Battery pack, which 18650?


#21

Hello. I have work a long time in battery manufacturing and BMS is a must have and not a nice to…

May be not for the consumption time who a fuse and cell monitoring can be enough but for the charging period.

It’s very important to balance your cells especially with cells we bought…


#22

@Vincentbraillard Without a BMS you can still balance charge 2x 6S with standard chargers, plus if you monitor cells during discharge/consumption are you not getting most of the benefits of a BMS?


#23

I’m also thinking this approach isn’t a bad one if you are not using a BMS for discharge (which will be fused instead). Is there any negative to using a standard 6S balance charger on li-ion cells instead of BMS?


#24

You have to ensure that your cells never get used out of spec. How you do that is not important in the first place. An integrated BMS has the advantage of being much more convenient and slightly safer as you don’t get as much user error due to lazyness.
During charging and discharging no cell should get above or below minimum voltage. Then you should not charge with a too high current, but this is quite hard to do even in the last charging phase as the big battery packs can sink quite a lot of current. Then temperature monitoring is quite useful. For discharging a fuse and safety shutoff for the pack when any cell reaches mimimum voltage is good.
That said, I did my first tests with only a lab psu for charging. With fuses installed in the pack and only fuses for discharging, too. But I made sure I left a marging on my discharge voltage and checked the balance manually with a meter after use.


#25

It reminded me a guy on esk8 did in-depth post about most common 18650 differences. The 25R suffer massive voltage drop on even load as small as 5A


#26

I just put a set of 20700 4000Ah in one of my electric longboards. I was planning on going with those 12S

The downside to these is they are 15A cells, so you’d need at least 6 to get 90A which might not be enough so maybe 7 or 8P.

(no association)


#27

I got the LG18650M36 for my efoil pack. I didnt test them yet, but the data looks really good.
I needed to buy 400 cells to get a decent price and will use around 120 of them.

So if anyone is interested in building a pack of these cells, let me know. I would sell the other 280 cells for 3,10 Euro per cell, tax included.
I need to check how shipping these cells can be done. As those cells are unisolated, I will only ship them in the original carton with the cell holders and as I only have two cartons, I can only split the 280 cells in two parcels… I hope that makes sense in english :smiley:


#28

Has anyone been looking into li-fe-po4 cells? they are 10-20% more than 18650 cells, but don’t have voltage drop during high current and they are 2000+ recharges vs 300-500 meaning in the long run you save 75% of the battery cost not having to replace a $1000 battery ever year.

If you want to save a couple pounds and are a stickler for weight you may not want them, but a couple extra pounds don’t do much considering it will save you more or less $800-1000 for a battery 3x over a few years.


#29

I doubt that anyone would come close to the maximum number of recharges on their pack before dumping it anyway for different reasons (changed requirements, capacity loss etc.).
You would need to be on the water several times a week, the whole year, for 3 years to reach 400-500 recharges.


#30

I get it, for the masses/individuals they may not need 2000 uses but keep in mind these batteries don’t have a capacity loss like like others until 2000+ charges so thats not an issue and if you don’t draw them down to complete low they last another 1000+ charges beyond that.

My build doubles as an efoil and jet surfboard and its build for durability and multiple uses per day as efoil and jet surf rental business’ need something that can be used repeatedly. Renting is not nearly as profitable if you have to spend $1000 - $3500 a battery every year. 10 jet boards thats $10,000 - $35,000 a year in battery costs, VS spending an extra $200 up front for the proper cell type. Just saying…


#31

I don’t say that these cells aren’t worth being considered.
I did a quick research to be able to judge this topic a bit better and I have to admit these things look good on the paper (Wikipedia).
But when I calculated the price for different LiFePo cells in a German shop and compared it to Samsung Q30s I am more at 40-60% higher prices (depends on the cell type, very large capacity ones seem to be cheaper in relation). And the weight is more than double:

5Ah cells: 32 €/Ah, 420 g/Ah
8Ah cells: 27 €/Ah, 446 g/Ah
10Ah cells: 26 €/Ah, 448 g/Ah
15Ah cells: 28 €/Ah, 424 g/Ah

Samsung Q30: 18 €/Ah, 196 g/Ah

So can you give me a source for cheaper cells? And is the manufacturer as important as with Li-Ion cells? What are good manufacturers then? I read about A123.

Edit: the above calculations are assuming 14S for LiFePo and 12S for the Q30.


#32

Hello everyone,

I made this cool spreadsheet of the best performing 18650 battery cells for high current draw (140-150A). The information is based on tested reviews found on the following website:

https://www.e-cigarette-forum.com/blog-entry/list-of-battery-tests.7436/

The total cost is based on reaching 140 or 150A continuous discharge rating with a 12S voltage.

Also added an updated spreadsheet which aims for 200/210 Amps instead of 140/150. Also includes a premade R/C lipo battery.

Hope it helps!


#33

too expensive , but interesting web site: https://www.gettitanpower.com/products/31-5ah-22-2v-1-080w-endurance


#34

Hi all I just came across these Re-Volt 18650 cells for $2.45/cell, has anyone used them?

They are a 2600mah 10Amp ICR18650. The guy that is supplying these is a reviewer on YouTube and is buying them direct from supplier with his branding. Not sure which supplier.

I’m also considering using these solderless nese 3D printed modules to assemble the battery. Not too expensive if you can 3D print the modules yourself.


#35

I would be cautious with no name cells, often they are massively overrated. This can be an exception though, someone needs to test it. But for me personally 2600 (will be less even for genuine cells) is a bit too low.

I can’t imagine those modules are appropriate for our high power use case, welding is the only safe option in my opinion.


#36

Hi, I coudn’t find the correct topic but a user in Esk8 named PXSS has tamed the battery argument couple of times, has done a lot of bench testing and what not, definitely check it out

Battery Knowledge Base - WIP - Rough Draft


#37

My choice (will build a pack in spring or summer, starting with small lipo packs for now) are also the Samsung 30Q, you can get genuine ones for around 4€, not worth risking no-name cells for 1-2 bucks off.


#38

Yes PXSS came to the same conclusion - they’re very much on par with 25R (price adjusted), but 30Q’s thermal and voltage zag charectaristics are MUCH better

Preferred choice in esk8, If I recall correctly


#39

Thanks for the feedback re welding is the only safe option. I like the idea of the NESE modules but cannot find rated current of each module. Good idea for other applications maybe.

The guy selling these Re-volt cells has a pretty good ‘youtube reputation’ and has done alot of research into the cells as he build powerwalls etc.The 2600mah is claimed actual capacity to 3.0V.

But yes the name brand 3000mah batteries should provide more capacity. Where is everyone getting there Samsung 30Qs from?


#40

I will buy mine at nkon.nl. At least in Europe this is about the cheapest price and the shop has good reputation in esk8 and elsewhere.