Al123
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Joined: Sun Nov 17, 2019 5:07 pm

12V battery cumulative drain higher then overall charging.

Thu Jun 18, 2020 4:08 am

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
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Re: 12V battery cumulative drain higher then overall charging.

Thu Jun 18, 2020 9:27 am

Al123 wrote: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
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Al123
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Re: 12V battery cumulative drain higher then overall charging.

Thu Jun 18, 2020 12:38 pm

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
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Re: 12V battery cumulative drain higher then overall charging.

Thu Jun 18, 2020 2:32 pm

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
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PV1
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Re: 12V battery cumulative drain higher then overall charging.

Thu Jun 18, 2020 5:28 pm

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.
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Al123
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Re: 12V battery cumulative drain higher then overall charging.

Thu Jun 18, 2020 7:08 pm

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
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Alarm system active?

Thu Jun 18, 2020 7:28 pm

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.
kiev = kenny's innovative electric vehicle

Al123
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Re: 12V battery cumulative drain higher then overall charging.

Fri Jun 19, 2020 4:35 am

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
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Re: 12V battery cumulative drain higher then overall charging.

Sat Jun 20, 2020 11:42 pm

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!
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Don
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Re: 12V battery cumulative drain higher then overall charging.

Sun Jun 21, 2020 7:43 am

Al123 wrote: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
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