EV power siphon?

AppleBananaGigachadRatZoo

AppleBananaGigachadRatZoo

New Member
I had an idea today for a way to charge a power-starved EV from another that had lots of charge left. It goes like this:
  1. Plug 12V to 120V inverter into donor car's cigarette lighter/12v
  2. Plug 120V EV charger into inverter inside donor car
  3. Plug EV charger into receiving car
Any reason this wouldn't work? I understand that it would probably be extremely slow, but that's beside the point.
 
What is the 12V cigarette lighter fused at, 10 Amps? 20? Let's say 20. That's 240W before losses in the inverter and connector. Call it 200W to the MINI.

I'm not sure that even covers the hotel load. If it does, barely, it would be weeks to fill the traction battery.
 
The smallest control pilot duty cycle is for 6A x 120V or 720W.

You can however charge a battery and then hook it up to a 120V inverter..but that is very slow.
 
teslarati97 said:
I meant a standalone battery like a solar generator.
Click to expand...

ecoflow has a solar generator that might do the trick. They have a cable that allows you to hook two of them together to provide 240V.

It is an interesting solar generator. It has inputs for solar panels, and amongst its other outputs, it has a 20A Anderson power pole connector (common in ham radio devices).

But, in spite of all of the features, I wouldn't rush out and buy one. Less than a year ago, I purchased two of them, to use in case the Texas power grid went tits up. One has already failed. (It will be replaced by another one guaranteed to last only until the end of the original warranty period.) There's nothing like waking up in the middle of the night and smelling burning plastic, and finally realizing that what is burning is a 3.6kW Li ion battery.

Now, when I leave home with my remaining solar generator providing power for Spider Farmer lights (for my--wink wink--ghost pepper plants), I wonder if I'll come home to a house fire. :(
 
Minis suck a few hundred watts just to have the charging system alive. I did want to make a curved solar panel roof for mine. But, the power output would have been very similar to minimum charge power (85V x 6A), and I'd have been kissing goodbye to maybe 2/3 of the generated power in charger overhead. More complex plan B of a small buffer battery to pulse charge the car at higher power looked doable, but a PITA. If I move off grid, it's an option.
 
Charging another EV, not worth your time and usually require some grounding trickery to get the EVSE working.

Emergency usage is much more useful. Do this with a 1000w inverter directly on 12v and vehicle tricked into staying drive ready. Depending on load and starting SoC it will keep a few essentials running for a day or two.

Haven’t tried yet with my SE but pretty much all EVs will do this.
 
carrrl said:
Emergency usage is much more useful. Do this with a 1000w inverter directly on 12v and vehicle tricked into staying drive ready. Depending on load and starting SoC it will keep a few essentials running for a day or two.
Click to expand...
Tesla voided the warranty of a driver who did that (posted on Facebook) and subsequently revised the warranty by adding the stationary power source limitation. Then again the Model 3 and S are also warranty voided if you drive "off-road" (nobody knows what that really means).
 
teslarati97 said:
Tesla voided the warranty of a driver who did that (posted on Facebook)
Click to expand...
That’s interesting, curious if most other EVs even have that sort of logging. MINI feels technologically neglected so I’m personally not too concerned if I ever truly need it. Unless it’s explicitly in writing it should fall under Magnus Moss and on the manufacturer to prove your actions messed things up.
 
Yeah, it's probably not a good idea to use the 12V battery from your EV. If someone is serious about backup, they should consider putting money towards solar+battery+backup since the IRA gives a 30% federal tax credit on the total system! Literally worth a $7,500 tax credit if you spend at least $25,000 and you can still claim the $7,500 EV tax credit (if applicable)!
 
teslarati97 said:
Yeah, it's probably not a good idea to use the 12V battery from your EV.
Click to expand...
Use what you have in an emergency, this wasn’t an every day suggestion. Sitting on a ~30kwh battery during a week long grid failure would be silly. Solar is well and good while grid is up and you had the foresight, location, roof, and funds to do so. Batteries (Powerwall like products) are a poor value right now at around $1k/kWh. They don’t last forever, have basically a single use, and never pay off.

SameGuy said:
Don’t forget that Peukert will affect such an energy-sharing scenario (unlike normal driving).
Click to expand...
Does that apply here? If you are not taxing the system DC-DC handles the entire load not the 12v battery. Most EVs I’ve researched and tried can do ~1000kw (total, including car accessories) entirely fed by the traction battery.
 
carrrl said:
Batteries (Powerwall like products) are a poor value right now at around $1k/kWh. They don’t last forever, have basically a single use, and never pay off.
Click to expand...
Most hybrid grid tie systems don’t use Powerwall or lithium packs, but SLA or AGM, and add about 40% to a solar installation’s price. Powerwall can easily double or triple a price. Nice to have if money is no object, but will never pay for itself.
carrrl said:
Does that apply here?
Click to expand...
Assuming we are still talking about charging one EV from another one, then I would think it does apply, because the rate is not constant. I’m not saying it would prevent V2V charging, just that it should be taken into account in the calculation of charging losses or efficiencies.
 
carrrl said:
Use what you have in an emergency, this wasn’t an every day suggestion. Sitting on a ~30kwh battery during a week long grid failure would be silly. Solar is well and good while grid is up and you had the foresight, location, roof, and funds to do so. Batteries (Powerwall like products) are a poor value right now at around $1k/kWh. They don’t last forever, have basically a single use, and never pay off.
Click to expand...
It really comes down to your use case. In the UK, the tariffs are over $0.70/kWh for daytime use and $0.15kWh overnight so the arbitrage is certainly available. In that situation, the payback is 2-3 years for batteries alone! Many regions also tack on hidden variable fees in addition to retail charges (transmission & distribution fees) so a high electric consumption household (i.e. net zero) could benefit.

Aside from self-consumption and backup, a DC coupled battery system workaround PV sizing limitations. For places like Hawaii, there is no payment for exporting energy back to the grid so self-consumption is the only option. In regions of Australia, there is a 10kW AC limit so a Powerwall would be 5kW AC and the max inverter would be 5kW (even worse with microinverters). A DC coupled battery would allow for a full 10kW inverter and PV array over sizing opportunities (charged from clipped energy). Some other regions have peak demand charges (max load in ANY 15 minute interval), but generally it is more applicable for DC Fast charging to grid charge the batteries (i.e. Tesla V3 supercharging). In the future batteries might become part of the grid load balancing like they do in parts of California already.
 
i have one of those portable chargers. Can I plug it into the lighter of a charged EV, then plug it into the disabled EV? If I do it a dozen or so times i may be able to get a mile?
 
Tommm said:
i have one of those portable chargers. Can I plug it into the lighter of a charged EV, then plug it into the disabled EV? If I do it a dozen or so times i may be able to get a mile?
Click to expand...
That would theoretically be the idea but the minimum output has to be 6A x 120V so at least a 800W AC output. but ideally the max Level 1 12A x 120V for 1.44kW. Factor in the charging losses and DC->AC (battery inverter) ->DC losses (on board charger) of about 35%. If it's a super efficient 4.0+mi/kWh then you can make it to the nearest Level 2 or DCFC station, but a 1.2 mi/kWh Ford F-150 Lightning winter efficiency might take some time.

Some vehicles are equipped with 1500W 120V AC like a Toyota Sienna or the 9600W Ford Pro Power Onboard.
 
teslarati97 said:
That would theoretically be the idea but the minimum output has to be 6A x 120V so at least a 800W AC output. but ideally the max Level 1 12A x 120V for 1.44kW. Factor in the charging losses and DC->AC (battery inverter) ->DC losses (on board charger) of about 35%. If it's a super efficient 4.0+mi/kWh then you can make it to the nearest Level 2 or DCFC station, but a 1.2 mi/kWh Ford F-150 Lightning winter efficiency might take some time.

Some vehicles are equipped with 1500W 120V AC like a Toyota Sienna or the 9600W Ford Pro Power Onboard.
Click to expand...
So theoretically, in reality, I would be screwed without my AAA card or a long extension cord?
 
You must log in or register to reply here.
Back
Top