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Discussion Starter #1 (Edited)
So, I have a Level 2 240v EVSE that can step down to Level 1 if it’s on 120v. Is there any benefit in adding a step down switch for the wall outlet I use so I can choose between Levels 1 and 2? I’m very new to owning an EV and have gotten conflicting information online about whether or not Level 1 is better for your battery life in general. That being said, adding a switch would be easy (and relatively cheap) for me if there is any reason it would be useful.

Thanks!
Mike
 

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Short Answer: In general, the slower you charge a battery, the greater its life expectancy, but even L2 is pretty slow by battery industry standards, so use the slowest method you have time for. L1 fully recharges the average US daily drive overnight, so just switch to L2 when you drive more than that.

Long Answer:
Battery industry charge/discharge current standards are measured in "C" rate. "1C" is zero-to-full (or full-to-empty) in 1 hour. 2C is 1/2 hour. 3C is 1/3 of an hour. Etc... Life expectancy really drops off at 4C.

With its 24kWh batt, 1C in a Fiat is 24kW, but its L2 6.6kW onboard charger limits it to only 0.275C & its only 0.06C on its stock 1.44kW L1 charge cord. 1C (24kW) discharge on a flat road is about 70mph.

Our Samsung SDI battery cells are rated for 3,200 cycles from 100% to 20% at 1C drain & 0.5C charge, at 77 degrees F (25C), by which time capacity will have dropped to 80%. In other words, by EPA specs, after driving 211,000 miles under the above conditions we'd have 73 miles total city range, BUT...:

We can't even charge at 0.3C, or to 95%. I'm not sure what temperature range our batteries' cooling systems are set for, but the user reports show on average over half their battery's lifetimes spent between 20 & 30 degrees C. In other words, even if we abused our batteries as much as possible, it would be reasonable to expect them to retain more than 80% range after 3200 cycles.
 

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You don't have to do a step-down to modify the outlet itself like that... you can buy adapters that change whatever your EVSE plug is into a 120V plug. It just fits on top like any other plug adaptor. Then you plug the 120V adapter plug into any 120V outlet (regular common household outlet in the U.S.).

I've done this with a Juicebox which uses a J1772 plug, and they sell the adapters to convert to a 120V plug on their website.

But if it's cheaper to do the switch, then I guess do whatever is cheapest?
 

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Battery industry charge/discharge current standards are measured in "C" rate. "1C" is zero-to-full (or full-to-empty) in 1 hour. 2C is 1/2 hour. 3C is 1/3 of an hour. Etc... Life expectancy really drops off at 4C.

Fiat's 24 kWh batt needs 24kW to be 1C, but its L2 6.6kW onboard charger limits it to only 0.275C & its only 0.06C on its stock 1.44kW L1 charge cord. 1C (24kW) discharge on a flat road is about 70mph.
A few references etc for C ratings, as I've never heard of it being a "zero to full rating", but in terms of Ah or mAh per cell (or rated pack).

http://www.batteriesinaflash.com/blog/battery-c-rating-explained-and-demystified/


The C rating is from the individual cells, which in our case is 63Ah
https://pushevs.com/2017/03/06/future-holds-fiat-500e/

This means 1C would be 63Amps (charging OR discharging).
Because our packs are a 97S1P (97 cells in series, 1 cell in parallel) this 63 amp 1C would be for the entire pack. This would be different if we had 18650 packs like the tesla, etc where cells were in parallel as well as series. (I think this is where your explanation of "zero to full" falls apart, for other packs, not necessarily our packs)

365VDC at 63Amp is ~23kW.
Considering our onboard charger is MAX 6.6kW we're only charging around a 0.29C rate maximum (as you pointed out) I'm not worried about cell longevity when charging at full kW.

My main reason for charging slower (I set my Level 2 charger to 6A240VDC ~1.4kW) is to reduce the efficiency losses due to heating of the charging electronics (charge controller, inverter, etc.) Have I checked this efficiency? (by verifying the amount of charge I actually get vs amount of power I'm feeding the charger) Nope. and it may be that I'm actually hurting the efficiency due to amount of heat loss over a longer period of time. Though I don't believe that is the case for my setup/how i'm doing it.
 

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While charging, a cooling pump runs constantly (fluid flowing in the top of the reservoir) so running it longer by slow-charging might reduce efficiency.

Thanks for clarifying C rate, with links. I must have seen the "for dummies" version (1 killowatt per killowatt-hour). Either way, if we try, we can reach or even exceed 1C discharge*, but not even 0.5C charging**. At least not until the DC rapid-charge kit comes out, at around 1.74C, which reminds me that should be pretty soon now (announced as available late this year).

* Temporarily under acceleration or short uphills, or consistently at about 70mph or more, &/or long uphills.

** Except during strong regen: I've seen negative 64kW on my "motor power" display.
 

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Discussion Starter #6
You don't have to do a step-down to modify the outlet itself like that... you can buy adapters that change whatever your EVSE plug is into a 120V plug. It just fits on top like any other plug adaptor. Then you plug the 120V adapter plug into any 120V outlet (regular common household outlet in the U.S.).

I've done this with a Juicebox which uses a J1772 plug, and they sell the adapters to convert to a 120V plug on their website.

But if it's cheaper to do the switch, then I guess do whatever is cheapest?
The reason I was going to do the switch was so I didn’t have to worry about plugging/unplugging anything and just leave it mounted on the wall. And yeah, the switch was going to be cheap for me since I’ve already got everything on hand from other projects and can wire it myself. :)
 

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Discussion Starter #7
While charging, a cooling pump runs constantly (fluid flowing in the top of the reservoir) so running it longer by slow-charging might reduce efficiency.

Thanks for clarifying C rate, with links. I must have seen the "for dummies" version (1 killowatt per killowatt-hour). Either way, if we try, we can reach or even exceed 1C discharge*, but not even 0.5C charging**. At least not until the DC rapid-charge kit comes out, at around 1.74C, which reminds me that should be pretty soon now (announced as available late this year).

* Temporarily under acceleration or short uphills, or consistently at about 70mph or more, &/or long uphills.

** Except during strong regen: I've seen negative 64kW on my "motor power" display.
There’s a DC rapid charge kit coming out???
 

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There’s a DC rapid charge kit coming out???
Supposedly. QuickChargePower announced that they'd be releasing a kit. That was nearly a year ago. Cost is supposed to be around $3000. It's a Chademo retrofit.

There's been no updates from QCP in months. So the status of the project is frankly unknown.

Personally I wonder if the utility if it does come to fruition is worth the investment. Since the battery pack on the 500e isn't going to get any larger, it will not facilitate anything close to useful longer distance travel. While clearly there will be more flexible local charging options, I feel there is some debate of that utility considering the investment necessary to get it.

ga2500ev
 

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It depends on personal & local variables.

For example:

- I drove from Seal Beach to Bigbear in an early-model 83-mile-range eGolf with the DC charge option, stopping for about half an hour to DC-charge in Highland at the bottom of the mountain.

- Doing the same in my Fiat (without a DC kit) would require a fairly impractical 3.2-hour stop to charge on L2.

A used eGolf with DC costs over $3000 more than a used Fiat.
 

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It depends on personal & local variables.

For example:

- I drove from Seal Beach to Bigbear in an early-model 83-mile-range eGolf with the DC charge option, stopping for about half an hour to DC-charge in Highland at the bottom of the mountain.

- Doing the same in my Fiat (without a DC kit) would require a fairly impractical 3.2-hour stop to charge on L2.

A used eGolf with DC costs over $3000 more than a used Fiat.
It's not a question of the utility of DCFC. It's a question of the cost to add. Knowing what I know now, I would have valued DCFC quite a bit more than I did at the time and focused on EVs with DCFC such as Chevy Spark EV or Kia Soul EV. But $3k for an aftermarket add I would find difficult to justify as while DCFC adds flexibility in terms of charging, that the rarity of that flexibility makes the cost excessive. All of course IMHO.

ga2500ev
 

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:) Right. As they say, "YMMV": I agree $3k is a big proportion, since it's such an inexpensive used car, but like I noted, that still totals less than the next-cheapest option* I know of (eGolf SEL). If its local usefulness is going to be a rarity for you, save your $3k for rental car days.

It all depends on your own situation. I was tempted by the Spark's DC option too, but knowing what I know now for MY own local use, I'm glad that I valued it less than Fiat's twice-as-fast L2 recharge.

Again, YMMV :)
* Addendum below
 

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*Addendum: I just found a used Spark with CCS for only $6,600
For MY OWN personal local use, its half-speed charging on L2 makes it less useful than a 500e, so I hadn't been considering it as an option.
 

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*Addendum: I just found a used Spark with CCS for only $6,600
For MY OWN personal local use, its half-speed charging on L2 makes it less useful than a 500e, so I hadn't been considering it as an option.
Of course circumstances dictate its utility. Metro Atlanta has CCS well distributed in every direction. Faster charging at home for me is pretty irrelevant as most days I'm still charging on 120V with the OEM charger. Two years in and I finally bought a 30A Bosch 240V EVSE. But even now I'm only using it occasionally via an extension to the dryer circuit.

My point has always been that CCS gives power/time flexibility when one is out and about. If CCS is well distributed in the area, then the difference in speed for L2 is much less relevant because when one needs to charge while out, 15-20 minutes on CCS is far superior to either 3.3kW or 6.6kW L2. As you've clearly pointed out it's personal for each of us. Personally, I'd much rather have the opportunity to charge much faster when I need to giving up faster daily charging which I don't take advantage of anyway. If I really needed a faster charge when I'm close to home, the nearest CCS is 4 miles from the house and can do a 0-80% charge in 20 minutes. That would be a winner for me personally.

ga2500ev
 

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Metro Atlanta has CCS well distributed in every direction. Faster charging at home for me is pretty irrelevant as most days I'm still charging on 120V with the OEM charger.
I too use OEM at home, but on both of MY usual drives there's only ONE costly DC charger, & lots of free L2s, so I use those when I don't mind waiting while I catch up on my phone. I wouldn't want to wait twice as long for a Spark though :)

Hi - you will have greater losses at 120V.
So a better option for the original poster might be iron's method of using 240V & lowering the current, if possible.
 
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