not sure where to post this but since this is for my coming E63S just decided to share it here.

basically, i don't want to mess with the fuse panel and not risk to have the battery being depleted. also, i want to have an external power source to power dash cams and other stuff, like a 4G/Wi-Fi hub.

this is work in progress but here is the circuit, based on an automotive DPDT (double pole, double throw) relay.
the system basically performs the following function:
1) when the car is running, the battery starts feeding the power bank/jump stater and dash cams via the 12V cigar lighter socket. so dash cams draw power from battery and power bank/jump starter is not giving power, only charging.
2) when the car is off, power bank/jump stater starts powering the cams and does not draw any power from car battery.
3) all happens automatically

considerations:
1) probably need to add 1 or 2 fuses for surge protection
2) eventually add a capacitor to smooth the current and store some energy for more demanding dash cam setups (i will be using 4 dash cams setup, in a 360º system)
3) eventually add a charging regulator for charging the power bank/jump starter
4) ground connection?

 

also, place the portable jump starter/power bank within a lipo safe bag (two for OCD guys, like me! one with Velcro flaps and zipper, and another with only a zipper)

 

I can't speak to a WiFi hub but battery backups for dash cams are common place. Based on the dashcam and the use of an extender pack, they can support up to 3 days? of parking recording and don't touch the car battery.
Is that not an option? Seems safer to buy a commercial product IMO...

 

thanks for the input. yes there are commercial versions that offer a little more safety by using a better kind of Li-ion batteries based on LiFePo4. That is the case for the tops dogs Blackvue Power Magic Pro and Cellink Neo. However, they are way too expensive and the price is unjustifiable for the benefits they bring. The only justification is that they have no competition yet. Thus, a DIY solution. The above circuit is very safe and I'm working on it to make it full proof.

The only major issue is the power bank/jump stater battery having about 1 in a million chance of catching fire due to bad construction combined with hot environments. But that can be minimized with two LiPo safe bags. They are currently strong enough to contain a fire and/or explosion from a Li-ion battery. The major consequence would be covering the inside of the car with lots of smoke and burn smell.

currently a 4 dash system takes around 700mAh and a jump starter with 18000mAh can power them for almost one full day.

 

Why a Wi-Fi hub? Why not use the built in hot spot? Does require a subscription however.

 

good question. AFAIK the Wi-Fi in the E63 goes off when one leaves the car. also i believe there is no option to navigate freely on the net thru the MB WiFi. it's a closed system.

in my case I am taking advantage of an additional mobile 4G SIM card that my 4-play service (mobile phone, land phone, TV and Internet) provides with 1.5GB of data per month. it should be sufficient for parking mode.

 

My wife and kids use the MB Wi-Fi quite a lot. Does turn off at some point once you leave the car. Unlimited plan, and as far as I know it doesn't restrict where on the net you go. They browse web sites on their iPhones or computers and watch a lot of YouTube video. Haven't tried to visit any **** or other potentially restricted sites to see if they have blockers, but use of NordVPN or similar VPN would create a tunnel so they can't see what sites you're visiting anyway, or hack your Wi-Fi signal and steal credit card info and so on.

 

interesting. i wonder if this is dependent on the country? i was told that it was not open. could use only with the car apps.

anyway, my major issue is with parking mode and be able to power cams and get remote access to them. and with the hot spot turned down i have to resort to an external solution.

 

I've been thinking about the same for my dash cam, but rather than use Lithium I was thinking a small sealed lead acid batt. They're cheap, they work, and safer depending on what you consider safe. Then stuff it in the spare tire well.
As for wiring, I was thinking the kiss method. Simply have the cam feed off the aux batt at all times, and have the aux batt charge via a fuse that is Ign on only w/ a 6A diode to prevent back flow. Seems reasonable to me... Sure lead batts don't like being cycled heavily but Lithium have a cycle life too. Not sure which would last longer per $, but I can always change it later. Option two; buy a deep cycle for the car and make a circuit to kill the cams when V drops to say 12. Too bad I/we don't have solar panel sun roofs!
I want a 4-cam 360 too, so I can catch the F'ers that open doors on me. All I found, that I liked, was a 2-cam Chanun Ace for $200. I like it since the cams are really small, but it sucks down the data so the 32G (max) card is full in a few hours. I need a much bigger card or ideally a hard drive, which I'd add to it if I knew how. The unit will reject a card larger than 32G, even if formatted to exfat, and I don't know how to get around that....
I do not see a need for a cap since a battery is a better cap than any you could buy. You do need a charging circuit for the Lithium, unless they fixed that issue. Last I remember is if you over charge them, like you would normally do to any other batt, they explode. If that issue has not been fixed then I guess you could, possibly, get away with a pack of ~14.5V so hopefully your car will never exceed it. But as I recall the batts need pretty much close to full voltage to fully charge, kinda like a lead acid won't charge much on 12V, but 13 and it's happy.
So your 4-cam system interests me, tell me more...

 

Has anyone used or heard feedback on the Owl Dashcam... https://owlcam.com

The product seems to be cheap and effective, and shuts off after 24hr, so for daily commuters is a good idea. Or not. Not the cleanest wiring option, but I'm sure that can be hidden too.