Nice- One viewer suggested adding a fuse onto the aux battery, which is a great idea!

I think you could put the battery in your frunk with some added extension cables , and also a longer battery vent tube. I have a nice frunk bag that I do use, so I think I will leave the battery in it's existing location for now. I am still looking for a lithium replacement for the 12V battery, when I find one that meets all of the criteria, I will post a video on it. Thanks for watching!

I did indeed code the car to the new battery. I have read that also (overcharging of new battery), but there are also many comments of people not 'coding' the new battery. It is a simple thing to do if you have the bimmerlink app. Thanks for the comment!

If the 12v battery is weak, it can cause other errors to start to pop up. I would definitely look into checking the 12v battery,especially if it hasn't been replaced in the last 3 to 4 years.

Interesting idea... I should have put a fuse on my alligator clips! My concern would be that the 'cigarette lighter' plug turns off after ~15 minutes (not connected to the 'always on' side of the power bus) so you would need to work fast! You could also attach power to the fuse panel under the passenger foot well, one side is always on and one side the power is shut off by the system- I tapped into this panel for a project to automatically recharge the 12V battery when low (part 1 video coming out in ~2 weeks).

@@bmwi3diy782 What size fuse would you recommend?

Good question! If the high voltage supply disconnect is already pulled (disabling the 400 volt inverter), I think it is the same as when you would 'jump start' a regular car. Just make sure the pos and neg are connected correctly. If the existing battery is completely dead, then I would not do this, since the dead battery might pull the voltage of the 2nd battery too low to be helpful (and the computer systems are likely already compromised anyways at that point).

If I understand your question correctly, you're asking if leaving the OBD connector and a USB connection attached is a problem? I don't think they would cause an issue. If you are asking if they would power the computer system when the battery is disconnected, the answer is no. The USB port is not bidirectional, the OBD connector battery should just be powering the memory circuits (of course I don't know your specific device). Safest thing would be to remove those devices when swapping out battery since it is easy to do. Also, remember to always pull the high voltage disconnect first. As another viewer pointed out, the auxiliary 12V battery I attached should have a fuse in the line, in case of an accidental short. Finally, take care that the battery terminals are not accidentally shorted in the frunk when you are changing out the battery (protect the positive lead from grounding to metal/other)- the voltage spikes from this may be bad for the electronics/cause errors! Thanks for the feedback & watching the channel!

@@bmwi3diy782 The OBD memory saver is a adapter specially for swapping out internal combustion car 12v batteries & is powered by a 9v battery or a cellphone charger/USB plug. I just wanted to know if I can use this on the I3 if wanted to trickle charge the 12v a easier way. Thank you

Oh, I know what you are referring to now. I don't know of anyone using this device on an i3, but it may work, and would be better than not doing anything. My only concern would be that even a low 12V battery can cause the system to register errors/faults, so hopefully 9V doesn't do the same... Good luck if you try it, and let me know the results!

I think you could charge the 12V , however I would pull the high voltage disable first, so there would not be an issue with the EME (inverter) turning on at the same time, just to be safe. I would not want to blow the fuse in the EME. As one viewer suggested, placing a fuse on the auxillary battery cable would be a good idea too. Thanks for watching!

Without some DC to DC downconversion of voltage from 350 volts to 14 volts, it would be unwise to try and use an HV battery to jump start a 14 volt battery. The EME in the BWM I3 already has a DC to DC converter to perform the down conversion in order to charge the 14 volt battery when operating. The problem comes when the batteries are old (e.g., 5 years) and/or you do not drive it much to allow the HV to charge up the low voltage 14 volt battery. In the US your house, voltage is 110 volts AC current. The HV batteries are around 350 volts or more of DC current. The HV battery in these cars has more force (energy) behind it (more than 3 times) and is therefore more dangerous than the voltage in your house.

Interesting idea. From the literature, an AGM is supposed to have longer life, less corrosion risks, better cold temperature performance. However, Lead Acid is cheaper, higher cranking amps, easier to monitor state of charge. I have seen my charging inverter charge as high as 15.1V, which is way above the 13.8v nominal charging voltage recommended for lead acid batteries. I would be worried about generating hydrogen gas unless the software is changed for a non-AGM type battery with a lower nominal charging voltage. I have been looking /working on installing a voltage monitor that would 'wake up' the car if the 12v battery charge gets too low... automatically recharging it from the main battery. Stay tuned!

@@bmwi3diy782 the literature is nonsense as we all know, even the manufactures of the battery admit they are rubbish as I contacted them when it failed. when the AGM goes it fails catastrophically ( mine was less that 1v ) the lead acid I have used has been used on 3 cars now over about 5 years without trouble and the lead acid is listed as an option on a USA parts list ( which is where I got the part number from ) as it apparently fits a 1 series and they had it in stock. You will need to remove and modify the battery tray to suit the battery when fitting a non AGM battery but this is easily done as the straps are aluminium

@@Eatcrow I had a AGM battery in my Mazda MX5, stock one lasted 12 years, switched to led acid which died after about 5 years, then back to AGM which is now about 13 years old. I switched to a desulphating charger when stored and do the same to my i3 when I park it during the winter for 3 months. The battery is now in its 4th year and still good.

@@mnztr1 I think the problem with the BMW i3 is that the battery does not charge unless the ignition is on so if it’s left switched off for any significant period it just bricks itself . Also the actual capacity of the original AGM BMW battery is tiny compared to a lead acid one, so what I have done on both my BMW i3’s now is to remove the battery tray and modify it to take a BMW one series battery which helps to run all my extra electrics like dash cam and phone charger. After the catastrophic experiences with BMW original AGM batteries I would never risk putting one of those time bombs in my car ever again. Recently I heard of somebody who had a battery go and his local dealer told in the car was written off because it needed a whole load of electrical modules replacing as well.

@@Eatcrow How is that different from any modern car? The battery also charges when you are charging so there is ample battery charging on the car. But if you are gonna park it for an extended period you have to plug in the car or disconnect the battery. On an ICE car you have to either use a trickle charger or disconnect the battery.