Charging speed for 120h UK i3

I'm a new i3 120h user (without range extender) UK version. The VIN decoder says I have "Quick charg.altern.current multi-phase + Rapid charging, direct current". Am only getting fastest charge rate of 3.7kWh from 3-phase 240v AC charger rated as 11kWh. EV set to maximum charge, but it takes 10hrs+ to charge empty to full v 3 hrs per BMW 'Living with my i3 website'. BMW dealer says nothing wrong with car or cable. What am I doing wrong (or maybe the charger is at fault?) .

Dealer says maybe it's because I don't pre-condition the battery, but can this be true as the temps (8-15degC) are well within tolerances? My understanding is that precondit is only necessary if temp below 5degC or above 25degC. Is this correct?

Any advice appreciated.

PS this is a repeat of my post under a different heading.

What amperage is your charge cord - 16, 24, 32, 40? Volts is the 'size of the pipe', amps is how fast the flow of electricity through the pipe is - higher the amps, faster the 'flow', faster the charge. From your charge time, I am guessing it can supply up to 24 amps. My i3 is a 2015 60h, and on 240 volt, 24 amps, takes five hours from empty to full charge, so for your 120h i3 to take 10 hours seems normal if your circuit is supporting 24 amps. Never heard of any one claiming 3 hours or under to charge an i3, unless using DC fast charging which is 480 volts, 100 amps.

This info is based on the 2017 90h i3, for reference.
https://www.pluglesspower.com/learn/bmw-i3-charging-ultimate-guide/


Do you have a link to the web site claiming 3 hr charge time?

Have you set the charge rate in the menus to Maximum, as these are usually set to minimum at the factory (for safety).

MKH & BoxBrownie: thanks for your replies.

The charging cable is rated as 32amp 250v, as supplied with new car (+ the domestic supply cable).

The charger is rated as 16amp 11kWh.

The car has been set to fastest charge.

The car is on charge est completion in 11hrs from 15% to full.

Should I be able to get faster?

The website link is https://livingwithi.bmwlaunchpad.co.uk/ It says "94AH Charging duration; AC Fast; up to 16 A; three-phase, up to 11 kW (80%): approx. 2 hrs 45 min." Does this assume that a tethered public charge cable is available of 94amp?

There are surprising few high speed charging points near me. I recall looking at Zap Map & there were only 1 or 2 that were fast, working & not Tesla in a city of 300k pop. - a fact not mentioned when choosing an EV! Even the local BMW dealer's charging points are inoperative & have been for months (due to inadequate local power supply); something also not mentioned by the salesman.

Looking forward to further advice.

I think that 32 amps is as much 'juice' as the 120h i3 can accept, hence the 32 amp cable that comes with it. If your charger is limited to 16 amps - then that's what the car is getting, and 11 hours from 14% to full is actually pretty normal. Think of the battery as a water tank fed by hose. A 120volt hose is your garden-type hose, while a 240volt hose is a commercial hose, and a 480 volt hose is a fire hose. Amperage is the water pressure of the water at the tap connected to the hose, which is feeding into the tank (battery). Think of 16 amps as average kitchen tap pressure, so it is going to take longer to fill the tank, than 32 amps, which would be double the pressure - no matter what size hose you use.

On the website under 'Charging' it shows the BMW Wallbox taking 5 hours and 6 minutes to charge the car from empty to full. That will be at the max 32 Amps. Same for public charging. It also shows the DC fast charging at 1 hour and 22 minutes. That will be the 440volt, 100 amp service (firehose connected to a hydrant)..

So with your 240 volt, 32 amp charge cord. You have a commercial hose that will take feed from a high pressure tap, but connected to a 16 amp faucet, you still get only house-tap pressure through that commercial hose, if that make sense.

Basically at 16 amps, it is going to take 10 hours or so to charge the car, empty to full.
At 32 amps, it is gong to take 5 hours or so to charge the car, empty to full.

Times will also tend to be slightly longer than the 'ideal' time, as some of the charge is used to warm or cool the battery pack to optimum charging temperature, and do 'maintenance', like cell-balancing.

The charger is rated as 16amp 11kWh.

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Something is wrong with this statement. Ignoring that the charger would be rated in kW and not kWh, 16 amp is close to 4kW at ~240v. For 11kW at 16amp, you'd need 688volts.

MKH's points are all valid, just wanted to focus attention on the 16amp, 11kW inconsistency.

MKH said:

I think that 32 amps is as much 'juice' as the 120h i3 can accept, hence the 32 amp cable that comes with it. If your charger is limited to 16 amps - then that's what the car is getting, and 11 hours from 14% to full is actually pretty normal.

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I've been waiting for a European i3 owner to reply, but it hasn't happened so far. Single-phase North American i3's have different chargers than 3-phase European i3's. I probably don't understand the differences, but I'll give it a shot hoping that a European i3 owner will correct me.

All i3 charging modules support 16 A 3.7 kW charging. North American i3's have 2 of these charging modules connected together in parallel which allows 32 A 7.4 kW charging from a single-phase 240 V electricity supply (also described as split-phase because the voltage is the sum of 2 phases separated by 180º). European i3's with 3-phase chargers have 3 of these charging modules, not connected together in parallel as in North American i3's but connected to each phase of the 3-phase electricity supply. Thus, each phase allows 16 A 3.7 kW charging, or 48 A 11.0 kW in total assuming the European 230 V nominal voltage.

To realize the full 11 kW charging power requires a 3-phase EVSE (i.e., wall box), a 3-phase charging cable, and all 3 charging modules operating correctly. If the EVSE or charging cable is only single-phase, or only 1 charging module is operating correctly, the maximum charging power would be the 3.7 kW that Colin is experiencing. If Colin's dealer is correct in stating that his i3's charging modules and his charging cable are working correctly, the wall box is the only other component of the charging circuit that could be faulty. Maybe Colin's wall box is a single-phase wall box or is a 3-phase wall box connected to only 1 phase.

To verify his dealer's assertions, Colin could try charging his i3 with his charging cable but using a different wall box known to work correctly. If this results in full 11 kW of charging power, his wall box is to blame. If this results in only 3.7 kW of charging power, he could try using a known good 3-phase charging cable. If this results in only 3.7 kW of charging power, 2 of his i3's charging modules aren't working. However, if this results in 11 kW of charging power, only 1 conductor of his 3-phase charging cable is working or he has a single-phase charging cable instead of a 3-phase charging cable.

Unfortunately, the i3 does not display the charging power while charging, so one would need to calculate the charging power by measuring the time required to add a certain amount of energy to the battery pack. I don't know the usable energy capacity of a 120 Ah battery pack, so I'll assume 40 kWh as an example. Using the charge level percent display of the i3's trip computer and ignoring charging losses of ~7%, each percent of charge level added would be approximately 0.01 x 40 kWh = 0.4 kWh. 11 kW of charging power would increase the charge level 1% in 0.4 kWh / 11 kW = 0.4 h or 0.4 h x 60 min/h = 2.2 min. So I would charge for 5 min to see how much the charge level percentage increased (this should be done with the charge level below 90% to avoid charge power tapering as the charge level nears full).

Or, I don't understand 3-phase 11 kW European i3 charging and something else is to blame.

3pete said:

Something is wrong with this statement. Ignoring that the charger would be rated in kW and not kWh, 16 amp is close to 4kW at ~240v. For 11kW at 16amp, you'd need 688volts.

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I assume that you are North American and aren't familiar with 3-phase electrical power because 16 A on each of 3 electrical phases at the European nominal 230 V voltage would be 11 kW of charging power. Nothing inconsistent about that.

It just shows how unfortunate it is that the U.S. chose residential electricity that is split phase (2 120 V lines 180º out of phase connected together to provide 240 V single-phase power) rather than 3-phase (3 230 V lines 120º out of phase not connected together). 3-phase motors can be more efficient than single-phase motors. 230 V lines need to conduct about half the current for the same power compared with 120 V lines and thus can be about half the size saving huge amounts of rather expensive copper.

Do UK destined i3's have 3-phase charging circuits? I think I read somewhere that 3-phase is only fairly common in a few countries in Europe (and some in other parts of the world - Australia, maybe?). If that's so, the car may be limited to only using one of the modules, and thus 3.7Kw.

jadnashuanh said:

Do UK destined i3's have 3-phase charging circuits? I think I read somewhere that 3-phase is only fairly common in a few countries in Europe (and some in other parts of the world - Australia, maybe?). If that's so, the car may be limited to only using one of the modules, and thus 3.7Kw.

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If the electricity at Colin's home is single-phase 230 V, the dealer should not have offered the 3-phase charger option without explaining that only one charger phase (3.7 kW) would be used when charging at home. Instead, his i3 should have had the rapid or fast charging AC option as we have in the U.S. so he could have charged at 7.4 kW assuming that his home has a charging circuit capable of safely delivering a continuous 32 A.

Maybe for some i3 owners in the U.K., there are so many convenient, reasonably-priced 3-phase AC public charging stations and no possibility of charging at home that having a 3-phase i3 charger would make sense. This doesn't seem to be Colin's situation.

wow, I'll need to do a degree in Elec Engineering to fully understand this!

Can I reset the debate by confirming:

the EV is i3 120Ah 2019 UK model

the BMW-supplied cord is labelled as 32 amp, 250 volt, 1 phase, 5 meter, public charging cable (+ separate domestic supply cable, which I'm not using)

the charger is rated as 3 phase 240v 11kW 16A

the car is set to maximum charge rate

last night it took 11 hours to charge from 15% to 100% full

the suggestion to try a public super fast charger is a good one, but as mentioned before they are like hens’ teeth around here. I’ll need the reassurance for when I make a long journey – spending 11 hours at a service station does not appeal!

ACTION: in order to get a fast charge at home, do I need to upgrade the charger from 16 to 32amp AND replace the cable from single phase to 3 phase???

Thanks for all advice.

It just shows how unfortunate it is that the U.S. chose residential electricity that is split phase (2 120 V lines 180º out of phase connected together to provide 240 V single-phase power) rather than 3-phase (3 230 V lines 120º out of phase not connected together)

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Part of the legacy of having the hard-core industrialist Thomas Edison use scare tactics and propaganda to crush Nikola Tesla in the fight for who got control of the electrification of America.

Watching the proliferation of distributed DC rooftop solar power generation and seeing California on fire yet again due to a fire started by transmission lines in the centralized-generation AC power grid, I'm starting to think that Edison's original plans would have been the better choice!

Seeing somebody's local campaign here against public J1772 charging stations where they are intentionally slashing the permanently-attached power cables to stop EV drivers from using them, I'm starting to think that the European charging station model where each driver brings their own cord might also be the better choice for future public charging stations.....

Watching the proliferation of distributed DC rooftop solar power generation and seeing California on fire yet again due to a fire started by transmission lines in the centralized-generation AC power grid, I'm starting to think that Edison's original plans would have been the better choice!

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https://www.scientificamerican.com/article/edisons-revenge-will-direct-current-make-a-comeback-in-us/

I assume that you are North American and aren't familiar with 3-phase electrical power

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Ah, both these assumptions are true, so today I learned something!

So, ColinP, since you have a 3-phase i3 it seems like your answer should be to upgrade the cable to 3-phase. One other question I didn't see definitively answered (but based on not being familiar with UK electricity I'm not sure if it's a foregone conclusion or not): are you sure you have 3-phase service to your house (and connected to the EVSE)?

Colin as far I know you need to wire the charger with 3 phase, I had the same problem, I have al so a 11kw charger but that delivers it only wen connected to 3 phase and not on monophase.

To 3pete & KrisM: my charger is definitely 3-phase (240v 11kW 16A); the limitation seems to be that it is only 16amp (not 32amp). I don’t know whether the cord being labelled as single phase (32 amp, 250 volt) is also a problem.

ColinP said:

To 3pete & KrisM: my charger is definitely 3-phase (240v 11kW 16A); the limitation seems to be that it is only 16amp (not 32amp). I don’t know whether the cord being labelled as single phase (32 amp, 250 volt) is also a problem.

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Part of the problem of us understanding your problem is terminology. The "charger" is in your car. The device connected to your home's electricity supply and to your car when charging is called Electric Vehicle Supply Equipment (EVSE) in the U.S., at least, and maybe just a wall box in the U.K. When you write that your charger is 3-phase 11 kW, to many that indicates that your i3 has the optional quick charger option as opposed to the standard 3.7 kW single-phase or the optional 7.4 kW single-phase charger. So i3's can be configured with 3 different chargers although all 3 options aren't available in all markets.

3-phase 230 V 16 A provides 11 kW of charging power. 3-phase 230 V 32 A provides 22 kW of charging power. No i3 has a 22 kW charger although some European EV's have offered such a charger (Renault?).

Using a single-phase charging cable would limit the charging power to that provided by one phase, 230 V x 16 A = 3.7 kW, so you definitely need to buy a 3-phase charging cable. If BMW sold you a single-phase charging cable for an i3 with a 3-phase charger, BMW should allow you to exchange your charging cable for the correct one.

The only other potential problem might be that your 3-phase wall box is wired to only a single phase of your home's electricity supply. If it is truly a 3-phase wall box, it seems unlikely that your electrician would have made this mistake. However, if your wall box and home electricity are single-phase, using a 3-phase charging cable would be useless and you'd be limited to 3.7 kW of charging power.

To summarize, to experience 11 kW of charging power, your entire charging system must be 3-phase including your home's electricity supply, your charging wall box, your charging cable, and your i3's charger. If any of these is single-phase, your charging power would be only 3.7 kW.

Thanks, alohart

You’re right – for ‘charger’ read ‘EVSE’ in my posts.

The EVSE supplier confirmed that the system (2x wallboxes) in my apartment block is 3-phase (240v 11kW 16A), but I understand from your post that there is no point in asking them to upgrade to 32amp for a faster charge because: “3-phase 230 V 16 A provides 11 kW of charging power. 3-phase 230 V 32 A provides 22 kW of charging power. No i3 has a 22 kW charger”.

I’ll ask BMW to substitute a 3-phase for my single phase cord.

How do I know if my i3 charger is capable of 3-phase? Local BMW dealers know next to nothing about EVs. The VIN decoder says I have "Quick charg.altern.current multi-phase + Rapid charging, direct current". Does that mean 3-phase capability or the standard 3.7 kW single-phase or the optional 7.4 kW single-phase charger (latter 2 per your post) or something totally different?

Thanks, again

PS (see previous post) I just looked on https://evconnectors.com/ev-plug-bmw-i3-cable They offer 32amp, 3-phase, 22kw cords @ £135-170. This implies that some i3s ARE rated to 22kw, but how do I determine the charging capacity of mine? No point in buying a new cord if the car will not accept a higher, faster charge. If the EV will take 22kw, then it’s back to the EVSE supplier to upgrade to 32amp?