Charger tripping

BMW i3 Forum

Help Support BMW i3 Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

huytonman

New member
Joined
Dec 22, 2015
Messages
3
Since January when I collected my 2014 i3, my home charger has occasionally tripped. The frequency of this has increased and its now occurring probably once/week. I also tried to use the free Chargemaster facility at Wisley a week ago and some time into the charge (adding maybe 10%) the charger ceased to charge and when I returned to the car it had error messages on the charger panel. My home charger is made by Rolec.
I have read elsewhere that earlier cars have had issues with their charging circuits, does anybody have a view on what I have described?
Thanks Keith
 
Does the car or the EVSE indicate a fault? When you say tripped, does that mean it trips the circuit breaker? If the line supplying the EVSE is not dedicated to that device, depending on what else is on, that could easily cause the breaker to trip.

Would need more information to make any kind of assessment as to where the problem is.
 
Yes, the circuit breaker is tripping, did it again last night. The charger has a dedicated supply line and the AC is pretty clean and stable were I live. The charger does not have a display so cant check that and the car shows now error messages. As with the the Wisley charger (this is a national garden in the UK) last night the car charged partially before the circuit breaker tripped.
Thanks
Keith
 
Out of interest, is it the circuit breaker in your consumer unit or the breaker on the rolec?

The one thing I did notice was the charger cable on the Rolec getting warm when the car was pulling 7kw. Have you got the cable fully unwound when charging?
 
What size wire is used to feed the EVSE?

What is the rating of the EVSE?

The i3 (nor any EV) should not ask for more current than the device announces it has via the pilot signal, and if the EVSE is rated at 30A or more, the i3 should not be able to overload the EVSE in the first place. FWIW, the EU rates these at peak while the USA rates them as continuous, which is why the 30/32A ratings seem to differ for essentially the same device. But, if your supply voltage was say 220vac, compared to the more typical USA supply of 240vac, you'd need those extra amps to get the same power out.
 
Gif said:
Out of interest, is it the circuit breaker in your consumer unit or the breaker on the rolec?

The one thing I did notice was the charger cable on the Rolec getting warm when the car was pulling 7kw. Have you got the cable fully unwound when charging?

Its the Rolec unit that is tripping and yes I always fully extend the cable, the wiring conforms to UK regulations and is more than adequate for the current that the unit should draw, the supply voltage is extremely stable around 240 Volts.

The car will need to be serviced in a couple of months and I'll get them to check this out, no issues then it looks like the Rolec unit may have a problem.

Thanks Keith
 
I thought the Rolec breaker was an RCD device and not a simple circuit breaker akin to a fuse? May be wrong there though as I haven't go the spec sheet in front of me.

As you say, it may indicate a problem with the internals of the Rolec or the charger unit in the car.
 
Assuming the breaker is not defective, it could be either the EVSE or the car. Is your cord tethered, or are you using a separate one? In the US, we generally do not put something like an RCBO in the device, it is at the power panel, and protects all of the wiring up to the unit. The UK does things differently. IN the USA, the EVSE also has what is functionally a GFCI (ground fault circuit interrupter). If the cord is damaged, if any current is leaking to ground, or not to the path it is intended, that shuts power off because that power could be trying to go through you (a ground fault)!

With the protection device built-into the EVSE, if it trips, and is not the protection device itself that has failed, the car is trying to pull more current than the EVSE is designed to provide. Two things could cause that: the EVSE is announcing it has more than it should be and the car is just then asking it to delivery what it said, or the car is not interpreting the signal properly and pulling more than it should, there's a ground fault (bad cable or component somewhere in the circuit), or, there's a short somewhere pulling more than can be supplied.

What are the error messages/lights showing once this happens? I'd expect the car would announce charging interrupted when the thing shuts off, and that's not by itself, a car error.

Does the EVSE supplied with the car work?
 
Mine is doing the same. I3 with a Rolec home unit. Now tripping much more frequently (at least weekly).
 
The car won't try to pull more current than the device is reporting it has available. If the unit itself is tripping its circuit breaker, the only thing I can think of is that the EVSE's pilot signal is not calibrated properly, and is reporting that it has more power available than it really is designed for, the car tries to draw that amount, and the circuit breaker ends up tripping. Well, if the CB is actually defective, that could cause it as could a loose connection, and the surge as things connect and disconnect is causing it.
 
Okay, my Rolec has started doing the same now after 6 months use. Seems there is a pattern emerging here!

Randomly and not all the time, the charger trips the circuit breaker on the consumer board whilst charging. It's not when it switches on but mid charge so it's not surge.

All wiring / connections appear sound and there is no sign of any damage / heat to any components in the circuitry.

I currently have fast charging set down to "Reduced" from "Max" to test it and it's happily charging suggesting to me that the car / charger is trying to pull more than 32amps through the CB when set to "Max". Either that or the CB is knackered. But given these posts on the forum, it suggests a more common fault is occurring somewhere between the car and Rolec unit.

Installer coming out next week to take a look.

Out of interest, on the current spec sheet for the Rolec, it says it has a "Built-in 40amp, 30 mA Type A (DC sensitive) RCBO". Why would it have an RCBO capable of handling 40amps and yet a 32amp CB to limit current flow?
 
Hi. Loads of info on other forums regarding Rolec units tripping. Google is your friend, but in summary earlier units were fitted with a B32 RCBO which on occasion trips and burns out the neutral cable connection on the top. Later units are fitted with a D40 RCBO. I have a current clamp on my charger feed cable and my i3 would pull nearly 34amps - thus regularly tripping the RCBO in the unit. Since changing to D40 I have no more issues.

I would contact whoever fitted your charger and armed with the above info get them to look at it.

Read this:-

https://speakev.com/threads/rolec-charger-dangerous.37841/
 
FWIW, while I know the USA isn't the UK, in the USA, for a 32A device like an EVSE, it requires a 40A circuit. In the USA, for a circuit that is expected to be on over a certain time factor, it must be derated to 80%, so to get 32A out (potentially, continuously for awhile), it DOES require a 40A circuit. The basic engineering on this is universal, so it's not country specific, but implementation may be spotty. Many breakers won't trip immediately when you've exceeded their current listing, but will over time. That curve can be specified by the manufacturer, and unless there's a sharp peak, verses a continuous level, momentary loads could exceed sometimes as much as 300-400% or even higher than their long-term rating before they trip. FOr a 32A device, being asked to supply 32A could trip long-term. In the USA, the circuit breaker is designed to protect the wiring, not the device itself. But, when it is inside of the device, that should be designed to allow the device's full normal output, and only protect it if that is exceeded. Typically, that also will be higher than the actual load. In the USA, my EVSE does not have a fuse or circuit breaker in it...it does require some protection on the wiring leading to it, but there's nothing wrong with that to be significantly higher capacity than the actual device connected. IOW, my wiring to the EVSE could just as well be sized and protected to be 200A, while the EVSE only draws 32A. Europe tends to put fuses in the device (and there are some in some devices sold here), but primarily, from the plug on the wall to the device, there is no further protection than what is there to protect the dwelling's wiring. I'm not going to get into which way is better...it is what it is.

Assuming that the car is working properly, it won't try to draw more power than the EVSE is reporting it has. The EVSE could be miscalibrated, but in this case, since the i3 itself won't ever try to draw more than about 32A because of the internal power supply design, even if the EVSE was miscalibrated, it shouldn't trip the unit.

All of that being said, if the EVSE trips a power safety device, it is almost certainly not the car's fault.
 
So by way of update, I've had the car set at "Reduced" now for a while and no sign of the CB tripping. This suggests to me that the CB at 32amps is just too close to the continuous rate that the car and charger are pulling on "Max".

If it was something breaking down in the circuitry, I'd expect an RCBO to trip on the unit or the house.

Given that the innards of the charger all look sound I think I'll be asking the installer if it should have a 40amp CB instead. The wiring to the charger is more than capable of handling up to 40amps so no great danger on that front and the charger / car shouldn't pull anywhere near 40amps anyway.

Will report back on Thursday hopefully after they've taken a look at it.
 
In the USA, a continuous use item (the EVSE qualifies) is required to be protected at 125% of the load (actually, they word it as no more than 80% can be used). So, if your EVSE can provide 32A, and it had a 32A protection device, once it had been on for awhile at that max rate (about the max the i3 can draw), then it SHOULD trip...you need some buffer there. How much the i3 will pull is dependent on first, the pilot signal from the EVSE announcing the maximum available, then, the car itself and that is based on the current state of charge, the battery temperature and any limitations you might set in the idrive menus. Depending on the input voltage, the i3 could be trying to pull 32A for quite awhile. Power=volts*amps. What's limited on the EVSE is the max amps available, but the i3 internally, is limited by the max amount of power it can pull. IF the voltage is low, it might be able to pull max amps. If the voltage was higher, it might not because it could reach the max power with fewer amps. In my case, I can often have nearly 250vac available to the EVSE, so I'd max out the i3 with less than the max amps available. But, say your actual input voltage was 220vac, the car would try to pull the maximum amps the thing had (governed by the pilot signal as the upper limit). Confused yet?
 
No, that was my thinking too. Have I read somewhere that the i3 will take 7.4kws? That's what the stated output of the BMW Wallbox is so I am assuming that's designed for the car's Type 2 max output setting.

Standard UK equipment setup is for a power supply delivering 220-240vac giving an average of 230vac. This makes all the difference!

7,400 / 240 = 30.8 amps

7,400 / 230 = 32.17 amps

7,400 / 220 = 33.63 amps

With a CB of 32 amps, pulling the power at anything under 231vac would exceed the rating :?

I suppose the only odd thing is why it has happily charged the car since September and has started doing this now which does suggest some form of degradation somewhere.
 
The pilot signal may no longer be quite as accurate, indicating that it has more power available than it should be reporting. Up to a point, the car will try to take advantage of it.

Also, at least where I live, the supply voltage tends to be lower in the winter than in the summer. There are always exceptions, like if the weather is extremely hot, many more air conditioners are running, and it might dip, but typically, I can see 10vac more in the summer than I do in the winter. While not that many people use electricity to heat with, at least at night, there are lots more lights in use than in the summer.

Anyways, for a device able to properly deliver 32A, to have the protection device set to that same level, won't work reliably long-term...it will tend to trip.
 
KJHXXX said:
earlier units were fitted with a B32 RCBO which on occasion trips and burns out the neutral cable connection on the top. Later units are fitted with a D40 RCBO. I have a current clamp on my charger feed cable and my i3 would pull nearly 34amps - thus regularly tripping the RCBO in the unit. Since changing to D40 I have no more issues.

ChargedEV just been, swapped out RCBO B type for D type. We'll see if it solves the problem. But like Jim says, I still can't understand why you would fit a 32amp circuit breaker to a circuit which was designed to pull 32amps. Asked the guy and he said that's what they do with them all and other than the RCBO problem it wasn't an issue.

Whacked the charging rate back up to Max and here's hoping!
 
Boom! It tripped again last night so the Rolec RCBO is not the cause of the problem. I doubted it was as there was no sign of the burning shown in posts elsewhere regarding this part / unit.

So today I have isolated a single power socket to give me live data from my smart meter and to ensure there is no other power draw. Base load is 2w for running the device so I know there's nothing else in the house burning.

IMG_0612.JPG


So next I put the Fast Charge setting on the car back to "Max", set it to charge immediately and plug in the charger unit and switch on. The car is at around 50% SoC so is going to want juice at a fairly high rate. As predicted, it quickly winds itself up to exactly 7.4kws. Watched it for a while and it occasionally wandered to 7.41kws

IMG_0614.JPG


So next I removed the consumer unit cover and took a voltage reading off the supply to the EV circuit breaker. It's flipping between 232 and 233vac so call it 232.5vac average

IMG_0616.JPG


(And as I'm sat here constructing this message the circuit breaker has just tripped again after about 20 mins on charge :roll: )

So the maths at the extremes of those readings are as follows :-

7410w / 232v = 31.94 amps which is mighty close to the 32amp circuit breaker rating.

The wiring circuit is ever so slightly warm i.e you can tell it's not at the ambient temperature in my garage which is cold.

I'm thinking I'll swap the 32amp CB for a 40amp and observe what happens?

Any thoughts / observations welcome.

PS All of which made me consider my school physics lessons. As the wire circuit heats up, its resistance will increase? Doesn't that mean a higher current would be necessary to push the same juice through?

PPS 40amp CB in and car charging while I monitor the situation!
 
Given that many (if not all in the UK) have 32 amp circuit breakers I wonder why they dont trip and your does?
 
Back
Top