Samsung 25R/LG 18650HE2/ Sony VTC5 high power 18650 battery

[BoomerChomsi]

Thanks 8)

Wooww I didn't know there is very big difference
Most battery packs are using brass strip for spot welding?

 

[riba2233]

No, they are nickel strips!

 

[BoomerChomsi]

Thanks 8)
So even worser

 

[riba2233]

Yes, even worse, that's why I recommend to spot weld cells in parallel with thin nickel strap, and then use copper wire to connect them in series.

 

[BoomerChomsi]

Thanks mate! 8)
I will choose copper for these connections, I don't have a spot welder

 

[madin88]

Are kapton tapes good against chaffing? Because that will wear these down over time

not sure how good it is against chafing, but it will be better than nothing. as im going to stick epoxy plates on the pack there will not be much vibrations between the cells..

 

[BoomerChomsi]

Well due of space problems I can't use holders.
It is really necessary to use isolators between the cells?
What is the big purpose of this?

I mean if one cell is shorted, other cells in parallel connection will also be shorted....

 

[riba2233]

Unless you implement cell fuses into your design.

 

[BoomerChomsi]

Thanks! you mean like Tesla style fuse system?

What kind of copper wire do you recommended for 25R cell?
I have 1mm copper wire, I think it is to big for buring up when cell shorted.
0,3mm or 0,5mm would be a better choice?

O well I will order some 0,4mm and 0,6mm copper wire.

The only issue I think resistance between this connection?

 

[Nobuo]

Well due of space problems I can't use holders.
It is really necessary to use isolators between the cells?
What is the big purpose of this?

I mean if one cell is shorted, other cells in parallel connection will also be shorted....

If You mean anode isolators, that avoid individual cell short circuit. If one cell is shorted, it will explode/get on fire with a 99% of chance to destroy the whole battery pack, that will depend partially on how high the Voltage is on that cell. A self short circuit it only can happen if the two layers of anode isolation are pierced, thats almost imposible in nickel spot welded shrink wrapped packs, and a little more likely to happen in cooper bars / nails / iron soldered packs.

Thanks! you mean like Tesla style fuse system?

What kind of copper wire do you recommended for 25R cell?
I have 1mm copper wire, I think it is to big for buring up when cell shorted.
0,3mm or 0,5mm would be a better choice?

O well I will order some 0,4mm and 0,6mm copper wire.

The only issue I think resistance between this connection?

Instead of looking for a cooper diameter that would disintegrate if a short happen, I would look for a strong stick / secured way. If You are making a significant resistance in the whole bus wires, you are making a mess, not efficient junk. :?

 

[parabellum]

Thanks! you mean like Tesla style fuse system?

What kind of copper wire do you recommended for 25R cell?
I have 1mm copper wire, I think it is to big for buring up when cell shorted.
0,3mm or 0,5mm would be a better choice?

O well I will order some 0,4mm and 0,6mm copper wire.

The only issue I think resistance between this connection?

Avoid copper for fusing purposes, it conducts to much heat out of fusing point, preventing fusing. Must be something with hi current, low heat conductivity and low fusing temp. For example: 1x0.13mm cooper strip 25mm long will fuse at ~30A somewhere in the middle, but if you shorten it to 3mm and have cooper bars on both sides it carries hundreds of Amps.
Edit. 0.2-0.13mm

 

[BoomerChomsi]

Thanks for help all!

Yeah I thought the same, when shorted (whole)pack will burn.....
So no more thinking of using copper fuse wires

Okay I will use 1mm copper the one I have
Lenght between is very short (from bus bar to cell).

I will use some teflon sheets between negative and positive cell terminals for mounting 10X1mm copper bus bar.

Thank you very much!!!

 

[liveforphysics]

Thanks for help all!

Yeah I thought the same, when shorted (whole)pack will burn.....
So no more thinking of using copper fuse wires

Okay I will use 1mm copper the one I have
Lenght between is very short (from bus bar to cell).

I will use some teflon sheets between negative and positive cell terminals for mounting 10X1mm copper bus bar.

Thank you very much!!!

Teflon is amazing stuff when you need chemical resistance, but UHMW wears a lot better if your objective is just reducing chaffing on bus bars.

 

[BoomerChomsi]

Thanks for your tip!
Hmmm I don't have any UHMW stuff...
I have some teflon sheets in stock doing nothing, so I will it...

I did a quick soldering test with 1mm copper wire.
It is super easy and quick, so heat transfer to cell is in safe zone (I think).

 

[RiverRat]

Im building up my 25r pack now after life getting crazy for a while. Originally i went for this idea using core flu for cooling effect but seems ill run out of space in the A frame for all the batteries. Going this way ill have to settle for 14s 11p instead of 14s 14p. Ive moved down south and it wont get quite as hot here with average high temp being 29c or 84f and much cooler in winter. So do I still need to sacrifice space for the cooling effect or just reglue them all together side by side? 6 or half a dozen?


By the way my dn10 spot welder came and works well after some tinkering. The foot pedal was crumpled but worked just....., the fixture for the heavy welding lead to the front shroud was broken and the fan was loose from the back shroud with no screws to it at all and the fan wasn't even connected to the circuit board. Easy to slot it back in though and screw the fan in with new screws . Also the light for the extra (turbo) power button dosnt work but it still has function. Otherwise it works perfectly and seems to plenty of headroom to go way past the .3 thickness if needed.

River

 

[Brake]

Riverat, just curious how long it took for the welder to come in. Glad it's working good for you after some "fine tuning".
Can't really help with the glue or no glue on the 25r. Although I've glued my 18650 packs together with the glue gun, kinda like the Russian guys, and haven't had any problems. That's what I plan on in the future too.

 

[douglashart]

hi river, how did you get your DN-10? Ive been fishing around with no luck. tried to register at the Chinese site, no luck. need help, my project is nearing the battery stage and ive no room for solder. thnx

 

[ridethelightning]

hotglue is good stuff.
its easy to separate out a dud cell if you need to.
to get it off, put the cells in the freezer for a spell, the glue comes off really easily cause it goes brittle :wink: ]

getting a cell out that is in cell holders can be a real pain in the arse.

 

[cwah]

Im building up my 25r pack now after life getting crazy for a while. Originally i went for this idea using core flu for cooling effect but seems ill run out of space in the A frame for all the batteries. Going this way ill have to settle for 14s 11p instead of 14s 14p. Ive moved down south and it wont get quite as hot here with average high temp being 29c or 84f and much cooler in winter. So do I still need to sacrifice space for the cooling effect or just reglue them all together side by side? 6 or half a dozen?


By the way my dn10 spot welder came and works well after some tinkering. The foot pedal was crumpled but worked just....., the fixture for the heavy welding lead to the front shroud was broken and the fan was loose from the back shroud with no screws to it at all and the fan wasn't even connected to the circuit board. Easy to slot it back in though and screw the fan in with new screws . Also the light for the extra (turbo) power button dosnt work but it still has function. Otherwise it works perfectly and seems to plenty of headroom to go way past the .3 thickness if needed.

River

What is the grey thing you use to separate cells?

 

[RiverRat]

Brake It took a couple of weeks after they'd miscalculated the shipping and stuffed me around for a while. Communication wasn't the best.

douglashart I bought the dn-10 from here. http://www.cart100.com/Product/15904562609/

Cwah This is core flu, the stuff you see real estate signs, and election posters on the side of the road made out of. My idea was that the long air tubes would allow for airflow between batteries.

 

[cwah]

oh, the core flu idea is interesting but I don't know to what extent it can help dissipate heat?

what I'm looking for is something that protect against chaffing, luke mentioned uhmw:
http://www.directplasticsonline.co.uk/UHMWPESheet/Natural/5mm/
maybe these would be good to keep cells protected against chaffing abrasion?

 

[Simple818]

Anybody have experience with victpower?

I got the following quote

Quotation as below:

Item: Samsung INR18650 25R 2500mah 3.7V li-ion cell

Qty: 150pcs

Unit price: US$3

The price of 150PCS : US$450

The freight: US$96

Total value: US$546 (without any handling charges).

The above price is on FOB Shenzhen.

Payment terms: T/T, ESCROW, WU, Credit card only can be accept.

Lead time: 1 day after got your payment.

Pls let me know if any problems with this offer.

Best regards

 

[Ohbse]

Many severe negative reviews of Victpower on these forums. I would recommend dealing with EVVA or Shenzhen E-fire Technology Development Co.,LTD which I purchased my cells through. I bought LG HE4's but I believe they can both also supply the Samsung 25r's. They're also likely to be cheaper.

I have since built my cells into 20s10p using home built spot welder and 0.3mm nickel stripping. Balancing now with a 20mV spread across all cells. This battery is substantially 'stiffer' than my 20s 10ah of 20c lipo bricks, my peak power on a fresh charge has increased from 4.5kw to 4.9kw due to less sag, that more than overcomes the fraction more weight as well as having 3x the usable capacity. 100km+ range is nice.

I have some discharge curves and temperature logs for individual HE4 cells at up to 20a per cell, they hold up very well. Time will tell with regards to long term capacity and cycle count but I will be running them very unstressed and charging to ~4.05v, discharge to 3.75v for a return journey. I expect several years at that rate.

 

[parabellum]

Many severe negative reviews of Victpower on these forums. I would recommend dealing with EVVA or Shenzhen E-fire Technology Development Co.,LTD which I purchased my cells through. I bought LG HE4's but I believe they can both also supply the Samsung 25r's. They're also likely to be cheaper.

I have since built my cells into 20s10p using home built spot welder and 0.3mm nickel stripping. Balancing now with a 20mV spread across all cells. This battery is substantially 'stiffer' than my 20s 10ah of 20c lipo bricks, my peak power on a fresh charge has increased from 4.5kw to 4.9kw due to less sag, that more than overcomes the fraction more weight as well as having 3x the usable capacity. 100km+ range is nice.

I have some discharge curves and temperature logs for individual HE4 cells at up to 20a per cell, they hold up very well. Time will tell with regards to long term capacity and cycle count but I will be running them very unstressed and charging to ~4.05v, discharge to 3.75v for a return journey. I expect several years at that rate.

Please, hold us informed! Lipo is nice start but 18650s will certainly win the game.

 

[Green Machine]

HI guys,

I am acid testing my panasonic 3400 pack 48 20ah pack by climbing constant big hill at 30 amp continuous which is the maximum amperage my bms will allow. The pack is contained in a falcon ev triangle back with no ventilation...the pack gets pretty hot. Not to hot to hold but hot enough to go wow its hot. This baby is warm!!! It would be a nice heater on a cold day if you put it in your jacket.

I am wondering if this is anything to be concerned about...am i drastically reducing the life of my pack by allowing it to get so warm? Also i am thinking about all celll technology which uses honey comb technology so that each cell is insulated. I remember the reasoning for this is that cells in the middle in a pack like this get way hotter than the cells on the outside, and this causes those cells to fail quick which causes the entire pack to go bad too early.

Also i am thinking of getting some of these packs with the output amperage control disabled on the bms...allowing the cells to put out all they can.....is that a bad idea? OR should i say a sustainable idea....