Nicometer oppgradering

[elektrolux]

Har endelig funnet verdiene som skal til for at PSA går inn i begrensningsmodus.

Oversatt til Think bør disse ikke kjøres under 94 Volt

Skal en kompensere for strøm må en se etter total motstand i batteripakken på ca 1,4 ohm.

Forslaget mitt er at Nicometeret varsler med blinkende rød skjerm om disse verdiene overskrides.

[El rayo]

Oversatt til Think bør disse ikke kjøres under 94 Volt

Dette stemmer bra med Saft sin informasjon. Jeg har satt rødt felt til 95V på mitt nikometer.

[BauDemo]

Very interesting idea - I will test with a new parameter "Battery pack internal resistance" and see what is the best way to present it.
I remember I tested Ri calculation long time ago, but there was a time delay between the voltage/current reporting from the BMS. I will see if I can compensate for this delay in the calculations.

[BauDemo]

I have now implemented a internal battery resistance parameter for nikometer.
It was harder then expected since the BMS in the Think does seem to have a small delay in reporting the current.
Now the real question - what is a normal internal resistance per battery?
If we have green for "all ok", yellow for "watch out", red for "stop doing whatever you are doing", what would be the internal resistance values for these colors?

Just for info - I am currently getting values between 1.6 to 3.1 mOhms per battery module, with median value at 2.2mOhms. This is 41.8mOhms for the battery pack.

I need to do some more testing and see if I can speed up the analysis and will upload it. If anyone is interested to test it out, let me know and I will send you a test version.

[elektrolux]

Hello

I could test on my car, as I have a known problem with one battery only giving 62 Ahr.

A typical resistance on a good car would be 20V / 200A = 0,1 Ohm for complete pack. That is including cables and all.

Does your program allow for adjusting this resistance +/- in 0,01 Ohm steps?

[BauDemo]

Thanks elektrolux,
I will send you a test version tonight.

I am not sure what you mean when you say

Does your program allow for adjusting this resistance +/- in 0,01 Ohm steps?

So just to clarify what I did I am attaching a photo I took while testing in the car.

The new parameter is called "Batt. Ri" - see the lower right corner.
The value of that parameter represents calculated internal resistance per battery module.
To get the internal resistance value of the whole pack you need to multiply this value by the number of battery modules you have in your pack.
The background colors for the field displaying the Ri value are, as with all other parameters displayed in the nikometer, configurable.

Currently if the value is smaller than 7mOhm it is green, between 7 and 10mOhms - yellow, and red if it is bigger then 10. Any idea for a better coloring or different ranges?

[elektrolux]

The biggest resistans is in the cables. I frequently see 10mV loss on every cable between the batteries when running 20A through the system. That equates to 5mohm pr cable. There are 19 cables like this giving 0,1 ohm just in the cables. That again is 20 V loss at 200 Amps.

The best I have seen is just over 4 mV / cable compared to 0,5 mV / bar on the PSA cars.

"Unfortunatly" I had a window in my garage, and are now fixing my car. No worries though. I have other bad cars giving opertunity to test the new program.

[El rayo]

Elektrolux, har du fått noe resultat av Ri målingen med nikometeret enda? Jeg er veldig interessert i å sammenligne med mine; 2,5 - 3,2 mOhm.

Hvis "El Rayo"s måling av Ri er normal ser jeg ingen grunn til å senke batterikassa og ta en 10 års visuell kontroll.

[elektrolux]

Har lånt ut Nikometeret mitt til en kamerat som nettop har kjøpt Think, og derfor ikke sett på dette enda. Blir som du sier spennende å sammenligne, og ikke minst se om dette kan være brukbar kjøpstest. Tar tross alt litt tid å lade og kjøre 70+ km for å avsløre om alle cellene er OK

[hma]

Jeg har kjørt med Ri måling en uke nå og verdinen ligger mellom ca 1,8mOhm og 3mOhm (jeg rekondisjonerte pakken min i vinter).  Langs min arbeidsvei forserer jeg en 6km lang helt jevn stigningbakke. Der ligger jeg på konstant 100A i 55km/t (SOC = 60%).

[El rayo]

The recent cold weather has had no noticeable effect on the Ri, it's hovering around 2.7 mOhms. I've seen battery temp down to -7^o C with outside temperature -16. The Th!nk classic went 67 km with 19% left the other day, conservative driving.

Indicated Ri increases when the pack rests for a minute of so while opening the garage door. I think it's caused by the increasing voltage. Doesn't mean anything, it's just an effect caused by the method of calculating Ri.

By the way I found a used Ri meter.
It should arrive in a few days.

It's for NiCd, NiMH, Li-ion and Pb, but I don't know if it is suited for our 100Ah battery. Max voltage is 50, so it's not to be used for the complete EV pack.

In any case it can be used for my model airplane batteries and other rechargeables.

@ Elektrolux: let me know when you get the Robometers in stock. Remember one is reserved for me.

[Ken]

Jeg har blitt demonstrert en Ri måler og impedance målinger stemmer godt med blokkenes virkelig kapasitet. Det var brukt NiMH blokker i disse tester. Man kan spare masse tid og teste en hel batteripakke i en time!
Utstyret var dyrt så du kan har fått en skikkelig kupp El Rayo!

[elektrolux]

Gratulerer med Ri meteret. Her ligger en bruksanvisning: http://data.robbe-online.net/robbe_pdf/P1122_1-8422.pdf