nuggetgalore wrote: ↑
Wed, 22 Nov 2017, 18:55
Hi all iMiEV wizzards.
I'm not an iMiEV wizard at all, but none seem to have answered so far.
Because the 2010 iMiEV (at least mine) charges with 12.5 A, I use an Ampfibian when I charge at a friends place to legally plug it into a 10 A power point. It works but I have to reset the Ampfibian several times as it trips sometimes after ten minutes, sometimes 30 minutes.Not consistent (could be temp has an influence).
The Ampfibian doesn't magically cause the car's charger to draw less than 12.5 A. So my understanding is that the Ampfibian is correctly disconnecting the excessive load. But because it's marginally excessive (it might not always be 12.5 A, especially with Australia's notoriously high mains voltage), it takes some time before the over-current breaker finally trips. This is safe, because house wiring can tolerate a slight overload for a period of time; it just isn't guaranteed to tolerate it continuously. I believe that a typical 10 A outlet can supply more 10 A safely, as the active and neutral pins of a 10 A plug and socket are the same size as those of a 15 A plug and socket (only the size of the earth pin changes), so that's not an issue for occasional use.
Is there a danger to hurt the battery (unlikely)
No. The battery is used to seeing much more than 2.9 kW (12.5 A x 230 V) of charge power during regenerative braking, and of course it sees some 50 kW of discharge power during acceleration.
or the charger (more likely) ,if the charger gets reconnected soon after it was disconnected? Soon after, how soon if it was the case?
I don't know anything about the iMiEV charger, and I suspect that few people outside of Mitsubishi in Japan know either. However, it's reasonable to guess that the charger follows the same general principles as most high frequency power conversion equipment. In particular, there is sometimes an NTC (Negative Temperature Coefficient) resistor in series with the incoming mains. All that does is to make the initial current surge into the charger of less magnitude. That causes less stress on the components. The current through this resistor causes it to heat up, and this causes its resistance to decrease (most normal resistors would do the opposite). The lower resistance causes the NTC to have little influence after the first second or so of operation; by that time it's done its job. When you stop charging, the NTC cools down, ready to reduce the current surge the next time the charger is used.
But this assumes normal operation, where there would usually be many hours between uses of the charger. If you turn the power back on after only a few seconds, for example in the scenario you describe here, then the NTC may not have cooled down to near-ambient temperature, and so may still be rather low in resistance. This may cause the next turn-on surge to be of higher current than normal, which could stress the input capacitors and other components. My guess is that the NTC would have cooled down sufficiently after about 10 seconds, and certainly after a minute. These things are about the size of a five cent coin, except thicker, perhaps three coins stacked.
Having said all that, the iMiEV charger is likely to have a special input stage called a Power Factor Correction (PFC) circuit. These work a bit differently to the cheaper power supplies, and these typically don't have an NTC for surge protection. However, there are still large capacitors in such chargers, just that they are located after the PFC stage. Elcon and TC chargers for EVs are like this. Instead of the NTC, they have an input relay that shorts an ordinary resistor soon after power is applied. This allows the PFC stage to gently charge the large capacitors. So the operation is much the same. However, this time, the relay is powered by a small power supply that can operate over a wide range of voltages. What this means in practice is that the input relay won't drop out until some 30 seconds after the power is disconnected. It takes that long for the large capacitors, that are sized for powering multiple kilowatts for a fraction of a second, to discharge through the quiescent current drain in the charger (typically only control circuitry and the input relay). Until that input relay drops out, it's much like the situation with the NTC not having cooled down enough; the next connection could be quite hard on the input capacitors and a few other components, as the contacts of the input relay have essentially zero resistance.
Bottom line: there will be some sort of pre-charge circuit inside the charger, and the details vary widely. So it's difficult to put an exact time on how long to wait before re-applying power. However, it should be safe to re-connect after about a minute.
I'm sorry that the explanation ended up so long.