or with a key fob, or whether the car was accessed and then re-locked without turning the car on (PV1 note). The current was the same! I had presumed that locking the car activated the alarm system which would draw more current.
2) The current fluctuates as the voltage drop varies between 5.0mv to 6.3mv across a 0.5Ω resistor, yielding 10ma-12.6ma current draw. Repeated with a 5Ω resistor and obtained 11ma-11.5ma. I'll put an oscilloscope on this waveform to see just exactly what sort of pulsing the car is doing.
When the i-MiEV is just sitting there parked, irrespective of whether it is locked or unlocked, it is drawing no more than 12ma average current out of its 12v battery.
Using the vernacular of the Tesla forum, this is our Vampire Load
WHAT DOES THIS MEAN?
Converting the steady-state current load in Ampere-Hours sucked out of our i-MiEV -
12ma x 24 hours = 0.288Ah/day
0.288Ah/day x 7 days = 2.02Ah/week
0.288Ah/day x 30 days = 8.64Ah/month
Our OEM flooded-lead-acid (FLA) battery has a 20-hour discharge rating of 33Ah. The trouble is that FLAs are notorious for high self-discharge rates, typically 1%/day at a room ambient temperature
1%/day of 33Ah means -
Now, these above numbers are additive
, so here's the hit our poor little 33Ah i-MiEV FLA battery takes when it is simply parked -
Per Day: 0.62Ah
Per Week: 4.33Ah
Per Month: 18.54Ah
As a rule of thumb, we never want to discharge an FLA battery below 65% if we want a decent life out of it (and need to charge it back up right away). 65% of 33Ah is 21.5Ah or, looking at it as the maximum we want to take out of the battery, the number is 11.5Ah.
Thus, when our i-MiEV had a brand-new battery in it, you wouldn't want to leave the car unattended for more than about 18days (11.5Ah/0.62Ah/day).
Trouble with FLA is that in this amount of time sulfation starts to occur as the SoC drops and battery age gets into play and I've personally not liked that 65% rule of thumb, and ... I'm not going there.
Which is why I always put a float charger on my i-MiEV (solar float charger if left outdoors) when I know the car won't be used for more than a couple of days.
Finally, if dealing with lead-acid batteries, we can cut down that consumption by roughly half if we install an AGM battery instead of a FLA battery because the self-discharge rate of AGM is minimal in comparison.
Now, what sparked this question is:
For how long can the i-MiEV be parked if it is using the NOCO 7.8Ah (verified) LiFePO4 battery?
LiFePO4 has a negligible self discharge rate (compared to FLA) so we can ignore that above FLA number and only be concerned with what the i-MiEV vampire load sucks out of the battery. No hard and fast answer, as it's simply a matter of how long you want the battery to last and you can pick your own number here from Table 1 of this article:
https://batteryuniversity.com/article/b ... -batteries
The answer is: a couple or even three weeks should be ok
, or roughly the same amount of time as our with OEM battery.
When/if I install the NOCO, I'll probably feed it with an inexpensive MeanWell adjustable power supply set to 13.4vdc whenever I leave the car unattended for a couple of days or more.
BTW, Battery University has loads of articles and are a good reference: https://batteryuniversity.com/articles
More information than you every wanted to suffer through...
Mitsi wrote:We got her brand new Jan. 2017. I did plug in a OBDII and didn't find any fault codes, but I'm not sure I was using the right software. OBDZero doesn't seem to show them, does it? "iCarSoft"? What's that? I'll look into it.
Simply google "iCarSoft i909" and also check out this Reference thread which is still a work in progress: