[RFI] Mercedes Sprinter Charger RFI

[Jim Brown]

On 2/2/2025 4:47 PM, Jim McCook wrote:
> I just tracked a new, intense RFI source to my neighbor's brand new 
> Sprinter, about 150ft from my tower.  When he removed the charger the 
> RFI disappeared.  The RFI covers most HF bands, on 15m has broad, moving 
> S-7 peaks on my K3 (calibrated S-meter).  I assume it's an unfiltered 
> switching supply.  Has anyone had experience with such chargers of the 
> Sprinter or other electric cars?  Do Tesla chargers emit such RFI? 

My only experience is with my Tesla Model 3, which I've owned for four 
years. I remember listening for RFI from it when I first owned it, and 
don't remember hearing much, using my favorite near field probe, a 
vintage Kenwood TH-F6A talkie that has wideband RX from below the AM 
band to about 560 MHz, and detectors for AM and SSB. At that point, I 
was charging from a 120V 20A outlet.

> Are 
> analog chargers available for electric cars? 

I suspect that they are not. But most charge regulators use some form of 
pulse width modulation, so that could be the source. The batteries in 
EVs are mondo-expensive, so the companies place a very high priority on 
optimizing their life. This would likely preclude the use of charging 
systems not optimized for their vehicle, and I'd bet that for most 
vehicles, it's in the car's computer(s).

> The owner claims he needs 
> to charge constantly to avoid damage to the lithium batteries.

He may be mis-reading the manual, but maybe not. Tesla recommends that 
you leave the car plugged in, but it's far from necessary, and many 
owners of EVs have no charge capability at home. A year or so ago, I had 
a plain vanilla 240V 30A outlet installed at a convenient location, and 
charge every few days. PG&E has an EV rate plan that makes it MUCH 
cheaper to charge during their off periods, which begins at midnight, 
and Tesla allows the owner to program in a starting time. I haven't 
listened for RFI since installing that outlet.

BTW -- it's also entirely possible that the charging cable and or house 
wiring is acting as a transmitting antenna for electronics in the vehicle.

It might be worth suggesting to the owner that he look into the EV rate 
plan of his local utility.

I can confirm that Tesla sedans are relatively RF quiet, on the basis of 
the experience from a Texas ham who posted details of his install of 
first a VHF/UHF rig, and then an HF rig in his Model 3. I remember an 
observation that what RFI was heard correlated to regenerative braking, 
which all EVs use extensively. Our first was my wife's Prius, which 
she's been driving for about ten years, and into which she pours  petrol 
every few weeks.

73, Jim K9YC