I understand that the cigarette lighter might not work with my solar charger because it shuts off shortly after shutting off the car. My question is whether the cigarette lighter can be recoded so my solar charger keeps the battery strong while I am traveling.
Solar trickle charge
- Thread starter edicito
- Start date
Help Support BMW i3 Forum:
Your i3 has a large HV battery pack that maintains the 12V battery, especially while traveling. There's no need to try to charge its 12V battery with a solar charger except if your i3 were parked for more than a month. However, as you noted, the auxiliary power ports shut off shortly after turning an i3 off, so this wouldn't work. I've not read of anyone successfully coding the auxiliary power ports to always remain connected.
Back again, after 2 months away from 2017 REX (19K), which was left with a full charge. Getting only a "drivetrain malfunction" alert when trying to start. After manually opening charging door, my level 1 charger shows power but will not charge the traction battery. 12V no doubt the culprit, but will its replacement alone permit charging the traction battery or do I have additional problems? Many thanks.
Before buying a replacement 12V battery:
1. If you have a 12V battery charger, charge the battery after disconnecting the HV disconnect to the right of the frunk box.
2. If you don't have a 12V battery charger, leave your EVSE plugged in overnight to learn whether the i3's emergency 12V battery charging circuit can charge the 12V battery enough to start your i3.
3. If the 12V battery's charge level is still too low, install a replacement 12V battery but only after it has been fully charged.
Unless a 12V battery is in top condition, it might discharge too much over 2 months due to always-on vampire loads. It doesn't seem to be totally dead, so you might not have damaged it. Charging it with a 12V battery charger would resurrect it if it wasn't damaged, so buying a replacement might not be necessary.
Some i3's or some system software versions (I don't think we know which) include automatic 12V battery charging for 1 hour whenever the 12V battery's voltage drops below a certain level. That should prevent a 12V battery from discharging too much unless it's failing. If this occurs repeatedly due to a failing 12V battery, the HV battery pack's charge level might have decreased noticeably. Otherwise, it shouldn't self-discharge much more than ~1%/month. Because your 12V battery discharged significantly, either your i3 doesn't implement automatic 12V battery charging or your 12V battery is failing.
Your "drivetrain malfunction" error message suggests that the 12V battery's voltage decreased so much that spurious diagnostic trouble codes (DTC's) were stored. These could prevent the normal operation of your i3 even after its 12V battery is fully-charged or has been replaced. Sometimes, allowing an i3 to sleep overnight could clear some of these DTC's. However, it might be necessary to clear these DTC's using an OBD scanner like BimmerLink.
Note also that - according to BMW's documentation - the first stage of this recovery process will show no indication that anything is happening. You won't get any LED lighting at the charge port, nor any display on the dash - so you really just have to plug it in and come back later to see if it succeeded. At some point the emergency process will achieve enough voltage in the 12V battery for conventional HV charging to start (unless the 12V battery is too far gone).
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Well, it was worth a try.
I don't recall ever reading of an i3 owner who successfully charged a discharged 12V battery by plugging in an EVSE even though this is a documented feature. Maybe in almost all cases, the 12V battery is failing and won't accept a charge, has an internal short circuit, etc., so even charging with a battery charger would fail.
This is exactly what happened. The Hv would not accept a charge due to apparent total failure of the 12v, so I replaced it, solving the problem. After replacement, the guessometer showed 105 miles. In fact, the HV refused further charge because the REX was past the maintenance cycle period.
The failed 12v was an BMW original battery and I had anticipated its failure 3 years ago by purchasing its replacement. However, by this time, the "new" replacement battery had discharged to 1 volt and 48 hours of slow charge was needed to bring it back, which Battery Warehouse guys doubted might happen. Seems to be fine now.
This is what I have done during our 10 years of i3 ownership. However, the replacement 12V battery needs to be charged about every 6 months to prevent self-discharge from discharging it so much that permanent damage might occur. An AGM battery like the i3's AUX18L has a slower self-discharge rate than a flooded-cell lead-acid battery, but it does self-discharge over time as you learned.
