Best state for non-use

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DougC

Active member
Joined
Mar 23, 2015
Messages
41
Location
Between Flint and Detroit, Michigan
What is the best state to leave the car out of use of 4-6 weeks?

Half battery charge with trickle charger on the aux battery?

Half charge only?

Leave it connected to the level 1 charger?

This will be in the summer temperatures.
 
Definitely wouldn't leave an EVSE plugged into the car. I'd say half charge or less, probably 5-6 bars. I suppose a trickle charger on the 12 volt wouldn't hurt.
 
PV1 said:
Definitely wouldn't leave an EVSE plugged into the car. I'd say half charge or less, probably 5-6 bars. I suppose a trickle charger on the 12 volt wouldn't hurt.
Agree, with the "trickle" charger being a modern smart 'float' charger (like a Battery Tender) and not an antique trickle charger which would murder the 12v battery in that timeframe.
 
I had no problem after a week, but I don't know about 4-6 weeks. The issue with the i-MiEV is, if the 12 volt goes flat and can't start the car, you'll get the EV warning light and it can only be cleared with the programmer tool the dealers have (a few members here have it, too). Better safe than sorry.
 
DougC said:
Will the aux battery hold up for that long or is there a big parasitic load? My other car will not go for more than 2 weeks without draining the battery
It all depends upon the state-of-health of your 12v battery, which is probably unknown. If a dealer let the car sit on the lot unstarted for a few months and let the battery go dead and then jumpered it, it has probably sustained significant sulphation damage that I wouldn't trust it sitting for more than a couple of weeks. Our 12v batteries actually live a very benign and stress-free happy life if the car is used on a daily basis.
 
DougC said:
Returned after 5 weeks with the 12v battery on a harbor freight battery tender. Traction battery still at the same 1/2 level that I left it. All is well
Good, glad it worked out for you. BTW, I normally would not entrust my i-MiEV's 12v battery to one of those Harbor Freight "Automatic Battery Float C h a r g e r" (had to space that last word because this website alters that word and links to something else - :x ) - I bought a dozen of them and every single one had a different voltage that it 'regulated' to (I returned most of them). In your case, no harm done since, unlike Lithiums, the 12v lead-acid battery is very voltage tolerant. Unrelated, now that you're back, don't forget to check your tire pressures.
 
Our 3 year old car has been sitting now for 5 weeks - This thread got me to thinking maybe I ought to go put it in the 'Ready mode' so the traction battery could top up the 12 volt battery. It 'started' just fine and I let it sit in ready for about 5 minutes. Think I'll do this once every 5 or 6 weeks just to keep things topped off. The traction battery is sitting at 4 bars

Don
 
Good thread. Good to know that if I use it every now and again during the Winter my 12v should be good
 
Don said:
Our 3 year old car has been sitting now for 5 weeks - This thread got me to thinking maybe I ought to go put it in the 'Ready mode' so the traction battery could top up the 12 volt battery. It 'started' just fine and I let it sit in ready for about 5 minutes. Think I'll do this once every 5 or 6 weeks just to keep things topped off. The traction battery is sitting at 4 bars

Don

5 Minutes isn't long enough, More like 30 minutes minimum. Better to use a smart charger to give it an actual full charge cycle every four weeks. For decades I have charged daily driver batteries with a good charger at least every 6 months and more often every 3 months. Once on a 10 amp smart charger, a daily driver car battery will take 2 to 3 hours to finish a full charge cycle. Car batteries are chronically under charged. For the 'i' it's some better than for an ICE since it charges the 12 volt both when driving and during traction pack charging. Much better than an ICE charge profile which is only charging when the engine is running. A sitting 'i' is no better off than an ICE though.

Take my word for it . . . do you know anyone else who averages 8 to 12 years on their car batteries?

Aerowhatt
 
I wonder if the i-miev has this same flaw?
http://jalopnik.com/5887265/tesla-motors-devastating-design-problem

The older (year?) zero electric motorcycles had a similar flaw and they fixed it so Tesla must have fixed it for the Model S. The problem is basically the BMS (Battery management System) stays on or the Tesla has a lot of continuous parasitic loads.

Maybe the i-miev main battery is protected by the 12V battery taking the abuse. That would a much smarter design.

On my VW Golf I installed a small solar panel on the roof with a very small charge controller. No more dead battery from high parasitic loads! The whole combination was cheap to buy and simple to install. For the imiev I would only use the solar charger for long vacations.

How long before the 12V is dead?
 
The i-MiEV would have to sit for a long time and be parked at near empty. Unlike Tesla vehicles, the i-MiEV completely disconnects the drive battery from the drive inverter and DC converter when the car is turned off. Tesla vehicles, however, keep the battery connected all the time to power telemetrics, BMS and thermal mangement, and (Model S) power the door handles. The Roadster is the worse offender, as a circulation pump runs nearly continuously even if the car is off and unplugged. I'd say that the Roadster is the noisiest EV I've driven with all the pumps running.

They've improved idle power consumption in the Model S numerous times since its release, plus there is a button on the touchscreen to completely power down the car, though it says that should only be used in emergencies or if work is needed to be done on the HV system. Not quite sure on how the car is powered back on :? .

When the i-MiEV is off, the EV-ECU and other ECUs are powered by the 12 volt battery. Only the cell management boards in the battery pack are powered by the cells (I believe, this is how other BMS work) in the main battery. Leaving the i-MiEV sit too long may result in the 12 volt battery going flat (as would nearly any other car). I've left mine for a week without issue, but when my car was at the dealer for a faulty cell, I did start to receive 12 volt low warnings from my OVMS module. Could have been caused by the mechanics accidentally leaving a light on (I suspect my LED lights as the switches were both off when I got it back). That still took 2 weeks before the 12 volt was low.

I'd recommend the small solar panel as you have on your Golf for storing the i-MiEV, though it would need to be tied direct to the battery as the interior accessory outlet only works with the key on. Between the panel and storing the car with half a charge on the main battery, you shouldn't have any worries about several months-long storage.
 
Thank you for the excellent reply! It's nice to see the i-miev is actually superior to a Tesla in terms of simple basic reliable design! :D :D :D Overly complex gadgets just makes more problems if you don't need it.

PV1 said:
The i-MiEV would have to sit for a long time and be parked at near empty. Unlike Tesla vehicles, the i-MiEV completely disconnects the drive battery from the drive inverter and DC converter when the car is turned off. Tesla vehicles, however, keep the battery connected all the time to power telemetrics, BMS and thermal mangement, and (Model S) power the door handles. The Roadster is the worse offender, as a circulation pump runs nearly continuously even if the car is off and unplugged. I'd say that the Roadster is the noisiest EV I've driven with all the pumps running.

They've improved idle power consumption in the Model S numerous times since its release, plus there is a button on the touchscreen to completely power down the car, though it says that should only be used in emergencies or if work is needed to be done on the HV system. Not quite sure on how the car is powered back on :? .

When the i-MiEV is off, the EV-ECU and other ECUs are powered by the 12 volt battery. Only the cell management boards in the battery pack are powered by the cells (I believe, this is how other BMS work) in the main battery. Leaving the i-MiEV sit too long may result in the 12 volt battery going flat (as would nearly any other car). I've left mine for a week without issue, but when my car was at the dealer for a faulty cell, I did start to receive 12 volt low warnings from my OVMS module. Could have been caused by the mechanics accidentally leaving a light on (I suspect my LED lights as the switches were both off when I got it back). That still took 2 weeks before the 12 volt was low.

I'd recommend the small solar panel as you have on your Golf for storing the i-MiEV, though it would need to be tied direct to the battery as the interior accessory outlet only works with the key on. Between the panel and storing the car with half a charge on the main battery, you shouldn't have any worries about several months-long storage.
 
I've wondered... Other than the car being derived from an ICE design, is there a good reason for us to have a separate 12V "starter" battery?
 
I think the 12V battery is there to save the main battery from accidental destruction from parasitic loads! The 12V is a sacrificial battery for powering the ECU etc when not driving.
 
The 12 volt battery is necessary because all the accessories run on 12 volts - Lights, wipers, radio, the car's computer, the heater fan etc, etc. The battery acts as a filtering load for the DC to DC converter which converts the traction battery voltage down to 13 or 14 volts to run all the accessories, plus it's needed to keep the computer alive when the car isn't running

Why they chose an antique lead acid battery is an excellent question - I'm sure it probably boiled down to cost, but a lithium would have been nice, or at least a small motorcycle AGM. When mine dies I'll probably replace it with a smaller AGM

Don
 
Except it appears that there has been a break through in lead acid batteries, the ultrabattery:

http://www.thebatteryshow.com/resources/news/2015/09/10/ultrabattery-car-running-five-years-strong/
 
Phximiev said:
Except it appears that there has been a break through in lead acid batteries, the ultrabattery:

http://www.thebatteryshow.com/resources/news/2015/09/10/ultrabattery-car-running-five-years-strong/

Lead is really heavy, and lead acid batteries are several times heavier than lithium batteries.
This inherent disadvantage is unlikely to be overcome.

I suspect this is really only for micro hybrid's with much less total capacity. Unless they reduced the weight to be much closer, much of the HEV efficiency benefit is lost due to carrying all the extra weight.

http://www.electric-vehiclenews.com/2015/10/mercedes-open-to-battery-alliance-with.html
"The battle is currently focused on (lithium) solid state battery development..."

Look at the BMW i3 as to where the auto industry is heading.
 
wmcbrine said:
I've wondered... Other than the car being derived from an ICE design, is there a good reason for us to have a separate 12V "starter" battery?

I've worked on many EV conversions dating all the way back to the 80's oil embargo days. Most had an "Accessory battery" regular 12 volt car battery or an AGM deep cycle. A couple of them didn't have the 12 volt battery but instead ran the DC to DC converter full time (high voltage conversion to 12 volts to run all the things in a car that are 12 volt). Basically over time it became apparent that the accessory battery was a superior choice. The ones without one needed to run the DC to DC converter 24/7. Often the losses in the DC to DC converter were far more power than the parasitic loads of the cars existing systems. The main traction pack could be damaged by a longish parking stint away from a plug (some were). You can jump start an 'i' if the 12 volt were to die at the wrong time (is there a right time?). Then drive it to a shop that sells car batteries. Not possible if your accessory systems run off of the main pack, have run it down and perhaps even damaged it.

The systems in the 'i' are very well thought out. Even the choice of a starting battery for the accessory battery, it takes stress off of the DC to DC by mediating large load swings on the Accessory systems. I intend to replace mine with an Odyssey AGM battery when it becomes necessary to replace the OEM battery.

Aerowhatt
 
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