Could you rate these 18650 cells for me?

Brand: Panasonic
Model: NCR18650
Capacity: 2900mAh Rated
Voltage: 3.60V Nominal
Charging: 4.20V Maximum
1925mA Standard
— mA Maximum|
| Discharging: |2.50V Cutoff
580mA Standard
5400mA Maximum|
| Description: |Gray Cell Wrapper
White Insulator Ring
18650 Form Factor|

Hi guys,

I'd like to replace (3) SLA lead batteries rated at 12v 12ah, in series, 10s4p of these lithium 18650 cells. Do you think these will work for me? It's for an Eglide skateboard. I'm worried about the low discharge of these lithiums bought off of Ebay...

I recently bought and tested some Panasonic NCR18650PF GA Cells, new. These were rated at 2900mAh, high drain hybrid, 10A and have a light green wrap and white washer. Attached are my curves.

View attachment 1

Thank you, but I'm not technical enough to understand your graph.

I think mine at 5400 or 5.4 amps max discharge per cell is about half the amps of the batts you tested. I'm just not sure if they would work in a skateboard / scooter application.

My thoughs are to build as a 10s5p.

ryan380golf said:

Hi guys,

I'd like to replace (3) SLA lead batteries rated at 12v 12ah, in series, 10s4p of these lithium 18650 cells. Do you think these will work for me? It's for an Eglide skateboard. I'm worried about the low discharge of these lithiums bought off of Ebay...

Click to expand...

Short answer, no. Long answer maybe.

There's a few facts that would have been helpful, so I googled/derived them.

Eglide: 800w Nominal, 1500w peak, 36V battery

800w/36v = 22.2A nominal
1500w/36v = 41.7A peak
Note - the manufacturer has quoted this as output, which is either odd, or wrong. If it's odd but right, then electrical power requirements will be 20-25% higher.

By your specifications, standard max discharge is 580mA standard * 4 (parallel) = 2.32A. So if you want a long life, you cannot use these.
By your specfications, peak discharge is 5400mA * 4 = 21.6A, so it could theoretically do it, but will be hot as hell, and you won't get much life out of it.

But, I think either your source is wrong, or you've not copied it correctly. Every stat you've got there is right except discharge:

https://voltaplex.com/panasonic-ncr-18650-battery-ncr18650

If my link is right over yours, then standard discharge is 12 * 4 = 48A, which means even peak output of the motor will not threaten these batteries.

If you've already bought them from eBay and you don't think you'll get a refund, then may as well give it a try, but watch the temps. If they get too hot, stop it, before you set something on fire. If you can get a refund, you should test, or get tested these cells. There's a few ways you can do it, but let me know before I take the time going into a fairly deep technical subject you may not be interested in.

Thanks so much for taking a look at these.

Perhaps they are this battery. https://voltaplex.com/panasonic-f-18650-battery-ncr18650f

https://secondlifestorage.com/t-Panasonic-NCR18650-Cell-Specifications

This is where I pulled my info... It's was used in a medical device of some kind. I have enough cells to make a 10s5p.

I was impressed with the NCR18650PF. Tested total of 32. All virtually the same. Manufacturer's spec sheet gives rating of 2750mAh, 2700 min. My charger was only getting cells to 4.05-4.10V which accounts for some slightly low Ah readings. I was able to fully discharge at 10 amps as per spec. At 12A, I thought cell was too hot and terminated early. That shows on the graph.

I'm able to find retail sources for these cells, new, at $2.50-4.00 US each. At prices like that, why screw around, especially if you're unable to test each cell?

Good luck,

major

Ref.

https://endless-sphere.com/forums/viewtopic.php?f=14&t=98546&p=1444693&hilit=ncr18650pf#p1444693

ryan380golf said:

https://secondlifestorage.com/t-Panasonic-NCR18650-Cell-Specifications

This is where I pulled my info... It's was used in a medical device of some kind.

Click to expand...

This looks like the official datasheet for your cells:

https://engineering.tamu.edu/media/4247819/ds-battery-panasonic-18650ncr.pdf

If you have a look at the bottom right graph, they discharge the battery at 2C (Discharged in 1/2 an hour), or 5.8A. Since you've got 4 in parallel, this 23.2A - marginally above the nominal rating of your bike.

I know you said you're not technical enough to read the graphs, but have a look at the far left of the graph. The cell which should be 4.2v, when placed under a 5.8A instantly drops to around 3.8v. That's a lot of stress on the battery, because of a concept called "internal resistance", which means that the battery is effectively "consuming" those 0.4v as heat, rather than sending it to the motor as motion.

Its down to guessing now, but I'm going to say it's *really* borderline. If you trip is a nice smooth flat road, and you're rarely at top speed, you should be fine. If there are hills, a lot of starts and stops, or you're constantly near top speed, I'd say these batteries are going to have a very short life.

Can you consider getting two packs and running them in parallel? Or at least change to a 10S6P arrangement?

If it was me, i would not even bother trying it. 2C cell ar le going to live a month a best before dying for good. Get some 5C or more 18650 cells for an eboard. I can garantee you you ll be disapointed otherwises. Keep these cells for future batery banks, but dont put them in a EV

Matador said:

If it was me, i would not even bother trying it. 2C cell ar le going to live a month a best before dying for good. Get some 5C or more 18650 cells for an eboard. I can garantee you you ll be disapointed otherwises. Keep these cells for future batery banks, but dont put them in a EV

Click to expand...

To be frank, I would back this advice. I personally tend to over-engineer everything to make it last, but I'm aware that not everyone does that, and since you had already bought them, I thought it was worth a shot... It is a lot of effort to assemble a pack, not being sure if it will last or not.

Yeah thanks guys. I think I'll just write this down as a cost for my battery education and use these for another project. I really appreciate all the help. I think you guys saved me from assembling, running a bms, etc,having a crappy non performing pack, or going down in flames... Will cut my loss now.