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Charging time question

Posted: Sat Jan 02, 2016 2:10 pm
by davesw1
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

Re: Charging time question

Posted: Sat Jan 02, 2016 2:56 pm
by alohart
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.

Re: Charging time question

Posted: Sun Jan 03, 2016 8:34 am
by cmj912
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.

Re: Charging time question

Posted: Sun Jan 03, 2016 12:13 pm
by alohart
cmj912 wrote: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.

Re: Charging time question

Posted: Mon Jan 18, 2016 1:22 pm
by Schnort
alohart wrote: 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...

Re: Charging time question

Posted: Wed Jan 20, 2016 2:28 pm
by Georgios
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).

Re: Charging time question

Posted: Wed Jan 20, 2016 6:04 pm
by alohart
Schnort wrote: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.

Re: Charging time question

Posted: Wed Jan 20, 2016 7:37 pm
by Schnort
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...

Re: Charging time question

Posted: Wed Jan 20, 2016 10:20 pm
by jadnashuanh
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.

Re: Charging time question

Posted: Sun Jan 31, 2016 8:52 pm
by SteveMondragon
Schnort wrote:
alohart wrote: 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.