How to figure out how long it takes my car to charge?

[nkane]

Whether it takes 8, 12, or 15 hours to get a full charge will matter quite a bit for which electric rate plan I choose, and also whether it's worth it to invest in a level 2 charger. Is there a way to see how long it's taking to get to full charge? I looked through the MMCS and PHEV watchdog (I have an ODBII thingy) and haven't found it yet.

Thanks!

 

[ThudnBlundr]

It's quite simple. The car takes roughly 9kWh to charge when it shows empty. Divide 9 by your charging power and you have a rough figure for the number of hours. You need to add a bit as the rate slows near full. We charge at 3.6kW at home, so it takes less than 3 hours. The granny is 2.5kW, so you're looking at more like 4 hours

 

[nkane]

Huh. So we have weak 120V plugs here in the US and the charging brick always says it's charging in 8 amp mode.

Plugging those into an online calculator (https://www.inchcalculator.com/amps-to-kilowatts-calculator/), that gives charging power of .96 kW.

According to your formula, that would be 9.4 hours, plus a bit due to slowing at the end.

This online calculator says 10.25; not sure what assumptions they're making that are different. https://www.inchcalculator.com/electric-vehicle-charging-time-calculator/?capacity=9&power=.96&current_charge=0&target_charge=100

I'd love to measure charging time, though, not just estimate it! At least in a way that doesn't require waking up every hour overnight.

 

[ThudnBlundr]

The car has an overhead power consumption to run the onboard computers while charging. While the power required is small, charging at less than 1kW means it becomes quite significant, hence the extra time required

 

[angainor]

The explanation of how they computed the result is lower in the page. This is what they write:

In other words, the time it takes to charge in hours is equal to the size of the battery in kilowatt-hours divided by the charging power times .9, which is the average power efficiency.

The charger also has it's losses (heat), which are here estimated to 10%. Also, except for slowing down at the end I've noticed that after a slowdown the charging accelerates again, and slows down again. So I don't think there is an easy way to give you an exact number.

Also, if you want to be really precise, you have to take your actual battery capacity and not 9kWh. Mine is currently around 7.5, so that would theoretically give you faster charging. Although not sure that's so good in this particular case.