Advice on new battery for long term use (Samsung 50E 52V setup)

[Chaadr]

Hello everyone,
Long time reader, first post however.

I am building myself a Cargo fat bike with a long range capacity, and I just want a second opinion on a few things.
First of all, I got my hand on 200 Samsung INR-21700 50E, and I was planning on making myself a long range cargo bike with it in a 52V battery.
https://www.thunderheartreviews.com/2019/01/samsung-50e-capacity-test-5000mah-or-not.html
https://zeroair.files.wordpress.com/2018/11/samsung-inr-21700-50e.pdf

So, 14x14=196 = 3450Wh of energy in 12.6Kg of Battery.
All of that, powered by a Bafang G510.

Now, my first question would be, Considering that the charge voltage is of 4.2V and that the cut-off is at 2.5V, I was considering limiting the charge and the cutoff by the BMS at 57.4V and 37,8V (4,1V & 2,7V) Which would still let me around 3100Wh of battery to play with.

Would it be right, or am I just wrong ?

 

[john61ct]

I would stop discharge lots earlier.

0.1Vpc might only be 10% capacity but triple your lifespan cycles.

need to use resting voltage for apples to apples

 

[goatman]

id go 4.15v to 3.0v with settings but try not to go below 3.2v while riding. whats the continuous amps?

 

[markz]

id go 4.15v to 3.0v with settings but try not to go below 3.2v while riding. whats the continuous amps?

Yeah that would be nice, 4.15V for a top charge and then 3.25V or 3.20V for a low voltage cutoff. What would be even better is to have a switch that will have the ability to go down to 3.00 or 3.05V. The key though is to have enough capacity (Ah) that you never ever really reach LVC for your normal day to day riding and only really reach LVC when your just cruising around aimlessly chilling out and grinning the entire time its that e-grin.

 

[Chaadr]

I would stop discharge lots earlier.

0.1Vpc might only be 10% capacity but triple your lifespan cycles.

need to use resting voltage for apples to apples

This is why I am aking for opinions, I really want to make sure to chose the good Lvc.
What is the resting voltage exactly ?

id go 4.15v to 3.0v with settings but try not to go below 3.2v while riding. whats the continuous amps?

Oooooh, I see my mistake now
Looking at the graph below, I see how I misunderstood it..
SO yeah, a LvC at 3.2 and a switch to allow a little extra to 3.05 would be a great idea.

The batterie setup is going to be 14s14p 50,2V and the controller used in the engine is the standard Bafang Ultra, which can suck up to 30amps continuous.
But I should be doing around 50v 10-20A most of the days I think, unless I really plan for a hard route (which will come too)

id go 4.15v to 3.0v with settings but try not to go below 3.2v while riding. whats the continuous amps?

Yeah that would be nice, 4.15V for a top charge and then 3.25V or 3.20V for a low voltage cutoff. What would be even better is to have a switch that will have the ability to go down to 3.00 or 3.05V. The key though is to have enough capacity (Ah) that you never ever really reach LVC for your normal day to day riding and only really reach LVC when your just cruising around aimlessly chilling out and grinning the entire time its that e-grin.

This does sounds like an interesting option, allowing for a little extra in case I empty the battery a little too much.
The rated capacity is of 69Ah (doing the math with 100% capacity) so probably around 64/65Ah with the limiths and cutoff.
So, not 4,1Vpc but 4,15 would be preferable ?

Also, This is also kinda the point of this Battery, I will use it quite a few times at 90% of capacity but I will also use it in my everyday life while only using 10/20% a day.

 

[Andy123]

Hello Chaader
The weight of the battery 12,6 kg for 14x14 cells 50E is not possible ( 69x14x14=13524 g) only cells. And we have to add wires, BMS, outer package.
I have 14S6P with Samsung 50E and it is about 6 kg weight battery for Bafang ultra too.

 

[Andy123]

Cut off voltage-Low battery protect:
Biktrix recommends 47 V for stock controller Ultra with 52V battery (14S). It is 3,36 V/cell and this voltage is approx. 15% SOC.

 

[john61ct]

I would stop discharge lots earlier.

0.1Vpc might only be 10% capacity but triple your lifespan cycles.

need to use resting voltage for apples to apples

This is why I am aking for opinions, I really want to make sure to chose the good Lvc.
What is the resting voltage exactly ?

An hour isolated should be enough when calibrating.

The SoC% estimated by voltage under load varies too wildly by the amps drawn.

Once you get a feel for what **resting** voltage results from **your** setup stopping at say 3.4Vpc to start

then you could start adjusting LVC down in increments if you want to sacrifice some longevity to get a bit more range.

 

[MadRhino]

‘Long term use’ is not best achieved with LiCo chemistry. There are batteries that last much longer, at the cost of extra size and weight. LiCo was made for high power and/or compact size requirements, at the cost of short life and higher risk of fire or explosion.

 

[john61ct]

50E are NCA chemistry not LCO.

And highly recommended both for high power density and relatively good longevity under conditions most in other use-case contexts would consider abusive.

Plenty of test reports from expert forum members give objective proof of that, out of hundreds of batteries on the market only a handful come even close.

 

[john61ct]

LTO and LFP certainly last a lot longer, but deliver a fraction of the energy density.

 

[Chaadr]

Hello Chaadr
The weight of the battery 12,6 kg for 14x14 cells 50E is not possible ( 69x14x14=13524 g) only cells. And we have to add wires, BMS, outer package.
I have 14S6P with Samsung 50E and it is about 6 kg weight battery for Bafang ultra too.

Cut off voltage-Low battery protect:
Biktrix recommends 47 V for stock controller Ultra with 52V battery (14S). It is 3,36 V/cell and this voltage is approx. 15% SOC.

Hello Andy123,
Yes, sorry I made a mistake (actually quite a few) on the weight, And you are right, I meant to say that I have 13524 g of cells. The planned estimate for the whole battery was of 13800g without case.

As for the cut off voltage, I am now planning on slowly going from 3,5Vpc to maybe 3,4 (as John61ct stated under) or 3,35.

That's interesting to see that you have a similar setup, how does your battery hold the charge ?
How much do you get out of it ?

50E are NCA chemistry not LCO.

And highly recommended both for high power density and relatively good longevity under conditions most in other use-case contexts would consider abusive.

Plenty of test reports from expert forum members give objective proof of that, out of hundreds of batteries on the market only a handful come even close.

Thanks, for a second I thought I made a shit choice haha

 

[john61ct]

Pajda test results.

https://endless-sphere.com/forums/viewtopic.php?f=14&t=103092&start=425#p1555683

Only a couple of LG models, likely NMC? matched the longevity - holding performance of the Samsung 50E.

Can you share how much they cost delivered and link to your supplier?

 

[MadRhino]

50E are NCA chemistry not LCO.

Ah! Sorry I didn’t notice.
Yep, nickel does add much better stability to cobalt/lithium ion transfer. Thus much safer chemistry. Cycle life is generally longer too, but at near full c rate usage it is very similar to modern quality LiCo.

I agree that, with conservative usage one can make them last pretty long, and they are the best choice when performance is required, but not a priority.

 

[Chaadr]

Pajda test results.

https://endless-sphere.com/forums/viewtopic.php?f=14&t=103092&start=425#p1555683

Only a couple of LG models, likely NMC? matched the longevity - holding performance of the Samsung 50E.

Can you share how much they cost delivered and link to your supplier?

At first, I got a deal for 750€ delivered, but supplier didn't deliver (I suspect because of Coronavirus).
Then, I went to nkon.nl and ordered them there for a price of 4,25€ a piece. 850€ total + shipping and french tax, so it got around 915€ for the 200

Not the cheapest battery ever, but when I see common brands asking for 500€ for 500Wh...

50E are NCA chemistry not LCO.

Ah! Sorry I didn’t notice.
Yep, nickel does add much better stability to cobalt/lithium ion transfer. Thus much safer chemistry. Cycle life is generally longer too, but at near full c rate usage it is very similar to modern quality LiCo.

I agree that, with conservative usage one can make them last pretty long, and they are the best choice when performance is required, but not a priority.

The battery is rated for a nominal current of :
137A at 2C
13.7A at 0.2C
20.58A at 0.3C
27.44A at 0.4C
34,3A at 0.5C

I do not think upgrading to the exess controller and stick with the original bafang one, so I wouldn't get over those currents needs.

 

[Andy123]

Hello Chaadr
"That's interesting to see that you have a similar setup, how does your battery hold the charge ?
How much do you get out of it ?"-The maximum, that I used was about 1000 Whrs from my theoretical capacity 1550 Whrs (14S6P, Samsung 50E) after 100 km trip in the mountains. I don´t use max. power from Bafang ultra.

 

[john61ct]

The battery is rated for a nominal current of :
137A at 2C
13.7A at 0.2C
20.58A at 0.3C
27.44A at 0.4C
34,3A at 0.5C

Those are not "ratings" so much as just the output of plugging the supposed capacity into math.

In reality capacity is something that the user needs to measure, and will vary a fair bit by the discharge current used.

If you increase your current rate by a lot, and have a need for decent range, best to also increase your battery capacity. Lower C-rate and higher avg DoD% will also help your batteries last a lot longer.