[Milkfloat]

In the early days of this forum, there was quite a bit discussion about charger efficiency. You may notice in the current mileage thread that I put in details of an incredibly fast DC charge. During that charge, the radiator fan did not come on. When I got home after a 93 mile run, the battery temperature was just about mid scale. Normally, I leave it for an hour to let heat dissipate and normalise but this time I needed the car 90 minutes later so I put it on charge as I got home. Now with 7kW AC charge, the radiator fan came on 30 minutes later. No wonder, as feeling the circulatory piping, the coolant was hot. From this, I deduce that the inverter is the biggest chunk of AC charging inefficiency. Anyone else paid attention to this?

 

[Thebriggie]

Milkfloat, interesting. Up until now I only knew that Hitachi supplied the motor and high efficiency inverter but no more details than that.

While we already know the general specs of the MX-30, Hitachi Astemo revealed this month that it is the supplier of the electric motor and inverter for the car. The motor is 107 kW and 271 Nm peak.

"The motor adopted in the "MAZDA MX-30 EV MODEL" has high output and high efficiency performance enabled by our unique technology. The compact, high output inverter is made possible by our unique double-sided direct water-cooling power module."

However given the size and weight constraints of loading the Inverter into the car (as opposed to it being built into the charger like dc charging) I assumed it couldn't be brilliantly efficient, especially with cooling required, but have never delved into that subject matter in any real depth or been able to garner any technical data online.

Alan

 

[Thebriggie]

Just found this explanation which helps me better understand the basics of the system;

To charge with an AC charger, be it a 3 pin plug, a home wall box or a public charger like the Pod Points at Tesco, you need to convert that AC into DC. That’s done in the car’s charger/inverter, which rectifies the alternating current wave by flipping the negative pulse and smoothing it out into a flat voltage. That is then sent to the DC/DC converter to boost the voltage (at the cost of current) to match the batteries’ charging voltage then finally it can be sent to the battery to charge it.

The advantage of AC charging is that it’s really pretty simple. You basically hook up mains power straight to the car – or if it’s a fast charger you might need to combine the 3 phase power the charger gets into a single high power phase, then send it to the car, but either way it’s pretty simple. The downside is that it’s not the most efficient.

Alan

 

[Milkfloat]

Alan, indeed it's an Astemo inverter/drive system. When that was announced last June, there was the oft mentioned statement that Mazda weren't committed to EV's as they had bought in the drive system! Several of us debated the %age loss in the AC charge system and the range 9 to 11% seemed to cover most views, including mine, but I hadn't twigged that most of that must be the inverter. The best way to feel the coolant temperature is to grab hold of the metal section of the feed and return pipes as they run down the back of the motor. Cool on DC charging but hot on the much lower AC charging.