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Juicebox Pro 40 or Tesla Gen 3 Wall Connector?

Ghaniba

Member
Mar 31, 2017
13
0
Northeastern CT
Hey folks,

Looking at the specs, I was expecting that I'd be replacing my old Juicebox Pro 40 with a new Tesla Gen3 Wall Connector. Their graph shows:
40amp circuit 7.7kW, 23mph
60amp circuit 11.5kW, 34mph

I took Delivery of my 2020 Model S LR+ yesterday, when I got home for the night, I plugged it in using the Tesla supplied J1772 adapter, and I experienced 34 mph charging, according to the Tesla app on my phone. Now, I don't know what to think. Other than the little adapter wearing out, is there any point? The Wall charger is only $500, so that's about $100 cheaper than my current charger, but now I'm just not sure what the point is, even if it is a bargain to me...

Thoughts?

Dave aka Ghan
 

Snerruc

Member
Apr 16, 2016
973
1,365
Palm Bay
If what you have works, why change until something wears out or breaks? A Tesla charger is the elegant solution, but just having a 14-50 or a dryer plug works fine. You already have the most expensive part, the circuit.
 

ucmndd

Well-Known Member
Mar 10, 2016
6,522
12,210
California
Miles per hour is a terrible measurement because it’s worthless for comparing between different car models. The 23/34mph numbers you posted above are for the Model S.

A Model 3 is more efficient than a Model S, so it gets more “miles per hour” from the same charge rate.

Upgrading to a 60 amp wall connector will net you ~44 miles per hour in a model 3, but you’re right in wondering what the point would be. How often would you ever need to charge that fast at home?
 
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maximizese

Member
Jan 16, 2018
473
453
California
I'd say it depends on your needs. If you own or plan to own a non-Tesla EV, then your Juicebox Pro would be more versatile despite having a slower max charge for your Tesla. But how often do you need to charge at a rate above 40A? I've got the old kickstarter version of the Juicebox Pro 60A (it's on a 50A circuit) to charge our Model S, Fiat 500e, and any EV a friend might bring over. I've only needed to crank up the charging to 40A three times in the 5 years that I've had it.

The 3 times were when I my wife brought the Tesla back home really late in the evening and needed a full charge by 6am the next morning. Most of the time I'm charging at 12A so the battery will reach its limiter right before the car is to be driven so the battery will be warmed and ready to go.

The Tesla EVSE looks a whole sleeker than my "Mad Max" looking DIY Juicebox.
 

r1200gs4ok

Active Member
Jul 17, 2019
1,370
467
Irvine
I have a gen 2 Tesla wall charger with a 50a breaker...I charge my M3 and get 35-37mph charge and my Model S get 30-33mph.....I think this is great and hope it contuse at this rate.....
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,252
7,298
Boise, ID
Looking at the specs, I was expecting that I'd be replacing my old Juicebox Pro 40 with a new Tesla Gen3 Wall Connector. Their graph shows
Wait, wait, wait. Whose graph? Are you talking about some documentation from Juicebox? I've seen this, where the maker of a charging unit tries to give some ballpark estimate of the charging rate for "electric cars" in miles per hour. But EVs can be all over the place for efficiency ratings, so that's not going to be very accurate most of the time.

The real answer to the question you're asking is that the brand of charging unit can't make a difference in charging speed. It's just closing a switch to connect your house's circuit into the car, where the magic happens. So if you have a 40A rated circuit that can pass 32A into the car, you will get the charging speed that your car can do, regardless of whether the unit is from Juicebox or Tesla or Bosch or Blink or whoever.
 

tccartier

Supporting Member
Oct 27, 2015
918
956
AZ.
Miles per hour is a terrible measurement because it’s worthless for comparing between different car models. The 23/34mph numbers you posted above are for the Model S.

A Model 3 is more efficient than a Model S, so it gets more “miles per hour” from the same charge rate.

Upgrading to a 60 amp wall connector will net you ~44 miles per hour in a model 3, but you’re right in wondering what the point would be. How often would you ever need to charge that fast at home?

The op said he had a Model S
 
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ucmndd

Well-Known Member
Mar 10, 2016
6,522
12,210
California
The op said he had a Model S
I swear it said Model 3 earlier, but yes you’re right.

Illustrates the same point though - as you can’t really even use miles per hour to compare WITHIN models. A new LR+ Model S is much more efficient than earlier Model S - so they too get more miles per hour for the same input power.
 

Snerruc

Member
Apr 16, 2016
973
1,365
Palm Bay
While the actual technical numbers for the charger are certainly the scientific way to measure charging, in the everyday world the mph figure is easier to use in estimating time to charge. On the road especially I find it easier to estimate how much time to reach the needed charge to complete the next leg. It also tales car efficiency into account.
 

ucmndd

Well-Known Member
Mar 10, 2016
6,522
12,210
California
While the actual technical numbers for the charger are certainly the scientific way to measure charging, in the everyday world the mph figure is easier to use in estimating time to charge. On the road especially I find it easier to estimate how much time to reach the needed charge to complete the next leg. It also tales car efficiency into account.
If that works for you, all good I suppose.

In that specific example though, I find the actual power provided to be more useful. 7.5kw charger gives 7.5kwh in an hour, and that’s ~10% of my battery. The contrived “miles per hour” rating has all the trappings of the “rated miles” estimate to begin with, and the gross inaccuracy of that in most real world scenarios.
 
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tccartier

Supporting Member
Oct 27, 2015
918
956
AZ.
If that works for you, all good I suppose.

In that specific example though, I find the actual power provided to be more useful. 7.5kw charger gives 7.5kwh in an hour, and that’s ~10% of my battery. The contrived “miles per hour” rating has all the trappings of the “rated miles” estimate to begin with, and the gross inaccuracy of that in most real world scenarios.

That doesn't work out either because the charging rate is not linear.
 
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Ghaniba

Member
Mar 31, 2017
13
0
Northeastern CT
Yes, can confirm, it's still a Model S. I even went to check. (just kidding!) So As an update - it turns out it started off at the 33/34 mph charging, but at some point thereafter, it dropped to 22mph charging, and this was not while nearing the end of the charge cycle, like we all know and love... That said, wall charger gen3 ordered within minutes after seeing this drop!

Thanks for all the thoughts folks!
 

davewill

Active Member
Feb 5, 2014
1,825
1,975
San Diego, CA, US
Yes, can confirm, it's still a Model S. I even went to check. (just kidding!) So As an update - it turns out it started off at the 33/34 mph charging, but at some point thereafter, it dropped to 22mph charging, and this was not while nearing the end of the charge cycle, like we all know and love... That said, wall charger gen3 ordered within minutes after seeing this drop!

Thanks for all the thoughts folks!
There no particular reason to think that's the fault of the Juicebox. You may see the same sort of slowdown on the wall connector.
 

maximizese

Member
Jan 16, 2018
473
453
California
There no particular reason to think that's the fault of the Juicebox. You may see the same sort of slowdown on the wall connector.

I agree. My guess is the power quality coming in is not good enough to deliver and sustain the peak amperage. I believe the Tesla's onboard charger(s) reduced the threshold of amps received to safeguard against this. Juicebox offers a graph of the energy throughput so you might be able to see if there are any spikes or dips and at what time they occurred.

My Tesla drops the max amperage from 40A to 34A whenever our 20 year old 5-ton A/C compressor causes our house lights to dim. I don't fault the Tesla or Juicebox because I'm certain it is my house's electrical. I've taken my Juicebox to my friend's house to see if the amperage dips on his electrical supply, it did not.
 

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