Battery pack on Panasonic NCR18650B cell

[etriker]

I am thinking the specs in their data sheets is for brand new cells not even a month old ?

I don't know that I have ever had cells that new. That is what I am thinking brand new means ?

For sure fresh new cell straight from Panasonic.

Have not seen them in laptop packs yet and have done no tests on recycled Panasonic cells.

Where did you find for real brand new Panasonic cells ? How do you know if they did not come straight from Panasonic ?

I like Panasonic. I used to work for them.

http://industrial.panasonic.com/www-data/pdf2/ACI4000/ACI4000CE54.pdf

.2C cutoff at 3v ?

2C cut off at 2.5v ?

 

[agniusm]

I am getting them from victpower. As usual, cat in a bag but.. never the less i will test them and report back. When they were produced i don't know, perhaps will find out when i have them in hand. I bought 6 extra cells for some violent testing and if there is one dud or something like that. They state 2.5V absolute minimum so 2.8V should be safe enough i suppose?
if they weren't discharged, that means they are brand new. Self discharge for lithiums is like 3%.

 

[etriker]

I guess. That is why I would test with adjustable lipo alarms first to be sure.

 

[SamTexas]

They state 2.5V absolute minimum so 2.8V should be safe enough i suppose?

I use 2.5V on all of my packs for perfomance reason, not to squeeze all energy from the pack. 2.8V is conservative enough in my view. But if it makes you worry then it's not worth it. 3.0V is perfectly safe but you do give up a little in performance (hitting LVC on hard acceleration).

 

[agniusm]

This pack is for my scooter. The motor i got is 350W in 12" wheel fashion. My calculations are 8.3A draw on fully charged pack and 11.6A nearing the end. Take it that cells are 3000mAh, 15AH 5P the draw would be 0.77C at most, averaging at 9.78A which is 0.65C. How much they will SAG i will see in real life situation i guess.

 

[dnmun]

did you order that BMS? lemme know how much it ends up costing. they may add a $29 air freight charge at the last minute.

 

[agniusm]

yep, will do. Still waiting on price for the small one.
I knocked up few sketches of the battery from these. I would use 2mm Polypropylene plastic and try to form side cover with vacuum former i just build and wrap it all in with 1mm aluminium strip for some heat dissipation with kapton tape on inside:

There will be two briks 5S5P each.

 

[agniusm]

Here it goes again. Fu*k, fu*k, fu*k, what the fu*k is wrong with those Chinese? Bought 56 NCR18650B cells, got 48 + fu*k knows what others. Second purchase with them second fu*k up. Fu*k

This is bad even before i start testing them, might be dry or something else like 20AH A123 i got from them. Fu*k..

 

[SamTexas]

And what the heck is that "ICR18650..." label? Substituting with one cell with another without prior consent from the customer is simply not acceptable.

Time to make a Paypal claim.

 

[agniusm]

The label i think is for customs and shipping on that. Seen this type of labeling on perfectly good 20AH A123 cells so i am not concerned about that but 8 different cells bugs me off. I am 2 cells short for 10S5P pack and this will further delay the build. Crap, pissed off right now

 

[SamTexas]

... but 8 different cells bugs me off. I am 2 cells short for 10S5P pack and this will further delay the build. Crap, pissed off right now

Don't tell me you are going to accept the 8 LG cells!

 

[agniusm]

No, i am talking with them at the moment to send me out 8 Panasonic cells, if they will agree all is bad but not totally fuc*ked. Those grey ones are LG 2000mah cells so even if i was dumb enough to mix them i wouldn't because capacity.

 

[agniusm]

I got some news from Henry regarding BMS. Its 10S 15A CH/DSCH with temp sensor. Attached spec. Total 31.50USD with shipping. He said they will have programmable BMS in two months. He also said they can develop BMS regarding functions one might need at cost of 150-300USD.
Photo:

 

[agniusm]

Started on charging these cells. First 6 was 3.65V out of the box. Will fully charge them and the check the capacity, one ful charge discharge cycle, then back to storage for a few weeks or a month to check self discharge until i get missing 8 cells.
Here is my primitive rig for charging 6 cells simultaneously:

Using iCharger to power BS168 cause was laze to look for another power supply.

Just knocked it up today for single cell discharge, don't know if i am doing it right, will see. I put 60W car bulb but cell voltage is 4.2 so i don't know how to calculate the max load on it or if it will work at all:

Also got most stickers off, bugged me a bit...

 

[SamTexas]

Something that I can NOT confirm: It's not a good idea to keep lithium battery FULLY charged for such a long period. It stresses the cell and shortens its life.

Things that I can confirm: Brand new laptop batteries from Compaq and HP are shipped at around 3.9V. The batteries come with specific instruction to fully charge the batteries before use.

What I do: Charge to 4.20V. Check voltage in about 48 hours, any bad cell will show low voltage by then. If I don't plan to use the cell in the next 7 days, I drain it down to around 3.9V.

 

[agniusm]

Thanks, that makes sense.

 

[SamTexas]

What current are you charging these cells? Looks like 2.0A? If so, that's a little high. Maximum charge rate is 0.5C. I never exceed 0.3C.

 

[migueralliart]

That's bad that they screwed your order.

You could also check the IR of the cells with the icharger. It's going to be an approximation but at least it filters the possibilities.

 

[agniusm]

What current are you charging these cells? Looks like 2.0A? If so, that's a little high. Maximum charge rate is 0.5C. I never exceed 0.3C.

Yes, probably but standard charging current is 1625mA. I'm planning on using 240W charger for this project.

That's bad that they screwed your order.

You could also check the IR of the cells with the icharger. It's going to be an approximation but at least it filters the possibilities.

Yes, i will try to measure IR but i think it is way inaccurate, well at least for consistency.

 

[Punx0r]

If the bulb is 60W @ 12V then it's resistance is 2.4 ohms

At 4.2V the bulb will pull 1.75amps or 7.35W

 

[Rafaelrz]

These Panasonic NCR18650B are around 2C max discharge rate right? Is this acceptable for an ebike? What's the C-Rate for the a123 LiFePO4 cells?

 

[agniusm]

These Panasonic NCR18650B are around 2C max discharge rate right? Is this acceptable for an ebike? What's the C-Rate for the a123 LiFePO4 cells?

Which ones?
Most powerful are orange 4.4ah, least yellow 1100mAh

 

[Rafaelrz]

I mean the green ones people use are used to buy, the 256650 M1 what are their C rates?

 

[agniusm]

I haven't played with them but from what i read they are very good cells. Perhaps up tp 20C with adequate cooling, up to 10C without cooling would be my guess.

 

[Rafaelrz]

I haven't played with them but from what i read they are very good cells. Perhaps up tp 20C with adequate cooling, up to 10C without cooling would be my guess.

What do you think it's better for an ebike, the a123 green cylindrical cells, the orange ones or the K2 Systems ones?