21700 for low P count battery

[HughF]

I have a 13s pack to build, needs to be compact and deliver enough current for a tsdz2 going on a single speed. I'm thinking of going for Samsung 21700s from nkon.nl

Is the INR21700-50E really OK for 10a discharge? I think a 13s2p pack would fit in the space i have. I could limit the tsdz2 to 13-15a to be safe.

 

[Centurio]

Hi,

You did not mention the your disired discharge rate.

I built a 14s4p pack wtih the LG 21700 M50T cells. I ordered them by nkon.ru and it seems to be everything allright. Alltought I had not much opportunity to use it for commute purpose yes. This because of covid-19 and home office

The pack is uses for my Bafang BBS02 750W and limited to 24 Amp discharge (yes I modified the Bafang controller settings).I did 2 rides only but after all I am not sure if it was the right decision. The run most often at their max discharge rate. Maye the Samsung 40T would have been better.

If you plan a 2p pack, you are better off with the Samsung 40T because the 50E might be running at max discharge rate often. This if you desire to commute about 40kmh.

Hope it helps

 

[goatman]

I wouldn't pull more than 5 amps from a 50e and if I had to choose between the lg m50t id take the lg over the 50e just because the battery guys like the graphite anode in the Lg. the 40T is what im planning to use at max 10 amp discharge

 

[NexusG]

I think the 50E is ok for 3P and TSDZ2 current limited at 15A

But for a 2P configuration, Samsung 40T would be best if you want TSDZ2 to operate at max power

 

[electric_nz]

you could also look at Sony/Murata VTC6A 21700 at 4000maH; they appear extremely durable, low internal resistance and low sag.

 

[Centurio]

because the battery guys like the graphite anode in the Lg.

What do you mean exactly with this? Can you provide some informations about "the battery guys"?

 

[goatman]

because the battery guys like the graphite anode in the Lg.

What do you mean exactly with this? Can you provide some informations about "the battery guys"?

https://endless-sphere.com/forums/viewtopic.php?f=14&t=103092&start=375#p1537058
im looking for a battery that can do 7amp and get about 750-1000 cycles but I don't think lg makes one.

 

[Centurio]

Uh, thx for this link! Great post. I used to charge my 30q to 4.1v only and limited discharge to 2.9v. But reached the discharge limit only once or twice. But I never did a capacity check. I remember the internal resistence not changed a lot after 4500km 20s10p pack. But hve been only about 100 cycles totally.

 

[goatman]

Uh, thx for this link! Great post. I used to charge my 30q to 4.1v only and limited discharge to 2.9v. But reached the discharge limit only once or twice. But I never did a capacity check. I remember the internal resistence not changed a lot after 4500km 20s10p pack. But hve been only about 100 cycles totally.

if my battery guy had 30q I would buy them, hes sold out but he has 40t so when my battery tester comes in im going to test it like the 30q at 7amp discharge and 2.5 amp charge 750 times to see if its the same as the 30q

 

[MJSfoto1956]

I will likely be rebuilding my current 50Ah pack in 2021 or 2022, with a goal of doubling its Ah. That being said, if I were to do it today I would seriously consider using QB26800 cells to achieve 100Ah. Previous thread here: https://endless-sphere.com/forums/viewtopic.php?t=98327

 

[john61ct]

Need to keep C-rate to mostly 1C, only occasional 2C peaks

in order to get 5-700 cycles

and that's not tested but data sheet maker claim.

Makes for a pretty big heavy pack

certainly not comparable to VTC6 HG2 etc

Good power density **and** longevity is apparently ery expensive.

 

[Smoke]

I was looking at discharge curve tests on a flashlight forum and the LG M50 seemed to do as well or better than the Samsung 50E cells if the discharge is less than 10A per cell. I was looking at the 7-10A discharge rates and the LG just looks great so I bought 54 of them to make a 13s4p pack (with two spares).

They are on sale for $4.49 each which is about as good as it gets for new cells with a useful discharge rate. I saw someone say they got cells for $3.99 but that supplier was sold out.

I didn't pay too much attention to the discharge charts at 1C (5A) and less but they are better than 7 and 10A discharge and they come really close to hitting the 5,000 mAh rating even at 10A.

I believe the rating LG gives the battery is 7.4A which is odd because Samsung 50E is rated at 10A but seems to have lower capacity at 10A discharge.

My "33A" motor controller should keep my discharge to 8.25A per cell and hopefully my throttle will keep it under 5A.

I think every indication points to a battery that will give me a good long life. I hope it works out that way.