Solar Powered Supercharger

[Zrockguy]

So I’m am in the planning stage of building a massive 100kwh battery supercharger system for my Tesla in my garage. I am looking at using lifepo4 A123 cells due to the longevity and cold weather usability.

Looking for about 50kW output at 48v about 1000amps

My question is what do I need between the battery and the Tesla charge cable, if anything at all.

Solar Panel’s —> MPPT Controller —> Battery —> ??? —> Tesla plug cable

 

[harrisonpatm]

Solar Panel’s —> MPPT Controller —> Battery —> ??? —> Tesla plug cable

220v Inverter. However, you said 48v at 50kw. Unlikely you're going to be able to find an inverter in that power ranger.

 

[gromike]

If you plan on doing this DIY, good luck. I suggest you study the applicable NEC for your jurisdiction first.

 

[Zrockguy]

I was thinking I didn’t need an inverter, due to Teslas capability to charge from DC Power.

 

[amberwolf]

Is the tesla dc charge source at their stations current-controlled by electronics in the station?

If so, you require a current-limiting conversion device (usually a DC-DC) between the battery and the charge port output.

Otherwise you have a battery with an "unlimited" current output, and if there's nothing in the car itself to do this limiting and conversion from the DC source (whcih it definitely does have in it's charger from the AC source), then as soon as you connect the battery DC source to the car it would have current limited only by the resistance of the wires and connector contacts. This *should* blow fuses in the car's protection system (but then you probably have to take it to a dealer to have those replaced unless you can do this work and it doesnt' void your warranty). But it could damage contacts in the charger/car connectors at the initial connection; you might even get an arc flash if the voltage difference is high enough.

If the car has it's own internal DC-DC then yhou don't need this, but if it doesn't, you do.

 

[dominik h]

There is no car that will charge from 50Vdc.
These DC-superchargers ask the car which voltage and current it can be charged with and then provide this.

Cheap chinese 30kw DC charging stations cost 5000Usd

The easiest thing is AC-Charging.
There you can buy standard Solar Inverters that provide enough AC Power.

 

[jonescg]

Why do you need to charge your EV so fast? I charge my EV at 3.6 kW on a sunny weekend and never need more power than that.

 

[bananu7]

For 50kW _output_ the easiest way would be to slowly charge the batteries to a really high voltage (slightly above the desired car battery level) and then use a buck converter current source for efficient transfer to the car's battery. Otherwise you'd need to boost the battery voltage up to charge the car during charging and that will be a bit more inefficient.

Conversion to AC just to convert back to DC at such powers is going to be impractical, to say the least.

 

[harrisonpatm]

Conversion to AC just to convert back to DC at such powers is going to be impractical, to say the least.

I agree with you. And yet, depending on which model Tesla OP has, battery voltage could be 350-800vdc. So you're suggesting an 800-900vdc solar system, and an 800v buck converter, and a solar battery pack voltage of 900v. Once you start looking at the availability and cost of equipment in that price range, you may be rethinking your definition of 'practical.' Oh, dnd even if one were to decide to go that route, you would then need to hack your car's communication protocol to enable direct DC charging. Maybe it's easy, I personally haven't researched it, but I doubt Tesla makes it easy.

Let's say all that is overcome, and someone is fine with building a 900v home battery pack and hacking their Tesla to accept output from an 800v buck converter, so they can charge at 50kw. Big assumption, but okay. Even if that happens, you would be wanting 50kw of solar to replenish your battery! OP stated a goal of a 100kwh battery, which would be depleted in 2 hours at 50kw of charging. How long would it take to recharge that battery? 50kw of solar panels, assuming 400w panels... that's 125 panels. That's also assuming constant even sunlight on all of them...

Anyway, all I'm saying is while the idea is technically possible, and I would genuinely love to see someone do this, it's really not worth it: time, resources, space, equipment, money, just to shave a few hours off charging times.