[Caevlist] IEEE charging article

Mon Apr 21 14:10:02 PDT 2025

It is tempting to reuse the inverter power section, and at first looks valuable. I even have a couple Roaster inverters here from 2008 that do that. But there are costs due to the increased isolation required and the massive capacitance between the HV bus and the vehicle chassis ground plus the high current switches required to disconnect motor phases. Then you have a poorly optimized charger making a lot of EMI. Motor controllers usually optimize to different power devices than chargers running soft switching. The higher frequency chargers are cheaper and smaller to filter for EMI.
My understanding is that when you balance those things it’s cheaper and more reliable to use a dedicated isolated on board charger. 
Happy to go into more detail about it at the next gathering. 

Otmar Ebenhoech

2255 SE Crystal Lake Dr.
Corvallis, OR 97333
cafe.electric at gmail.com
Shop Voice and TXT 541-862-1606

> On Apr 21, 2025, at 11:43 AM, Lawrence Winiarski <lawrence_winiarski at yahoo.com> wrote:
> 
> ** Ouch **??  Is that a metaphorical or real reaction?
> 
> My hybrid and all my solar inverters already test for isolation and fault the contactors if isolation doesn't exist.   I thought that was common.   But trusting my life on it...that I'm not so sure.   I mean I think the isolation transformer is a good thing.
> 
> But isn't the point about making the car's inverter be capable of doing the charging something worth considering?   I mean the cars drive circuit is designed for hundreds of amps bidirectionally you've got essentially a giant DC battery charger (while regen'ing).  Would it be so bad to figure out a way to use this as the main charger?   Since it's basically taking the output of a 3 phase generator (the motor) and charging the batteries with it...couldn't the external charger be modified to provide 3 phase in such a way as to replicate what the car is doing through regen?    That sure, at the face of it, might seem to be a path to make everything much simpler.
> 
> I'm certainly not a power engineer, but I think I see why it might seem attractive to make the car's inverter do double duty.
> 
> -- If we don't halt population growth with justice and compassion, it will be done for us by nature, brutally and without pity - and will leave a ravaged world. Nobel Laureate Dr. Henry W. Kendall 
> 
> 
> 
> On Monday, April 21, 2025 at 09:56:54 AM PDT, Otmar Ebenhoech <cafe.electric at gmail.com> wrote:
> 
> 
> Oh Ouch! As a former power electronics engineer that’s painful to read. 
> More misguided well intentioned musings missing the mark. 
> 
> Wally and Alan have been trying to make non-isolated charging practical since the 1990’s when AC propulsion patented “Reductive” charging in the T-Zero. It has many complications and vehicle side costs that they don’t mention (Tesla moved away from it quickly after the Roadster charging issues) They seem to be stuck in a concept that has not proven viable. 
> 
> Fortunately they are also way off on their estimate of $300/kWh for isolation. They may be correct for the small manufacturers, but not the leader. The whole systems, including dispensers and power equipment is closer to $180/kWh today trending toward $80/kWh. 
> 
> Clearly, Wally and Alan are not aware of how the leader in low cost EV fast charging, which is also the most reliable and largest network (That would be Tesla of course) does it. 
> 
> "Recent estimates indicate that the average equipment cost per Tesla Supercharger stall in the US is approximately $40,000 to $45,000. This figure comes from statements by Tesla’s Director of Charging North America, Max de Zegher, and is supported by various reports and posts on X. For instance, a 2025 article from evchargingstations.com <http://evchargingstations.com/> notes this range for current Supercharger stalls, with expectations that the upcoming V4 Superchargers could cost less than $40,000 per stall despite higher power output (up to 500 kW).” -Grok3
> 
> Here’s hoping the others stop reading articles like this, satisfied with small gains and instead start studying the leader so they can better help accelerate the worlds transition to sustainable energy. 
> 
> 
> -Otmar
> cafe.electric at gmail.com <mailto:cafe.electric at gmail.com>
> 
> 
> 
> 
>> On Apr 21, 2025, at 9:09 AM, Brent Myob <brents.comcast at comcast.net <mailto:brents.comcast at comcast.net>> wrote:
>> 
> 
> There is an article in the current issue of Spectrum about how to lower the cost of fast charging. You engineers might be interested. I thought it was well written so that it even made sense to a software guy like me.
> https://spectrum.ieee.org/ev-charging-2671242103?utm_source=dhtml_image&utm_medium=hp&utm_campaign=sp-ev-charge&hp_pos=11 <https://spectrum.ieee.org/ev-charging-2671242103?utm_source=dhtml_image&utm_medium=hp&utm_campaign=sp-ev-charge&hp_pos=11>
> Of course with the approaching pole shift our electrified fantasies might be all null and void but we got to keep the illusion of hope alive, right?
> Best wishes,
> Brent
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