Charging time question

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davesw1

Active member
Joined
Jul 8, 2015
Messages
40
I've used the same 7Kw charging point 20 or so times, and every time I use it, it is a lottery of how long it takes to charge, yesterday i went from 14% full to fully charged in just over 3 hours other times i've been about 55% full and it takes 6 hours to get fully charged! can anyone shed any light on it? thanks
 
If the EVSE shows its current charging power (e.g., 7 kW), then the charging time should be consistent.

If it doesn't show its charging power, then it might not be providing 7 kW consistently. If the demands on the local electrical grid are high, the voltage at the EVSE might be low which would increase the charging time. If your battery pack is quite cold or hot, your car's battery management system could be reducing the power that it is willing to accept. If your car's charging electronics (KLE or EME) aren't functioning correctly, the charging power that your car would accept could be low. The i3's original KLE was defective. BMW updated the software that controlled the KLE to reduce the charging power to protect the KLE from failure. Some replacement KLE's have failed which reduces the charging power by half.
 
I notice a couple of strange things. At Level 1, the app and the timer thingy inside the car report super-long charge time estimates. But when I get up in the middle of the night for a glass of water or something and check on it the car is often done three, sometimes four hours earlier than estimated.

The other thing I notice is that the app will show that the car is charging at Chargepoint but the dash display shows a white plug if you press the button on the display.
 
cmj912 said:
At Level 1, the app and the timer thingy inside the car report super-long charge time estimates. But when I get up in the middle of the night for a glass of water or something and check on it the car is often done three, sometimes four hours earlier than estimated.
Many have noticed that the charge time estimates are pessimistic, so your experience seems normal.
 
alohart said:
Some replacement KLE's have failed which reduces the charging power by half.
Huh. I wonder if that's happened to me.

A friend at work has a Tesla, and he's shown me the EVSE provides 30A @ 208V or so to his car(so about 6.2KW). It takes me about 3.5h to go from 50% to 100% on the same EVSE, which seems like about 3KWh...
 
Do you set departure time? I believe it delays the charging. If the car knows it will leave in 8 hours it won't charge in 6, it goes slower. I notice it with 3.7kW charging too (scharging at a rate of 2.4kW for example).
 
Schnort said:
A friend at work has a Tesla, and he's shown me the EVSE provides 30A @ 208V or so to his car(so about 6.2KW). It takes me about 3.5h to go from 50% to 100% on the same EVSE, which seems like about 3KWh...
That seems slow, but the charging rate decelerates considerably as the SoC approaches 100%. A better test would be to measure the time required to charge from some low SoC to less than 80% to avoid the charge rate tapering.
 
Yeah, I think I'll run it down low and see how long it takes.

I just wish BMW would let us see this information directly.

Do the public chargers like charge point say the delivered power?

I'd gladly pay the few dollars to see, rather than go through the hoops to get a volt/ammeter combo on my charger...
 
For less than $20 I bought a panel mount volt/amp meter on Amazon and a switch, fuse and cover plate. Then mounted it to monitor the power going through my EVSE from the electrical box the thing is wired into. Quick and easy if you have any skills. My normal line voltage is 246vac and I see a max of just under 30A, which is very close to the i3's maximum charging current, and well within the accuracy of the device, so I'd guess it really is maxed out prior to the taper off near the end of the charge. The input voltage can affect the power delivered as is depicted by the P=IE formula. Many commercial installations use 208vac while most homes have nominal 240vac, which with an EVSE set to announce 30A, will have a noticeable difference in total power delivered.
 
Schnort said:
alohart said:
Some replacement KLE's have failed which reduces the charging power by half.
Huh. I wonder if that's happened to me.

That's what happened to me, and my i3 REx is currently at the dealership right now.

Just waiting to hear from them (tomorrow) whether the part is in stock locally within So Cal, or if they have to order it from Germany as that will take 2-3 weeks.
 
I've used the same 7Kw charging point 20 or so times, and every time I use it, it is a lottery of how long it takes to charge, yesterday i went from 14% full to fully charged in just over 3 hours other times i've been about 55% full and it takes 6 hours to get fully charged! can anyone shed any light on it? thanks

Question about the charging point. Is this your personal charging point or a public charging point? If it's a public one, does it have more than 1 charging port? Can another car plug into the same port at the same time?

The reason I ask is because if there are multiple charge ports on a single charge point, there's only the same amount of power to go around. The ChargePoints near me are listed at 6.6. If Its only me plugged in, I can pull the full amount (sometimes I even pull up to 6.9). Is someone else is sharing it, I can only pull around 3.3 kw. 3.3kW, with the reduced charging rates towards the tail end of your battery charge would run around 6 hrs.

Thanks,

RExingIT
 
Reduced rates tend to be more common with CCS units when multiple ports are available, but it could easily be incorporated with level 2 units if they were interconnected so the computer would know. The max you can draw is determined by the pilot signal from the EVSE...the car will never try to draw more than what is announced that is available.

Keep in mind also that the amount of amps drawn and resulting watts provided is still based on the simple equation Power=Volts*Amps...so the voltage could easily vary depending on the time of day, and the load on the power grid. Most commercial units tend to use 208vac in the USA verses 240vac that many have at home, and that does result in reducing the watts, as the only thing constant tends to be the max amps drawn...so, as you can see from the P=VA equation, any reduction in volts has a direct relationship on how much power is drawn, even when amps remains constant.
 
Hrm, so I brought my car to BMW to get the annual maintenance and software upgrade, etc. and told them about the slow charging time.

The service manager said they tested it and "5.8KWH is totally normal".

Where do I go from here? How to elevate it?
 
Schnort said:
Hrm, so I brought my car to BMW to get the annual maintenance and software upgrade, etc. and told them about the slow charging time.

The service manager said they tested it and "5.8KWH is totally normal".

Where do I go from here? How to elevate it?
Assuming a 208V EVSE and a maximum normal 30 amp charging current, that would be 6.2 kW. If your KLE or EME were defective, the maximum charging rate would be 50% of normal, or 3.1 kW. That's way below the 5.8 kW (not kWh) that you're experiencing, so it's almost certain that your KLE and EME are working normally. If the EVSE's voltage is low, which could happen when delivering 30 amps or when the local voltage is low, in general, the charge level of your battery pack is high enough that charge power tapering is occurring, or your battery pack is hot enough that the charging power is reduced, 5.8 kW would be within the normal range. It doesn't seem like you have a case that would warrant an escalation.

Did your dealer deny your software upgrade request because your charging rate was considered normal? If so, I'm surprised because I would think that your dealer would have installed the stronger motor mount bolts and the current software update that reduces the probability of breaking a motor mount bolt.
 
Schnort said:
alohart said:
Some replacement KLE's have failed which reduces the charging power by half.
Huh. I wonder if that's happened to me.

A friend at work has a Tesla, and he's shown me the EVSE provides 30A @ 208V or so to his car(so about 6.2KW). It takes me about 3.5h to go from 50% to 100% on the same EVSE, which seems like about 3KWh...

Which software version you are using? there is an older version slow down charging.

My experience is that with 30A / 208V, you will only get about 5.7 kW. Mine will take about 2.5h from 50% to full. i3 will take its time to fill up from 90% to 100%, usually 1 hour or a little bit more.
 
I just got the 'new'/march software (supposedly) this morning, so I'll pay attention going forward.

It did go from 90% to 100% in an hour when I plugged in this morning, which seems quicker than the ~3 hours for 75%-100% I usually get.

I really wish you could see this information directly from the car's infomatics, rather than trying to divine it.
 
I've got a similar problem - this morning it was saying it would take about 6 hours to charge fully from about 35%. I've got a 32A charger, it's all 240V (as I am in the UK) and I've got a BEV (no DC charing option). I've made sure I've got all of the charging setting set to maximum so it just seems to be charging up incredibly slowly. Currently it is at 74% and is saying it will take a further 4 hours to get to fully charged - I know it tapers off after 80% but I'm sure it has charged much quicker in the past.

I've got a 32A Rolec charger and not sure at all if this could be at fault - I don't think so as I've used a local fast charging station and that has been slow also.

Do you think its a trip to the dealer or can anyone at BMW look at it remotely (he says in hope!)

Thanks, Ian
 
I suppose that a worn (loose) charging cable plug could slow the charging rate down. Do you ever get a warning that charging was interrupted? That can occur for multiple reasons, mostly caused by the cable and power. If you feel the outside of the plug, is it hot? That indicates a poor connection (higher resistance) which will lower the voltage available to the car, and slow things down. Are you sure you've pushed the plug in fully? The US plug is a little less prone for that than the Menekes one used in Europe.
 
Hi-I'll have a look but seems to be fitting okay. Will be pretty much on empty by the end of tomorrow so will try to charge up at my local charging station to see how that goes and rule out my charging point. Thanks again.
 
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