Don
Site Moderator
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Joined: Thu May 10, 2012 3:55 pm
Location: Biloxi MS

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

Sun Jun 21, 2020 7:55 am

JoeS wrote: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
2012 iMiEV SE Premium, White
2012 iMiEV SE Premium, Raspberry Metallic
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon
2006 Itasca Navion Sprinter Motor Home

coulomb
Posts: 198
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

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

Sun Jun 21, 2020 4:55 pm

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
Posts: 14
Joined: Sun Nov 17, 2019 5:07 pm

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

Sat Jun 27, 2020 9:12 am

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
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Location: The Heart o' Dixie
Contact: Website

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

Sat Jun 27, 2020 10:00 am

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.
kiev = kenny's innovative electric vehicle

DBMandrake
Posts: 284
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

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

Mon Jun 29, 2020 12:29 pm

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.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

pbui19
Posts: 185
Joined: Tue Jan 07, 2014 12:17 pm

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

Wed Jul 01, 2020 4:19 pm

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-s ... gJFxvD_BwE

JoeS
Site Moderator
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Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

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

Thu Jul 02, 2020 8:19 am

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 -

Image

Image
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

pbui19
Posts: 185
Joined: Tue Jan 07, 2014 12:17 pm

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

Wed Jul 08, 2020 3:39 pm

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
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Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

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

Wed Jul 08, 2020 5:16 pm

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... :geek:

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
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

Don
Site Moderator
Posts: 2982
Joined: Thu May 10, 2012 3:55 pm
Location: Biloxi MS

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

Thu Jul 09, 2020 11:21 am

pbui19 wrote: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
2012 iMiEV SE Premium, White
2012 iMiEV SE Premium, Raspberry Metallic
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon
2006 Itasca Navion Sprinter Motor Home

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