EEVblog 1507 - Mida: A surprisingly good cheap portable Electric Car EVSE Charger

Teardown of the cheapest portable electric car charger EVSE available in Australia, the 15A Mida Type 2 portable electric car charger.

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[midaevpower]

Thank you for your recognition and evaluation of our products

[AdamBakerBaker]

I do love it when you say "yankee bucks"...

[mikeselectricstuff]

Latching relays are really common in these - it's about coil heating. You'll probably find it unlatches immediately on power-up. I think I've seen one with a big cap that unlatches on powerdown

[DrTune]

As a person who works on these; with big 50+A relays the coil thermal dissipation is substantial. We definitely pay attention to the latching vs holding current and do stuff like adaptively PWM the coil after contact. PCB trace dissipation also all adds up, we have a lot of thermistors.
Also; things like UL safety tests for these can be a bit of a PITA...

[ingolfmuller]

I learned, to leave the ground wires always a bit longer, in case of a damaging pull at those cables, the 'hot' cables will disconnect first.

[Miata]

Uncommon these days to see a consumer electronics teardown that isn't shoddy or downright dangerous. Good on Mida.

[emmettturner]

As for the thermistor:

Believe it or not, they more often insist on it more for use with low amperage outlets which might not be able to safely handle sustained loads from vehicle charging. They can get hot and melt. This was contrary to your speculation so I thought I’d mention it. I have a real-world example, if you are interested:

I have two EVSEs with the exact same ClipperCreek Gen2 EVSE board inside, one running GM’s firmware with a NEMA 5-15P 120v plug and a 12A limit (bundled with the Chevy Volt/Bolt) and the other running ClipperCreek’s firmware with a NEMA 14-30P 240v plug and a 16A limit (sold as “AmazingE” brand). Only the GM firmware with the 5-15 plug has the thermistor… and it won’t work without it unless you use a resistor to bypass. I know because I found the populated PCB for $30 as a new GM spare and used it to build another EVSE, so I really have three with the same board. ;) The AmazingE unit does not have/require the thermistor/resistor because they expect a NEMA 14-30R to easily handle 16A without getting hot. A NEMA 5-15R, on the other hand, is often worn out and gets hot. Though his Volt would default to 8A on 120v my brother would routinely override and set it to the theoretical safe limit of 12A until the outlet in his garage melted. After that we converted his GM unit to 240v and gave it a NEMA 14-XX plug (no neutral to fit more receptacles).

[mikeselectricstuff]

EVSEs that ignore the diode are surprisingly common - the standards do require diode checking, but I tested one that had been tested by TUV that didn't. Strange as it's not hard to do.

[jwardell]

I have a 32A version (identical on the inside and outside, another brand, again cheapest on Amazon) and it has been charging my car wonderfully for 6 months. Love the extra display

[kataraluna]

They should also attach the ground together with a wire instead of just the board. If the board breaks it has no more ground connection. (even if its hard to break, it can happen.)

[DeKempster]

Would like to see the earth wire longer than L/N. If the cable would be janked out the earth would disconnect last

[andrewsydney]

In 2000, Australia converted to 230 V as the nominal standard with a tolerance of +10%/−6%

[kreature]

The NTC is for the input cable so it can monitor the connector temperature.
Not sure where it is mandatory but some places it is. Especially if passing the 10 amp limit on a schuko.

[marvingudel]

Hope the price doesn't go through the roof after this review, I'd definitively get one of these if I ever need one ;)

Also the rounded traces on the bottom are a real joy to look at.

[SkaBob]

Good to see easily replaceable power cables on both ends.

[txbrent]

As an Aussie who has 15A equipment in my garage, I know exactly why you may want to limit the current to

[mikeselectricstuff]

Surprising that they have the metering stuff in there, and the load current sensing - no need at all for these in a low-cost EVSE and some significant cost savings possible without impacting functionality or safety. Also the display for that matter...

[pnjunction]

Nice! I like the curvy PCB traces. Somebody had fun 🙂

[travcollier]

I love these teardowns. Cheap Chinese equipment these days can be quite good quality, but can also be absolutely crap. Nice to see the examples of manufacturers over there upping their game. Nerds taking some pride in their work

The reason for that power monitoring chip is that you have to limit RMS current and it's really hard to measure RMS current if current is not sinusoidal, which you bet it isn't, particularly when you are driving the car charger at very low load factors, down to 1kW for a 22kW charger.