Speak EV - Electric Car Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter #1
Going out of town for about 3 months. Storing imiev in a lot with no electricity. On my ice vehicles I always disconnect the lead acid battery in those circumstances. Should I disconnect 12 volt battery on imiev? Manual says no, but it says use a trickle charger. I know on Leafs people disconnect the 12 volt battery for storage. My inclination is to disconnect the 12 volt battery. I've also read somewhere that the traction battery should be around 40% or so when storing.
 

·
Registered
Joined
·
3,422 Posts
The traction battery should be left between 40% and 80% for long term storage as leaving it fully charged for a long period of time in hot weather would cause unnecessary accelerated degradation.

Either disconnecting the 12v battery or leaving it on an intelligent 12v trickle charger should be OK.

If you leave the 12v battery connected without using the car for 3 months and without a trickle charger it will almost certainly be flat when you come back, especially if the 12v battery is nearing the end of it's life. (I replaced my 12v battery recently and it had only about 1Ah of usable capacity left)

While the standby power drain is very low there is no automatic top up of the 12v battery from the traction battery when parked and turned off on these cars unlike some other EV's. The 12v battery is only charged when the car is either in READY mode or is actively charging the traction battery.
 

·
Registered
Joined
·
20 Posts
Discussion Starter #3
Thanks, Simon, I will disconnect it. I just purchased the imiev and the previous owner replaced the 12 volt battery recently.
 

·
richi.uk
Joined
·
55 Posts
If you disconnect the 12V for "too long," you may find that the BMU loses its history. This is said to be true on the Outlander PHEV, and I believe the triplets' BMU is similar. It will then need to re-learn the state of health, which might involve over-discharging the cells a few times before it catches up.
 

·
Registered
Joined
·
3,422 Posts
I'm not sure what the alternative is when the car is going to be parked somewhere for 3 months with no power available to trickle charge the 12v battery...

There's no way it will last 3 months without fully discharging the 12v battery and that deep discharge will do a lot of harm to the 12v battery (capacity loss) and leave the BMU powered down for an extended period of time after it discharges anyway...
 

·
Registered
Joined
·
2,191 Posts
You might have a lot of bother with no power source from 12v, loss of memory has already been highlighted as an issue with BMU.

I would look at installing an AGM battery on the basis that this kind of battery had low self discharge. You can put the battery inside the car, run wires through the door seals and into the bonnet area.

I would start by making some accurate measurements of the current consumption with the car switched off and rested for several hours. You want to eliminate door lock RF controls, maybe pull a fuse for this.

When you come back to the car, have a new battery with you. If it's been dead for only a month, you will have avoided the BMU issues.

Alternatively is there someone whom you trust that can put the 12v on a periodic charge.

Regarding traction battery, my instinct would be charge up to say 80%.
 

·
Registered
Joined
·
3,422 Posts
Citations for BMU problems with the 12v being disconnected for too long ?

If the problem is the BMU just has to learn the Ah capacity of the battery again that's not really a problem because it will do so on the first full discharge.
 

·
Registered
Joined
·
20 Posts
Discussion Starter #11
From what I’ve read, Leaf owners disconnect the 12 volts for extended storage without harm. Not sure if that is relevant to an imiev or not.
 

·
Registered
Joined
·
251 Posts
Hi all, I bought an i-miev that has been sat with a flat battery for 2 years - and i've got it working with no major issues. So I can confirm that no major harm can come from being sat with a flat battery for an extended period.

Perhaps it will lose some recent data from power consumed during journeys but nothing that will stop the car from working.

Thanks.
 

·
Premium Member
Joined
·
9,921 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter #15
Would a solar trickle charger plugged in to the 12 volt power socket in the cabin cause any issues? I have no clear idea of how the 12 volt battery and the traction battery interact and how the BMS would respond to that trickle voltage
 

·
Registered
Joined
·
251 Posts
On my 2012 i-miev the 12v socket in the cabin is off when the car is off, it comes on in the accessory key position. If I was going to store my car for any period i'd get the traction battery to roughly 50% and disconnect the 12v battery.
 
1 - 16 of 16 Posts
Top