Charging a portable power station from the Tesla 12V battery

Been mulling this one over since I saw a few people mention it in the van life threads.

On my narrowboat I've got a proper Victron setup so it's not something I need to do, but I can see the appeal for someone wanting a simple portable solution without tapping into the main system.

The Tesla 12V is a standard lead-acid (or LiFePO4 on newer models) auxiliary battery — same principle as any other vehicle. Technically you can run a portable power station off it, but I'd be cautious about a few things:

• Draw rate — most portable stations will pull a fair amount through the 12V socket or directly off the terminals. Worth checking your PSS's input rating.
• Regen/charging cycles — the Tesla's aux battery gets charged differently to a conventional ICE car. Not sure how happy it'd be with sustained heavy loads whilst parked.
• Isolation — does the Tesla actually isolate the aux battery properly when the car's "off"? Last thing you want is a dead 12V and a car that won't wake up.

Has anyone actually done this with a Bluetti or EcoFlow unit and tracked the effect on the aux battery health over time? Would be genuinely curious to see some real-world data rather than just speculation.

Feels like one of those things that's probably fine occasionally but might not be great as a daily habit.

Mate, charging a power station from a 12V auxiliary that's really a glorified door-handle battery is like filling a swimming pool with a watering can — technically possible, deeply optimistic.

@DazHenderson77 makes a fair point about the 12V aux being tiny, but the actual technical concern worth flagging is the charge rate vs. source capacity mismatch.

Most portable power stations will happily pull 8-10A via their car charging input. Tesla's 12V aux (actually 16V lithium on newer models) is kept alive by the main pack through a DC-DC converter rated around 2kW continuous — so it's not that feeble.

The real gotcha is Tesla's sleep/idle behaviour. Leave something drawing 80-100W and you'll wake the DC-DC constantly, which nibbles the main pack more than you'd expect overnight.

For anyone doing a van conversion using a Tesla donor vehicle, I'd honestly just tap the DC-DC output directly with proper fusing rather than faff through the 12V aux terminals. Cleaner install, same source.

@ExSquaddie49 go on then, don't leave us hanging like a Fogstar delivery that never arrives — what's the actual technical concern?

@SaltyViking replied:

@SaltyMechanic @ExSquaddie49 Aye, do finish that thought!

While we wait — the other thing worth considering is when you're drawing from that 12V aux. Tesla's LV battery management is a bit peculiar; the car will spin up systems to recharge it, but if you've got the car parked up for a fortnight and you're steadily sipping from it with a power station, you could theoretically trigger enough wake events to start nibbling into the HV pack just keeping itself ticking over. Bit of a roundabout way to drain your main battery really.

For occasional light loads it's probably fine, but I wouldn't make it a habitual charging setup. A small dedicated leisure battery wired sensibly would sort you out far more elegantly and let you sleep without worrying about it.