10 amp charging better or worse?

[hcsharp]

I connected up 240v charger to get the AC to kick on and cool down ESS (if the pack is warm), then after the pack is cooled down, I then unplug and plug in at 120v at slowest charge rate. This accomplishes three things, the pack stays cool as I live in cool place, and charge rate is low enough not to heat up the ESS. Also now on 120v I don't do wear and tear on the air conditioner system as it will not kick on, additionally the charging components are under less load and will last longer.

Are you sure the charging components suffer less wear and tear at 120v? I would think the opposite. The charging system uses more energy to add the same miles to the ess at 120v.

 

[spaceballs]

Are you sure the charging components suffer less wear and tear at 120v? I would think the opposite. The charging system uses more energy to add the same miles to the ess at 120v.

Less efficient doesn't necessary mean less MTBF of all the components in the ESS. For example less efficient inductor(s) does generate more heat in them, but when you reduce the MTBF of the inductor in the ESS, it is still magnitudes more longer than the MTBF of the mosfets, capacitors, and resistors in the ESS.

 

[DanielFriederich]

The HVAC (cooling the battery by using the climate system when reaching 41.5 degrees C.) won't kick in when charging at 10 amps. It will kick in when charging with 13 amps.
Heat dissipation losses when charging whit 13-24 amps should be more or less almost equal given the shorter charging time when going on higher amps. C-rate of the cells should not be a big topic at those "low" rates but what you should always keep in mind is the electrical installation in you house. My master circuit breaker becomes a nice heating system (sarcasm) when I charge at 32 amps (230V), especially with the S (three phases but one with the Roadster)...
HVAC system maintenance can be done with any garage (I started a thread once about that).
The cooling pump will run always when charge level is above 90%
Using the IGBTs as rectifiers/inverters when charging results in not very high temps inside the PEM since amps are quite low compared to driving...

 

[spaceballs]

HVAC system maintenance can be done with any garage (I started a thread once about that). ...

When I was talking about HVAC I meant the HVAC box itself, yes easy to service, but more expensive to replace if it fails than pump or PEM fan.

The cooling pump will run always when charge level is above 90%...

Is this in Normal mode, or Range mode? In either case this is the first time I've heard of this.

Using the IGBTs as rectifiers/inverters when charging results in not very high temps inside the PEM since amps are quite low compared to driving...

You would think so, but I've noticed the PEM Fans are temp sensitive, and are are loudish at 240v @ ~30amps, but nearly silent at 120v @ ~12amps.

 

[EdMcConnell]

Since I've adopted the car only last month, temps have been in the 85-95F range and I've seen my trip usage typically around 9kWh and my charging cost around 17kWh (with 120V/15A). In the last 3 days, it's been raining quite a bit and last night, temps dropped below 70F. So, over the weekend, by trip usage was 8.8kWh and my charging cost was 14kWh. Single data point of course, but probably shows a bit, how ambient air temp impacts charging cost.

I use a simple model for calculating cost based MPGE = trip miles driven / Charging Cost in $ x $2.25 per gallon (regular).

For me, that means that my cost based MPGE for the Roadster is 53 - 58 (10-20% better than the Prius that I used to drive, which gave me right around 50 MPG). My 2016 MX-5 is giving me right around 40 MPG. I'd like to see better for the Roadster, so even though my driving pattern doesn't need 240V, since I can "fill-up" overnight without issue with 120V, and if I calculate the time that it's going to cost to recover the investment in a 240V circuit from power consumption, I'm pretty sure that it will be a long time, but I'm going to do so anyway, just because I don't like the perception that I have that the MPGE of the Roadster at 120V is not much better than the MPG of a Prius or MX-5.

 

[DanielFriederich]

Some insights for the nerds among us

 

[EdMcConnell]

Nerd question: are SOC% values relative to absolute 100% (as in what is displayed for range mode) or relative to standard mode where 100%~85% absolute and 0%~10% absolute. Relates to "coolant pump always on above 90% SOC).

 

[DanielFriederich]

imo standard charge, since my pump is running when above the 90%

 

[gregd]

Since I've adopted the car only last month, temps have been in the 85-95F range and I've seen my trip usage typically around 9kWh and my charging cost around 17kWh (with 120V/15A). In the last 3 days, it's been raining quite a bit and last night, temps dropped below 70F. So, over the weekend, by trip usage was 8.8kWh and my charging cost was 14kWh. Single data point of course, but probably shows a bit, how ambient air temp impacts charging cost.

I use a simple model for calculating cost based MPGE = trip miles driven / Charging Cost in $ x $2.25 per gallon (regular).

For me, that means that my cost based MPGE for the Roadster is 53 - 58 (10-20% better than the Prius that I used to drive, which gave me right around 50 MPG). My 2016 MX-5 is giving me right around 40 MPG. I'd like to see better for the Roadster, so even though my driving pattern doesn't need 240V, since I can "fill-up" overnight without issue with 120V, and if I calculate the time that it's going to cost to recover the investment in a 240V circuit from power consumption, I'm pretty sure that it will be a long time, but I'm going to do so anyway, just because I don't like the perception that I have that the MPGE of the Roadster at 120V is not much better than the MPG of a Prius or MX-5.

Given that charging at 240v / 40 amps is nearly twice as efficient as 120v / 12 amps (see Tom's article, referenced above), your MPGE for the Roadster will improve substantially by simply switching to higher voltage and current charging. Back of my envelope says that the Roadster is something closer to 100 mpg than 60 - i.e. double the Prius - unless your electricity is very expensive and gas really cheap.

 

[EdMcConnell]

hope so, but will see after I get 240V to use with my new UMC and CAN SR.

 

[EVDRVN]

I started another thread (somewhere) re low power (under 10kW) charging. Surprised, when i asked if anyone does low power 240V charging, & the larger consensus was that it was kinda lame (or some other less inflammatory word). Anyway - i can't help but notice that charging overnight less than 40 miles, at 5 amps seems to stop the damnable parasitic loss. So that's what we do.
.

Yet you have larger overhead losses that are always on during charging for a longer period. Better to use a 12V battery tender.

 

[gregd]

Yet you have larger overhead losses that are always on during charging for a longer period. Better to use a 12V battery tender.

Mmmm, careful. There is no single 12v bus that runs through the whole car, fed by the 12v battery, as in an ICE. Further, the Roadster's electrical system (at least mine) isn't like the Model S, where the car runs off the 12v battery while it's asleep, then recharges it when necessary (cycling several times per day). My 12v battery is maintained at a 13.77v "float" voltage, apparently from a DC-DC supply within the ESS, regardless of the car's state. Putting the 12v battery on a battery tender may not make a difference, and could theoretically cause problems if you end up back-feeding the system from the external source. Or, the tender may end up being a net draw on the system, making overall current draw worse. At best, I think it would have no effect.

Also unlike the Model S and later cars, there is no source for new parts to effect a repair, should you fry something in your quest to quell the vampires. In my opinion, it's best to let them sip as they were designed to, and focus on efficient charging (240v, 40-ish amps). My car spends a few minutes a day topping off the main battery, for a daily consumption of about 500wh. At our $0.28/kwh marginal rate, that's about 14 cents. Not worth the risk.

 

[Bill25cycle]

Yeah when I owned my 2011 base Roadster I saw at least a 30% penalty by charging at 120 volts. Most efficient seemed to be in the 6 - 8 kw range, which just so happens to be the size of the most popular wallbox (if you picked up a J1772 adapter, and your UMC has died, as they were prone to). I was told I was the first roadster buyer to charge at 240 without using a Tesla docking station or UMC.

I used a modified Schneider ( to prevent the thing from overheating, and to also prevent the grnd flt tripping) at 30 amperes which seemed quite efficient.

 

[BestHand]

For my usage, I connect up an 240v charger to get the AC to kick on and cool down ESS (if the pack is warm), then after the pack is cooled down, I then unplug and plug in at 120v at slowest charge rate. This accomplishes three things, the pack stays cool as I live in cool place, and charge rate is low enough not to heat up the ESS. Also now on 120v I don't do wear and tear on the air conditioner system as it will not kick on, additionally the charging components are under less load and will last longer. btw in this setup I don't care about efficiently, just minimal stress on all components with an cooled ESS to extend life of all things. Note this might wear the ESS's fans down faster, but it's one of the easiest things to service compared to the other components. But it might not either as it doesn't spin up the ESS's Fan very high at all compared to 240v charging. The pump does wear faster as it's on longer, but it's also one of the more easier to service parts compared to the AC system (in my view).

Somebody wrote that if you limit charging 240V 5A fans are off.

 

[hcsharp]

I was told I was the first roadster buyer to charge at 240 without using a Tesla docking station or UMC.

Hardly if you had a 2011 base. You would have had to own a low VIN 2008 v1.5 for that to be possible.

I'm curious how you modified the Schneider to prevent the grnd fault from tripping. That was a serious problem for several years before they fixed it. Now Siemens is making the same mistake.