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Discussion Starter · #1 ·
I just went to connect the BM2 to the car's 12v battery. My notes from the forum said - you only need to disconnect the negative. Then it 'hit' me! Surely you can only connect the + and - BM2 tabs by disconnecting each terminal, even if only singly? I could take off the negative as advised, and reconnect it after slotting in the tab - but I still have to remove the +ve.

Lawrence
 

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Discussion Starter · #4 ·
Thanks - however, I have a bigger, unexpected problem! I cannot work out how to remove the -ve cover! the +ve cover has a simple clip so I lifted it up to see the terminal. The +ve has a left screw terminal and a right screw terminal. Is it OK for me to remove one of the small bolts and then fix the BM2 +? How do I remove the -ve cover? It seems to have something of a clip but it is covered by the earthing strap.

Really sorry to ask about this basic stuff but the last time that I checked a car's 12v it was an ICE. The manual makes no reference to methodology.

Lawrence
 

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2020 Ioniq 38 2016 Leaf 30 gone
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Thanks - however, I have a bigger, unexpected problem! I cannot work out how to remove the -ve cover! the +ve cover has a simple clip so I lifted it up to see the terminal. The +ve has a left screw terminal and a right screw terminal. Is it OK for me to remove one of the small bolts and then fix the BM2 +? How do I remove the -ve cover? It seems to have something of a clip but it is covered by the earthing strap.
On the red positive battery terminal I unclipped the cover and placed the red BM2 connector over one of the terminal threaded bolts and secured it with a 6mm nut and washer. I managed to place the BM2 cable so the cover would click shut. On the negative terminal I placed the BM2 connector on the threaded terminal bolt and again secured it with a 6mm nut and washer. The negative battery terminal on my Ioniq has no plastic cover.
 

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Discussion Starter · #10 ·
Yes - some progress made. I did the negative exactly as shown above. The negative cover has cut-outs (y) 😀

However, after I connected the positive, I realised that this cover has no cut-outs. Bum! For the moment I disconnected them both until I can solve this problem of the positive terminal. The pic above shows the lead exactly as I connected it - until I discovered that there was no hole or slot for the cable. I really don't want to deliberately break the cover just to make a slot.

So close! Meanwhile, during the minute or two that the BM2 was connected -it reports poor battery charge of 36%!. Oh dear. However, I do have a car charger and will use it once the BM2 is properly connected and giving data.

TIA
Lawrence H
 

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So close! Meanwhile, during the minute or two that the BM2 was connected -it reports poor battery charge of 36%!. Oh dear. However, I do have a car charger and will use it once the BM2 is properly connected and giving data.
With the bonnet and or a door open the cars systems will be powered on in readiness, so the 12V battery will be under load. A few minutes after the car is locked the systems will then shut down and a true 12V battery voltage via the BM2 monitor can be read (when its installed). There was a small cutout in my batteries plastic positive terminal cover that allowed me to squeeze in the BM2 cable so the cover would continue to click shut.
 

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Discussion Starter · #12 ·
I finally managed to fit the BM2 to the battery, mostly using the pictures above (y). What was a last minute problem (which I solved) was fitting the earth/negative terminal. The BM2 cables were several cm shorter than needed. I ended up managing to coerce the positive cable under the cover where there is a cut-out (not realised by me), and then twisting the negative cable in via the lower right - trying to avoid the earthing strap when re-fitting the cover! Very fiddly and it leaves the BM2 box slightly dangling on the battery's surface. I then used the sticky patch to anchor the BM2 to the battery itself. All seems well. A cm or two longer would have allowed a neat job.

Meanwhile, back at the app, it reports a healthy 69% charge :). I should now be able to learn something about its behaviour and whether or not I should periodically charge it via my 12v charger. So I am now 0.5 nerd ;)

Lawrence
 

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Discussion Starter · #13 ·
OK fellow nerds, how about this for a surprise! I reported a day or two back that I was surprised/concerned to find my battery was showing 'low charge' of 36% during the few minutes that I was holding the leads during connection efforts. It was then left disconnected while I sought advice. Today, ever since I connected the BM2 the charge has been steadily increasing !! from 36% two days back to first 70+ this afternoon, and currently 94%. How can this possibly be? Just because I have fitted a BM2? Measuring its voltage can have no effect on charge rate so the result is bewildering. FWIW the Honda's front charging indicator light has not been showing 'on' - at least not when I have looked.

Comments please for a puzzled 0.5 nerd!

Lawrence
 

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Comments please for a puzzled 0.5 nerd!
The cars electronics monitors the 12V batteries voltage, if the car is not used and the voltage is below 12.6V the battery receives a maintenance charge from the big traction battery. Depending on your cars BMS version this happens once every 24 hours. However, a recent BMS update modifies this to once every 4 hours. If the battery is above 12.6V then it is seen as fully charged by the cars electronics so does not receive a maintenance charge.
 

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How did you manage to find this out? It not exactly detailed anywhere that I know about despite my interest in knowing.
I’ve had a BM2 battery monitor fitted to my Ioniq for ages, checking the app readouts often you get to understand the 12V battery maintenance routine. My 12V battery however was failing and not holding a charge, it also let me down 3 times, plus, I constantly received low battery warnings from the BM2 app.

My Ioniq was serviced last February and received a BMS update, prior to the BMS update the 12V battery received a maintenance charge if not driven only once in every 24 hours. After the BMS update the 12V battery then received a maintenance charge every 4 hours if not driven, and the BM2 app low battery warnings were not so frequent.

I replaced my failing 12V battery a few months ago, mostly for peace of mind. As the new 12V battery holds its charge and stays mostly around 12.7 to 12.8 volts in between driving and being parked up, the maintenance charges have reverted back to once in every 24 hours, and sometimes even less. I no longer receive any BM2 app low battery warnings.
 

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BM2 estimates the 12V SOC from the voltage of the 12V battery.

You can also use ELM327 bluetooth dongle to read the status of the 12v battery via the diagnostic socket and see some more parameters: 12v %SOC calculated by BMS, battery voltage and current. This connection works only when car is powered on or charging.
 

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Discussion Starter · #19 ·
You are aware that tapping on the first graph provides one for the entire day? This is how you monitor the charging. Just to check, when you configured it you set it as a “regular 12v lead-acid battery“?
I have not been able to find an option to set the type of battery. When first configured the option was given; I tried to confirm by checking the battery but by then it had changed. The system settings offers no choice. FWIW, a discovery: the battery charge is stable at 100% and 12.94v. 2 - mostly stable around 13v with spikes to 14+v.

Lawrence
 

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I have not been able to find an option to set the type of battery. When first configured the option was given; I tried to confirm by checking the battery but by then it had changed. The system settings offers no choice. FWIW, a discovery: the battery charge is stable at 100% and 12.94v. 2 - mostly stable around 13v with spikes to 14+v.

Lawrence
Click the gear wheel (upper right), click "bluetooth device", click Edit...
The spikes are topups - note their frequency and duration over a 24hr period for a sense of what is normal.
 
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