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charging a portable lithium battery

dboysen

New Member
Jun 20, 2021
3
0
CA
I have a 2021 Model Y and have purchased a portable lithium battery (1500W) recently that can be charged w/a 12V vehicle battery. It's not clear to me though, as I deplete the 12V battery in the Tesla, does the vehicle's lithium battery pack serve as a back-up to the 12V? Is it the case that the 12V battery doesn't get depleted because it can draw on the lithium battery as a supplement? Maybe after I drive around for a bit? Appreciate any insight to the advantages/disadvantages of charging the portable battery w/the Tesla 12V battery. Thanks!
 

Randy Spencer

Active Member
Mar 31, 2016
3,608
3,649
Alameda, CA
Why do you have this battery? Yes you can charge it with the car but why? The Traction Pack will turn off after some time not driving, but the 12v will always be on, running bluetooth and the car computer and such. Maybe when you are charging your car charge the battery? Or just charge it at home? What's the battery for?
 

dboysen

New Member
Jun 20, 2021
3
0
CA
Why do you have this battery? Yes you can charge it with the car but why? The Traction Pack will turn off after some time not driving, but the 12v will always be on, running bluetooth and the car computer and such. Maybe when you are charging your car charge the battery? Or just charge it at home? What's the battery for?
I live in an area of high risk of power outages and want the portable battery to keep my refrigerator running. The fridge largely depletes the battery on a 24-hr basis. The portable battery is rechargeable via solar panels that come with it but I want a fall-back in case smoke reduces the effectiveness of the panels and so that I have a night-time option for charging the portable if needed. The outages mean, of course, that I can't charge the Tesla, but these outages are often not a surprise so I expect to have the car fully charged when the outage begins.
 

Randy Spencer

Active Member
Mar 31, 2016
3,608
3,649
Alameda, CA
If you turn on Sentry Mode I think the 12v battery will continue to be refreshed, the traction battery won't go to sleep until it's down to 20%

There is a limit on how fast the circuit will charge, and I imagine that Tesla will complain that your 12v battery needs to be replaced if it sees too much power disappearing into the battery.
 

dboysen

New Member
Jun 20, 2021
3
0
CA
If you turn on Sentry Mode I think the 12v battery will continue to be refreshed, the traction battery won't go to sleep until it's down to 20%

There is a limit on how fast the circuit will charge, and I imagine that Tesla will complain that your 12v battery needs to be replaced if it sees too much power disappearing into the battery.
Very helpful; thanks so much.
 

Crew Dragon

Ordered 5/20: MYLR 5-seat W/W No FSD, 19”, no tow
Jun 17, 2021
61
241
Toledo, Ohio
I have also wondered about that. While the Model Y doesn't have a 120V outlet, there should be some good use to that giant 75kWr battery pack in the garage during a blackout.
I have a 500Wr power pack at the house for blackouts. It gives me 120V, 12V USB-A and even 45W USB-C connections. It takes about 6-hours using a 85W from a 12V car adapter to charge it up. If the Tesla lets me, we could keep a sense of normalcy even with an extended power outage. That 12V outlet in the Tesla should be able to power a small AC inverter as long as you keep things within the 100W limit of that 12V circuit.
From what I have been able to find, the USB-C outlets in the 2021 Model 3/Y are not designed for Power Delivery and are rated for less than 30W. While it may be OK for a small tablet, they will likely not even charge my iPad Pro or MacBook Air. MacBook Pro or a big Windows laptop will need the inverter to charge.
 

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