Charging the 12 vdc Battery

[lcirino]

I left my "ignition" key on when I charged my iMiev overnight and the 12vdc battery discharged. Of course the car would not start the next day and everything was dead. The service manager asked me to recharge the 12 vdc batters with the conventional way, but asked me to disconnect the positive battery terminal before I did. I did this and when I put everything back together everything was perfect again. My question is, can the 12 vdc battery be charged through the 12 v accessory terminal (cigarette lighter) using a 2 amp trickle charger to bring the voltage up so that the computer can do it's thing, or can something be damaged doing this?

Is there a proper procedure for doing this?

PS: I have found my local Mitsu dealer service department extremely helpful. Their only problem is that they get very few occasions to service the cars.

 

[PV1]

Since the ACC position is controlled by the computer, I doubt it can be used if the voltage is too low to start. If you were to rewire the outlet to have a direct fused connection to the battery, then that would work.

 

[JoeS]

I left my "ignition" key on when I charged my iMiev overnight and the 12vdc battery discharged. Of course the car would not start the next day and everything was dead.

Was the car charging the entire time or had it shut itself off? The reason I ask is that the dc-dc feeding the 12v battery is active when the traction pack is being charged. Speculating, it sounds as though the dc-dc turns off when the traction pack charging stops even though the car is still plugged into the EVSE.

My question is, can the 12 vdc battery be charged through the 12 v accessory terminal (cigarette lighter) using a 2 amp trickle charger to bring the voltage up so that the computer can do it's thing, or can something be damaged doing this?

The accessory socket is normally open (disabled) and is enabled when the key switch is turned into the ACC or ON position, but only if there is 12v present to pull in the ACC POWER AUTO CUT RELAY. Thus, if the 12v battery is dead, you can't charge through that socket even if the key is turned on.

I added a small Anderson Powerpole connector (with inline fuse) to my i-MiEV 12v battery terminals. Can be used to charge the battery or run a small inverter or feed just about anything running off 12v.

 

[Don]

I believe he asked you to disconnect the positive lead first to make sure any voltage spikes from your battery charger didn't harm the car's electronics - Not all battery chargers are created equal and it's possible that an 'el-cheapo' charger which would work perfectly well on an ICE car, could possibly damage something on your 'computer on wheels'so he asked you to disconnect it to be on the safe side

This shouldn't be an issue for you in the future - The odds of you doing this again are pretty small . . . . right?

As Joe mentioned, the DC to DC charges the 12 volt accessory battery and so long as you remember to remove the key before you pout it on charge, you shouldn't experience future problems - Better to eliminate the source of the problem that to look for easier ways to 'fix' it after it happens. Running any lead acid battery completely flat takes away a significant portion of it's lifespan - If you make a habit of this, you'd be buying a new accessory battery every year or so

Don

 

[peterdambier]

At the connector for the radio there is (+12V battery), (+12V acc), (+12V light) and (+12V from the radio to the antenna) but no ground.

There are two screws fixing the dashboard to a metal rod. Both of them can get you ground.

Finding that connector in a shop is another story. PowerPoles are a good idea for hamradio in particular. The usual 12V lighter socket is messy. I used to do yoga but getting to the backside of the lighter socket I was not able to do.

A hole in the firewall and a gland nut to run the cable through is the usual way to get to the battery. Dont forget a fuse.

There are portable boxes with 12V 10Ah batteries and compressors arround. Those boxes often have built in jumper cables. Connecting those to the battery can both jump start your i-MiEV or charge the battery.

With the box connected the lighter socket will be working and now you can use a normal 12V charger at the lighter socket. No need for disconnecting anything as long as you dont feed more than some 3 amperes. I have slaughtered a jumper cable from lighter socket to lighter socket and put Powerpoles close to the ends. The are not good for jump starting ICE cars but for an i-MiEV ther are great.

Yet another idea, a 12V power supply for CB-radio or hamradio.

Cheers
Peter and Karin

 

[PV1]

Maybe this is a point towards level 1 in the debate/discussion on benefits of level 1 vs. level 2 charging. Since level 1 takes longer, the 12 volt system has power from the converter the whole time during the charge. With that, there is less chance of the i-MiEV not starting in situations like this since there is not as much time to drain the battery.

 

[jray3]

Has anyone logged the behavior of our dc-dc converter or experienced problems with the 12V battery without obvious user error?

Seems to be happening in LEAFS... :twisted:

http://daveinolywa.blogspot.com/2014/10/new-battery-observations-no-not-that.html

 

[PV1]

I've plugged a volt meter into the car while driving, and got 14.1-14.3 volts. Per OVMS 'DIAG?' command, my car coming off of charge at 1:30 PM (hour and a half ago) has a voltage of 12.9.

I have been noticing that my car will finish charging, then some random time later, will kick in and balance the main pack. It's apparently always done this, as I have gotten two range figures on OVMS (notification is 1 higher or lower RR than the car says). My use and charging habits have changed a bit, and I think that's why I'm noticing it more.

No problems with a dead 12 volt (though one close call with the Cavalier a few years ago), and as far as I know, the DC-DC converter is active only when charging and driving.

I wonder if the LEAFs affected by the dead batteries have the solar panel on them (SL model). It's supposed to maintain the 12 volt battery.

 

[montybazbaz]

So do we have a definitive answer as to when the 12v battery gets charged ? Just when charging the traction battery or when the traction battery is powering the car too ?
also....is there a low voltage protection on the 12v dc circuits ? We bought our c zero recently and had some electrical gremlins (ie internal light not working etc) but after a few charges of the traction battery everything works fine.

Had it got low whilst on the dealer's premises ?

 

[Don]

So do we have a definitive answer as to when the 12v battery gets charged ? Just when charging the traction battery or when the traction battery is powering the car too ?

Yes, both

The DC to DC converter runs every 12 volt accessory in the car while you're driving - The computer, the radio, lights, wipers, rear window defroster, heater fan, heated seat, etc, etc while 'charging' the accessory battery at the same time. The output of the converter is a bit above 14 volts, which is correct to charge any 12 volt automotive battery

Don

 

[JoeS]

I have been noticing that my car will finish charging, then some random time later, will kick in and balance the main pack...

PV1, perhaps what you've seen occasionally is the 'timeout' characteristic of the i-MiEV's charging system whereby some time after the car is plugged into J1772 the car stops charging for anywhere between six-ten minutes (sometimes as much as 20 minutes) and then starts charging again. Once it starts charging again it continues all the way through balancing without stopping until it shuts itself off.

I've never checked it, but I strongly suspect that the dc-dc shuts off also during this 'timeout' as the usual purpose of such a 'timeout' in a battery charging regimen is to check to see if any cells are sagging before continuing with the charge cycle.

 

[PV1]

I've seen the mid-charge timeout, and the contactor stays engaged. What I've been seeing is the car will do a charge cycle completely and finish, then a few hours later if I keep it plugged in, will engage the contactor and begin a separate cycle, apparently topping off the pack. Two separate behaviors.

 

[JoeS]

I've seen the mid-charge timeout, and the contactor stays engaged. What I've been seeing is the car will do a charge cycle completely and finish, then a few hours later if I keep it plugged in, will engage the contactor and begin a separate cycle, apparently topping off the pack. Two separate behaviors.

Veddy interesting... during the timeout it draws zero from the wall so that's another reason I think the dc-dc is disengaged.

... a few hours later if I keep it plugged in...

Never been there, as I can't recall ever having fully charged and then left it plugged in for a few hours. Usually, I time it so it stops fully fully charging and within a few minutes we're off driving. I know, I know, battery preservation paranoia and undoubtedly technically silly Nevertheless, I'm willing to try an experiment and since it's now cool around here I might just leave her plugged in overnight and then examine the TED (The Energy Detective power monitor) data in the morning to see if the charger kicked in again. PV1, thanks for the input.

 

[PV1]

That's how I noticed it was by changing my charging habits to adapt to cooler weather and keep the battery warm. Normally when it's warm out, I let the car sit until about 10-11 PM, then start level 2 charging and it finishes sometime during the night. For cooler weather, I drop down to level 1 and try to time it for about an hour before I leave. This also helps keep the 12 volt battery up.

Let me know what you find out if you try it, and maybe it'd be good to split this off onto another thread. I'll make a backup of my comments :lol: .

 

[DenisTyumen]

There is an idea to make a spoiler with a solar panel on the similarity of the Nissan Leaf.
https://www.drive.net/l/5390471/
You can use a 12 volt battery as a "spare fuel cans" to "refuel" in case of no-reach to the wall outlet.

 

[acensor]

....This shouldn't be an issue for you in the future - The odds of you doing this again are pretty small . . . . right?

.... Better to eliminate the source of the problem that to look for easier ways to 'fix' it after it happens. ....

Don

I like tbe way my son's engineering professor expressed that attitude:

"Designing great rubber gloves to address the problem of leaky pens is not good enginneering."

 

[BradfordImiev]

Hello

ive just been reading the posts re the 12v battery on the imiev. I am I correct in understanding that while the car is on charge the 12v battery under the bonnet gets charged and the cigarette lighter is also powered or topped up whilst its on charge?

My reason for asking is that i had just ran out of charge on my imiev earlier, I was in the middle of knowhere but found a national trust charging station, but was freezing sat in the car with no heat. I did however have a 12v electric blanket which i plugged in, however I was concerned this might flatten the 12 v battery under the bonnet.? I had one of those 12v electric heaters in the boot which is 150watts which i was wanting to put on but again was unclear if this would flatten the 12v battery under the bonnet..???

 

[PV1]

Welcome to the forum.

Yes, while the drive battery is charging, the 12 volt battery is also charging. Sitting in the car, you can turn the key to ACC or ON position and use the accessory port without running the 12 volt battery down. The heated seat works with the key ON, and the 12 volt port works with the key in either ACC or ON.

If the car isn't charging or stops charging, the accessory power gets cut after 10 minutes with the key in the ACC position. If the car is charging, accessory power remains on indefinitely.

 

[BradfordImiev]

Ok thats great thank you, so I could of actually plugged my little car heater in then whikst charging and not risked flattening the 12v battery then.. glad ive asked, ill know next time when sat freezing in the car getting slow charges in the winter thanks

 

[Aerowhatt]

I've always had the habit of doing a top up charge on ICE cars once a month. They are chronically undercharged since they only charge when the engine is running. I thought this would be a thing of the past with the iMiev since it charges the 12 volt while the traction battery charges and also while driving. On L1 you are OK the 12V will get fully charged at least some or most of the time. On L2 my 12 volt starts falling behind in cold weather and still needs a boost charge once a month to be fully charged.

Simplest solution is to do a nice long L1 Charge once a month (at least 6 to 8 bars to replace). But in really cold temps even that won't quite do it since the DC to DC output does not show any indication of being temperature compensated. It will be much better than what an ICE does though and get you by adequately.

I always carry a "geniusboost" unit in every vehicle just in case.

Aerowhatt