Twizy's charging configuration

Renault Twizy
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#1

Hi guys. I’m new here.

I am doing a master degree in Electrical Engineering in the area of Power Electronics. I am researching and constructing a wireless power transfer charger for a Twizy (2016 Model).

I need some information that is unfortunately not easily found. According to the vehicle user manual, the traction battery’s voltage is 58 V (so far I don’t know whether it is nominal or maximum voltage). That’s all the information I can get about the battery from this manual
(link: http://gb.e-guide.renault.com/sites/default/files/pdfs/eng/X09/Twizy-913-12_ENG.pdf). I don’t know about other EV’s manual, but this one is ridiculous. It doesn’t tell anything about the ac voltage range (220 right?), energy, current drawn from the grid (it does tell me the protection = 16 A). I hope Renault upgrades it.
With that being said, I found a brochure from UK
(link: https://www.cdn.renault.com/content/dam/Renault/UK/brand-and-editorial/Brochures/Vehicles/twizy-brochure.pdf) that contains way more information regarding technical information than the manual itself (mind, a brochure!).

Battery’s information are:
Capacity = 6,1 kWh
Battery type = Lithium Ion
From 0 to 100% = 3,5h
Slow charge = 10 A

The AC voltage = 230 V (brochure from UK)

Now, let’s do the math. Usually, a lithium cell is about 4.2 V to 4.1 V maximum voltage
I found a video of a guy using a “power box” to hack/tune the Twizy. It could be seen, indeed, that the maximum voltage was at 4.135 V. Of course you don’t wanna over charge a lithium-ion cell, so probably the charger will charge up to 95 ~ 99%. Nevertheless, round up to 4.2 V.
In the video, it was shown the amount of series cells s = 14.
So,

14 x 4.2 = 58.8 V. Which means, that the information that is given in the manual is apparently related to the maximum voltage of the battery pack, and not the nominal.

Searching even further, the Wikipedia says that the battery pack is supplied with LG Chem modules. Then I found this datasheet (link: https://www.s-power.cz/wp-content/uploads/lg-chem-resu-datasheet.pdf).
For a specific power module, it exactly states:

Energy 3.3 kWh
Capacity 64 Ah
Nominal voltage: 51.5 V
Voltage range: 42 to 58.8 V
Weight: 28 kg
So, in this case, my guess is 14 cells in series (14 x 4.2 = 58.8 V) and 22 cell in parallel (taken the Panasonic lithium-ion cell’s capacity = 2.9 Ah = > 64/2.9 = 22).

Considering all guesses are correct =>

6100/51.5 = 118.44 ah (Hopefully they have informed the energy (kWh) using the nominal voltage, and not the maximum voltage)
118.44/2.9 = 40.84 cells in parallel => 41 cell in parallel in the Twizy battery pack.
Total amount of cell = 14s x 41p . Can anyone confirm if this guess is correct? I really need to know the capacity of each cell from the Twizy.

Now, coming back to the brochure information:
Consider V ac = 220 V.
If it can charge from 0 to 100 % in 3,5h the amount of 6100 Wh
=> 6100/3,5 = 1742 W delivered to the battery considering power is constant.
Consider now efficiency of the power converter = 85%
=> 1742/0.85 = 2050 W. Therefore, the battery charger is designed to be able to operate at 2kW.
However, charging a battery uses 2 modes (constant current and constant voltage) and not constant power. So, there might be a peak power (Suppose 2.2 kW), which yields:

220 V x 10 A = 2,2 kW
Therefore, the information in the brochure (10 A - Slow charge) is related to the current drawn from the ac grid, and not the battery!
This way,

2200*0.85 = 1870 W delivered to the battery at peak power condition.
1870/51.5 = 36.31 A (avg) = constant current to the battery pack.
Therefore,
Iconstant = 36.31/41 = 0.885 A. for each cell

Usually, constant current Iconstant charges between 0.5C. The Panasonic example was 0.7 C
=> C = 0.775/0.5 = 1.55 Ah

or
C = 0.775/0.7 = 1.1 Ah

You see, it is important to know the capacity of each cell to be able to manage the power the way you want(charge quicker, discharger quicker… and so on).

Which means that my previous guess on the capacity C = 2.9 Ah is not very correct…

Well, these were all guesses that I hope someone can help me or at least I hope it can be helpful for the community

1 Like
#2

Some I can answer but most will need to come from @kennethnilsen69

In the Uk:-
240+ Volts
Up to 10amps drawn (slightly less on the MK2 charger) But work on 2200w
3.5 hours to bulk charge and a further few hours to balance again depending on the charger. So battery and charger losses is approx 7.7kwh

I work on 2mins per 1% when charging except between 97% and 100% when it can be 5 mins per 1%

Most of this fits with your findings.

1 Like
#3

Thanks for the quick reply, osbrook!
Let us hope more information.

#4

There is a Twizy service manual floating around on this site according to @osbrook, but damned if I can find it.
Perhaps you may have better luck finding it on the internet, alas I have not.

#5

No the full service manual was a private download some one offered.

#6

Couldn’t find the link to that either :frowning:

#7

I tried, but couldn’t find. There seems to be a paid version (link: https://www.emanualonline.com/Cars/Renault/Twizy/2016-Renault-Twizy-Service-and-Repair-Manual.html). But I’m not sure if it trustworthy.

#8

2050W is the max peak power shown on public (11kW or 22kW) charging points when I charge my 2018 Twizy…I have 16A/3,6kW adapter (type2 / shuko)

#9

Hi.
Perhaps a help for you :
The traction battery consists of 7 modules each with 6 lithium cells (2 serial blocks each containing 3 cells fitted in parallel).
Range: For each cell: 3.75 V / 43 Ah Traction battery: 7 KwH / 52.5 V
The battery + terminal can be isolated from the vehicle via the two power connectors connected to the charger and to the traction battery as well as the 60 A fuse. The inverter power relay is controlled by the inverter whereas the charger power relay and inverter supply relay are controlled by the charger/converter. Maximum voltage for the traction system: 60 V. Common earth for the vehicle and the traction system.
Kind regards.
Philippe

1 Like
#10

Thank you very much. So, basically, each has 43 Ah and there are 42 cells at total.

#11

Hi…I ask myself for some time if it would be possible not to load the twizy to 100%, because mostly LI batteries don’t like to be fully loaded.
Of course the Twizy has no setting for that, a solution could be to stop loading when the current drops below 2000w for example.
Does sonoff pow r2 gives you control to stop the power when the power flow drops below a certain level?

#12

I’ve always assumed the battery management system takes care of this?

However, if you do want to stop charge prior to 100%, this setting is available when using a PowerBox.

Screenshot_20191102-081825
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#13

I also use sonoff pow r2 to stop charging before 100%, to preserve battery life. But there are some issues to consider:

-during constant I charge (up to ~80-90%) twizy takes around 2kw constant but not always. During summer, if the battery is too hot, it derates charging power to around 1,6kw or less.
-you cannot permanently use minimum power limit setting on pow r2. That is because when you go from off to on, twizy consumes few tens of W during charge initialization sequence (4-5 seconds), only after that it jumps higher. If you have minimum limit set, it will disconnect before starting to charge. So, the proper way to do it is to go from off to on without any limit set. After you see the consumption jumps, then you enable the limit. I use 1500w from almost a year, I already have one year and 13k km since purchase. Battery health read from can bus was still 100% 2 months ago. Unfortunately this forces you to manually start charge each time, you cannot use automatically start at some hour, because you have to disable then reenable the minimum power limit. I asked the developers of sonoff to create a setting to temporary disable power measurements or to ignore limits for few seconds after starting device, but no reaction yet.
-stopping charge before 100% will skip cell balancing sequence. I advice to let it fully charge once or twice per month, to allow balancing to take place.

#14

This is key and will have more effect, if balance of the cells gets a long way out it will take longer to re-balance and you may have to charge to 100% several times in a row.

If you lease the battery charging to 100% is not an issue.

#15

Dear All
I had small issue with my Twizy while I was driving around at last place I stop for about 1 hours, when I turn on my twizy I had service light on and speed was dropped. I took it to same garage where they fix it before and they informed me one unit of 7 battery is not functioning to receive charge which made my charging only reach to 19% on 3 hour charging time.
Now if I need to build a battery does any one can give me the right voltage per unit and Amp since when I open the battery case I see 7 unite and each unit it has 8.285 volt x 7 = 58 volt

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