Page 2 of 2

Re: 12v Battery - All You Ever Wanted To Know

Posted: Fri Sep 20, 2019 7:26 am
by JoeS
GdB, thank you for adding the information to this thread. I took the liberty of editing your post to make the links visible even though you have the text nicely covered. The fourth link shows the related hardware.

Re: 12v Battery - All You Ever Wanted To Know

Posted: Fri Apr 17, 2020 12:53 pm
by JoeS
With many of us sequestered and cars sitting idle, I'd just like to remind everyone to remember their 12v battery and activate the car every few days or else attach a float charger directly onto the 12v battery. For the last six weeks my i-MiEV hasn't left home except to drive the garbage cans down to the main road once a week, and my wife goes down in her i-MiEV to retrieve mail from the post office, also once a week. We're very fortunate that our next-door neighbor with a large family (and an i-MiEV) includes us on his shopping list. Stay safe, everyone.

Re: 12v Battery - All You Ever Wanted To Know

Posted: Fri Apr 17, 2020 7:14 pm
by PV1
I've been keeping my fleet moving. Since my home internet is a joke, I've been bopping into town to use free Wi-Fi while sitting in the car. (Thanks, Panera Bread. Promise I'll make it up to you. ;) ) Haven't had to make many supply runs since we normally keep a few weeks' stock on hand anyway, and we doubled up before everything was shut down. One of the benefits of living outside of town; the distance discourages daily trips.

Both of my i-MiEVs got new 12 volt batteries in the last year or so, and haven't had a dead battery since I discovered the trick of starting the car in the middle of a door unlock-lock cycle. The Bolt got a big AGM battery in it, so it'll sit for a long time without needing a charge.

Both of my i-MiEVs have this quirk where if the car is locked, and I go to retrieve something out of it with the simple process of unlock doors with key fob, open a door, close it, and lock the car with the fob, I'll have a dead 12 volt battery within a week. If I unlock the doors with the fob, open a door, start the car, shut it off, close the door, and lock it with the fob, the car can sit for a month+ and be able to start without a jump. Whatever drains the battery, having the car fully cycled before locking the doors lets it power down successfully.

Re: 12v Battery - All You Ever Wanted To Know

Posted: Sat Apr 18, 2020 5:56 pm
by Don
I put Miata AGM batteries in two of my three cars - One of them has been in use now for 4 years or more and both are working fine. No issues ever with a dead battery, even if the car sits for a month or so

Don

Re: 12v Battery - All You Ever Wanted To Know

Posted: Mon Apr 20, 2020 12:51 pm
by pbui19
We discovered the "quirk" early on, that the 12v gets drained if locked by the fob. Since then, I have into the habit of locking by pushing the lock button on the door on the way out, making sure key is in hand.

Replaced the 12v with a sealed 12v from Harbor Freight a year ago, seems to be holding up fine.

Re: 12v Battery - All You Ever Wanted To Know

Posted: Sat Jul 04, 2020 3:03 am
by martinwinlow
GdB wrote:Do not keep the auxiliary battery removed for a long period of time (approximately 1 month or more). (The BMU will not be able to comprehend the main battery status.)
If the auxiliary battery has necessarily been removed for a long period of time (approximately 1 month or more), perform "BMU Learning Value Manual Writing." (Refer to GROUP 00 - Precautions before Service - Procedures for Writing BMU Learning Value .)


"BMU Learning Value Manual Writing." Why is this necessary and what does it do? Is this a MUT3 function or from a different diagnostic tool?

Re: 12v Battery - All You Ever Wanted To Know

Posted: Mon Sep 07, 2020 4:10 pm
by RonSmithJr
OK, I am not a car person, even though I owned my first Electric car in 1965 (long story).
Anyway, I am having some awful problems with my 2012 I-Miev. It will not do anything, even the key will not turn beyond the 'ACC' position.
This started two days ago, when the temperature went over 104 Fahrenheit here in S. California.
I'm hoping the problem is simply the 12v battery, which is what I am looking at first anyway.
However, as I said, I am not a car person, and have never had any interest in cars.
So this is probably a dumb question, but I cannot find any answer to it anywhere online, so I am asking here.
I can see on the battery where the high and low lines are for the necessary amount of water, but I do not see anyway of telling how much water is currently in the battery. How do you tell how much water there currently is?

Re: 12v Battery - All You Ever Wanted To Know

Posted: Tue Sep 08, 2020 1:27 am
by martinwinlow
RonSmithJr wrote:... how much water is currently in the battery. How do you tell how much water there currently is?


I would be surprised if it needs topping up but maybe your climate demands a design of 12V aux battery that requires it...? I haven't seen a proper 'flooded'-type car battery (that needs regular maintenance ie topping up) for decades.

In any event, the key question that needs answering is; what voltage has the 12V aux battery? In my experience (of European and Japanese i-MiEVs) it needs to be a good 10V to get the drive-sytem to turn on. Even so, at less than this (down to below 9V) *something* should happen at the 2nd key position ie dash lights etc. If you aren't even getting that then it would seem the aux battery is completely stuffed or it isn't connected!

Re: 12v Battery - All You Ever Wanted To Know

Posted: Tue Sep 08, 2020 5:47 am
by kiev
If the key is physically restricted from moving past the ACC position, then the gear shift lever is not fully engaged in the Park position or the cable has become dislodged. There is a mechanical interlock between the key switch and the gear shifter.

Re: 12v Battery - All You Ever Wanted To Know

Posted: Tue Sep 08, 2020 6:08 am
by martinwinlow
Ah, yes... RTFM...?!