I'm wondering if my lithium jump starter is underpowered for my car.
I recently had a flat battery and connected the jump starter. The first push of the ignition button brought the dashboard lights on but didn't start the engine. I pushed the ignition button again 20-30 seconds later and then the engine started. The engine starting sounded dirty but I can't explain why. There's been no problems since.
Is it expected & normal that I needed to start the car twice before the engine came on, or is it a sign that the jump starter is underpowered? My concern is that the jump starter will fail to start the car in more adverse conditions, e.g. a flatter battery or freezing temperatures.
Details:
I have a 2022 Toyota Prado with a 2.8L diesel engine. The flat battery read about 6V when I put my multimeter across it. The battery was pretty dead, the remote key & central locking didn't work. The lithium jump starter was a brand new noco boost GB50 1500A which says it should be good for a 4.5L diesel. As the jump starter was fresh out of the box it was only reporting about 75% charge. It was a warm winter afternoon in Sydney, about 15-20°C.