Following on from something that sonicii posted in another thread about towing with a V37 hybrid, I recently had an issue with mine, and thought I'd share.
As someone else worked out, I'm not in Australia, I'm in New Zealand. A the end of August I did a road trip around the south island. Started from home in Wellington, jumped on the ferry to the South Island (Bluebridge), drove down to Christchurch, a bit of time there, down to Dunedin for some family stuff, then back up to Christchurch of the night, Picton, and got the ferry back to Wellington. Amazing road trip, a heap of fun. The cruise control + active lane control + all the other sensors made it pretty much self-drive along the Canterbury Plains. I love driving in the South Island so much more than the North Island. The car went amazing, other than 'the issue'.
On the return ferry trip back to Wellington, we looked around Picton, then driving through the port slowly, the car was running on batteries the whole time, so by the time we got to the ferry, the batteries were pretty much flat. Once we start driving up the ramp onto the ferry, the tread on the car ramps is very rough, and my poor sports suspension wasn't a fan of it, so we're driving pretty slow. Then we're directed up to the top deck, which has a pretty long, steep ramp, up past the other decks, all the way to the outside of the ship. By this stage, we're going about 2kmh, batteries are flat, car is doing that odd 'labouring the petrol engine while running on electric' that it sometimes does on the motorway on ramp in heavy traffic. As we're getting to the top of the big ramp, a caution light comes on, the display in the dash tell us that the hybrid system has over heated and we need to stop. At this point we're about 5m from the top of the narrow ramp, so all we can really do is keep going. About 5 seconds after we get to the top of the ramp, the warning lights went away, the message is gone, and everything is fine.
Now, what sonicii posted is "These cars don't have a torque converter in the transmission and rely on the low/reverse brake to act as a clutch at very low speeds (lower than idle speeds in 1st gear) and they don't like to slip for extended periods." I'm guessing that for that low speed it's actually just charging up the battery, using 100% electric for moving the car, and I can see how doing that for 5+ minutes constantly would cause things to heat up pretty quickly. Add in low air movement, and being inside a ship, this all starts to make sense.
When we headed south on the same ferry, we were on a lower deck, and were running on the electric motors for a shorter period that I don't think we ran into that issue. I've since worked out that if I leave the car in Standard, slide the transmission into tiptronic mode it pretty much makes the petrol engine behave as a stop start mode, meaning that the low speed in the dock would have used the petrol engine, so the batteries had some juice in them once we got into the ship. Also opening the drivers door with the car running starts petrol engine, but will only charge the batteries up to 50% and then stop the petrol engine; while waiting to disembark, I had the door open to charge the batteries back up.