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HPWC: what level do you set it at.

hill

high fiber member
Apr 21, 2015
1,363
767
either MT or TN
48? ..... 72? .... Lower? .... higher? During the day i find we typically have about 5kW's of Surplus that we would have feeding back onto the grid from our solar. Thus, since that works out to ~20amps of 240V - i set the X's max charge power level down to 20 amps - & w/in 3 to 4 hours, turning on season & drive patterns, that does the trick for our daily use & keeps the post-harged range no higher than an 80% charge. anybody else have any particular HPWC patterns? we got a $300 deal on the unit & I wired it in myself, so it could run @ 72amps in a pinch. The unit seems kind of overkill, but for those rare exceptions when we need much more charge, much quicker, I didn't want to pass it up, even though we always have enough range on hand to get to the closest supercharger, regardless whether we had north, south, or east.
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aesculus

Still Trying to Figure This All Out
May 31, 2015
4,830
2,784
Northern California
On a 100 amp breaker and it's set to 72 amps always. I have only once had to charge quickly but when I did, it was nice to have it.

I have come home very late at less than 10% and needed to go out the next day. While I am sure a lower charger and setting might have made it OK, it was nice to know that somewhere around 4AM I would be good to go again.
 
HPWC has 100 Amp, 2-gauge copper circuit. Two scenarios, two power levels.

A. Daily use. 20 - 40 Amps. During the winter, I try to juggle start time and current so charge is nearly complete - 60% - 70% - by the time my wife will use the car. That provides a warmer battery. No problem falling short, it takes several days of local driving before the battery is as low as 25%.

B. Prepare for a trip. Charge to 90% at same, relatively low current the night before. An hour or so before departure reattach the charger. Dial up to the S100D's full 72 Amps, set the limit to 100%, pack the frunk & trunk...

Last Sunday a friend with a dual-charger S85 visited. His car pulled the HPWC's full 80 Amps. I thanked him for verifying the electrician's work. He reported that was the fastest charge he'd had without a Supercharger. His car was back to 100% by the time he hit the road again after a short nap and dinner with our family.
 

aesculus

Still Trying to Figure This All Out
May 31, 2015
4,830
2,784
Northern California
Installed my HPWC on a 50a breaker so I charge at 40a. Better electric rates. It would cost me $20 more per month to go higher.
Can you explain this? I guessed you are an Austin Energy customer and could find nothing on their website that stated they would/could adjust a price by delivery rate, just tiered usage (ie total consumption).
 

brkaus

Well-Known Member
Jul 8, 2014
8,542
7,178
Austin, TX
Can you explain this? I guessed you are an Austin Energy customer and could find nothing on their website that stated they would/could adjust a price by delivery rate, just tiered usage (ie total consumption).

Pilot program for off peak ev charging.

https://austinenergy.com/ae/green-power/plug-in-austin/residential-time-of-use-rate

*A flat rate of $30 per month applies for EV drivers requiring a demand of < 10kw. For a demand of greater than 10kw, the fee is $50 per month.
 
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hill

high fiber member
Apr 21, 2015
1,363
767
either MT or TN
This is really scary. Electrical circuits should be installed so they work "in a pinch" The device should be set at the design capacity of the circuit. (that's not just the self-instlled breaker current)
help me understand. So what's wrong w/ dialing down the car's max (amps) accepted delivery rate? And ... Why would the HPWC even have a 48amp setting, if as you say, it should be set at the capacity of the circuit?
With a temperature-managed battery, the less time spent charging, the better ...snip...
why.....
- maybe direct me to a link i can read? seems the documentation on the car's "range" mode/setting says something about (for example) range mode warming the pack "up" if it's too cool (besides other range-extending functions) - because the warmer battery, compared to cool will be providing a more optimal range. So regardless if we set charging at 70 40 20 or 5 amps ... it'd make sense the thermal management would either cool or warm the pack accordingly - as needed. No?
And thanks, everyone - for providing the rational for your choice of charge/current speeds.

.
 
Last edited:

aesculus

Still Trying to Figure This All Out
May 31, 2015
4,830
2,784
Northern California
Pilot program for off peak ev charging.
Very interesting. I suspect we will see more of these types of programs emerge in the future. With a sub meter they can do all sorts of thing such as figuring out when best to charge your car to meet grid needs or to try to balance your demand in premise etc.

And of course for those of us who have whole home energy systems built around a cheap EV charging rate, this type of solution will negate that.
 

brkaus

Well-Known Member
Jul 8, 2014
8,542
7,178
Austin, TX
Very interesting. I suspect we will see more of these types of programs emerge in the future. With a sub meter they can do all sorts of thing such as figuring out when best to charge your car to meet grid needs or to try to balance your demand in premise etc.

And of course for those of us who have whole home energy systems built around a cheap EV charging rate, this type of solution will negate that.
Yes, I believe somewhere in the contract I agreed that they can control the power. Even replace, at their cost, my EVSE with one of their choosing.
 

aesculus

Still Trying to Figure This All Out
May 31, 2015
4,830
2,784
Northern California
help me understand. So what's wrong w/ dialing down the car's max (amps) accepted delivery rate? And ... Why would the HPWC even have a 48amp setting, if as you say, it should be set at the capacity of the circuit?
There may be some confusion here perhaps in all of the posts. I can see nothing wrong with dialing down the car to a lower rate so you don't exceed your solar output. In fact that is a great idea.

And yes, in very cold situations (probably not going to happen in Lake Forest) if you go too low you will not get the added benefit of having the charging warm the battery, so the car would have to make up for this when you start your drive. But that use case is a bit complicated anyway as you have to time your charging to match your departure time etc.

As long as you have your HPWC set to no more than 80% of your circuit capacity (breaker plus conductor), you should be fine.
 
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