Home charging puzzle!

[mg2000]

I’ve recently bought an MG4 Trophy Long Range and an Ohme Epod home charger. The car display says the car is not charging above 5.7 kW, but Ohme customer support have logged onto the charger and tell me that the Epod is charging at 6.5kW! Ohme say I should see if there is any way to adjust / recalibrate the car display! I don’t even know if this is possible!
Has anyone out there experienced something similar and can anyone suggest a solution?
Thanks!
Mark

 

[webhiker]

It might be a bit large, but 5.7 to 6.5 could just be normal loss

 

[siteguru]

The onboard charger (assuming you have a MY23 Trophy, the one with the rear wiper) is rated to 6.6kW charge rate. I recall reading that the Ohme reads the charger capability and sets that as the maximum charge rate, so you'd always get less charge rate into the car due to losses. (The numbers you've stated seem fairly normal in terms of losses).

The Ohme should really let the car control the charge rate (like my Wallbox Pulsar Plus does ... I get 7.2kW in the Wallbox app and 6.4 to 6.5kW in the iSmart app).

 

[Tight Git]

Yes that's about right after accounting for losses.

 

[unbornidentity]

As above, Ohme thinks the MG4 can only charge at 6.6 kW so tells the car to charge at that max rate when it sets the schedule.

They get the data from EV-database.org and the speed there is wrong, along with several other cars. Try changing your car in the Ohme app to one that has a higher speed and a similar capacity battery. The closest match I can see is Smart #1 Pro+ it says that can do 22kW so your charger should go flat out as it can’t supply that fast. The rest of the difference is just charging losses.

I keep meaning to try this myself but haven’t gotten around to it. Changing to an ID.3 in the app should work too but the battery capacity is a bit smaller or much bigger depending which model so could get some odd schedules. I also haven’t bothered yet as by charging slower you get more cheap rate slots outside the normal cheap rate period!

Better still talk Ohme into setting the MG4 profile up with the actual rate the car can charge at but doubt you’ll get anywhere with that.

 

[mg2000]

Thanks for the comments so far! I’m still new to EV ownership, so what are ‘normal losses’? Thanks

 

[siteguru]

As above, Ohme thinks the MG4 can only charge at 6.6 kW so tells the car to charge at that max rate when it sets the schedule.

They get the data from EV-database.org and the speed there is wrong, along with several other cars. Try changing your car in the Ohme app to one that has a higher speed and a similar capacity battery. The closest match I can see is Smart #1 Pro+ it says that can do 22kW so your charger should go flat out as it can’t supply that fast. The rest of the difference is just charging losses.

I keep meaning to try this myself but haven’t gotten around to it. Changing to an ID.3 in the app should work too but the battery capacity is a bit smaller or much bigger depending which model so could get some odd schedules. I also haven’t bothered yet as by charging slower you get more cheap rate slots outside the normal cheap rate period!

Better still talk Ohme into setting the MG4 profile up with the actual rate the car can charge at but doubt you’ll get anywhere with that.

The speed there is correct (for a MY23 car - it's wrong for a MY22 LR car) ... the problem is that Ohme are setting the charge rate the same as the car's capability rather than setting it higher to account for losses.

 

[Bam Bam]

Thanks for the comments so far! I’m still new to EV ownership, so what are ‘normal losses’? Thanks

About 10% seems normal according to what people report on here.

Lost to heat and converting AC to DC.

I'm wondering if losses will be higher when the temperature rises. Electrical resistance in metal rises with temperature after all.

Still, even 20% is a lot less lost than a combustion car (which is 65% or more lost to heat and friction)!

 

[unbornidentity]

The speed there is correct (for a MY23 car - it's wrong for a MY22 LR car) ... the problem is that Ohme are setting the charge rate the same as the car's capability rather than setting it higher to account for losses.

I think we are saying the same thing in a different way? EV-database has the rate the onboard charger can actually charge the battery not the power it can draw.

By commanding the on board charger to charge at 6.6 kW it doesn’t actually draw the maximum power (effectively slowing down by the predicted charge losses).

Or do you mean there is a version of the car that can only draw 6.6 kW and that’s the figure ev-database has?

 

[Corindikev]

My ZJbeny single phase wall charger has a maximum output of 32 amps at 230 volts which is 7.36 kW. Voltage can legally vary + 10% to - 6% (253,3 volts to 216.2 volts) so I often see voltage of 240 during the day when there is a lot of solar infeed so that means at 32 amps of current the charger can feed in 7.68 kW to the car.

The cars charger shows 6.6 kW going in to the battery when the charger is delivering 7.0 kW, a loss of 400W. This is 5.7% lost to heat, resistance and other factors.

 

[siteguru]

I think we are saying the same thing in a different way? EV-database has the rate the onboard charger can actually charge the battery not the power it can draw.

By commanding the on board charger to charge at 6.6 kW it doesn’t actually draw the maximum power (effectively slowing down by the predicted charge losses).

Or do you mean there is a version of the car that can only draw 6.6 kW and that’s the figure ev-database has?

The SR car (all versions) and the MY23 LR/XP cars have a single phase onboard charger rated at 6.6kW output. (i.e. charge rate into the battery). The MY22 LR cars have a 3-phase onboard charger rated at 11kW, but which gives 7kW from a single phase source.

So what I'm saying is that the Ohme is reading ev-database (I have no reason to doubt your assertion on this) and then setting the maximum output of the Ohme to 6.6kW, rather than just letting the car determine what maximum charging rate it wants to use.

 

[unbornidentity]

The SR car (all versions) and the MY23 LR/XP cars have a single phase onboard charger rated at 6.6kW output. (i.e. charge rate into the battery). The MY22 LR cars have a 3-phase onboard charger rated at 11kW, but which gives 7kW from a single phase source.

So what I'm saying is that the Ohme is reading ev-database (I have no reason to doubt your assertion on this) and then setting the maximum output of the Ohme to 6.6kW, rather than just letting the car determine what maximum charging rate it wants to use.

Yeah we agree then.

To be fair to Ohme, it’s a bloody good bit of technology. They don’t let the car decide so they can create some utterly bonkers schedules to help balance the grid and charge when it’s cheaper for them. The car has ultimate control though, as I discovered when I had my ID.3 that had a software bug that throttled all charge speeds in half.

A typical charge with my Ohme will vary speed all over the place and often have multiple pauses. Yet it’s always within 1 or 2% of the charge I requested at the given time.

The biggest bonus is you aren’t confined to the cheap rate period. You can set the Ohme app to add whatever you need (say 30% by 8pm) and plug in at, say 11am and it will come up with some bonkers schedule and be ready within 1 or 2 % at 8pm with all that extra cheap rate electricity!

 

[Corindikev]

The car always has the final say as to what goes in to the battery. Wall chargers are not chargers at all, they are Electric Vehicle Supply Equipment (EVSE)s. The charger is in the car itself and that consists of an inverter to change AC current to DC current and software to determine how much DC current it will allow the battery to accept. The maximum output to the battery through the inverter is 6.6 kW.

You can set the maximum current on the Charging screen in the infotainment system as well. There are 3 steps but most EVSEs allow you to determine the level of input current in AC to the inverter. I can adjust my EVSE from 1 amp to 32 amps.

Of course intelligent EVSEs can make changes automatically on the fly by knowing the rates and timeframes as well as output from solar systems etc.