JoeS
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Posts: 3895
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

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

Fri Sep 20, 2019 7:26 am

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.
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

JoeS
Site Moderator
Posts: 3895
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

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

Fri Apr 17, 2020 12:53 pm

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.
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

PV1
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Posts: 3055
Joined: Fri Apr 27, 2012 4:22 pm
Location: Pittsburgh, PA

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

Fri Apr 17, 2020 7:14 pm

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.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015
"Photon" - 2017 Bolt EV LT in Orange with QC - 7/31/2017

Solar-powered since 10/10/2013

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

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

Sat Apr 18, 2020 5:56 pm

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
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

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

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

Mon Apr 20, 2020 12:51 pm

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.

martinwinlow
Posts: 66
Joined: Sat Sep 01, 2012 3:02 am

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

Sat Jul 04, 2020 3:03 am

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?

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