Electrically Challenged

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Joined
Apr 30, 2015
Messages
17
Location
Bay Area
Ok searched around and can't find answer for this question, I apologize if it's not the smartest of questions ;-)

To go from 0% to 100% is there any electric bill price difference between a 110 volt charger or a 240 (or is it 220) 30 amp charger? All other things being equal.

So in my feeble mind what I'm wondering is since the 240 charges significantly faster is it cheaper to get the same charge level or does the 240 pull more "power" and so costs more per minute of charge?

We are renting now and so can't install a 240 but have bought a house I am being given a free brand new 240 volt 30 amp charger from VW, long long story why.

So I'm wondering if it is somehow cheaper as regards our electric bill to stay on 110.

Thanks and sorry for being dense,
Kevin
 
The only sure way to make the 120V charge cord charge your car more expensively than the 240V is to let it go too many hours so it runs over your Off-Peak electric rate time window.

Tesla-based cars like the Model S, RAV4 EV, and M-B B-Class have liquid cooling for the battery and on-board charger. Running the liquid pumps for many extra hours when charging on 120V makes the efficiency noticeably lower such that you pull more kWh from the wall to add the same amount of kWh to the battery. In cold weather, the Model S uses a significant amount of energy to warm the battery during charging too. If it's cold enough (like 0 F), the battery may lose energy even when plugged into a regular 120V outlet.

I don't have sufficient data about the e-Golf to make similar statements about it.
 
The 240V charge is more efficient. There is an overhead cost in the on-board charger that's a higher percentage at low charging rates than higher charging rates.

Say it's a 200W overhead. (example number. I don't know the actual overhead). 200W is a bigger percentage with a 1.5 KW EVSE than a 7.2 KW EVSE.

And, as miimura says, if you go long enough on a Time-of-use rate to go into high rate, that costs more.

But a kWh is a kWh, and is charged as a kWh whether you're drawing 2 or 7 at once, assuming your panel and wiring is up to spec.
 
Beyond the theoretic overhead and going into a different rate period/rate tier, there is really no $ measurable difference between charging with a 120V or 240V charger (let's forget about pennies here). The only real difference to the average Joe is that the 240V charger will charge much more quickly than the 120V charger.
 
Best way to think of this is like water.

Your cars battery is a bathtub.
You fill/charge it with a hose.
The water pressure feeding the hose is the voltage
The flow of water in the hose is the amps (amperage)

PG&E charges you by the bucket full of water

With high voltage/ high pressure (240V) the flow in the pipe will be quicker. But you still get charged by the bucket full.

Hope that helps

Barry
 
In the hose analogy, the current is the diameter of the hose.

I think there is a small improvement in efficiency to use a 240V EVSE vs a 120V. The charger in the car has lower loss mostly because of the shorter time, but also because of the higher input voltage. This is also true of computer power supplies - there is a ~2-4% improvement in efficiency at the higher voltage.
 
Again, nice theoretical discussion...but we're talking about $.04 per charge which doesn't mean much in the real world.
 
An EE on the LEAF forum measured the charging efficiency of his 2011 LEAF (3.3 kWh OBC) using L1 and L2. It was 75% at L1, and ca. 85% (don't remember the exact number; might have been as high as 87%) using L2. The charger and electronics have to be cooled, regardless of whether the battery is. The overhead for that (around 300W IIRR) was slightly higher at L2 versus L1, but it's a lot smaller % of the total power, so the efficiency of L2 comes out ahead.
 
Wanted to confirm the max charging rate for the egolf. The new CarNet page lets you select 5, 10, 13, Max Amps. Is the "max" 32amps? Which would require a 40amp breaker?

I have an L2 CC charger but it's only running 15amps for my 3.3kwH Ford Energi.
 
oftheseven said:
Wanted to confirm the max charging rate for the egolf. The new CarNet page lets you select 5, 10, 13, Max Amps. Is the "max" 32amps? Which would require a 40amp breaker?

I have an L2 CC charger but it's only running 15amps for my 3.3kwH Ford Energi.
Yes, the max current for the e-Golf is about 32A
 
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