# 8 mph Charger



## major (Apr 4, 2008)

I was thinking about EV charging. And it really boils down to how fast the system charges, or a charge rate, and that turns out to be a figure which can be expressed in miles per hour 

The usage on my recent acquisition (the Think) is about 32 miles per day. The typical recharge time is 4 hours. Therefore I have an 8 mph charger. *

I haven't actually timed the charge. It is just estimation. I usually just leave it on overnight. It turns off automatically. That is with the L2 EVSE (230V AC) and 3.3 kW on-board charger. If I use the 110V charge cord, it drops to 4 mph.

I realize this charge rate in mph depends on your particular EV efficiency and driving style and weather and probably other factors. But it seems like a useful number which can be applied to your typical daily use.

On the subject of charging, I found this article interesting: http://www.torquenews.com/1075/how-powerful-charger-required-kill-electric-car-range-anxiety

*edit: Looks more like 10 mph. See post #12.


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## dougingraham (Jul 26, 2011)

I started telling people the recharge time in miles per hour a few months ago. They look puzzled for a moment then usually they get it. I am not sure where I first saw this being done. Your EVSE could support a charger almost twice as fast as the one you are using. At these low charge rates you probably get to over 95% SOC before the amps taper off.

It is a good way to answer the question of how long does it take to charge.


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## Ziggythewiz (May 16, 2010)

Yes, it makes sense to measure charge rates that way, though it feels weird to talk about it in MPH.

Here's a list of max charge rates I put together recently, obviously actual numbers are somewhat lower, YMMV, etc.

Standard Outlet
110 V AC, 20 Amps - 7 miles charge/hour

Dryer/Range Outlet
220 V AC, 50 Amps - 35 miles charge/hour

J1772-2009
Level 1 120 V AC, 16 Amps - 6 miles charge/hour
Level 2 240 V AC, 80 Amps - 61 miles charge/hour

CHAdeMO
Level 3 500V DC, 125 Amps - 200 miles charge/hour


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## GizmoEV (Nov 28, 2009)

Ziggythewiz said:


> Here's a list of max charge rates I put together recently, obviously actual numbers are somewhat lower, YMMV, etc.
> 
> Standard Outlet
> 110 V AC, 20 Amps - 8 miles charge/hour
> ...


I don't see how you can get an 8mi/h charge rate on a 110V 20A plug with your bug. Especially if you have lead acid batteries. With lead acid batteries in my Gizmo I got a 4mi/h charge rate and when I went to LiFePO4 I get 6-6.5mi/h charge rate. This is pulling only 1100W or so from the wall. I don't count the time for the last few Ah where the charger is tapering back since it represents only about a mile of range out of over 70 miles.

If your bug uses 250Wh/mi then it would take a minimum of 2000W of power from the wall, more for inefficiencies, to get a 8mi/h charge rate. Have you actually timed a charge and measured your range for that charge time like Major did?

I give my actual range gain/hour of charge as giving a theoretical maximum is just plain misleading and there is too much of that in the EV crowd.


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## Ziggythewiz (May 16, 2010)

I don't. My 'Quickcharger' gives me ~ 3 m/h. That list is just circuit maximums. Obviously I don't charge at 500V DC either.


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## ev-converter (May 24, 2012)

Ziggythewiz said:


> I don't. My 'Quickcharger' gives me ~ 3 m/h. That list is just circuit maximums. Obviously I don't charge at 500V DC either.


You have brought up a very important factor in designing conversions. The charge time. All new plug ins are now having to explain their charge times and range. Therefore, the rule of thumb now is a charger at least 6kw and a battery pack of 20kw for small cars and 30kw for mid size cars. Anything less and the value upon selling is zilch. If the doner car is not a desirable car, its almost worthless. One thing you can consider, if you have the room, is to add a parallel 3k charger that would reduce charging 50%. With the new laws taking place limiting public chargers to 4 hours, this is going to be a key factor in future designs. Are you using your car as a daily drive now?


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## Ziggythewiz (May 16, 2010)

My limit is not the charger, but the house circuit. That's why I posted empirical data instead of anecdotal. To apply one's "real-life experience" to someone else you have to account for all the variables, like exact circuit voltage, breaker trip point (my 20A circuit trips under 14), extension cord gauge and length, battery chemistry and age, charger efficiency, temperature, humidity, sunspot activity, etc...

I'd rather share empirical data with the caveat that it is a max and real results are somewhat less than to guess at what someone else can expect. They can crunch the numbers for their own scenario.

Mine's been a daily driver for nearly 2 years, and I couldn't care less about resale value.


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## tomofreno (Mar 3, 2009)

I used to have a small sign in the side windows of my ev with some stats on it, one of which was: *Charging time: 2 to 4 hours typically (about 16 miles per hour charging)* 
I've driven to charging stations and left my car to charge while I went for a hike or bike ride for a few hours. Also stopped and charged on the way to a destination that was beyond my range, gaining enough charge to drive back without charging again. But long trips would be pretty tedious I think. For example, to drive about 230 miles I would have to recharge 4 times for about 4 hours each time, adding 12 hours to the typically less than 4 hour ice powered trip. With Valerun's 10 kW charger I would still need to charge for a bit over 2 hours each stop, adding 8 hours to the trip.


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## GizmoEV (Nov 28, 2009)

Ziggythewiz said:


> I'd rather share empirical data with the caveat that it is a max and real results are somewhat less than to guess at what someone else can expect. They can crunch the numbers for their own scenario.


Then you need to use the 80% continuous rating of the circuit not 100%. Otherwise it is just plain misleading. You give the uninformed reader/listener the false impression of how fast a typical car would charge. Furthermore, all of the commercially available chargers I know of which are plug & play (ie. not Manzanita Micro) and auto switch between 120V or 240V will only draw 80% of a 15A circuit at 120V or less. This means that it will only draw 12A so a maximum of 1440W. That is what I'm talking about.

It is just like Nissan claiming a 100mi range on the LEAF. They needed to have several non-EV drivers just drive it normally and see how far they got and then use that number. I could get 100 miles out of my Gizmo but I only quote a 70 mile range because no matter how I drive it that would be my minimum unless it was all up hill. My 70 miles is a real number, not an inflated "if you drive it just right down wind and down hill for the whole time" number.

We all want EVs to proliferate but if we keep spreading false information it will only server to turn people off when reality really hits. The recent article about your EV did just that. Gave a false sense of reality. It is no different than using the theoretical energy capacity of a LiFePO4 battery as claimed capacity rather than the actual real world capacity.


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## ev-converter (May 24, 2012)

Ziggythewiz said:


> My limit is not the charger, but the house circuit. That's why I posted empirical data instead of anecdotal. To apply one's "real-life experience" to someone else you have to account for all the variables, like exact circuit voltage, breaker trip point (my 20A circuit trips under 14), extension cord gauge and length, battery chemistry and age, charger efficiency, temperature, humidity, sunspot activity, etc...
> 
> I'd rather share empirical data with the caveat that it is a max and real results are somewhat less than to guess at what someone else can expect. They can crunch the numbers for their own scenario.
> 
> Mine's been a daily driver for nearly 2 years, and I couldn't care less about resale value.


why don't you go to the main breaker box,, install 2- 40amp breakers and wire up a J1772 from HD for $700.00. This is what is necessary for ALL production EV's and should be a example for us to follow. Should also improve the resale for your house over time.


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## Ziggythewiz (May 16, 2010)

Because I don't need 40 amp breakers, or a J1772, and I can find better uses for $700. The whole point of DIY is building to your needs. An overnight charge is just fine for me, and there is nowhere else for me to charge at. I'm considering pulling out the onboard charger anyway as I've plugged in away from home a whole 2-3 times.


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## major (Apr 4, 2008)

*Really 10 mph Charger*

I was able to keep a closer eye on the charging tonight. I put on 37.2 miles today and it appeared to bring the dashboard meter up to full in less than 3.7 hours. That makes it a 10 mph charger. The wall meter indicated 11 kWh, so about 295 Wh/mile. Maybe 80-85% of the trip was 60 mph and remainder 35 mph stop and go.


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## ev-converter (May 24, 2012)

Ziggythewiz said:


> Because I don't need 40 amp breakers, or a J1772, and I can find better uses for $700. The whole point of DIY is building to your needs. An overnight charge is just fine for me, and there is nowhere else for me to charge at. I'm considering pulling out the onboard charger anyway as I've plugged in away from home a whole 2-3 times.


You mean you do need the breakers and the J1772 but don't want to spend any money. Be honest with the readers.

If you don't want to use the public J1772, that's fine. Probably because it costs money. Isnt it good others don't walk in your shoes when driving a EV needing a charge? I don't push anything, contrary to your unfounded remarks which seems to be a pattern with you. It is the standard for ALL EV's and we should use the standard as a guide. I don't get royalties on anything, another remark using your poor taste.


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## Ziggythewiz (May 16, 2010)

ev-converter said:


> You mean you do need the breakers and the J1772 but don't want to spend any money. Be honest with the readers.


Um...no. I don't need them. I'm usually home for 16 hours, why do I need to charge in 4?

I don't know why you're pushing the J1772 so much, it's like you get royalties on it or something. A J1772 is WORTHLESS to me. I wouldn't install it if you paid me to.


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## dladd (Jun 1, 2011)

Ziggythewiz said:


> I'm considering pulling out the onboard charger anyway as I've plugged in away from home a whole 2-3 times.


I no longer have a charger in my car. I pulled it out a few months ago when I was doing some work on the car, just never got around to re-installing it. No big deal, for the once a month or so trip where I think I may charge away from home I'll throw it in the trunk, but for the most part I do all my charging at home.

Fwiw, I charge at around 3 mph and it fits my driving needs just fine. I do have the itch to get a much higher power charger, but it's definitely a want and not a need.


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## JoeG (Jul 18, 2010)

Hi All,
After reading thru this thread, it seems to me that the MPH way of describing charging leaves out the watt per mile factor.
If your car uses 500 watts per mile then it will charge 1/2 as fast with the same charger as a car that uses 250 watts per mile, right? 
Also uphill miles are not the same as downhill miles in charge usage.
So, why is this an improved way of discribing charge rate over staight energy input?
Joe


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## Ziggythewiz (May 16, 2010)

That's correct. It can be specific to your car, or you can use a generic value like 250wH/m, which makes math easier as well. It's just a way to make it easier for people to relate to, by saying I charge at x mph, instead of speaking in Klingon about amps and watts and volts.

Just like normal MPGs, they don't account for up or downhill, speeds, etc.


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## major (Apr 4, 2008)

JoeG said:


> Hi All,
> After reading thru this thread, it seems to me that the MPH way of describing charging leaves out the watt per mile factor.
> If your car uses 500 watts per mile then it will charge 1/2 as fast with the same charger as a car that uses 250 watts per mile, right?
> Also uphill miles are not the same as downhill miles in charge usage.
> ...


Hey Joe,

I mentioned in post #1: 


major said:


> I realize this charge rate in mph depends on your particular EV efficiency and driving style and weather and probably other factors. But it seems like a useful number which can be applied to your typical daily use.


The mph figure is more of a personal metric, not a sales specification for chargers.

Regards,

major


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