internal resistance battery pack

[Erikjan]

I have a battery with Samsunt 29E cells. 7s6p.

The battery is from 2014 and is still doing well. Now I saw on the CA3 that the internal resistance is indicated.

Does anyone know the resistance of a new package with 29E cells.

The CA3 gives 0.102 Ohm for my battery.

Is this very bad or is it not too bad.

 

[serious_sam]

See awesome test data here (click on the little up arrow):

Another charts delivery. Samsung 29E7 700 cycles

That data indicates that the DCIR for 29E7 is fairly stable at around 0.030 ohms through many gentle cycles. Note that this is for V7 cells. Do you know what version you have? Anyway, probably doesn't make too much difference.

A new pack same as yours should be about 0.035 ohms in cell resistance. But that's just the cells. Everything in between the cells the CA contributes to the overall resistance that it calculates. Inter-cell connections. BMS. Wiring. Connectors. Totally variable depending on your installation. If your BMS has MOSFETs, then there's possibly some decent resistance just in that alone. Who knows.

Ideally you'd measure that resistance with the pack when it was new as a reference. Then measure at intervals to monitor degradation. But if you're still happy with the pack, then just record your current results, and continue to check into the future. Or not. If you're still happy, why spoil that emotion with cold hard data. Just keep enjoying it!

 

[Erikjan]

Thanks, I don't know what version it is I didn't make the package myself it is from em3ev.com.

I will continue to use the package until it is no longer sufficient. I am actually amazed that it is still good after so many years, and I was especially curious whether something can be derived from that value.

My battery is used in summer on a mtb with dual mac motors 25A per motor.
And all year round in an electric scooter @ 35A but only.

The cells are really good. They are also in my wife's bicycle. She uses them 5 times a week for several hours as a mail deliverer.
That battery has also been doing perfectly since summer 2014

 

[999zip999]

Just remember to keep some charge in the battery do not store flat. 3/4 charge ok for storage. You battery sounds fine. Would you buy from em3ev again ?

 

[Erikjan]

Yes I know the rules for lithium batteries. I have also been using lipo for the model flying hobby for years.
Also am aware of the risks, learned it the hard way and burned down my house.


My ebike charger has a mode that charges up to 90% full, which I always use unless I know that I go far that day.

I will definitely buy from em3ev again if the batteries are worn out. I also bought the MAC hub motors and the CA3 there.

And in 2016 a 2nd battery for my wife's bike for more range of em3ev.

 

[Okami]

Damn burning down house seems rough and i suppose that wasnt a joke.

Well i think 10mOhm for 18650 cell is quite ok, i know older cells have it at like 30-40mOhm more or less.

But yeh, depends on wiring and what device measures it.

There was a discussion on how single device should be used for measuring your packs age and degradation, otherwise u would need to use professional meter which has some sort of standardized measuring protocol

Sent from my ALE-L21 using Tapatalk

 

[Erikjan]

Tanks, i dont have the proffecional enquipment only the cycle analist.
Next charge i check the capacity when bms cut off. When it was new it was little more then 25Ah years later is was arount 24 Ah.
After then i never checked it.

Unfortunately the fire was no joke. The entire top floor has been burned out and a new roof had to be placed on the house.
Een overladen 6 cellen 5000mah pack was de oorzaak. Eigenlijk de lader te ver is doorgeladen.

This are the pictures, never ever charge lipo's at night they will try to kill you.

https://www.112hm.nl/2014/02/06/uitslaande-brand-verwoest-grotendeels-woning-aan-de-tuinstraat-in-boskoop/