Dumb Wall Box Units - 32 Amp 7.00 Kw Compared To 16 Amp 3.60 Kw Unit's ?.

[Lovemyev]

Hi - Can anybody explain what is the different between a wall box when it is sold as rated at either 7.0kw or 3.6kw unit.
Of course, I understand that the 7.0Kw unit can supply double the speed of the 3.6Kw unit, if the car can accept the higher load of course.
But my question is this :-
What internal components ( if any ) are interchanged to allow for the lower / higher Kw rating outputs of the units being sold.
If we use a Rolec dumb wall box as an example in my case ( steady now folks ! ).
Are still available in both ratings, either 7.0kw - 32 Amp or 3.6Kw - 16 Amp versions.
As I can see, there are only three main components inside of these unit's.
A communication module / RCBO breaker and the main contactor.
The communication module sold by Rolec is 32 Amps ( fixed no 16 Amp Version ) the contactor sold by them, is also single rated item at 32 Amps.
The RCBO is the same unit for both units as well ????.
A Type 2 cable IS sold as either a 16 Amp or 32 Amp carrying capacity, so is this the only difference then between both of these units then ????.
It would appear then ( please correct me if I am wrong ) that there appears to be NO internal controls that is built into the unit to make them either 7.00 or 3.60 Kw's ?.
Why not just stick with the single unit then ???.
You may think that this is a strange question to ask ?.
But ever since my car has received the latest BMS update about two weeks ago, when plugging in to charge it has taken on a strange behaviour pattern.
About 70% of the time, when plugged in to commence the charge, it will charge at the normal and expected 7.0Kw / hour.
For the other 30% of the time, it will commence the charge ( and continue the charging ) at only about 3.8 Kw's ?.
The finger of blame is firmly being pointed at the wall box !.
However, I am having a real hard time agreeing with this theory, as the wall box has never been a problem prior to the update.
Today, we returned from a short trip to the super market.
I placed the car on charge and straight away, it reported a charge time to complete at about 4 hours, given the remaining mileage on the car, I knew this was incorrect.
I then checked the house energy monitor and it verified my suspicious, because it reported a consumption of only 3.7 Kw.
So, I unlocked the car and ended the charge.
Re-plugged in the car and started the charge again within about 3 minutes, this time the car reported the charge would complete at 2 hours because the car was now pulling the expected 7.0 Kw's !.
Now maybe you can understand why I am questioning the wall box, if there was an item inside of the wall box or a issue with the cable that COULD reduce the power supplied to the car then this COULD be the reason why I am witnessing this behaviour, but in reality I think the problem lies with either the software of the BMS or the built charger in the car.
The car is performing just fine otherwise, I have owned the car long enough now to understand how it ticks.
Why it behaves like this NOW on a intermittent basis, I have absolutely NO idea.
This present situation makes it very difficult to judge just what length of charge I need, when I am using a delayed charging method of charging when charging on "Off Peak" electric !.
Am I getting 3.6 Kw's or 7.1 Kw's in the middle of the night ???.
I could well end up with only 50% of the range I needed to suit my needs because the car charges at the lower rate and leaves me short of range for my trip.
Yes, I could over come the issue by charging to 100% every single time, but I don't need or want that !.
Any opinions on either wall box ( other than Rolec is crap ) or the car would be gladly received folks.
Cheers.

 

[dprager]

Hi,

A few ansers to your questions. No ther is no significant difference between a 3,6 and a 7,2 kW charger but the components are not interchangeble.

The communications module isn't realy communicating. It's sending out a 1 kHz pulse using pulse modulation to tell the car how much current it can draw. So yes, you could put in another relais in a 3,6 kW charger but the pulse with would keep telling the car it can only draw 16 Amps.

When your battery is filling up the car, the car is limiting the current to the battery. This way of charging is good for the battery life cycle. That is why you can fast chare at 80kW up to 80%, after that the current dops down.

So in short it is not the wallbox that is limiting the current, its the car! There is an exeption however. If you have load balancing then the wallbox will tell the car to draw less current when other appliences need that power.

Hope this helps/clearify's it

 

[Lovemyev]

Hi,

A few ansers to your questions. No ther is no significant difference between a 3,6 and a 7,2 kW charger but the components are not interchangeble.

The communications module isn't realy communicating. It's sending out a 1 kHz pulse using pulse modulation to tell the car how much current it can draw. So yes, you could put in another relais in a 3,6 kW charger but the pulse with would keep telling the car it can only draw 16 Amps.

When your battery is filling up the car, the car is limiting the current to the battery. This way of charging is good for the battery life cycle. That is why you can fast chare at 80kW up to 80%, after that the current dops down.

So in short it is not the wallbox that is limiting the current, its the car! There is an exeption however. If you have load balancing then the wallbox will tell the car to draw less current when other appliences need that power.

Hope this helps/clearify's it

Thanks for your response @dprager .
You says that there is no significant difference between 3.6 and 7.0 units, and that the items are not interchangeable.
But when checking on the Rolec website, they only sell a 32 Amp Com's unit and not a 16 amp.
Therefore a 32 Amp com's device must be suitable for both boxes surly ?.
If the com's unit IS sending the incorrect signal to the car to draw less power on an intermittent basis, could this be the reason why it is choosing the incorrect supply and the incorrect time.
To the best of my knowledge, there is no load balancing on the basic Rolec dumb wall boxes.
I have tried speaking to the Tech team at Rolec last week, but I can not get them to return my call.

 

[dprager]

Thanks for your response @dprager .
You says that there is no significant difference between 3.6 and 7.0 units, and that the items are not interchangeable.
But when checking on the Rolec website, they only sell a 32 Amp Com's unit and not a 16 amp.
Therefore a 32 Amp com's device must be suitable for both boxes surly ?.
If the com's unit IS sending the incorrect signal to the car to draw less power on an intermittent basis, could this be the reason why it is choosing the incorrect supply and the incorrect time.
To the best of my knowledge, there is no load balancing on the basic Rolec dumb wall boxes.
I have tried speaking to the Tech team at Rolec last week, but I can not get them to return my call.

I don't realy know, but technically yes but when the charger tells the car it can draw 32 Amps, that current will go through a 16 Amp relais. I can see how that could be a problem. This explains it better then me:

 

[macd2401]

The wall box isn't really a charger as such. The charger is under the bonnet, the box is just a connection to the mains supply.

 

[Lovemyev]

The wall box isn't really a charger as such. The charger is under the bonnet, the box is just a connection to the mains supply.

Yes thanks, that's why it's referred to as a wall box and not a charger.

 

[Mike]

Unless I’ve missed this in the above posts, a big difference could be the supply cable from the consumer box to the wall box. If the cable is only rated at 16A ish, then a 32A load might melt the cable.

 

[chowbenter]

I was watching this video last night on a pair of Aliexpress EV charging units like the OHME unit where he takes a look inside both units to compare them.

 

[Kithmo]

ISTR reading somewhere that on the Pod Point the output is selected by dip switches in the unit.
There may be a difference in the cable thickness or it may just be 32A cable anyway, I don't know on that one.

 

[chowbenter]

I was watching this video last night on a pair of Aliexpress EV charging units like the OHME unit where he takes a look inside both units to compare them.

Ooops! I put the wrong video up

 

[Lovemyev]

Unless I’ve missed this in the above posts, a big difference could be the supply cable from the consumer box to the wall box. If the cable is only rated at 16A ish, then a 32A load might melt the cable.

Hi @Mike - The wall box is a Rolec tethered unit and is about 5 years old, it was installed by an approved EV installer under the OLEV grant, who is also a EV driver himself !.
I had a VW PHEV at the time and he recommended installing the 32 Amp 7.0 kw unit to future proof ourselves, this was a great shout !.
It charged the PHEV faultlessly for that four years, then we moved over to the ZS EV.
The dumb wall box has a Wi-fi relay installed ( by the EV installer ) 12 months ago and has charged the ZS EV on our "Off - Peak" tariff with absolutely no problems at all.
Now it has become a total "crap shoot" of what you are likely to get when you plug in the car.
I have been keeping a record of it's behaviour over the last two weeks.
You can plug it in two days on the run, and it will demand 7.0 kw's from the box with no problem at all.
Then completely out of the blue, on the third day it will only pull 3.7 kw's.
Just a quick "Snap - Shot" on Friday ( 05.02.21 ) it pulled 7.0 kw's.
Saturday, on first starting the charge, it pulled 3.6 kw's.
This was confirmed by my energy meter inside of the house.
I unplugged, left the car for 5 minutes then returned.
Started the charge again and BINGO 7.0kw's.
It did the very same thing again today ( Sunday ).
Plugged in, received 3.6 kw's.
I stopped the charge, removed the charging plug and instantly returned it.
The charge commenced and straight up to 7.0 kw's !!!!.
It has become extremely difficult ( almost impossible ) to carry out a overnight charge now, because unless I charge to 100% - I have no idea how long to set the time scale for now.
As little as I understand about this type of behaviour pattern, it can only be caused by a few things.
Either there is a problem with the software applied to the BMS and it is conflicting somehow.
The charger itself ( which I somehow doubt ).
Or, the wall box / tethered cable ?.
The simple Rolec wall box only has three major components.
The RCBO breaker.
The communication module that speaks to the car and the contactor.
I think we can dismiss the RCBO and the contactor here.
That only leaves the com's module or the cable really.
I believe the cable does have 2 resistors in the low voltage lines.
I think one is there to protect cars with a smaller demand being plugging into a more powerful wall box.
It will scale back the charge allowed into the car running on a lower charging unit ( 3.7kw's )
Not 100% sure on these facts of course.
I would love to think it is a problem with the cable or the com's module and not the car.
But the wall box has been brilliant and this behaviour has only started as soon as I brought the car home.
What is the chances !.
The car runs and drives fantastic, I just need to get this problem sorted !.

 

[Lovemyev]

ISTR reading somewhere that on the Pod Point the output is selected by dip switches in the unit.
There may be a difference in the cable thickness or it may just be 32A cable anyway, I don't know on that one.

I would LOVE to think it was only the tethered cable at fault here.
It would be a HUGE coincidence if it was though.
Yeah - The cable is almost 5 years old and it does have a few small twists in the outer protective covering.
Nothing TOO crazy, the stuff you expect on a cable of that age that has been coiled around the wall box a few times.
I contacted Rolec last week and asked to speak to their Tech Team.
Just trying to ascertain if anything in the wall box COULD be causing this strange behaviour.
I was promised a call back - still not had one !.
If the fault was there every single time, it would be easier to pin it down.
But as I have proved twice on Saturday and Sunday, you plug it in and your only getting 3.6 kw's.
You stop the charge by unlocking the car, remove the cable, plug in back in and re-lock the car, the charging restart and you suddenly achieve 7.0 kw's ??????.
My brother also has a ZS EV and he would be willing to try his car on my wall box, the trouble is the problem is far too intermittent.
I can not get the car to replicate the problem twice on the run on my own car.
All was brilliant with the car, until it went in for the service work etc.

 

[notdodgy]

I would LOVE to think it was only the tethered cable at fault here.
It would be a HUGE coincidence if it was though.
Yeah - The cable is almost 5 years old and it does have a few small twists in the outer protective covering.
Nothing TOO crazy, the stuff you expect on a cable of that age that has been coiled around the wall box a few times.
I contacted Rolec last week and asked to speak to their Tech Team.
Just trying to ascertain if anything in the wall box COULD be causing this strange behaviour.
I was promised a call back - still not had one !.
If the fault was there every single time, it would be easier to pin it down.
But as I have proved twice on Saturday and Sunday, you plug it in and your only getting 3.6 kw's.
You stop the charge by unlocking the car, remove the cable, plug in back in and re-lock the car, the charging restart and you suddenly achieve 7.0 kw's ??????.
My brother also has a ZS EV and he would be willing to try his car on my wall box, the trouble is the problem is far too intermittent.
I can not get the car to replicate the problem twice on the run on my own car.
All was brilliant with the car, until it went in for the service work etc.

Noticed with mine that it charges at 7kW and drops to 3KW when the charge gets to 97%.

My battery does not appear to be too unbalanced.
I wonder if when the battery is unbalanced, that the charging gets reduced as soon as a single cell reports as being charged to 97 %.

 

[Mike]

@Lovemyev doest it take 7kW on a destination charger? i.e. anywhere else but at home. If it does, that suggests its your setup and not the car.

 

[Lovemyev]

@Lovemyev doest it take 7kW on a destination charger? i.e. anywhere else but at home. If it does, that suggests its your setup and not the car.

Hi @Mike .
The whole situation is complicated by a few factors.
Wales is in lockdown so all non essential travel is out.
Also, although the problem is very real alright, but it is very sporadic at the same time.
If I used a public post, it may charge just fine the first time I try it, but who knows what is likely to do the next time ?.
I do see your point though, it is hard to nail down just what is at fault here.
It is extremely frustrating right now.
Question :-
If the dealer down loaded the data package from the OBD port and set it to MG Tech, would they be able to see the strange charging patterns ?.
I guess the charger BMS and the battery BMS info is visible to them ???.
Just an idea.

 

[Lovemyev]

Noticed with mine that it charges at 7kW and drops to 3KW when the charge gets to 97%.

My battery does not appear to be too unbalanced.
I wonder if when the battery is unbalanced, that the charging gets reduced as soon as a single cell reports as being charged to 97 %.

Completely normal I would say.
I have been monitoring the charging behaviour on my car on an almost hour by hour basis on a few occasions now.
Trying to get my head around what the hell is going on.
The car should pull 7.0 kw's from your wall box at any stage when plugging in for a charge, up until it reaches about 97 - 98%.
At this point, it will throttle back the charge to 3.6 kw's until the car is 100% charged.
This is when I believe my problem is coming from, it appears to be confused somehow.
When the has reached 100% charged, it will then reduce the demand right down to around 500 watts.
At this point the MG logo has stopped pulsing and is now at a constant steady glow.
This indicates that the balancing process is in progress.
The wall will still have the green charging light displayed because it is still providing some power.
When the green light on your wall box returns to blue, and the MG logo has gone out, the balancing has finished.

 

[TomLane]

Hi - Can anybody explain what is the different between a wall box when it is sold as rated at either 7.0kw or 3.6kw unit.
Of course, I understand that the 7.0Kw unit can supply double the speed of the 3.6Kw unit, if the car can accept the higher load of course.
But my question is this :-
What internal components ( if any ) are interchanged to allow for the lower / higher Kw rating outputs of the units being sold.
If we use a Rolec dumb wall box as an example in my case ( steady now folks ! ).
Are still available in both ratings, either 7.0kw - 32 Amp or 3.6Kw - 16 Amp versions.
As I can see, there are only three main components inside of these unit's.
A communication module / RCBO breaker and the main contactor.
The communication module sold by Rolec is 32 Amps ( fixed no 16 Amp Version ) the contactor sold by them, is also single rated item at 32 Amps.
The RCBO is the same unit for both units as well ????.
A Type 2 cable IS sold as either a 16 Amp or 32 Amp carrying capacity, so is this the only difference then between both of these units then ????.
It would appear then ( please correct me if I am wrong ) that there appears to be NO internal controls that is built into the unit to make them either 7.00 or 3.60 Kw's ?.
Why not just stick with the single unit then ???.
You may think that this is a strange question to ask ?.
But ever since my car has received the latest BMS update about two weeks ago, when plugging in to charge it has taken on a strange behaviour pattern.
About 70% of the time, when plugged in to commence the charge, it will charge at the normal and expected 7.0Kw / hour.
For the other 30% of the time, it will commence the charge ( and continue the charging ) at only about 3.8 Kw's ?.
The finger of blame is firmly being pointed at the wall box !.
However, I am having a real hard time agreeing with this theory, as the wall box has never been a problem prior to the update.
Today, we returned from a short trip to the super market.
I placed the car on charge and straight away, it reported a charge time to complete at about 4 hours, given the remaining mileage on the car, I knew this was incorrect.
I then checked the house energy monitor and it verified my suspicious, because it reported a consumption of only 3.7 Kw.
So, I unlocked the car and ended the charge.
Re-plugged in the car and started the charge again within about 3 minutes, this time the car reported the charge would complete at 2 hours because the car was now pulling the expected 7.0 Kw's !.
Now maybe you can understand why I am questioning the wall box, if there was an item inside of the wall box or a issue with the cable that COULD reduce the power supplied to the car then this COULD be the reason why I am witnessing this behaviour, but in reality I think the problem lies with either the software of the BMS or the built charger in the car.
The car is performing just fine otherwise, I have owned the car long enough now to understand how it ticks.
Why it behaves like this NOW on a intermittent basis, I have absolutely NO idea.
This present situation makes it very difficult to judge just what length of charge I need, when I am using a delayed charging method of charging when charging on "Off Peak" electric !.
Am I getting 3.6 Kw's or 7.1 Kw's in the middle of the night ???.
I could well end up with only 50% of the range I needed to suit my needs because the car charges at the lower rate and leaves me short of range for my trip.
Yes, I could over come the issue by charging to 100% every single time, but I don't need or want that !.
Any opinions on either wall box ( other than Rolec is crap ) or the car would be gladly received folks.
Cheers.

Sorry but I am not going into all the details of why but for example the PodPoint 7KW box has several controls, one is via network so you access from anywhere of course and there is a legal requirement that the car charger has to take second place to the house/work or other power drawn. Second the car should only charge to 80% on max charge 7kw/22kw/50kw and then the charge slows to protect the batteries. this is why all the quotes on electric cars for the rapid chargers are quoted to 80% in 40 minutes or whatever - see example below.
If those figures were correct it should take two hours for the 22kw but it takes 6.5 hours this is because the charge from 0 to 80% is at 7kw (max car allows) then the charge drops off and charges slower until full charged is obtained to protect the batteries.
Hope this helped.

How long does it take to charge an MG ZS EV?

Rapid 50kW	Fast 22kW	Slow 3kW
40 minutes 0-80%	6.5 hours 0-100%	15 hours 0-100%

3 Jun 2020
https://www.zap-map.com/charge-points/mg-zs-ev-charging-guide/

MG ZS EV charging guide: how to charge MG's ZS EV - Zap-Map​

 

[Cocijo]

Sorry but I am not going into all the details of why but for example the PodPoint 7KW box has several controls, one is via network so you access from anywhere of course and there is a legal requirement that the car charger has to take second place to the house/work or other power drawn. Second the car should only charge to 80% on max charge 7kw/22kw/50kw and then the charge slows to protect the batteries. this is why all the quotes on electric cars for the rapid chargers are quoted to 80% in 40 minutes or whatever - see example below.
If those figures were correct it should take two hours for the 22kw but it takes 6.5 hours this is because the charge from 0 to 80% is at 7kw (max car allows) then the charge drops off and charges slower until full charged is obtained to protect the batteries.
Hope this helped.

How long does it take to charge an MG ZS EV?

Rapid 50kW	Fast 22kW	Slow 3kW
40 minutes 0-80%	6.5 hours 0-100%	15 hours 0-100%

3 Jun 2020
MG ZS EV charging guide: how to charge MG's ZS EV - Zap-Map

MG ZS EV charging guide: how to charge MG's ZS EV - Zap-Map​

Podpoint home 7kw chargers have limited functionality from the app - they’ve been promising to improve this for a long time! The reason a 22kw ac charger takes 6.5hrs is that the MG dc transformer accepts a max rate of just under 7kw - anything over that doesn’t charge any quicker.

 

[TomLane]

Podpoint home 7kw chargers have limited functionality from the app - they’ve been promising to improve this for a long time! The reason a 22kw ac charger takes 6.5hrs is that the MG dc transformer accepts a max rate of just under 7kw - anything over that doesn’t charge any quicker.

Thank you correcting me but please read my reply again my friend.
"0 to 80% is at 7kw (max car allows) then the charge drops off"

 

[Iain]

Pure guess which I hope does not cloud the issue.
During this cold weather is it possible that the very cold battery will only take the lower current?
After a few minutes charging at 3.7 kW the battery will be slightly warmer but will continue charging at the lower initial rate.
Stopping and unplugging the cable resets the car ECU and when you start charging again the rate goes up to 7.2 kW as the battery is warmer than on initial charge.
Please excuse my non technical language but when your clutching at straws!!!