working on a 120v fast charger. Good idea or waste of time?

[Zooomer]

I'm building myself a 120v fast charger.
I need this for going to the race track where only 110 is avail.
It could be used in condos or places where people can't install a 220 plug.

It's not super practical in mobility as it weighs a lot (from batteries) but is on wheels.
Unit works by accepted 110-120 from a single or multiple 115 outlets (on different circuits) which then feed batteries which in turn power a DC to 240AC inverter. You plug in using the cars 240 plug.

Charge speed depends on # of batteries, number of 120 sources but for my use will do the job as I show at our local track at 89%.

It could also be used for people who live in condos or apartments where adding 240 isn't an option and would allow them to charge enough to not have to add an outlet. Cost is a downside, it's expensive to make. like ~$1500 in parts but for some people could be a good option. Thoughts?

 

[compu85]

Or, just make a 2 headed box that plugs into 2 110v outlets. If you can find 2 on different legs you get 208 / 240v that you can still pull 12a against.

Only problem is it doesn't work with GFCIs.

-J

 

[Tozz]

3 things:

1. My thought is that it might be wiser to skip the conversion back to 240V AC and just go with a DC charger. Make a CHAdeMO charger out of it. This will save you the one out of 2 AC/DC DC/AC conversion losses. this adds to complexity and costs, but saves conversion losses.

2. Also keep in mind that Tesla specifically states you should not be charging the car from generators. The charger probably doesn't like nasty sinus or square waves either. So you need to be sure you have a high quality inverter with a true sinus output. Another reason is issue 4:

4. Tesla starts charging slow, and then slowly (in the course of a second or 10 or so) ramps up the amps. This allows your inverter to adapt. When charging is complete, it abruptly stops. In case of a generator or inverter this might cause a dangerous frequency peak. You should make sure there are no other appliances connected to the inverter when this happens and it might cause harm to the charging equipment (Tesla UMC)

When running a generator you can actually hear this happening. When you run a generator and you turn on eg. a coffee maker you will hear the generator adapt. It revs down for a second when you turn on the coffee maker, and it has to adapt and increase fuel injection. During that time the frequency of the output is off. Sensitive electronics don't like that.

5 . You need quite a few batteries to be able to draw a significant of power out of them. Don't know what your required charge rate would be, but to discharge 11 kW out of a battery pack you need quite a few batteries.

4. it is probably a lot cheaper to just get a 240V outlet at the location you want to use this.

@compu85's advise is risky. If the 2 outlets you are going to use are from the same leg you will:
1. Risk making a short circuit (if the polarity of the 2 sockets is reversed)
2. You break the functionality of the circuit breaker if the 2 sockets are behind different circuit breakers.

I would definitely not do compu85's advise on a property that is not yours or where there are other people. You risk lives by disabling circuit breakers or GFCI's and you increase risks of starting fires.

 

[compu85]

My suggestion does not bypass the circuit breakers. 12A is 12A, if there's too much current flowing either or both breakers will trip. The only possible fault condition would be one leg tripping and one remaining live... which will make the car stop charging.

If one outlet has the line and neutral reversed it would result in the adapter outlet only having 120v on it. The 120v neutral wires are not hooked up in the adapter.

-J

 

[NeverFollow]

I'm building myself a 120v fast charger.
I need this for going to the race track where only 110 is avail.
It could be used in condos or places where people can't install a 220 plug.

It's not super practical in mobility as it weighs a lot (from batteries) but is on wheels.
Unit works by accepted 110-120 from a single or multiple 115 outlets (on different circuits) which then feed batteries which in turn power a DC to 240AC inverter. You plug in using the cars 240 plug.

Charge speed depends on # of batteries, number of 120 sources but for my use will do the job as I show at our local track at 89%.

It could also be used for people who live in condos or apartments where adding 240 isn't an option and would allow them to charge enough to not have to add an outlet. Cost is a downside, it's expensive to make. like ~$1500 in parts but for some people could be a good option. Thoughts?

I think the concept idea of slow charging batteries in advance to deliver fast charging at a later point is interesting.

Any idea about the type of battery, number, and total capacity you plan to implement?

An other idea would be to use solar panels installed on a trailer.

I was just watching this talk with Rivian's CEO RJ Scaringe, and at 6:30 he was commenting about range issues when using EV for outdoor trips.
He was mentioning developing auxiliary batteries who can be used like a digital 'Jerry can' when going to the wilderness.

 

[ewoodrick]

I'm building myself a 120v fast charger.
I need this for going to the race track where only 110 is avail.
It could be used in condos or places where people can't install a 220 plug.

It's not super practical in mobility as it weighs a lot (from batteries) but is on wheels.
Unit works by accepted 110-120 from a single or multiple 115 outlets (on different circuits) which then feed batteries which in turn power a DC to 240AC inverter. You plug in using the cars 240 plug.

Charge speed depends on # of batteries, number of 120 sources but for my use will do the job as I show at our local track at 89%.

It could also be used for people who live in condos or apartments where adding 240 isn't an option and would allow them to charge enough to not have to add an outlet. Cost is a downside, it's expensive to make. like ~$1500 in parts but for some people could be a good option. Thoughts?

If you really know what you are doing, then good luck, hope you well.

But if you are investigating if it can be done, there are some serious drawbacks.

• If you think that plugging two plugs into a 120V duplex outlet is going to get you more power, then you may be incorrect
• If you think that a Dc to 240VAC inverter @40A is cheap, then you may be incorrect
• If you think that the "batteries" to do this is a couple of 12V car batteries, then you may be incorrect (think of a full Tesla battery)
• If you think that a 1500 watt 120V to 12V (125A) battery charger (times "multiple 115 outlets" is cheap, then you may be incorrect

Then again, a car already has essentially all of the parts, so if you can get the chargers, inverters and batteries from a junked car, then you may have a solution. Just have to make sure that you have all the control circuitry to enable all the parts and pieces.

Good luck in your endeavor.

 

[dhrivnak]

I am having a hard time seeing where such a setup would be of much value. If it is big and heavy the it would not be portable. And for home use it seems like a 240V outlet would be cheaper.

 

[Zooomer]

I don't need advice on the technical aspect of this. That's pretty easy.
Can be as simple as 10/2/50 Amp 12V Manual Charger With Engine Start
or DC 12V 5A 10A 15A 20A 30A 50A Regulated Transformer Power Supply For LED Strip | eBay
or even 12V 10A 10amp 120W DC POWER Supply ADAPTER Transformer for LED Strip, CCTV, PC 1 696277847891 | eBay
Literally any plug in 12volt output device will work. If you use something shitty, you have to make sure you have circuitry to not overcharge the batteries.

If you have 4 cords as example and you run them all on a power strip, all you're going to do is trip a breaker. Same with anyone plugging too much stuff into any outlet.

The batteries can be anything you want. Car batteries are cheap but heavy. Li Ion is expensive but a Tesla 24v cell module is about right at 5.3KW and weighs just over 50#.

The batteries are configured for correct voltage into the 240 volt output. I'd use a battery backup. Power is discrete and clean.
Somethings like an APC or Triplite UPS meant for computer systems.
------Anyway, that's the technical aspect of it which will work. I didn't want to muddy the thread with the details and assumed people knew I wasn't just randomly trying to ruin my car and start fires.

Tozz, you're right, it would be better to DC charge but I wasn't aware Tesla allowed you to do that. I'll do some research. If you have something LMK. It would eliminate a lot of cost and add efficiency.


Finally for those wondering, I'd say average would be two inputs as most people can find two separate circuits. Rather than charging 12 hours at home and adding 13KW in that time, My device would allow you to add over 30. Enough for most people to daily drive where 13 is not.

Also, I need this for racing. I need to add as much as I can in around an hour (between runs). The 120 outlets don't cut it. I could buy a gas generator and throw that in the back of the car and run it to charge the car but I'd look like a giant tool and suffer endless mockery from the ICE vehicles. Would defeat the point of bringing an electric to the track and having people be impressed. They already think the bat will be dead after a few passes. (uses about 2%)

 

[SigNC]

What in the world kind of race track are you going to that only has 120v outlets?

 

[Zooomer]

• If you think that plugging two plugs into a 120V duplex outlet is going to get you more power, then you may be incorrect
• If you think that a Dc to 240VAC inverter @40A is cheap, then you may be incorrect
• If you think that the "batteries" to do this is a couple of 12V car batteries, then you may be incorrect (think of a full Tesla battery)
• If you think that a 1500 watt 120V to 12V (125A) battery charger (times "multiple 115 outlets" is cheap, then you may be incorrect

-if the 120's are on separate circuits you can use as many as you want. Beauty of a scale-able system.
-a used UPS w/o batteries is reasonable. Most standard inverters are too dirty for this.
-car batteries are the lowest cost but they become weight restrictive at 3x of li ion per KW. I like the 52# Tesla packs at 5.3KW. You could do 4 car batteries at 100-200# for way less $ and get similar results. They are easier to charge too.
-You'd use smaller ones in parallel. w/o much research under $2/amp. US $16.02 44% OFF|Full Automatic Smart 12V 10A Lead Acid/GEL Battery Charger w/ LCD Display US Plug Smart Fast Battery Charger Auto Accessories-in Battery Charging Units from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group If you get to $1/amp (12w) and want to do 1400 watts per, you're at $120 per circuit.

What in the world kind of race track are you going to that only has 120v outlets?

https://us131msp.com/
I've also gone on road trips where the place staying only had 110. that's happened a lot.

 

[bedoig]

I have no advice I can give you, but would love to see how this turns out. Please do keep us updated.

 

[SigNC]

-if the 120's are on separate circuits you can use as many as you want. Beauty of a
https://us131msp.com/
I've also gone on road trips where the place staying only had 110. that's happened a lot.

https://us131msp.com/pit-area-upgrade-keeps-us-131-on-the-cutting-edge/

 

[mspohr]

I don't need advice on the technical aspect of this. That's pretty easy.
Can be as simple as 10/2/50 Amp 12V Manual Charger With Engine Start
or DC 12V 5A 10A 15A 20A 30A 50A Regulated Transformer Power Supply For LED Strip | eBay
or even 12V 10A 10amp 120W DC POWER Supply ADAPTER Transformer for LED Strip, CCTV, PC 1 696277847891 | eBay
Literally any plug in 12volt output device will work. If you use something shitty, you have to make sure you have circuitry to not overcharge the batteries.

If you have 4 cords as example and you run them all on a power strip, all you're going to do is trip a breaker. Same with anyone plugging too much stuff into any outlet.

The batteries can be anything you want. Car batteries are cheap but heavy. Li Ion is expensive but a Tesla 24v cell module is about right at 5.3KW and weighs just over 50#.

The batteries are configured for correct voltage into the 240 volt output. I'd use a battery backup. Power is discrete and clean.
Somethings like an APC or Triplite UPS meant for computer systems.
------Anyway, that's the technical aspect of it which will work. I didn't want to muddy the thread with the details and assumed people knew I wasn't just randomly trying to ruin my car and start fires.

Tozz, you're right, it would be better to DC charge but I wasn't aware Tesla allowed you to do that. I'll do some research. If you have something LMK. It would eliminate a lot of cost and add efficiency.


Finally for those wondering, I'd say average would be two inputs as most people can find two separate circuits. Rather than charging 12 hours at home and adding 13KW in that time, My device would allow you to add over 30. Enough for most people to daily drive where 13 is not.

Also, I need this for racing. I need to add as much as I can in around an hour (between runs). The 120 outlets don't cut it. I could buy a gas generator and throw that in the back of the car and run it to charge the car but I'd look like a giant tool and suffer endless mockery from the ICE vehicles. Would defeat the point of bringing an electric to the track and having people be impressed. They already think the bat will be dead after a few passes. (uses about 2%)

Interesting idea.
If 5 kWh (or 10 kWh if you use two modules) would be enough for you to top off your battery between runs, this could work.
The Tesla battery modules are 24v so that would work with a 24vDC to 240vAC inverter... provided you can find one to put out 5 or 10 kW.
If you can find two 20 amp 120v circuits, you could run them at 15 amps each continuous and get 3600 Watts from them to supplement your top up charge as well as recharge the battery. You would need to find 24vDC battery chargers but that shouldn't be a problem.
Interesting project. I can see other uses for it such as emergency/remote charging. I believe that VW announced that they were going to have a battery powered remote charging station similar to what you are designing.

 

[DonTom]

2. Also keep in mind that Tesla specifically states you should not be charging the car from generators.

That is because most people do not know how to check the waveform. I charge my Zero electric motorcycle from my RV generator when I am boondocked in a place that has no electricity. Some generators are really bad. Mine is very reasonable.

Here is my RV Onan 4KW generator's waveform, which is under load:

Here is what you do NOT want to see:

-Don- Reno, NV

 

[DonTom]

120v fast charger.

Sounds like an oxymoron to me.

What is "fast" ? Several days?


-Don- Reno, NV

 

[Sophias_dad]

So, lets suppose you wanted to make this thing out of a relatively large standard automotive battery like BCI group 35.

It stores 44 amp-hours at 12 volts, or about 528 watt-hours. So, in order to feed your hungry Tesla 10kwh, one time, you'll need an array of 20 such batteries. Have you done the math on the cost of such batteries?

Trying the golfcart battery approach, I see a 6 volt x 225 amp-hour battery for $279, it'll give you 1.35kwh each, but you'll still need 10 of them to get to 13.5kwh, again ignoring transfer losses. These batteries are 77 pounds each, so there's 770 points of batteries for you...

I have also neglected to check maximum sustained discharge rates. I bet if you ask for high output for either of these for a sustained(minute or five) period, you'll have a very bad day. That's probably more of a problem for the car batteries.

It will likely be cheaper to pay to have a 240 volt line installed.

Do let us know how it turns out.

 

[Cosmacelf]

It will always be cheaper just to install 240V receptacles. Any track is going to have lots of electrical panels around. It would be easy to add a 240V, 50A plug below a random electrical panel. $50 in parts. Couple of hours of labor.

Also, many tracks are going to have 240V receptacles for welders.

 

[Zooomer]

So, lets suppose you wanted to make this thing out of a relatively large standard automotive battery like BCI group 35.

It stores 44 amp-hours at 12 volts, or about 528 watt-hours. So, in order to feed your hungry Tesla 10kwh, one time, you'll need an array of 20 such batteries. Have you done the math on the cost of such batteries?

Trying the golfcart battery approach, I see a 6 volt x 225 amp-hour battery for $279, it'll give you 1.35kwh each, but you'll still need 10 of them to get to 13.5kwh, again ignoring transfer losses. These batteries are 77 pounds each, so there's 770 points of batteries for you...

I have also neglected to check maximum sustained discharge rates. I bet if you ask for high output for either of these for a sustained(minute or five) period, you'll have a very bad day. That's probably more of a problem for the car batteries.

It will likely be cheaper to pay to have a 240 volt line installed.

Do let us know how it turns out.

Any battery discharging over an hour is not a fast discharge. No issues there.
Your calcs are off because you're not assuming a feed from 2 or more 120v sources, 2.8KW or more.

For lead acid I'm trying this Alphacell 12V VLRA Battery 3.5HP. It's ~1KW and weighs ~65#. Capable of WAY more discharge rate than what I need (800 amps). 2 in series for proof of concept. Bats I got for $100/ea. To last an hour, 72 amp discharge, less than 10% of rated max. But for cost effectiveness, a Tesla 24volt module of 5.3KW would be best. Those are ~$1200. 1x Tesla Model S battery module, 24V, 250Ah,5.3kWh, Panasonic 18650 3200mAh cell | eBay

It will always be cheaper just to install 240V receptacles. Any track is going to have lots of electrical panels around. It would be easy to add a 240V, 50A plug below a random electrical panel. $50 in parts. Couple of hours of labor.

Also, many tracks are going to have 240V receptacles for welders.

That's just factually not true.

 

[Sophias_dad]

Your calcs are off because you're not assuming a feed from two 120v sources, which would be approx 2.8KW in an hour.

No, there's no 120V involved in the capacity of a battery, unless I suppose its a 120V battery! It doesn't matter how fast or slow they charge, they can store only so much power, in this case volts times amp hours equals watt hours.

 

[Blup85]

DC solar does this. seems like they are just off the shelf components. tow it with the 3.. lol
Products | DC Solar Solutions

They had offered my City 10 of them around town as remote charging stations. We are still chatting about it..