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Discussion Starter #1
Can anyone advise the best QC strategy once in the taper part of the charge. At what point does the QC rate equal the same as I would get out of a 7kw post? i.e. Does it make more sense to set off and use a fast charge en route rather than wait. I had thought this was when the charger reads 16A since I have a gen 1 leaf but now I realise that when the charger says this it is a 400V DC 16A output which is going to be more kW than a 230V AC 16A input will provide.

Basically when does it make sense to cut off a quick charge for a gen 1 leaf if you know there is a 7kw fast charger further on your route.

Thanks
 

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Discussion Starter #3
Ok I searched google for AC/DC power calculations and found this.


I put in 400V 16A DC and 230V 16A AC which suggests that the QC output is double the power at 16A

Plugging the kW for AC back in to the DC tool gives 9.2Amps on the quick charger as the point where you could switch to normal charging.


Interestingly if you have a Gen 2 leaf with the 6.6kW charger then you might as well disconnect at 16amps and use a 32Amp further on your route.

Hopefully someone will point out the flaws in my assumptions above :)
 

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This is it, with the fast chargers at some services I think there's an optimal "switch" time. This goes back to the general concept that a fast charger (or chargers) next to rapids as being a very sensible suggestion. Even better if drivers are educated as to when it would be just as wise to "switch over" to free up rapids.
 

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Interesting thread :)

One thing to consider is that the AC charger in the car is only ~90% efficient and that will reduce your AC numbers slightly.

Battery temperature may also be relevant.
 

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Discussion Starter #6
Thanks Kevin, I assumed the reading on QC was the output and so excluded the efficiency for that but totally forgot about the efficiency on the car's internal charger.

There is a practical reason behind this, I am travelling from Newcastle to Scarborough next Friday and since the last rapid charger I will be using in Middlesborough is £5 then the cut off point now has a financial consideration too as there are a couple of fast chargers beyond Middlesborough that are free.

Cheers
 

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So if you see the figures on the charger around this sort of value...

Power = voltage X current

Power = 400v X 16a

Power = 6.4kW

It might be worth swapping to a 32a post if you can be bothered .

Power = voltage X current
Power = 230 X 32
Power = 7.3kw - efficiency losses.
 

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Cheers[/QUOTE]
Thanks Kevin, I assumed the reading on QC was the output and so excluded the efficiency for that but totally forgot about the efficiency on the car's internal charger.

Cheers
I think he is talking about the efficiency of the on board AC to DC charger. Roughly 90% efficient.
 

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Discussion Starter #9
So if you see the figures on the charger around this sort of value...

Power = voltage X current

Power = 400v X 16a

Power = 6.4kW

It might be worth swapping to a 32a post if you can be bothered .

Power = voltage X current
Power = 230 X 32
Power = 7.3kw - efficiency losses.
Yes, unless you have a Gen 1 Leaf that can only charge at 3.6kw then you are better off waiting until the value is 400v x 9 Amps = 3.6 kw.

Two factors impact the "can I be bothered" factor
1) has a 32amp post been provided at the same location
2) is it costing £5/hour to stay on the rapid

:)
 

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8amp for a 3.6kw car/post and 16amp for a 6.6kw car/post.
 
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So if you see the figures on the charger around this sort of value...

Power = voltage X current

Power = 400v X 16a

Power = 6.4kW

It might be worth swapping to a 32a post if you can be bothered .

Power = voltage X current
Power = 230 X 32
Power = 7.3kw - efficiency losses.
Yes but depending on whether the efficiency losses have been applied before or after Nissan's stated charger rating you get different numbers. 6.6kW after losses or before? 6.6kW DC output, then the 400V/16A tipping point is right. Otherwise if you derate the 6.6kW charger by 10% we get to 5.9kW which would suggest holding onto the DC rapid until you dip below 15A.

Personally there are other losses to consider: patience, time, sanity. Not to belittle the thread, its intellectually interesting but I think I would simply stay as long as I needed to be sure of getting out of the dreaded motorway services flytrap and worry about bigger issues. :p
 

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Yep I agree with you. Lot less “fannying" around and yes I would just stay on the rapid for your desired SOC (unless someone was queuing and needed the rapid desperately) :)
 

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Discussion Starter #14
Looking forward to having even more data to geek over ;)

@Dean
I am not suggesting I would swap just for the sake of it.

My thought was do I stay here for another 20mins or plan another stop for 20mins at a 7kw charger in the Yorkshire charging wasteland.

My plan is now to use the free Ecotricity charger at Roadchef County Durham and then plan to stop at loftus to get enough to make the 71miles. I know I can make that distance with 100% start but if I leave with 90% it could be a bit of a stretch.
 

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Looking forward to having even more data to geek over ;)

@Dean
I am not suggesting I would swap just for the sake of it.

My thought was do I stay here for another 20mins or plan another stop for 20mins at a 7kw charger in the Yorkshire charging wasteland.

My plan is now to use the free Ecotricity charger at Roadchef County Durham and then plan to stop at loftus to get enough to make the 71miles. I know I can make that distance with 100% start but if I leave with 90% it could be a bit of a stretch.
So in F1 terms, are you talking about a 1-stop or 2-stop strategy? :)

Given that scenario, although Yorkshire is very beautiful, surely (all else equal) you're better off staying put for 20 mins to avoid the other overheads of making a pit-stop like slowing down, parking etc. whilst you could be gliding past on your 1-stop plan. There's the added bonus of avoiding the newly coined phrase 'charger anxiety' - what if your planned 2nd stop is broken or ICE'd?
 

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This is a very interesting question and one that I have been exploring myself recently.

I have noticed that the charge current starts to reduce at about 52%. The max current is normally 106A/393V... this is 41.6kW. It drops off pretty quickly and by 80% it is about 40A/393V or 15kW.

So, if I can stop charging at 52%, drive to the next charger and charge to 52% again then I am always charging at max power and not wasting any time charging more slowly.

So the best strategy for time is charge to about 50% and move on.

Of course, that assumes that the charger is free and available when you arrive. If you have to wait then all bets are off.

At 393V it would require the current to drop to about 17A before it is similar to a 7kW post but it is highly unlikely that it would be any quicker on the post. By that time the battery is pretty full and so it too would be throttling back on the 7kW post as it approaches full... it would free up the rapid a bit quicker though and so definitely worth doing if people are waiting.
 
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