Is 40 twice as fast as 20?

[Fisher99]

I understand that filling up the last 20% of a battery is slower than the first 80%. My question is this: Would a 40a circuit and EVSE perform that first 80% charge twice as fast as my current 20a circuit and TurboCord EVSE? Turn 4 hours into 2 hours? Is it simple math or are there mitigating factors?

 

[skeptic]

For level 2 charging, the i3 can charge up to 32A. Not sure what your current charger supports, probably 16a based on a 20a circuit, so you at likely looking at roughly half the charging time.

 

[eNate]

Adding to what skeptic wrote, yes, the charging time vs. wattage plot is generally linear, especially at the lower charging levels.

The tapering its most noticeable at DC fast chargers, which is where you see the battery temperature peaking.

On my most used scenarios, my 12A charger was a constant 3.5% per hour, my 16A L1 reliable provides 5% / hr., and 16A @ L2 tracks at 10% /hr. (94Ah battery)

I've rarely used 32A Level 2, so can't comment if it warms the battery enough to affect the top-end rate, but it ought to be 20% per hour at least to 80 or 90%.

 

[alohart]

Is it simple math or are there mitigating factors?

A mitigating factor would be charging with a battery pack warm enough to require cooling. The power required to run the A/C compressor would subtract from the power remaining to charge the battery pack. This is more likely when charging at higher power. So one might be able to charge at 16 A without cooling whereas charging at 30 A would require cooling (I've never read of anyone seeing more than 30 A). The battery pack in our 2014 BEV rarely needs cooling in our warm climate when charging with our 208 V 16 A EVSE.

 

[Fisher99]

Excellent info! Thanks Guys. Exactly what I was looking for!

My son just bought a nice, used, e-Golf and I'm debating giving him my TurboCord and buying a 32a EVSE for myself. But truthfully, while charging twice as fast is enticing, the TurboCord is meeting our needs. I'd be cheaper by far to just buy him a TurboCord and keep mine....

 

[jadnashuanh]

Newer vehicles tend to get larger batteries. Many of them can handle more power coming in. Some can handle 60A or so. At this point, on ACV, the most I've seen is 7400W on any BMW, but there are new ones coming out in about a year that probably will be able to handle more, and 7400W requires 232vac at 32A to achieve. Power=volts*amps. My typical input voltage is about 247, but it could be a bunch lower, and commercial units in the USA may be using 208vac. Each would result in a different amount of power going to the vehicle at the same amperage.

An EVSE sends a signal announcing to the vehicle how many amps it has (this is voltage independent), and then the vehicle decides how much it wants to draw.

Is your TurboCord 120 or 240vac? I've heard of it, but am not familiar with its specs. Note, the power supply IN the vehicle that converts the ACV to DCV for the batteries is less efficient at 120vac than it is at 240vac, so you'd save some money on that lost efficiency by upgrading to a 240vac EVSE, if that's the case.

It really depends on how fast you want to refill the battery, how much you're willing to pay, and somewhat, on how much spare capacity you have in your panel as upgrading that can add a whole bunch of costs if necessary. Last, is maybe how far and how difficult it will be to get power to your EVSE, as bigger copper wire starts to get expensive, and the labor to get it there might also be as well.

 

[Fisher99]

My TurboCord is 240v, 16a. When I first bought the i3 I kept a spreadsheet tracking charging rates with the 110v OU charger and then the TurboCord after I purchased it. The TurboCord is reliably 3+ times faster than the OU charger. A significant improvement for a reasonable cost of about $175.

 

[jadnashuanh]

Makes sense...240*16=3840W versus 120*10=1200W. Throw in the fact that 240vac is more efficient, and easily 3x faster. Since the i3 can handle nearly twice that, though, a 30-32 or larger unit would double that yet again.