New intelligent Power Box for Twizy :-)


(Kenneth) #242

Yes, unfortunately, sometimes someone gets a little tax and sometimes someone who does not get.
It’s like winning in a lottery.
It’s hard to discuss it with them since the product really costs 450 euros. The tax you have received is of 30 euros


(Dale Pearson) #243

Cheers Kenneth,

I am sure the bulk of it is a handling fee, and like you say it could be worse.
I just kinda expected nothing as the declared value being under the thresholds.
Oh well get it next week sometime hopefully. Your service has been great so far, so thanks :smiley:

(Dale Pearson) #244

Just collected my PowerBox from the customs desk.
Cant wait to try it out.

(Dale Pearson) #245

Loving the PowerBox :slight_smile:
Great work Kenneth

(Kenneth) #246

Thanks @dalepearson :slight_smile:


Can Powerbox show battery SOH info? Can you set charging current limit, i.e. 3 amps instead of 10?

(Kenneth) #248

BMS to Twizy does not have a value called SOH but it has something that is much better. We can read kWh as is what your warranty follows. SOH is not an important parameter.
Powerbox reads kWh today and the next firmware vesjon will also read out voltages on all the cells.

SOH shows the health conditions of the battery. you can easily lose 30 capacity and still have 100% health SOH does not follow normal wear and tear. If you have one or more cells that have less capacity than others then SOH will be lower. This is also shown clearly on kWh and cell volts.

as I have written once earlier.
A 60-year-old can have 100% health, but a man of 20 years will usually have much more capacity.

and yes Powerbox can reduce the charge current with 7 levels. But it’s not a perfect solution yet and is still under development

(Kenneth) #249

Hi @nakos
Sorry I do not know where my thoughts were when I wrote this.
Yes Powerbox also shows SOH :slight_smile: but the rest regarding how important SOH is was correct :-)))

(Frank Demes) #250

But isn´t the SoH in the BMS what´s important to Renault, when it is time to change the battery?
Renault is not able to give you a kW readout.

Here in Germany the Renault Bank/car dealers tried to do test drives to measure the range if you challenge them with low capacity.
A Friend of mine had to go through all this.
After insisting for a readout of the SoH and pointing out that this is the Threshold agreed in the battery lease, he got a new one!

(Kenneth) #251

No, it really depends on what is the reason.

at low SOH yes, then they need to replace the battery due to errors on the cells. (it means that some cells are more bad then other cells)

But your warranty is most relevant to the capability. That is, for normal wear and tear
All cells lose the capacity after how many charge cycles they have. (Temperature and various other reasons also wear out on the cells)
You can lose a lot of capacity in the cells without making any impact on SOH.
Therefore, you must think of the capacity regarding your warranty. and of course SOH, but that is only for abnormal problems with the cells.

If you lose more than 25% of capacity, you should be able to demand new battery.
4.57 kWh = 75% off 6.1 kWh.

And Yes Renault can read kWh if they want

(Frank Demes) #252

Nope, smooth sailing down to 75% with voltage diffs pretty much intact.
Thats why Renault tried to get away with this ridiculous range tests.

If one cell would have acted up, you would notice a sharp range drop while driving.

BTW My battery got tested at the end of my contract (and before my Twizy was send to the recycler :wink: , cause I totaled it).

All what Renault can say is, how many kWh the battery has recieved over it´s lifetime and how much you have driven.

BTW2: This is how Renault could say , if you used a tuning kit! (if the charging is more than 18% off, they know the power had to come from somewhere (higher recup).
This and the max logs in the Sevcon (motor rpm over 8000, max power output etc.) that you can´t delete!
Until now they just do not mind.

Thats what they see.

First value: Battery charge over time (inkl. recup) - 1676
Second value: Battery health 100%
Third from the bottom: ODO measured by the BMS - 20tkm
(The BMS has its own Odometer!!. My display was off by hundreds of km!!! Some in the 21xxxkm)

As you can see , this amounts to a power consumption of about 8kWh per 100km.
That´s save.(I floor the Twizy pretty much all the time.)
If this drifts somewhere to 9 or 10Wh/km then you might have to do some explaining :wink:

BTW: The Guy with the 75% had about 100tkm on the ODO in 2017.
Something our data predicted in 2015.!

And with the OVMS he could say that the voltages of the cells were A OK (for that age of the battery).

OVMS started in 2012 as a monitoring system that can monitor the cells in nearly real time.
I have a mostly uninterrupted log of my battery voltages over the last 20tkm in 5 second resolution :wink:

As other users also do. So we have a pretty vast size of data points to say, that the SoH has not much to do with defects in the battery.

Have a look at this thread.
There is a capacity and time factor in that BMS SoH. It just does not correlate 1 to1 .
(pretty big dropoff at 3-4 years and 40-50tkm)

But in the end, both graphs will meet.

(Kenneth) #253

You refer to the CLIP software that the Renault service people use. Quite right here, there are many parameters that they can not read with the CLIP software.
But in Norway, Renault has established its own battery service center that takes all the jobs inside the battery box for Renault. Here they read out all relevant parameters and provide a proper measurement of the batteries that can not be done by Renault service.

This is a common problem for all car brands that have electric cars. They can not measure the batteries properly. Most of them can not even test a regular 12v battery for how many Amp it contains. That’s how little they know about batteries.

SOH is not calculate by the difrents BMSs the same way. There are different variants on how they calculate SOH. Although they all try to calculate the health of the battery, there are different ways by the different BMS manufacturers on how to do this. (sorry for this bad grammar in this sentence :-)))

But anyway, it’s kWh which means something because it tells you how much power it’s in the battery.
If you only have 70% kWh and Renault tells you that you have 95% SOH and your battery is ok. Then you can not just accept it. The car business generally will do a lot to avoid giving you a new battery and trying a lot. that does not mean they are right. This applies not only to Renault.

For you who read this and do not know what kWh means:
kWh is the measurement unit we useto calculate the amount of power in a battery just as we use liters or gallons on gasoline tank

If you have a car that have a 10kWh battery and you measure it at only 6 kWh then it’s only 60% left of the capacity in this battery. How much SOH means nothing to me.
But of course, if I only have 70% SoH for an example, I’m worried because then my battery has bad health and it’s not good

But no matter how you want to measure, Powerbox has both :slight_smile: kWh and SoH value.:slight_smile:

Important: it is not the Powerbox that calculates neither kWh nor SoH. It’s your BMS inside the battery box that does this. The Powerbox only reads the values.

(Frank Demes) #254

But these values in the BMS are misleading.
They do not represent the capacity you are working with and for what you are “charged” for in your contract.
As much as we figured, they are total arbitrary and only a placeholder.

Nothing new!

That figure would put the Capacity of the battery to about 129Ah!!!
Realistically we work with ca 116-118Ah.(108Ah used)

Just have a look at what the cells are labeled with!

A cell has 966Wh.(there are 7 cells in a Twizy battery)
That´s 6762Wh total capacity.

Renault says you can use up to 6100kWh.
Its more like 6000kWh.
The charge end voltage is set a bit lowerby Renault so the BMS only charges to about 88-90%

The SoH deals somewhat with this values.

The best method still is to measure how much you can charge the battery.

With a bit empiric data you can figure out what losses you get from the charger.

A normal full charge with the OVMS looks like this.
(The OVMS continuously measures the power intake during the charge)

Charge Done
CHG: 5648 (~6477) Wh
Range: 79 - 68 km
SOC: 100.00% (5.04%…100.00%)
ODO: 15311.0 km
CAP: 99.4% 107.4 Ah
SOH: 100%

The charger only reports the power used in the primary circuit ( AC before the DC)

With a bit of above mentioned data collection you can assume and calculate the efficiency of the charger.

This will bring you to the second value 5648Ah for a 95% charge.

At the end of the lifespan(100tkm) %CAP (Measured by the OVMS) and %SoH (Set in the BMS) will meet again.
I only can assume that Renault does this on purpose to calm the minds of users.

In conclusion, relying on the SoH in the first years and the Capacity in the BMS does not help you when you try to figure out how much you really lost in range.

It´s not that easy. There is a bit of calculating to do!

BTW: With that numbers the OVMS calculates the Range independently(and temperature compensated) to the range displays by the UCH.

And that this range calculation is mostly spot on (other than the Renault values) says a little bit about the method and the data it´s based on

(Kenneth) #255

Sorry but that’s not right.
I have from sources directly from the battery factory that a cell is a LG 43 Amp.
The cell you refer to is not a cell but a battery bank that contains 6 cells
3 in paralel and 2 in serial. (There are 7 such battery banks in a Twizy battery)
The total kWh in the battery pack is 129 X 51.8 (51.8 is average volts) = 6682.2 kWh
but the battery is limited to about 6.1 kWh

in the battery bank that you are referring to is (43ax3) x (3,7vx2) = 954.6 Wh and the label says 966 Wh which is actually 11.4 Wh more than what it should have been. but there are small numbers and do not matter.

that you say that BMS calculates wrong, I do not think so.
It calculates from a shunt that measures current very accurate so I trust more on the BMS than from OVMS that calculates this just from the charger AC side.

A BMS measures the current from DC and not AC We do not pick up the numbers from the charger but from the BMS.
The charger also charges 12v battery and when we want to know kWh from the HV battery we can not get the measurements from the charger AC side. Current must be measured with a shunt that measures all current in and out of the HV battery as the BMS does

and one important thing: is that Renault states that you get 6.1 kWh, regardless of whether the battery pack is larger, but this does not mean anything because the warranty is based on 6.1 kWh

In other words, if you buy a car with the 10 kWh battery pack but they provide/state it is 6.1 kWh, the warranty then applies to 6.1 kWh and not 10kWh

(Dale Pearson) #256

On the PowerBox is there an easy way to see what tuning mode the car is currently in?
I assume it might be related to the TP value on one of the menu screens, but thought I would ask on here before working it out if someone already knows :wink:

(Kenneth) #257

yes it’s as you say.
TP value 1 = Light tuning
TP value 2 = Medium Tuning
TP value 3 = MaxPower Tuning
TP value 4 = Convert T80 to T45 Tuning

But if you disconnect the Powerbox and tuner another car, it will not know what tuning option you have chosen when you put it back to your Twizy (unless you used the same tuning on the other car).

It is only in the memory of the box. it does not check the car what tuning choice it is on it. It only checks if the car is tuned or in its original condition

(Dale Pearson) #258

As always Kenneth thanks again for the clarification. I will add this to my little cheat sheet.
So basically its remembers the last setting applied, which as you say may not be the setting of the car connected.
Not a problem for the single vehicle user.

Loving learning about this device, thanks for being some prompt with info, as I know it can be annoying with questions :slight_smile:

(Cosimo Terzani) #259

Hello! is there anyone interested in buying a used Power Box?


I am. But I am from Russia. Will you ship international?

(Cosimo Terzani) #261