12V battery cumulative drain higher then overall charging.

[Al123]

The 12V battery in my i-Miev just died. The battery was one year old, bought by the previous owner from Mitsubishi dealer.
I have measured the parasitic drain, and it is 13mA, but it goes higher with a door open.
The car does charge the battery when on or being charged.
We do only short infrequent trips. I have occasionally charged the battery with a charger. It was not good enough.
It got too low couple of times, and now one cell is dead.
From the forum, I see that this is a common problem.
To fix this problem, I have installed a kill switch that disconnects the battery minus from the ground.
To do it, I have removed passenger side headlight, behind it, I have drilled a hole to get to the car’s interior.
I have run a wire #10AWG (good for around 40A). I have disconnected the short ground cable for battery minus, and have attached it to the wire (now the battery minus is inside the car). I have brought the wire to the driver’s side under the dash. I have found at home a dual pole 20A switch (2 x 20A). Connected the wire to the switch (in parallel to get 40A), and connected the other side of the switch to multiple ground points I have found under the dash.
With a key in, and turned one click, the car draws bit above 2A. When starting, the highest current I have seen was just under 10A, but stays only for very short time. Once started, the current reverses, and the battery is being charged.
I had at home a 12V, 20Ah gel battery. Screw plate connections (about half the size of the original battery). I needed to convert it to top posts to fit the i-Miev.
I have used ½ inch copper pipe couplings as the posts. Sliced the coupling in the middle (across), but not all the way through, to flatten one half, drill hole, to install it on the battery.
I now switch the 12V battery off any time I don’t use the car. So far, I didn’t have any issues with it.

 

[Don]

The 12V battery in my i-Miev just died. The battery was one year old, bought by the previous owner from Mitsubishi dealer.
I have measured the parasitic drain, and it is 13mA, but it goes higher with a door open.
The car does charge the battery when on or being charged.
We do only short infrequent trips. I have occasionally charged the battery with a charger. It was not good enough.
It got too low couple of times, and now one cell is dead.
From the forum, I see that this is a common problem.

I'm not aware of the 12 volt battery repeatedly draining while the car is in use as a 'common problem' - For sure not if they're driven once per week or so

We have 3 iMiEV's and since so many things shut down in early March, two of them have been very infrequently driven or recharged. Both have sat for a month or more a couple times recently and no problems with the 12 volt batteries which are several years old. I have those two 'stored' at 1/4 charge and I just plugged one into the OEM 8 amp charger for about an hour for the first time in about 6 weeks yesterday. It started fine when I drove it into the garage to charge

Rather than modifying the car (which is a Band-Aid for the real problem) I would suggest finding and correcting what's really wrong

Don

 

[Al123]

Rather than modifying the car (which is a Band-Aid for the real problem) I would suggest finding and correcting what's really wrong

Here is a summary of the 12V battery charging and discharging two weeks ago. (over one-week period)
Charged around 8 hours during the whole week (120V level 1 charger).
I keep the main battery at around 70% charge.
Drove the car about 40 minutes the whole week combined.
Discharge: around 60 hours had the back gate or door open. The car drains 153mA with a door open. (no key in an ignition) That is 9.2Ah.
the car discharges 13mA all the other time. 108 hours resulting in additional 1.4 Ah.
I didn’t drive it at all last week, the doors were closed. That is another 2.2 Ah.
The reason I am airing the car so much, it has a smell.
The original Mitsubishi battery is probably around 35Ah, so it should be ok, but it is not a deep cycle battery,
and it degraded fast over the one year. I think, that before it died, it didn’t even have 10Ah capacity.
When I was topping it up with a charger, the charger shut off in 15 minutes.
I don’t think, that there is anything wrong with the car, other then the high parasitic drain,
and I think, that these levels are likely similar across all i-Mievs.
I don’t see the mod as a band-aid. I can leave the back gate open the whole day, and it doesn’t drain any.
If I want to work on a car, I can switch the 12V battery off easily. I will store the car in the winter, The 12V switch makes life easier.

 

[Don]

Still, I see no need to modify the car - If you want to leave the rear hatch open for a day or two or three, just put a trickle charger on the 12 volt . . . . or, leave all 4 windows down an inch or two and leave the hatch closed

But, it's your car, to do with as you choose - My only 'objection' was your suggesting that the car has a problem and needs to be modified, because after 8+ years of ownership and now with three of them, I don't see that being the case

Yes, the battery is small (no 'engine' to crank) and yes, like all cars, it does have small 'vampire' drains, but nothing that causes them to go flat quickly. I've installed AGM batteries (same batteries used in early Miatas) in all of my cars and they do self discharge slower than standard lead acid batteries, but even with the OEM batteries which lasted 5 or 6 years before I pre-emptively changed them, I've not had any 12 volt problems

Don

 

[PV1]

After several minutes, the dome lights turn off if a door or the hatch is left open, so that should limit drain, but then again your fix goes to the next level and cuts out all drain.

The only time I experience high drain, which hasn't been noticeable with new batteries, is when I unlock the car, open and close a door, then re-lock the car with the key fob. The 12 volt used to go flat within days when I did this.

If I repeated the above with the added step of starting the car then shutting it off (leaving it READY for about 15 seconds) before locking the doors, it could then sit for months without the 12 volt going flat. Like I said, I replaced both batteries (2 cars) and haven't had any issues since then even with the cars usually sitting a month+ at a time nowadays.

 

[Al123]

My i-Miev draws 13mA just sitting, no key in an ignition, no doors open, and no alarm set.
It is possible, that some I-Mievs draw less than others. My is 2012.
I was curious how that drain compares with other cars. I have tested our 2009 Chevrolet Aveo,
and it draws 3mA, that is 4.3 time less than the i-Miev. The battery in the Aveo lasted 10years, and was not dead when I changed it.
In 2 month, at 13mA my i-Miev would consume 19 Ah. I believe, a good quality deep cycle battery would be able to handle it.
If the parasitic current is not the same in all i-Mievs, it would be interesting to know how much the drain is on those, that can sit for several month, and still have charge left.

 

[kiev]

Are you using the key fob to lock the car? i haven't measured it but i think the alarm system gets activated with the key fob locking and it draws extra current. i have had the 12V aux go flat fairly quickly when sitting with the Alarm active.

But when i lock the car using the switch on the door, or by using the key in the door lock, then the aux battery seems to go several months. The best little smart charger i found is made by Yuasa, it's very accurate and does a great job. i have tried many of the cheaper versions, most are crap with wildly varying voltage regulation including boiling over at 15.9VDC with no sign of stopping or current cutoff in sight.

 

[Al123]

I lock the car using the switch on a door, or by using the locking lever on each door (together with the door handle)
if I have already switched the 12V off. I guess because of a habit, I open all our cars with a key.
Couple of times, by somebody else, the i-Miev was locked with a fob, and when I opened the car using a key,
the i-Miev had determined, that I am an intruder, and the beeping alarm started. I don’t need or want the alarm,
so I have disabled the lock button and the alarm button on the fob. I continue to unlock the car with a key, and since then the alarm never came on. I have a good charger. It was on sale at Canadian Tire store.
It is their own brand Motomaster, it is called Eliminator. It puts out 14.1V, and shuts off when it determines that the battery is full. I have had it for years, and have found it to be accurate and reliable.

 

[JoeS]

Just for grins, made a few current measurements by inserting a small precision resistor in series with the ground terminal and measuring the voltage across it...

Power OFF, car unlocked = 17.2ma
Power OFF, door locked using key fob = pulsing between 17ma and 20.6ma, faster than my DVM could track

Basically confirms Al123's measurement.

Realistically, I would not leave the car sit for more than a week without either running it (to recharge the 12v battery) or putting a float charger on it. Lead acid batteries do not like to be cycled. If outside, use a small solar panel + regulator. I have a fused Anderson PowerPole connector on every 12v battery in every one of my cars, which makes this quick and easy.

Had an 'interesting' experience: after I unlocked the iMiEV door with the key fob I then tossed the key fob onto the driver's seat through the open window... about 30 seconds later, the doors all locked themselves!

 

[Don]

In 2 month, at 13mA my i-Miev would consume 19 Ah. I believe, a good quality deep cycle battery would be able to handle it

I think any good battery could handle it - It's only about a 50% discharge and there's no engine to start, so no huge current needed to get it running

But . . . . you're not letting your car sit unused for 2 months, so something else is obviously going on. If you're driving it once a week or even once every 2 weeks, your battery should last at least 6 or 7 years - There are many 2012's out there still with the factory battery

I believe you have a problem you haven't actually 'solved', hence my 'Band Aid' comment

Don

 

[Don]

Had an 'interesting' experience: after I unlocked the iMiEV door with the key fob I then tossed the key fob onto the driver's seat through the open window... about 30 seconds later, the doors all locked themselves!

Many (most?) vehicles do this automatically. If you unlock the doors with a Fob, but you don't open a door, they relock everything 15 seconds later. This is a safeguard should somebody else's Fob with a similar code in a crowded parking lot unlock your doors, your car won't sit there unlocked. I *think* any car made in the last 15 or so years does this

On my Mercedes Sprinter based motorhome, the Fob unlocks the doors and also the walk in door . . . . but opening the walk in door doesn't reset things, so the van doors still relock 15 seconds later. Somebody noticed this and designed a hack with a magnetic switch for the walk in door tied into the passenger van door, so when you open the walk in door, it thinks the van door has been opened and that disables the relocking procedure

Don

 

[coulomb]

With the ~13mA drain, does it stay that high for ever? I mention this because I've been checking the current drain on my 2012 Leaf; it has terrible problems with auxiliary battery drain. The Leafs draw hundreds of milliamps for ten minutes (with a step down or two in that time, starting at over two amps!). I believe it's gradually sending various computers (ECUs) to sleep. I have no idea what they do in that 10 minutes, or what they are waiting for that they can't react to when asleep. It might have something to do with the telematics, even though I've had to change settings to disable most of that.

I have only been measuring the current with a clamp meter, and I usually only use the 400A range (max 399.9), as the 39.99A range drifts too much. So I don't see currents under about 100mA (depending on how it rounds, and the usual LSD uncertainty).

But maybe the iMiev does something similar over a multi-minute time scale. Has anyone checked by watching the current over say 15 minutes? Obviously, sampling roughly once a minute would suffice.

 

[Al123]

Thank you JoeS for taking the measurement. I have measured my i-Mievs drain again, and left the multimeter connected half an hour to see if the current goes lower after a while. It didn’t. It stayed at 13mA.
I have also checked with a door open, to see if the 153mA current was caused by a light inside the car, but no light was on. Only the door light on the dash. The current went down to 13mA after a long while, and the door light on the display went off (door was still open). My assumption, that the 153mA stays on was wrong.
The demand on the i-Miev 12V battery to drive or charge the car is minimal.
The battery as a source of power is needed only for short time of the car starting. After that, the 12V battery is charged by the car. Similar is for the car charging.
Yet the battery has to have 12V in order to start the car, or charge the main battery.
Virtually all the power consumption of the 12V battery goes to feeding the drain current.
After installing a switch to disconnect the battery negative, and using the car for 2 weeks, the only difference
I see is that it takes the i-Miev about 7 seconds longer to find the main battery charge level when the 12V was previously off. It finds the level correctly. There could be something, I have missed, but we just use the car for a short trip to a store, and don’t use any of its bells and whistles.
Thanks for everybody’s input. What I said above is my opinions and I am happy to be proven wrong.

 

[kiev]

After driving and the key turned to OFF, the dome light will stay ON for 20 minutes with the door open and then it goes OFF, even if the door is left open.

Same thing happens with the radio, it will play for 20 minutes after key in ACC, then shuts down.

The 13mA is quite a puzzle.

 

[DBMandrake]

Guys,

You're all barking up the wrong tree here looking for a problem that doesn't exist. A parasitic drain when the car is off and locked of 13mA is perfectly normal and in fact very good by the standard of many cars!

The parasitic drain of my older ICE car (which has an alarm and of course central locking) is nearly 50mA... and anything up to approx 50mA is considered "normal" parasitic drain on a car's electrical system.

Think about it - the original 12v battery is rated at about 32Ah. A 13mA drain would take 32/0.013 = 2461 hours to discharge the battery! Of course a regular 12v lead acid battery should not be discharged below 50% SoC, so call it 1230 hours of standby time.

That's 51 days or nearly 2 months before the 12v battery will be discharged to 50%, which is still plenty to start the car back up without any visible symptoms.

This is very good by most car standards. Many conventional ICE cars will not start after they've been left to stand for more than a month without any use.

The 12v battery will be charged both when the car is level 2 charged and when the car is driven, and if the battery is significantly discharged (say down to 50%) the charge current will be on the order of up to 50 amps or so initially, so you don't need to be charging or driving for long to top it back up most of the way again.

Mine was used very rarely in the first two months of the lockdown - once a week for a 2 mile drive to the supermarket, then left with the traction battery sitting at 80% until the following week. Zero problems with the 12v battery discharging.

Of course leaving the tailgate open 24/7 might discharge the battery at a faster rate, but that is hardly a design fault of the car. That's no different to leaving the interior light on manual override for a couple of days without realising it.

Personally I think it's a bad idea to connect a switch in series with the battery - the switch would need to be rated to at least 100 amps to allow for the peak charging current of a discharged battery or the load from the power steering. (which the battery acts as a buffer for)

It's also not generally a good idea to disconnect the 12v battery willy nilly on modern cars as it can cause some issues with ECU's. The i-Miev and clones do seem to be a bit more tolerant than some other cars that have a very specific "shutdown sequence" to be performed before battery disconnection, but why push your luck ?

Another reason it's a bad idea is if the battery is left disconnected for more than a month or so you run the risk of the BMU losing the traction battery Ah capacity and history - which requires a diagnostic tool to peform a recalibration. There is actually a warning about this in the service manuals not to leave the 12v battery disconnected too long.

My advice if the car is to be left in a high drain condition like leaving doors open (or just for a very long time at a normal drain, like going on holiday) is to put an intelligent 12v trickle/maintenance charger across the 12v battery and leave it connected until you're ready to use the car again. Don't keep disconnecting the 12v battery.

 

[pbui19]

Since my iMiev is mostly sitting around these due to the shelter-in-place, I have a solar battery maintenance panel on the dash and connected to the 12v . It's been left in place 24/7, even while driving on occasion.

https://www.harborfreight.com/15-watt-solar-battery-charger-62449.html?cid=paid_google|||62449&utm_source=google&utm_medium=cpc&utm_campaign=&utm_content=&gclid=EAIaIQobChMIneazr5it6gIVsiCtBh0sQgv2EAQYASABEgJFxvD_BwE

 

[JoeS]

pbui19, be careful, as I don't think that Harbor Freight "trickle charger" has a regulator. Even a small panel like that can overcharge a 12v lead-acid battery.

I also have an old larger Harbor Freight panel, but it's feeding the battery through an inexpensive controller -

 

[pbui19]

Thanks for the warning. I was concerned about over charging too, and the cheapy solar charger indeed does not have a controller, just a blocking diode.

I've kept an eye on the voltage with a cigarette socket volt read-out, the read-out is never above 12.4 v in ACC, then promptly goes to 14.xx in Ready . How can you tell when it's over charged ?

Thanks

 

[JoeS]

As soon as you turn the key to ACC, you're applying a load onto the battery (depending on whether the door is still open and whether the radio and what other gadgets are attached to the USB/12v outlet) and the voltage drops further than when OFF.

I just measured my wife's SE Premium and the voltage was 12.60vdc when OFF, measured at the battery, which is a bit lower than the 12.65v I expected. Opening the door dropped this to 12.46v and switching to ACC dropped the voltage further to 12.18v (and dropping) as the radio was blaring and the GPS and dashcam were drawing current. Oops, I just realized that a few months ago I had put my original 12v OEM battery back into her car as I had given the new one to a friend who had bought my original i-MiEV and was having issues with the dealer (long story) - I'd better replace this before the dashboard lights up... :evil:

For float charging of our i-MiEV flooded lead-acid battery, I prefer to see 13.8v or lower at room temperature. For attaching to a solar panel I prefer not to use a 'smart' charger as it may spend too much time at a higher voltage (e.g., up to around 14.4vdc) before dropping down to float when the current finally drops sufficiently for it to do that. Pbui19, to answer your question, anything over 14.5vdc at room ambient I would consider 'overcharging' (lower at high summer temperatures).

As a side note, for my 12v power supply in my garage I have a couple of paralleled (separated by a fuse) 8D batteries that are permanently attached to a 13.2v (float) charger and have been sitting like that with zero maintenance for over ten years - and they were old used discards when I first got them! Bet they're badly sulfated by now, but they just keep putting out...

For more than you every wanted to know -

https://batteryuniversity.com/index.php/learn/article/charging_the_lead_acid_battery
https://batteryuniversity.com/index.php/learn/article/charging_at_high_and_low_temperatures

 

[Don]

Since my iMiev is mostly sitting around these due to the shelter-in-place, I have a solar battery maintenance panel on the dash and connected to the 12v . It's been left in place 24/7, even while driving on occasion.

Where did you connect it to the 12 volt battery? Because, if you plugged it into the cigarette lighter, it's not doing anything because the lighter socket isn't hot when the car is turned off

If you're driving it at least once a month, it's really not needed and an unregulated charger might be doing more harm than good

Don