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How I charge – intro to the BMW OUC (Occasional Use Charger) included with the BMW i3 and i8

Many electric cars are supplied with some kind of included charger to allow the car to be charged from a regular mains power supply. BMW term theirs the ‘OUC’ – the Occasional Use Charger.

Regardless of the name, the included BMW OUC unit has become my daily charging solution for my BMW i3. I’ll explain more about why and how in another post, but for now I’ll focus on this little unit in a bit more detail.

More about the BMW charger

The BMW OUC is an EVSE. That’s enough acronyms for one sentence! What’s an EVSE? Well ‘Electric Vehicle Supply Equipment – a pretty general term for an EV charger.

More specifically, the charger BMW includes is best considered a Portable EVSE, and it’s designed to be bundled up and thrown in your front-trunk in case of needing a charge while on the road, and without a faster charging source.

Either way, I’ll just call it the BMW portable charger, or the charger, from here out.

One one end you have a regular mains power cord, taking 240V / 10A from your home power supplier. This is about as much power as an electric heater, and the cable is around 2 metres long.

On the other, you have a thicker, more durable cable and J1772 connector that plugs into the car. This cable is around 3 metres long, so all up you get about 5 metres of total cable range from your plug to the vehicle.

The lights on the front of the unit show you what’s going on – usually you’ll see orange (all plugged in and working and ready to charge) or green (charging OK).

The cable has a hefty warning label, with one of the warnings clearly offering a recommendation not to use the BMW portable charger as a ‘primary charging solution’, and not to use an extension cable.

I read the ‘primary charging solution’ comment as recommendation, not a directive. As for the extension cable, I personally see that as some arse-covering to ensure folks don’t use poor quality cables or overloaded extension blocks. You may see it differently, and don’t take my word for it.

How fast does the BMW portable charger, charge?

The charger is capable of charging only up to 1.92kw (240V at 8A = 1920 watts), i.e. less than the maximum a regular home socket will output which I understand to be 240V at 10A.

By comparison, the ChargePoint charger at my local Stockland or Westfield will charge the i3 around 3.5x faster.

At this rate, I can charge the i3 at about 25% of the total charge every 3.5 hours. The car sees around a 120-40km range, so that’s around 35km every 3.5 hours or 8-10km of real-world driving for every hour on charge.

This is fine given how we use our i3 – it’s a second car making frequent, local and lower distance trips. The school run is the longest, at around 45km total return – this pattern of charging is just fine for our usual needs.

I am also lucky enough to live close to two chargepoint options as a faster charge backup, which is helpful – but I use these far less than I thought I would when we bought the i3.

Can you use the BMW portable charger with an extension cable?

As I mentioned before, the unit’s warnings say not to.

If, by extension cable, you mean a cable that’s also powering other appliances then of course not, because the BMW charger is going to already be drawing the maximum power a household socket is rated for.

However, if you are just looking to extend the run of the cable, then I personally have found that using a cable that’s rated for 10A and is heavy duty has worked fine for me.

I am also plugging our cable and charger into a weatherproof, durable outdoor socket which gives me some more comfort.

Can you use the BMW portable charger as a permanent charging solution?

Again, the unit has a recommendation not to.

However, before I decided to use the OUC more heavily than recommended I did a bit of research through a number of Facebook Groups and forums and found many people using the OUC on a daily basis. This gave me comfort that I could do the same before purchasing the i3.

The community advice I received was to keep a close eye on the socket, and check the wall area around the socket frequently the first few times you charge to make sure your home’s wiring can handle the power being pushed through to the charger for an extended period without over-heating.

But note, I am not an electrician and every home and user’s circumstances are different, so do your own research and get your own advice.

Our i3 is usually charging at home for a few hours per day, during the day, when people are home. I have even timed the switch the i3 charges from to go off overnight for safety reasons – I don’t want anything going wrong when we’re all asleep. I am being conservative!

All up, I have now been using the BMW portable charger for six months with no issues.

Summing up

I believe a replacement from BMW would retail for around $750, and a similar product from an independent supplier would be around $500, so they are a useful and valuable piece of kit which I am glad is included with the vehicle.

If you buy a used BMW i3 or i8 (I wish) then you too should receive a unit like this with the car to enable you to charge from a wall-socket at home or elsewhere.

Before I bought our i3, I tested the OUC with the car on loan from the dealer to get a feel for how to charge it at home. I’m still a bit nervous (I am risk-averse, OK!) about using it day-to-day, however…

  • We never really need to charge the i3 from less than 50% charged
  • It’s always done during the day with someone at home and awake
  • I check the cables and unit once every couple of weeks while charging to make sure nothing is getting too hot or there are any signs of something untoward

I looked into installing a permanent home charger, but we are in a rental house so this felt like money down the drain if it wasn’t essential. I was keen to try the BMW-supplied charger, first.

I didn’t think it would end up being a more permanent charging solution, but 6 months later I’m still using it every day and it’s working well for us, and hopefully it could for others too.

Keith enjoys nerding out about Electric Vehicles, owning a BMW i3, Tesla Model X and now, running Drive Zero .