Level of charge for storage .. How long B4 runs down?

Going on 10 day vacation with ICE car. Obviously no big deal to leave EV sitting that long.

But curious... If anyone knows or guesses... How fast or slow battery would self discharge.
And what is optimal storage charge state? 50%?

Oh, Alex, that's a very good question but a brief search would uncover discussions and the answer (in many places). :? For example:

http://myimiev.com/forum/viewtopic.php?p=2775

When going away for a while, I typically leave my traction pack at between four and eight bars (it loses a negligible amount of charge just sitting there). The bigger issue is the 12v battery, as it's being drained slowly by the small standby and alarm currents. I put a smart float charger (NOT an old-fashioned 'trickle' charger) onto the 12v battery if I'm gone for more than a couple of weeks.

Best hands-on example was dakine who shipped his iMiEV to Rarotonga and put his traction pack at only three bars and disconnected the 12v before shipment. Don't forget, his iMiEV was to be sitting and roasting inside a storage container in the South Pacific.

http://myimiev.com/forum/viewtopic.php?p=5698#p5698

JoeS said:

.... The bigger issue is the 12v battery, as it's being drained slowly by the small standby and alarm currents. I put a smart float charger (NOT an old-fashioned 'trickle' charger) onto the 12v battery if I'm gone for more than a couple of weeks.....

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Humm. Hadn't thought about the 12 volt.
I imagine that two weeks should be no issue for that one either.
But it raises the to me interesting question as to how and when the 12 volt gets charged. :?:
Perhaps particularly so if doing much night driving with headlights on. .... as my understanding it the headlights, wipers, radio, and maybe the climate system fan, etc, all run on and only on the 12 volt.

You can easily see when charging in the dark, the lights get brighter as soon as you plug in. Same when you go from "ignition" to "Ready". Except when you are down below 3 bars.

There are some lighter plug cables around that can charge one battery from another battery for ICE cars. Those cables cannot be used as jumper cables for ICE cars at least and for ICE cars they are mostly not much use but for an i-MiEV they can actually serve as a jumper cable to let us engage the main battery and the inverter. As soon as the inverter is running we are saved.

It still has to be proofed whether Lithium batteries do self discharge or not. Nobody has seen them lose charge. When you want to store the i-Miev for a very long time, do disconnect the 12V battery. Without 12V the main battery stays disconnected as well.

After reconnecting the 12V battery the BMU needs one cycle of discharging the main battery down to 2 bars (until blinking) and then fully charging to readjust the fuel gauge.

acensor said:

But it raises the to me interesting question as to how and when the 12 volt gets charged. :?:

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This is another one that has been debated quite a bit. This is why we need to have 'sticky' posts that don't get filtered to the bottom and lost in the search engine.

acensor - everything comes from the traction battery. There is a DC/DC converter on board that recharges the 12volt battery as you drive. According to the owners manual, the 12v also gets recharged when you plug the car in. However, caution - if your 12v battery is drained then you won't be able to start the car or even charge it. Two weeks should be okay to leave your car sitting without any electrical input. Just leave the car around 50% and you'll be fine.

Edited 6/23/13 by JoeS, formatting correction

Last summer we left the IMiev at home while on vacation. I charged it to about 75% and disconnected the 12 Volt battery.
Upon return, I reconnected the 12 V battery. The main battery lost negligible charge. What a car !
BTW, we were gone for about 1 1/2 months.

psyflyjohn said:

Last summer we left the IMiev at home while on vacation. I charged it to about 75% and disconnected the 12 Volt battery.
Upon return, I reconnected the 12 V battery. The main battery lost negligible charge.

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How were you able to determine that negligible charge had been lost? The fuel gauge can't measure self-discharge loss, so it would still read the same level as when you parked your car. Fortunately, Li cells aren't supposed to suffer high self-discharge rates like Ni cells.

After you reconnected the 12 v. battery, did the fuel gauge read empty (i.e., had it lost its charge level information with the loss of 12 v. power?)? If not, maybe it stores the charge level information in a way that doesn't require 12 v. power.

Quote from the green 17 page owner’s handbook. Page 16 states “Make sure the battery’s energy level gauge shows 2-4 bars”. “Do not leave the battery charged with more than 4 bars”. “Check the battery residual every 3 months and if you see any discharge, please charge to 2-4 bars”.

joev said:

“Check the battery residual every 3 months and if you see any discharge, please charge to 2-4 bars”.

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I wonder how the fuel gauge can measure self-discharge since self-discharge doesn't involve current flowing through the electrodes.

When I reconnected the 12 volt battery, the number of bars was still at 3/4 charge level. Now, I'm not sure whether that reading reflected the last charge level before disconnection, or was updated upon reconnection. I assumed that it was an updated battery reading.

acensor said:

But curious... If anyone knows or guesses... How fast or slow battery would self discharge.
And what is optimal storage charge state? 50%?

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Lithiums self discharge very, very slowly (1% to 2% per month) if they have no load at all applied . . . . and our battery doesn't. If you left the car sitting with recommended 4 bars showing and came back a year later, there's a good chance it would show at least 3 bars when you fired it back up and maybe even still the 4 you had when you stored it. As others have mentioned, the small 12 volt accessory battery has several loads on it all the time and 3 weeks or a month would probably leave it too dead to start the car. Either disconnect it, or keep it on a small smart charger, like the Battery Tender Jr. I use 3 or 4 of those on motorcycle and boat batteries which frequently sit idle for months at a time

Don

joev said:

Quote from the green 17 page owner’s handbook. Page 16 states “Make sure the battery’s energy level gauge shows 2-4 bars”. “Do not leave the battery charged with more than 4 bars”. “Check the battery residual every 3 months and if you see any discharge, please charge to 2-4 bars”.

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joev, thank you very much for finding this gem in the green Owner's Handbook (not the gray Owner's Manual). I think this definitively puts the issue of the main battery storage charge charge level to bed.

Mitsu doesn't address the 12v battery, but our previous comments certainly apply; i.e., keep it on a smart 'float' charger or simply disconnect it.

Now if only Mitsubishi would educate their dealers - my iMiEV sat on a showroom floor (thankfully indoors) for two months at 16 bars before I bought it.