Ranamohamedshawky
Posts: 3
Joined: Sat May 23, 2020 11:09 am

What is battery discharging

Sat May 23, 2020 11:32 am

What is the marks that shows that the 12v battery has a problem i am having a icon showing about the battery discharging while stopped and is the 12 v battery has any relation about the car's charge ? Because it sopped while iwas driving it while it has 7 kms left!

alohart
Posts: 2023
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: What is battery discharging

Sat May 23, 2020 12:45 pm

When the 12 V battery is weak, a confusing message can be displayed indicating that a battery is discharging and to start the engine. This makes no sense for an i3 because the BEV has no engine and the REx engine doesn't charge the 12 V battery directly.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

jadnashuanh
Posts: 4916
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: What is battery discharging

Sat May 23, 2020 1:30 pm

There are a bunch of things in our modern cars that don't literally ever turn off. You'll also find out that most of the switches in the vehicle don't actually do the thing they're labeled directly. If you ever took the headlight switch module out, you'd see that it's plugged into a small socket with maybe 24g wires...nowhere near enough to literally turn the lights on or off. What does happen is that the switch goes into a small circuit board, and when you move something, it sends a serial message down those wires to a computer, and then the computer sends out a signal to something else, and that does what you asked.

Lots of these devices aren't needed when the car is 'OFF', so as part of the shutdown process, the computer sends messages out telling everything to go to sleep. If the data lines are noisy, the connection is bad, or the box is getting marginal, it's possible that one or more of those modules don't go into sleep mode. That ends up with them drawing more than a miniscule amount of power, and can draw the battery down quicker. The car has sensors that can track that. I'm guessing that that is what you're seeing...the car is sensing that the 'OFF' mode is using more power than it should. Also note that if the car is not used for longer periods of time, various things that can, may go from their 'OFF' mode, into hibernate mode, to help preserve the 12vdc battery charge.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

arodi3
Posts: 21
Joined: Thu Apr 26, 2018 10:21 am

Re: What is battery discharging

Sun May 24, 2020 12:05 pm

I got a "battery discharging while stopped" message a week or two before my 12V battery went out. Other people have mentioned similar timing. I would go ahead and order a new 12V battery now.

https://www.reddit.com/r/BMWi3/comments ... ave_money/ I registered mine with the Foxwell 512 NT
Elite that they mentioned. That scanner seems like a useful tool to have, but I have not got a chance to work with it yet, beyond the battery registration.

One note: when I connected the new battery, I was surprised at how much of a spark I got. I went and got a multimeter to watch the battery voltage as I connected again, and the voltage stabilized around 12.5V, so I was confident that there was not a short. As jadnashuanh mentioned, the electronics pull a fair amount of current and there is no on/off switch. There are probably some hefty decoupling capacitors too, which contribute to the arcing on connection.

Timjohn
Posts: 34
Joined: Mon Nov 11, 2019 9:37 am

Re: What is battery discharging

Sun May 24, 2020 6:11 pm

You got a spark when you installed the new battery?? I thought there is a YouTube video on this install and you have to disconnect the main power cable first. Maybe you got away with it this time. You could have fried a bunch of expensive electronics!

JohnWasser
Posts: 47
Joined: Sat Mar 07, 2020 6:15 pm

Re: What is battery discharging

Mon May 25, 2020 12:47 pm

Timjohn wrote:
Sun May 24, 2020 6:11 pm
you have to disconnect the main power cable first.
You are supposed to disable the high-voltage supply but that doesn’t disable all of the 12V loads. I got sparks when reconnecting the 12V battery. My guess is that the disabling of the high-voltage supply is to keep the car from trying to charge the 12V battery when the battery voltage drops to zero.

arodi3
Posts: 21
Joined: Thu Apr 26, 2018 10:21 am

Re: What is battery discharging

Mon May 25, 2020 4:51 pm

Timjohn,
I'm not sure where you got the idea that I didn't disconnect the high-voltage, but I can assure you I followed the instructions and did not skip that important step. I intended to post something about my experience with the reconnection but didn't get around to it; this post reminded me about it.

I read/watched quite a bit on the act of replacing the 12V battery in the i3 and am supprised the bit of arcing/sparks on connection is not mentioned more. This is the only mention I see: https://www.reddit.com/r/BMWi3/comments ... onnecting/

It has been a few weeks, but I remember that there was some arching on make, but not break of the connection. After a second or two, there was a click like a relay closing and some other encouraging sounds of things coming to life, perhaps a fan or something. I watched the battery's terminal voltage on a multimeter when I made the connection and it quickly stabilized around 12.5V, basically the open-circuit voltage of the battery. A lower voltage would have indicated a significant current draw and I would have quickly removed the connection.

The arcing/sparks on the connection event are probably typical for people used to working with automobiles but may be supprising for techy-types. If you were to just plop the contact over the post, you may not notice the arcing, but if you are cautious about making the connection and touch the contact to the post watching for sparks, you will see them.

Timjohn
Posts: 34
Joined: Mon Nov 11, 2019 9:37 am

Re: What is battery discharging

Mon May 25, 2020 6:24 pm

OK my misunderstanding...I thought you may have connected the battery right at the terminals with the main power cable first connected. My assumption was incorrect then. This just demonstrates that the battery is always in demand even when the i3 has been parked, shut off and doors closed. So this arching occurred when you installed the new battery and could be seen when you replugged the "orange coloured" cable in? Well that's something I will have to watch out for when I have to do mine. Good on you for performing this yourself and sorry if I offended you.

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