Failing 12V or Converter issue?

[GiantPeaches]

I've been having issues with losing HV charge at a rapid rate; about 50% of the charge(car was charged at 100% before parked and came back to 50% SOC) is lost in the span of 2 days of being parked
It looks like my dc-dc inverter is always on and charging the 12V battery. Car has been parked for 2 hours and voltage shows 14.05V.
Is this a sign of failing 12V battery or an issue with my EDME or DC-DC Converter?



0-8 range is from car being plugged in and charging. Spike in voltage for a short period of time is from my commute this morning.

 

[mojo]

You'll have to forgive me for not having any knowledge of the app that you are taking the screenshots from. The big SoC dial in the centre: what is this displaying - the HV battery or the 12V battery?

The problem I have is that even if the DC-DC converter were on 24 hours a day, I don't see that it would be likely to drop the HV battery from 100% to 50% in 2 days. That's just a gut feeling response - I haven't done any maths to confirm or refute this (partly because you don't say what spec you car is, and partly because I'm being lazy).

 

[EvanstonI3]

This is a result of either a failing 12v battery or a short in the 12v system that is draining the 12v battery and causing the DC-DC converter to remain on constantly trying to keep the 12 battery alive. I've seen a few anecdotal reports of owners with a failed headlamp module or something that was shorting out and causing a considerable drain on the system.

 

[mojo]

Ok, let's do some maths then. If we assume that the car is a 120 - that has an HV battery capacity of approximately 38kWh, correct? So half of that is 19kWh - I.e. enough power to run a 1kW heater for 19 hours. If that much HV battery capacity is vanishing in 48 hours, that represents 400 Watts, all of the time - that's a lot of power.

If we transfer that into current delivery at 12V, that's around 30 Amps, all of the time. Anything that's consuming that much power while at rest is going to get very hot!

So... something doesn't tie up here (not least because I doubt that the car's DC-DC converter is spec'ed to deliver 30A continuously). I don't know the source of the apparent lack of sense, because I don't know anything about what the app screenshots are showing.

 

[EvanstonI3]

Ok, let's do some maths then. If we assume that the car is a 120 -

previous posts show this is a 2014, so 60ah

 

[mojo]

It's still a ~lot~ of power. If I had to guess, I would suspect that the OP is misunderstanding what they are seeing, and the 12V battery is losing 50% of its SOC, but I might be wrong about that - it's just a guess, based on something that looks likely (the HV battery losing 50 % capacity may in fact be happening, but it does not look likely to me).

 

[GiantPeaches]

oops, sorry it's 2014 BEV. This is 12V reading, not HV

I guess two separate issues but I assume this is somehow related.
my HV battery loses 50% of its charge in two days; parked. Vehicle was parked at 100% SOC on the HV for two days and came back to only 50% SOC. So I figure the car isn't going to sleep or something else is happening here..

 

[mojo]

Ok, so is it the HV battery losing 50% SoC, or the 12V battery? The diagnosis would be completely different depending on that. If the latter, it's probably just that your 12V battery needs to be replaced.

Edit: since you edited your reply, I would agree - the two are probably linked. It's not unknown for a failed 12V battery to cause the car to lose track of how well charged the HV battery is. I have (on other forums) seen people complain that the car has gone to 0 miles range, even though they know that the HV battery is full.

So... unless you know that the 12V battery has been replaced recently, I would simply replace it (or have it replaced by someone else), then fully recharge the HV battery and see whether that fixes the problem. Note also that if possible you should charge the new 12V battery before having it fitted, and that if possible it should be coded in the car as a new battery.

 

[EvanstonI3]

One way to determine the source of the problem would be to Open the Frunk, pull the HV disconnect and then remove the Negative Terminal from the 12v battery. Let it sit for a few hours and then check the voltage on the 12v battery terminals. You might find it easier to check voltage at the terminals if you remove the Frunk Tray. If the voltage on the 12v battery is below 12.0 volts after sitting disconnected for a few hours, then it is most likely a failed 12v battery.

 

[GiantPeaches]

Ok, so is it the HV battery losing 50% SoC, or the 12V battery? The diagnosis would be completely different depending on that. If the latter, it's probably just that your 12V battery needs to be replaced.

HV but I had a gut feeling maybe dying 12V battery is keeping the converter running and draining the HV but I can't see it draining HV battery that much just to charge 12V

 

[mojo]

Please see my answer (edited in response to your edits) three posts further up.

 

[alohart]

You'll have to forgive me for not having any knowledge of the app that you are taking the screenshots from. The big SoC dial in the centre: what is this displaying - the HV battery or the 12V battery?

That screenshot looks like the UI of my 12 V system monitor app, so I'm pretty certain that these data are all 12 V system data including the output of the DC-DC converter as well as the 12 V battery when the DC-DC converter isn't on. However, it's on during the entire 10+ hour log which isn't normal.

The problem I have is that even if the DC-DC converter were on 24 hours a day, I don't see that it would be likely to drop the HV battery from 100% to 50% in 2 days. That's just a gut feeling response - I haven't done any maths to confirm or refute this (partly because you don't say what spec you car is, and partly because I'm being lazy).

After a failed coding of the IHKA module (climate control system), the HV system in our 2019 i3 did not turn off for over 48 hours. The 120 Ah HV battery lost ~25% of its energy. However, the DC-DC converter did not remain on during that period. All HV modules remained powered which apparently consumes a fair amount of power. I recoded the IHKA module which fixed this problem.

The DC-DC converter will turn on under various conditions which I don't know. One condition is obviously when the 12 V battery voltage drops below a certain level. Another seems to be when the 12 V system current exceeds a certain level. I know that the DC-DC converter doesn't remain on when active HV battery pack charging isn't occurring. It will be on for 1 hour then turn off. When the 12 V battery's voltage drops below a certain level, the DC-DC converter will turn on again for another hour, etc. I don't know why the DC-DC converter would remain on otherwise. The 12 V battery's voltage could not be measured until the DC-DC converter turns off. Maybe the 12 V system current remained high enough to keep the DC-DC converter on. If so, some 12 V load must have been consuming an abnormal amount of power.

 

[ksnax]

Quit overthinking it and test the 12V battery or just replace it if it is more than 3-4 years old. That may not be the problem, but until you address the 12V directly, it's a waste of time to mess with anything else.

 

[GiantPeaches]

Thanks for your input everyone. Looks like it was some how all connected to failed A/C unit shorting out. Long story short, HV battery drain issue is fixed now but A/C compressor is dead.

This first i3 for me and short lived, about a month of ownership

 

[alohart]

Thanks for your input everyone. Looks like it was some how all connected to failed A/C unit shorting out. Long story short, HV battery drain issue is fixed now but A/C compressor is dead.

Unlike with most vehicles, an i3 owner can't ignore a non-functional A/C compressor because the battery pack is cooled by A/C refrigerant. During warmer weather, the battery pack could overheat resulting in battery pack protection features reducing the battery pack's output and input power which could reduce the maximum speed. The A/C compressor needs to be replaced. An independent mechanic could replace your failed compressor with a used one which could save a considerable sum.

 

[GiantPeaches]

Unlike with most vehicles, an i3 owner can't ignore a non-functional A/C compressor because the battery pack is cooled by A/C refrigerant. During warmer weather, the battery pack could overheat resulting in battery pack protection features reducing the battery pack's output and input power which could reduce the maximum speed. The A/C compressor needs to be replaced. An independent mechanic could replace your failed compressor with a used one which could save a considerable sum.

yeah, I don't think we want to put more money into fixing this at this point. We only paid about 7k canadian for the vehicle. Just to do compressor at an independent shop they quoted about 3500 with tax including the compressor itself.

We are looking at 2018 i3s in a few days as potential replacement.

 

[TheAirman]

yeah, I don't think we want to put more money into fixing this at this point. We only paid about 7k canadian for the vehicle. Just to do compressor at an independent shop they quoted about 3500 with tax including the compressor itself.

We are looking at 2018 i3s in a few days as potential replacement.

Could it have been this part instead of the compressor?

https://www.ebay.com/itm/1540674623...4TLNBF76e1JFcXqGjly+Ng/1A6g=|tkp:BFBMluvMjLxj

 

[EdG]

I seem to be having a similar issue with a 2014 BEV that I purchased last week. The EDME was replaced under warranty and the 12v is new, but I'm losing ~5% in 24hrs with no usage.

What would be the easiest way to determine if it's the AC compressor? The AC seems to blow cold and no issues. Max capacity is showing around 15kw.

Located in Oahu/Honolulu area, but kept out of the sun so I don't think there's any AC running in the background for no reason.

 

[alohart]

I seem to be having a similar issue with a 2014 BEV that I purchased last week. The EDME was replaced under warranty and the 12v is new, but I'm losing ~5% in 24hrs with no usage.

What would be the easiest way to determine if it's the AC compressor? The AC seems to blow cold and no issues. Max capacity is showing around 15kw.

Located in Oahu/Honolulu area, but kept out of the sun so I don't think there's any AC running in the background for no reason.

The A/C compressor won't run unless an i3 is in drive ready state, being charged, being preconditioned, or when climate control is activated in iDrive for ~20 minutes after an i3 is turned off. It doesn't run to keep the battery pack or cabin cool at other times. The compressor makes a noticeable sound, so you would hear it if it were running when you didn't expect it to be. So I doubt that the A/C compressor is discharging your battery pack.

The battery management system (BMS) recalculates the charge level periodically. The charge level could be adjusted lower now that Honolulu evenings are cooler than recently. The charge level can't be measured directly so is estimated by the BMS using various criteria. However, I haven't noticed the charge level of the 3 i3's that we've owned in Honolulu over the past 10 years decreasing by 5% overnight, so this does seem a little unusual.

 

[EdG]

Unfortunately, I think this is worse. Now, another 24hrs later, it's down to 64% with only 7mi added to the ODO (which should represent about 10% use based on the 70mi range) so that's another 25% down in a day

Speaking with a friend who has had an i3, he thinks that one or more of the battery cells/modules may be bad.

I've called up BMW and they want ~$1k to update the software and run an HV diagnostic. My 1 week old i3 is already becoming a money pit.

Does anybody on Oahu have an independent shop that they would use for diagnostic and/or module replacement that they could recommend?
(pics all taken 24hrs apart from each other, 48hrs in total)