Big 100 Volt 54 ah Battery build

[johnnyz]

Have not been on here in a long while...thought I would begin posting my new battery build, trying to learn on my previous build of last year.
I modified an Emmo Zone for performance. I replaced the motor with a QS Motor 16 inch 6000 watt V3 , which has proven to be reliable and very very fast despite pulling 18000 watts.
Controller is a Kelly / QS type that is 300 amp capable. I had it limited to 240 amps for my last battery and setup.View attachment 8

The battery was a 24s14p made from Samsung 25r cells. View attachment 7
Even though I was able to pull 230 or so amps from this, I had huge sag at full throttle and off the line. 96 or 97 volts and would sag to 84 or so...cruising at 50 kph would only sag about 2 volts.I used 2 8 gauge wires for both the positive and negative and for the busbar in the battery (for series) I used 2 10 gauge solid core wire and soldered a thin 18 gauge wire to all the cells in parallel.
After talking to an electrician, he thought that the pack and positive and negative cables were far to light in gauge and suggested that the battery sag was mostly due to not being thick enough. He suggested no.1 wire and on the series connection for the batteries, I have spiral Copper equal to about 5 gauge.View attachment 5
...You can the difference between the 2 8 gauge wires and the one no.1 wire.
Even though I had about 140 cycles on the old pack the cells still had 91% capacity, probably because I never fully charged the pack up and usually only let it get to about 3.5 or 3.6 volts per cell (about 86 volts) before charging again. However the actual ah's I was getting out of the pack was about 60%. I am guessing that resistance was the main culprit, and hopefully with the Samsung 30Q cells rated at 3000 mah will be much better and with the bigger wire give me much better efficiency.

While I am waiting for the 440 cells to arrive I designed and 3d printed the cell holders and am putting them together so that they fit neatly in the case..the white cardboard represents the case dimensions..

View attachment 1

Ive soldered the wire for the parallel group to the main series wire via small torch so I know its on there, and soldering to the cells only takes less than a sec per cell, as I have a professional soldering gun.

Top speed last year was about 120 KPH and 0-100 was about 6.7 seconds.

Much more to come as I progress....suggestions are welcome...

 

[John in CR]

All that work and money to build a battery, so get a tab welder to make the final connection to the cells. More than likely it's heat damage from soldering that hurt performance of your original pack. I certainly wouldn't go to all that time and expense to build a pack that is suspect from the start. With the motor upgrade it looks like you have a great bike just waiting for a battery to match its potential.

 

[johnnyz]

How is the pack suspect from the start?...and use a tab welder using what exactly?..using nickle strip??..and you think that can take 250 amps???...It takes less than a sec to solder the 18 g wire unto the cell, and does no damage whatsoever.The other pack I made worked great, just didnt have the range and sagged too much, and after 150 or so cycles and 92% capacity left for a 250 cycle cell @60%, seems to indicate that soldering didnt hurt them?

Thanks

 

[John in CR]

Solder the nickle strip to your copper wire and then tab weld to the cells. Why build a pack with 250 cycle cells anyway? I went to automotive grade cells years ago. I did the soldering stuff for a long time and would never go back. Higher power, longer life, much better safety, and either already assembled or easily bolted together so less work...plus FAR CHEAPER per wh and moreso over the long run. The only negatives are finding the right dimensions and maybe a bit more weight.

Getting only 60% of capacity is what I mean by suspect. Doubled up 8 gauge should have been plenty though I too am a believer in more is better, but your motor phase wires are probably far less than doubled up 8 gauge, and they see higher current. Do they get hot? If any wires are too small, I think its the 18 gauge to the cells.

My posts aren't intended as criticism no matter how the written word can come across, just trying to be helpful, and I apologize if the "jackhammer prose" I've been accused of comes across other than as intended. If the problem is wire size then there's gotta be heat, making the location easy to find. Just ride hard with plenty of hard launches for 10-15 minutes and see what gets hot.

 

[johnnyz]

Thanks for the response and I take no offence..truth is truth, and if I learn something great..however Ive put together 25 packs and I have learned something in that time..
Done properly soldering to cells does not damage them either in performance or capacity (there are numerous studies proving this).
I believe an electrician when he looked at my wires and said that they were simply too small and that I was creating too much resistance..he even showed me the math.The contacts on the Anderson connectors were beginning to pit from the huge amps discharged. If anything and no offence,but the small wires soldered to the cells in parallel are plenty big as there is no real current flow..nothing in comparison to the current going through the series wire which takes the full pack current.If that were the case then they would have discolored or would have seen signs of heating (like melting the 3d printed holder).
I think you are confusing things...I used the Samsung 25r cells in my previous pack because at only 14 in parallel I needed something to handle 240 amps and at 20 amps per cell they would do. These cells have 250 cycle life @60%. My new cells that are coming have 300 cycle life @75%. I already stated that because I reduced the charging and discharging I had much greater life at 150 cycles than what would be expected.
Please inform me where I can buy enough cells that can safely be discharged at this amperage and in this form factor for $1350 Euro, because I would really like to know. The motor phase wires are 6 gauge and there is a difference between the phase wires from the motor and the neg and pos coming from the battery. The electrician also said that a wire doesnt have to get hot to prove there is resistance, simply getting warm is an indication, and the one time in the summer I did a nice hot run and came in, quickly took the tank off and felt the wires and they were warm....just didnt know if it was because of the weather or because they were heating up because of resistance.
I am hoping that people respond with comments to this post with real world experience so I can learn, not regurgitation, I guess the only way to find out is to build and test.

 

[amberwolf]

The contacts on the Anderson connectors were beginning to pit from the huge amps discharged.

With andersons, the only pitting that should occur is at the tips (angled "shovel" part) which is not part of the active contact surface--it's an ablative sacrificial surface there specifically to take teh arc damage that happens when connecting stuff together.

If you are getting pitting on the actual contact surfaces, then something is preventing the contacts from mating correctly. The contacts have to float in their housings, so that the springs in the housings will force the contacts flat against each other. If they can't float, they won't make flat contact, and will be high resistance or even arc.

The most common thing is too large a gauge of wire for the contact size, or too stiff a wire.

The next most common thing is similar, too thick insulation so it fills the housing tightly.

The next most common is wires exiting not straight, but forced into curves/angles/etc by routing, or wires tied down to a frame/etc really close to the housing, doing the same thing, which pushes against contacts and misaligns them.

Also, at least some of the clones have weak springs, flexible housings, etc., which compromise the contact alignment.

 

[johnnyz]

Thanks for the response. Yeah the only pitting was at the end or the tip...the 2 parts that are joined once they are put together are fine..however, you cant put a no.1 wire on an anderson connector ...I will be using these, nut and bolting them together and 3d printing a nice cover..

 

[Overclocker]

check out my method. pre-fluxed btw:

[youtube]0ZRwMXL-Rvs[/youtube]

i guess soldering is ok if done fast. but i don't do it anymore because spot welding is easier.

 

[johnnyz]

Nice soldering job and a gun like shown in the video solders so fast the metal on the positive side doesnt have a chance to transfer the heat to the but gluing cells together I have found invites potential problems...I had a pack I did in this manner and because they moved around slightly 2 parts of 2 cells rubbed the plastic enough that I had 2 cells that shorted...this is how the early chinese packs were all made except they used nickle strip and were welded...

 

[johnnyz]

Ok...as a sidelight and I didnt really want to focus on this but what the heck...
I have 2 identical cells..Panasonic 18650PF cells. They are both 8 months old, however, one has been badly soldered to a bunch of cells for all this time...the bottom has suffered some corrosion, as it appeared the person used the wrong kind of solder, so it was cleaned up a little so that my Imax could properly read it.
View attachment 2View attachment 1

I am going to fully charge up each and then when with full voltage I will test resistance with the Imax and a big resistor and measure both to see if there is any difference. I will then discharge both to see if there is any difference with respect to capacity.

Damaged by soldering?...Stay tuned..

 

[amberwolf]

however, you cant put a no.1 wire on an anderson connector .

Sure you can. You just need the right size.

If you're using just two wires (positive and negative) for high currents, then you can use the SB series, which goes up to connectors larger than my hand, with contacts bigger than my fingers, which will definitely hold big enough wires.

I think the SB120 or PP120 would work:
https://www.andersonpower.com/shop/wire-to-wire.html?wire_size=46


The largest ones I have in the pic below are only the size of my palm, with pinky-sized contacts (I don't remember which size those were (the other are SB50):

But bolt together can be even better than spring-pressed-togehter contacts, as long as the pressure is even and the bolts are secure.

 

[johnnyz]

Ok...well the test results are in....

Both the soldered cell (new but sitting soldered for 8 months) and the untouched cell(also new) were charged by my Imax to 4.2 volts and left to rest 30 mins.
The soldered cell came in at 4.157 Volts
The normal cell came in at 4.155 Volts
I discharged to 3 volts which is low as the Imax will go and measured the results.
View attachment 5


After the discharge was finished the soldered cell settled at 3.350 volts
The normal cell was at 3.358 volts

The following is the capacity measured by my Imax...

View attachment 2

The SOLDERED cell came in at 2498 when the timer stopped the discharge and the voltage was at 3.07 Volts.
The normal cell came in at 2498 as well but it's voltage was at 3.01 Volts.

This round was won by the soldered cell.

Next I placed the same resistor while they were both in their discharged state.

First the soldered cell...

Voltage dropped to 3.316 (for a voltage drop of 0.034 volts)

Next the normal cell...

Voltage dropped to 3.311 ( for a voltage drop of 0.047 volts)

In summary the soldered cell slightly outperformed the untouched cell. They are both unused and new except that the one cell was poorly soldered 8 months ago.

In my mind this is proof that soldering, even a lousy soldering job wont hurt at least these cells...I am not saying that keeping a hot soldering iron and heating the cell up trying to solder for 30 or 40 seconds wont damage the cell, because there is evidence that it indeed will.

 

[MJSfoto1956]

Nice soldering job and a gun like shown in the video solders so fast the metal on the positive side doesn't have a chance to transfer the heat to the [pack]

Speaking of which, where on earth can you purchase such a soldering tip with a hollow cup?
I've looked all over the internet and come up with nothing.
Any pointers greatly appreciated.

M

 

[dustNbone]

You can adjust the cutoff voltages on the B6, as well as disable/adjust the timer function. It's in the settings menu somewhere, buried quite deep if I remember correctly. I had to disable the timer when dealing with some 20Ah cells.

Just thought you might like to know.

 

[galp]

When I was doing calculations for battery for my high power e-bike build I came to conclusion that total battery wire resisitance (10 mOhms, including 2m wire) was about 10 times lower than total internal resisitance/impedance of cells (100 mOhms). I went with 0.5 mm copper in the end but could easily use 0.2 mm nickel strip and spot welding. My point is using really thick battery cables benefits little to battery performance.

You can also easily calculate this values and estimate voltage drop. Things you'll need to uderstand: ohms law, calculating resistance from specific resistance, data sheet of your cells to find internal resistance.

Oncw you get your cell IR (internal resistance) multiply it by cell series cound and devide by cell parallel count. Example: IR is 20 mOhm and you have 24S12P pack -> Total cell IR = 20mOhm * 24 / 12.

To calculate wire resitance use any of calculators by doing a quick google search. You can also find resistance per length tables for various wire gauges.

Sum both resistances. This is aproximatelly your pack internal resistance.

To calculate voltage drop at load use ohms law. Voltage drop = pack IR * current.

Hope this helps.

 

[bobmutch]

Even though I was able to pull 230 or so amps from this, I had huge sag at full throttle and off the line. 96 or 97 volts and would sag to 84 or so

Vs=I*Rp
so
Rp=Vs/I
so
(97V-84V) / 230A = 0.0565 or 56.5mOhm

I don't think 56.5mOhm is all the bad for a battery pack but let's take a look at the pack calculation.

Your using Samsung 30Q cells which have a 20mO IR DC
https://eu.nkon.nl/sk/k/30q.pdf




Rp = ((Sc + Pr) / Pc) * IRc

Rp = Resistance pack
Sc = Serial cells
Pr = Pack & BMS resistance (rated at 2P for all packs)
Pc = Parallel cells
IRc = Resistance cell (IR of cell)
Vs = Voltage sag
I = current in Amps

so lets fill out Rp = ((Sc + Pr) / Pc) * IRc

(26S + 2S) / 18P) * 0.02Ω = 0.031Ω or 31mΩ

Vs=I*Rp

230A*0.031Ω = 7.13Vs is what you should be getting if your cells DC IR are 20mΩ and the cell connections and BMS are not introducting more than 2S of resistance.

230A*0.0565Ω = 13Vs is what you are current getting.

1. have you removed your BMS and connected the loads NEG straight to B- on the pack and see if removing the BMS will make any different in the voltage sag. If you have CA3 the Vlt Cutoff works just fine for LVC and a BMS is not really needed except for balance charging.

2. Do a IR test on a few of the cells that are soldered into the pack and see if what you are getting for IR. Also if you have left over cells from his build test them also. Did you test the cells for IR before you did the build? and if you did how did they test out?

Your pack is a 26S18P right?

 

[bobmutch]

To calculate wire resitance use any of calculators by doing a quick google search. You can also find resistance per length tables for various wire gauges.
Sum both resistances. This is aproximatelly your pack internal resistance.

I don't see how you are getting the need to "sum both resistances".

Rp = Sc / Pc * IRc is the correct calculation.

Rp = Resistance pack
Sc = Serial cells
Pr = Pack & BMS resistance (rated at 2P for all packs)
Pc = Parallel cells
IRc = Resistance cell (IR of cell)
Vs = Voltage sag
I = current in Amps

I have added Pr (Pack & BMS resistance) as 2 addition serial cells.

so

Rp = ((Sc + Pr) / Pc) * IRc

 

[galp]

I don't see how you are getting the need to "sum both resistances".

I have added Pr (Pack & BMS resistance) as 2 addition serial cells.

Well you can assume resistance of wiring and BMS is same as resistance of two cells or you can calculate the exact value and sum it up to battery internal resistance. No?

 

[bobmutch]

Well you can assume resistance of wiring and BMS is same as resistance of two cells or you can calculate the exact value and sum it up to battery internal resistance. No?

I’m not sure which is the best way. Or I’m not sure which is the correct way. I guess the proper way would be to calculate the serial to serial nickel connection as an additional serial resister and the addition parallel to parallel Bickel connection as an addition parallel resister. Or perhaps the addition resistance should be added to the cell IR and then multiplied by S/P?

And how to add the BMS and B+ and P- wires to the load?

What do you think?

 

[leffex]

johnnyz

cool bike and pack!

How have the reliability been on your old pack and what changes have you decided upon the new pack not mentioning beefier wires and such modifications?

Have you ever measured the temperature of the packs sides and middle?

Do you have any air modification scooping air into the battery compartment on the motorbike

Do you have had any events or critical situations when your pack has "switched off" your electricity to your motorbike and its critical systems?

 

[j bjork]

Interesting build!
I can´t add much to your plans, but I am curious about your controller.
I am about to buy a controller myself, and I have been looking at some options.

Of kellys controllers it seems like KLS7250H would suit me best.
It looks like it is what you have, or something simular?
What conserns me is that some people say kelly have a slow start and and speed throttle that is not so precise.
I think their experience is mostly from KLS-S, but it seems to be the same program for all of the KLS. So I guess the behavior should be simular.
Whar are your thoughts about that?
If you or someone else have something to say about it, but don´t want to discuss it here, there is another tread:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=98792

 

[John in CR]

I haven't used 18650's in quite a few years, so thanks for the time and effort showing that soldering can work well. If I ever go back to that route, I'll be sure and get good soldering equipment like you and Overclocker use. When I made my comment before, I gave you less credit than was due...probably since you called an 89V pack a 100V pack. To me calling referring to a pack by it's top-of-charge voltage instead of nominal voltage is similar to the guys claiming ebike power using phase current limit X max voltage.