Bjron
Posts: 38
Joined: Tue Nov 13, 2018 11:05 pm

Chademo speed and max soc

Tue May 14, 2019 3:15 pm

Hello

What have been your ecperience on these?
I have btoken ac charge unit now and car is Chademo only use. Dcdc is working ok.

Czero charged yesterday to 82% first and with redo chademo did 95%.

Today i got only 86% not even redo helped or 5km driving and redo. Still just 86%. Quess it didnt like my emptying to just 10% 3.75v..

Yesterday i did empty to 15%. Well still anyway faster to charge 5% from 10% to 15% with 125a than 9% from 86% to 95% with 12A on chademo. Much better.

Czero get amps down very fast compared to miev. Guess its total much worst BMS on czero...

Bjron
Posts: 38
Joined: Tue Nov 13, 2018 11:05 pm

Re: Chademo speed and max soc

Tue May 14, 2019 3:46 pm

Miev was 70a until 70%. Czero is just 40a on 70%... But Fortum likes its 0.20cent/minute payment..

DBMandrake
Posts: 157
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Chademo speed and max soc

Wed May 15, 2019 4:43 am

Bjron wrote:Czero get amps down very fast compared to miev. Guess its total much worst BMS on czero...


Bjron wrote:Miev was 70a until 70%. Czero is just 40a on 70%... But Fortum likes its 0.20cent/minute payment..


The BMS in the C-Zero is identical to that in the i-Miev. The difference you will be noting will be due to either differences in cell temperatures (did you test at the same cell temperatures ?) or difference in the health of the cells.

Maximum charge speed will occur at about 25-35C cell temperature, any colder than 25C and rapid charging will be slower and taper off earlier.

Also, if you have any cells with high internal resistance rapid charging speeds will be dramatically reduced and tapering of the charge rate will start very early even when the cells are at the ideal temperature.

My car now has two cells with high internal resistance and rapid charging speeds are much slower than they were two years ago. Previously it would charge at a full 43kW up to about 50% SoC before gradually tapering back, and could get from 20% to 80% in about 20 minutes.

Now even if I plug it in at 20% SoC with optimal cell temperatures it will only charge at 43kW for under a minute before it starts tapering the charge rate and it within a couple of minutes it will pull back to about 30kW. By 40% SoC it will be down to about 25kW. Charge time from 20% to 80% is now more like 30 minutes with the latter half of the charging time being very slow.

This is because the two cells with high resistance reach the maximum 4.1 volts within a minute of starting the charge even while all the other cells are still only at 4.075 volts.

So I would say the difference between your two cars is that the one that is slow to charge will have one or more cells with high internal resistance. Not much that can be done about that apart from replacing the cells, which I'm considering on mine.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

coulomb
Posts: 171
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

Re: Chademo speed and max soc

Wed May 15, 2019 8:35 pm

DBMandrake wrote:This is because the two cells with high resistance reach the maximum 4.1 volts within a minute of starting the charge even while all the other cells are still only at 4.075 volts.

I suspect though if you replaced those 2 cells with brand new cells, then two or three others would limit the fast charging after 2 minutes instead of 1 as now. If you sorted the cells by internal resistance, I suspect there would be a gradual increase of internal resistance from best to worst, with no sharp delineation between "bad" and "still good" cells.

If two cells shot up to 4.1 V while the rest were at say 3.8 V, then it would be worth replacing those outliers, and you'd get a dramatic improvement in fast charge speed from "only" replacing those two cells (ignoring the huge hassle/cost of sourcing the replacement cells, safely getting access to the cells, and putting it all back together afterwards).

Edit: in other words, I'm suspecting that several of the cells presently pegged at 4.075 V are only prevented from reaching 4.100 V because the charge current had to be scaled back because of the two slightly worse cells that got to 4.100 V first.

Edit 2: Oops, I see in other posts that you seem to have measured the cell capacity and internal resistance carefully, so probably just ignore this post.

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