EV - DC home charger

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#2840735 31-Dec-2021 09:47

RobDickinson:

https://pod-point.com/guides/vehicles/hyundai/2021/ioniq-5

According to that the ioniq 5 is 11kw on 3 phase. Just like any ev over 7kw would be (outside of America afik).

thank you for clarifying that. I have learn't somehting valuable from that alone.

RobDickinson

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#2840739 31-Dec-2021 10:01

ShockProof:

I get the real world use arguement. Guess I just want to see what the far end looks like. My job used to be 85 km driving each day. Next job could be 125 km each day. Need to be charging five days a week to make that happen.

TBh if you are doing 125km a day any ev that will do it will save you a crapton of money vs a fossil car.

Thats about 30,000km a year for work, or about $4-5k in petrol vs about $1200 in electricity using 30c/kwh

ShockProof

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#2840745 31-Dec-2021 10:19

Obraik: Maybe it's time to find a different power provider if you're charging significantly longer than the free three hours. Meridian do an EV plan that offers a much reduced off peak rate (9c/kWh in Christchurch). It would take you a few decades of charging to get back what you spend on a DC charger just for free charging.

You could be right. I should find out what that is, what is available in my area.

I am also going to control my hot water cylinder for off-peak or free power time. Has 2 x 3 kW elements. Only starting with one element on time control (bottom one that can heat the whole cylinder). The top element on 24 hours per day. See how this goes anyway. So I need a plan that allows for cheaper electritiy while heating a HWC as well as an EV charging.

Dingbatt

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#2840746 31-Dec-2021 10:19

Edit: ref EV cost vs liquid fuel costs.

So 8 years to recover the extra cost batteries impose.

6 years if you qualify for the rebate.

5 years once ICEs get levied.

4 years once servicing costs are taken into account.

You have to want to do this for more than cost savings, but that certainly helps.

However, back to the OP. I wonder why there isn’t the option, particularly within the Tesla ecosystem to do DC charging from a Powerwall to a Car. There must be a market there, particularly if you have PV panels. Otherwise you are using an inverter to convert and then the Transformer/Rectifier in the car to convert again.

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RobDickinson

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#2840747 31-Dec-2021 10:22

DC charging would need a more expensive charging unit either in the powerwall, separate or in the car, they have AC chargers built in but not DC chargers.

Scott3

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#2840748 31-Dec-2021 10:30

Most (all?) EV's sold new in have a type 2 socket. No EV's (other than some trims of the zoe) that I know of will pull more than 32A per phase. Even with that trim of the zoe, to charge at more than 22kw (230v 32A 3 phase), required a special EVSE with a tethered cable and thermal monitoring of the socket. The ABB fast chargers in the waikato supported this, but now the New Zoe is going to DC fast charging, it is pretty much an orphan tech.

As a rule of thumb for EV's in NZ:

3.6kW AC charging = single phase, approx 16A (like my old leaf)
6.6 / 7.2kW AC charging = single phase, approx 32A (Like the kona)
11kW AC charging = three phase, 16A (Like current BMW i3, tesla model 3).
22kW AC = three phase 32A (Rare. Zoe's support this)

Most cars that support 16A three phase, also support 32A single phase (like current BMW i3's), but not all. The Merc B class, and older tesla's are examples where they could do 11kW 3 phase, but a max of 16A (cira 3.6kW) single phase. Some of the older tesla's it was possible to feed the same phase twice, to get them to charge at around 7kW.

In terms of DC charging at home, yes it can be done, and it has been done before in NZ (I know of one example a few years back where a tesla owner had one of those 25kW Delta chargers in their garage). But you definitely need a serious supply in order to support a 25kW charger. Budget for a three phase upgrade if you don't have three phase. On top of the $25k charger.

Realistically it is not worth spending big $$ to upgrade supply capacity, and buy DC chargers to optimize free power windows from power companies.

Which basically leaves you with the following options:

- Install a 32A single phase EVSE. This will replenish about 90km of range in a three hour window, and fully charge something like a 64kWh kona overnight.

- Upgrade to three phase power and install a 32A (or 16A) three phase EVSE. at 11kW this will replenish about 120km of range in a three hour window.

Unless you are some kind of super commuter, I suggest that 90km of range replenishment will cover your typical daily running.

If you are worried about overloading your pole fuse, either you can have a user reset able breaker installed on your prophet to protect it. Or you can get a EVSE with active load management, like the below. It has a clamp which goes over your main feed wire, and will slow down the car charging if you get close to overloading that.

https://oemaudio.co.nz/electric-vehicle-charging-products/ev-wallchargers/eo-mini-pro-2-wall-charger-white-active-load-management-package

Can also get setups that manage the charging to multiple cars under the same basis.

Really as long as you can recharge all (or most) of your range overnight, you are golden, little point in spending big money to charge faster at home.

I just charge my (100km range) leaf off a domestic socket at 1.8kW. A bit faster charging to top off during the day would be nice, but realistically I can pop into the the nearby fast charger if needed. Not ideal, but plenty of people cope fine charging longer range EV's on domestic sockets. As long as you can charge enough to recover your typical daily running overnight, it means you only need to deal with abnormal trips (say two back to back long day trips) via public fast charging.

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#2840750 31-Dec-2021 10:38

RobDickinson:

DC charging would need a more expensive charging unit either in the powerwall, separate or in the car, they have AC chargers built in but not DC chargers.

Not sure what your point is here? I’m not suggesting it can be done currently (no pun intended).

Of course adding a capability would cost more. But if the Powerwall acts like a DC charger, i.e. DC to DC thereby missing out two conversions on the way from the storage in the Powerwall battery to the storage in the Car battery, that must be a more efficient process.

And the clever engineers at Tesla could no doubt easily have the two communicate.

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RobDickinson

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#2840752 31-Dec-2021 10:40

But a powerwall can only do 7kw peak output, whats the point?

Dingbatt

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#2840755 31-Dec-2021 10:43

RobDickinson:

But a powerwall can only do 7kw peak output, whats the point?

Is that an inverter limitation or a thermal one?

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RobDickinson

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#2840756 31-Dec-2021 10:45

I've no idea, it just doesnt seem like a problem that needs a solution unless its involving V2G/V2H

Scott3

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#2840757 31-Dec-2021 10:47

RobDickinson:

But a powerwall can only do 7kw peak output, whats the point?

That's it's AC peak output, limited by (I assume) the size of the inverter, rather than the batteries peak output power.

DC - DC buck boost converters are much cheaper than inverters and could be sized to whatever was required (and would be more efficient than going to AC and back).

Still I'm not sure of the value offering. A powerwall is so small in capacity, it is going to be flat in pretty short order charging a big battery EV.

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RobDickinson

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#2840759 31-Dec-2021 10:50

yep , 13kwh, so if you doubled that 7kw it would be done in less than an hour for... well not much gain.

I just dont see the point.

Obraik

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#2840771 31-Dec-2021 11:26

Dingbatt:

Edit: ref EV cost vs liquid fuel costs.

So 8 years to recover the extra cost batteries impose.

6 years if you qualify for the rebate.

5 years once ICEs get levied.

4 years once servicing costs are taken into account.

You have to want to do this for more than cost savings, but that certainly helps.

However, back to the OP. I wonder why there isn’t the option, particularly within the Tesla ecosystem to do DC charging from a Powerwall to a Car. There must be a market there, particularly if you have PV panels. Otherwise you are using an inverter to convert and then the Transformer/Rectifier in the car to convert again.

Your time to recover does depend on the EV you buy vs what ICE you would have purchased. If you're buying a Model 3 but would have bought a new BMW 3 series then you're pretty much saving money right out of the gate. That obviously changes if instead you would have been happy with a Suzuki Swift.

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RobDickinson

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#2840772 31-Dec-2021 11:31

Yep the equivelant bmw ot my car is the M3, at 9.6L per 100km combined.

I've done 29,000km so around $500 in charging costs.

The M3 would be ~2800 litres of 95 octane at what $2.70? $7,500 ??

Thats if you get its stated average which is unlikely (Im using real numbers for the model 3)

Dingbatt

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#2840795 31-Dec-2021 12:49

No, I was just working off the roughly $30k it costs to have the equivalent car as an EV rather than ICE.

I thought a 5 year payback was pretty reasonable.

Edit: A Model 3 and a 3 series are about the same price and that’s where it ends. The real BMW that compares to the Model 3 is the i4, but that is $115k to $140k depending on spec.

“We’ve arranged a society based on science and technology, in which nobody understands anything about science technology. Carl Sagan 1996

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