docw009
1 MW
You've already got $1700 into this. Why risk damaging the battery with a soldered up kluge? I would suggest spending some more for a spot welder and giving it your best shot. Then the next battery will be cheaper.
AliExpress battery pack unboxing (for my eZuma project)
- Thread starter MJSfoto1956
- Start date
MJSfoto1956
10 kW
docw009 said:
There is that.
And a good Weller soldering iron is $72 from Zoro, which as you say could go towards a spot welder.
Much to think about...
I assume something like this might do the trick: https://malectrics.eu/product/diy-arduino-battery-spot-welder-kit-v3-2-2-full-bundle-lipo-battery/
M
MJSfoto1956
10 kW
So if I abandon a soldering approach and go instead with more traditional spot welding, the pack would now look like this:
Albeit more expensive than soldering (given that I need to buy a spot welder) the overall look is certainly cleaner.
Definitely considering this. Any remaining issues anyone can see with this approach?
M
Albeit more expensive than soldering (given that I need to buy a spot welder) the overall look is certainly cleaner.
Definitely considering this. Any remaining issues anyone can see with this approach?
M
TilmanBaumann
100 W
- Joined
- Feb 15, 2018
- Messages
- 120
Good plan I think. Even somewhat overkill.
Maybe you can borrow a spot welder. If you are in EU I can give you my kWeld for a while. Or sell you my suniko 787A+ for very little (my hiuse fuses are too small)
Maybe you can borrow a spot welder. If you are in EU I can give you my kWeld for a while. Or sell you my suniko 787A+ for very little (my hiuse fuses are too small)
MJSfoto1956
10 kW
While I ponder the "weld vs. solder" debate, in the interim I have started to wire everything up on my test bench to see how it all works together. Pretty much fired up the first time I flicked the switch, yay!
Components:
Components:
- 2000W QS 260 hub motor
- 72V 20s17p AliExpress Li-ion battery pack
- PowerVelocity 20kW controller + Bluetooth app
- 125A circuit breaker
- 10A circuit breaker
- 2A circuit breaker
- ZEVA Smart Precharger
- Tyco EV200 Contactor
- Bussmann 2P Miniature Distribution Block
- 2AWG and 4AWG marine cable
- Wuxing half-twist throttle
999zip999
100 TW
Hook up your temp gauge
MJSfoto1956
10 kW
999zip999 said:
That's next on my list...
M
MJSfoto1956
10 kW
So I will be updating the internal wiring of my "as shipped" 120A AliExpress battery pack. Lots of little corners that were cut by the vendor (but were hidden from view under the shrink wrap) that need to be addressed.
View attachment 1
The key thing to address is adding two thick copper busbars to distribute the power evenly on both the positive and negative sides.
The big surprise for me is that Chinese pack builders are using what looks like "big & beefy" wiring but upon closer inspection reveals that it is merely 10AWG cable. Surprisingly, the super-fine braided copper in these cables measure a whopping 3.8mm in diameter! As a point of comparison, the PCB hole into which they are soldered is 4mm in diameter which should be able to support up to 6AWG. So it appears to me that on the Negative side, I could easily shove solid bare 6AWG copper cable into the two PCB holes and use that as a framework to solder four 8AWG "distribution" cables to the bus bar (see photo). An analogous approach is used for the Positive side. While this is definitely OVERKILL for this particular BMS, I intend on upgrading the BMS (eventually) to a 150A smart BMS which can then profit from this prior investment in upgraded 8AWG cabling.
View attachment 1
The key thing to address is adding two thick copper busbars to distribute the power evenly on both the positive and negative sides.
The big surprise for me is that Chinese pack builders are using what looks like "big & beefy" wiring but upon closer inspection reveals that it is merely 10AWG cable. Surprisingly, the super-fine braided copper in these cables measure a whopping 3.8mm in diameter! As a point of comparison, the PCB hole into which they are soldered is 4mm in diameter which should be able to support up to 6AWG. So it appears to me that on the Negative side, I could easily shove solid bare 6AWG copper cable into the two PCB holes and use that as a framework to solder four 8AWG "distribution" cables to the bus bar (see photo). An analogous approach is used for the Positive side. While this is definitely OVERKILL for this particular BMS, I intend on upgrading the BMS (eventually) to a 150A smart BMS which can then profit from this prior investment in upgraded 8AWG cabling.
MJSfoto1956
10 kW
Boy that was fast shipping. 3/4" x 1/8" Copper busbars via eBay have arrived already. I'll need to tin these.
MJSfoto1956
10 kW
Making progress:
Still waiting on some key parts to finish this puppy.
- Put together the Malectrics spot welder kit (fast shipping too!)
- Tinned the copper bus bars (something I've never done before)
- Fabricated the 4* 8AWG negative-side power distribution harness
Still waiting on some key parts to finish this puppy.
Interesting approach of buying a Chinese pack and making improvements here ...and some good ideas on improving it. Can I ask what are the physical dimensions of this pack? Also, which LG cell did they use in this pack? Do you know the discharge rate of the cells? Thanks, Richard
MJSfoto1956
10 kW
Headrc said:
- The dimensions are 220mm x 320mm x 140mm, which fits perfectly in my existing battery tray.
- The pack is made up of 340 cells, LG F1L 18650 3350mAh 4.8A.
M
MJSfoto1956
10 kW
Headrc said:
Not entirely convinced it was the right approach, but it is what it is.
I'm learning as I go and hopefully others can gain insight from this as well.
M
MJSfoto1956
10 kW
Some minor progress. Split the pack and got the core of the serial busbars spot welded into the "missing" slots. Used the Malectrics spot welder for the first time and it was very straightforward -- highly recommend it. Finally, I wrapped the bulk of the battery in Kapton tape, leaving the final positive and negative strings exposed so that I can add copper busbars to them.
Still awaiting some other bits and pieces before I can finish the pack and get on with the rest of upgrade.
View attachment 3
View attachment 5
View attachment 2
M
Still awaiting some other bits and pieces before I can finish the pack and get on with the rest of upgrade.
View attachment 3
View attachment 5
View attachment 2
M
MJSfoto1956
10 kW
While waiting for the remaining bits and pieces, here is a sketch of the "kill switch" I'm considering implementing:
hemo
100 W
A battery and a half, good work in bettering it.
MJSfoto1956
10 kW
hemo said:
Won't be hard. The corners cut are pretty easy to identify.
M
Tolkano
100 W
Really nice work man but you obviously could have built the whole pack by yourself to begin with :lol:
Do you do anything to make it safer against a short between the series groups?
On a bike where the pack will be exposed to vibrations the thin insulation could chafe off or get squashed, and then
Maybe i missed that, but are the cells got stuck together?
If not i would add a drop of CA in each gap where the series cells touch. This should add support to the insulation and make it stiffer.
I thought the same
nice drawing skills
On a bike where the pack will be exposed to vibrations the thin insulation could chafe off or get squashed, and then
Maybe i missed that, but are the cells got stuck together?
If not i would add a drop of CA in each gap where the series cells touch. This should add support to the insulation and make it stiffer.
tolkaNo said:
I thought the same
nice drawing skills
MJSfoto1956
10 kW
tolkaNo said:
As I got into it that was my first thought. I was hoping for better quality. Would be great to find a dependable AliExpress fabricator that knew how to build packs the "right way" instead of cutting corners. Ah well. Lesson learned.
Actually, not a bad way to learn (i.e. how not to do it!)
M
MJSfoto1956
10 kW
madin88 said:
They are indeed hot-glued together. Notwithstanding, I also plan on adding sheets of 6mm Twinwall Polycarbonate between the top, middle, and bottom of the two halves to act as a ventilation/stiffening/protection mechanism. See: https://www.greenhousemegastore.com/polycarbonate-panel-6mm-clear
You have me curious: what is "CA"?
(superglue?)
M
P.S. here is a cross-section of my pack design:
MJSfoto1956 said:
I have to disagree. I've actually dealt with this vendor and they are very accommodating. I have no doubt had you asked for "more" and paid for "more" they would have provided "more". They did for me. Andy answered all my emails and technical questions very quickly and honestly.
Basically what I'm saying is you cut corners. You had to know how cheap that is for a 57aH battery. If you could find someone willing to build you that spec'd battery for $1700 in NA do you think it's going to come with copper bus bars and a smart BMS? I couldn't even source the cells here for my battery for the price I paid for one shipped to my door in 3 weeks, but I'm in Canada.
Anyways, good on you for doing the tear down and mod. People should read this so they know what to ask for when they order a battery. But they should also expect to pay a little more as well.
MJSfoto1956
10 kW
furcifer said:
Actually I did indeed ask for more -- the original battery I inquired about was 20s15p with 70A BMS. I asked if he could build a 20s17p with 120A BMS to specific outer dimensions (to fit my existing battery tray) and he quickly posted a link on his AliExpress site just a day later. I agree he was very easy to work with with fast, understandable responses.
However, the issue with any endeavor is knowing (or more to the point, not knowing) what to ask. Being a newbie, I did not go into any build specs other than what was mentioned above, mostly because I just "assumed" this battery would be just like their other offerings (which apparently it is). As I mentioned previously, I think it pretty safe to now conclude that this battery is likely typical of what you would get from most AliExpress vendors -- i.e. a "good enough" battery pack.
Can Andy make a better pack? Given my limited dealing with him, I feel confident that the answer is likely yes, with the caveat being that only if one were to insist as such á priori. At a minimum I'd want to insist on serial zinc bus bars for each cell and a beefier terminating arrangement for the positive and negative connections. But again, one would have to remember to request that with the understanding that the prices listed on his AliExpress site almost certainly don't include such refinements.
From a marketing point of view, Andy could easily distinguish his "high end" batteries from his "good enough" batteries simply by using a different color shrink wrap PVC. e.g. Black for high end and blue for the others. But perhaps there is no such mass market for that in China? I haven't a clue. The general focus on AliExpress seems to be cheap at all costs.
Good to know Andy is amenable to build to spec. Could you provide an example of the kind of battery pack specs you requested of him previously?
Thanks!
M
I think it's worth pointing out that's a huge battery. So right off the bat it's not really "typical". My point being I don't think the average vendor on Aliexpress would even build a battery that big, or even carry a 120A BMS. And from my experience Aliexpress doesn't release the funds until a few weeks after you confirm getting a functional product. So there's quite a bit of incentive for them to provide you with a functional product. So cutting corners is kind of overstating it. I mean sure, they want profit, but the margins are thin and the cost of failure is pretty high.
I've just discussed a couple batteries with him. I found he didn't want to oversell me or undersell me. He seemed pretty familiar with the cell characteristics of the batteries I was looking at. Which was what I wanted to see. Someone that was technically proficient and not just a salesman. That was my impression from him/them when I bought it. So I could be wrong but I really didn't get the impression Booant was typical in the sense they were high volume/low quality get em' out the door as quick as possible.
There's also the other side of this where overbuilding these ebike batteries is a waste of money. I mean what's the point of building a n ebike battery that will hold together for 15 000 cycles if the cells are only going to last for 1500? From a mathematical standpoint what's "good enough for the masses" when you're talking about 1 billion trials is EXACTLY where you want to be. From a manufacturing standpoint that's perfection. :lol:
I've just discussed a couple batteries with him. I found he didn't want to oversell me or undersell me. He seemed pretty familiar with the cell characteristics of the batteries I was looking at. Which was what I wanted to see. Someone that was technically proficient and not just a salesman. That was my impression from him/them when I bought it. So I could be wrong but I really didn't get the impression Booant was typical in the sense they were high volume/low quality get em' out the door as quick as possible.
There's also the other side of this where overbuilding these ebike batteries is a waste of money. I mean what's the point of building a n ebike battery that will hold together for 15 000 cycles if the cells are only going to last for 1500? From a mathematical standpoint what's "good enough for the masses" when you're talking about 1 billion trials is EXACTLY where you want to be. From a manufacturing standpoint that's perfection. :lol:
