A123 20AH LiFePO4 cells interconnexions

Dui said:

999zip999 said:

#1 safety. Yes I found the high quality of these cells is the #1 they stay balance just bulk charging. What is the source for these cells and how much will you be paying ? I understand the need for a strong battery with that bike. What motor and controller do you run. Nice ride. Taking the let out and putting some high-powered cells in you would have a hard time keeping the front wheel down

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Thanks

I'm using a 3000W QS motor and a software unlocked version of the sabvoton 72150, currently set up at 200 Amps continuous.
That's nice but not really amazing in terms of perfs so far. About an equivalent to a 125 or 200cc bike I guess.

I plan to make some mods to the sabvoton, using shunts to the current sensors to hopefully go around 300-400 Amps if it can actually go that far (still have to open it to check the mosfets first).
In which case, of course, I'll add watercooling so that it won't explode instantly

First step is to get the right battery and then I'll upgrade the other stuff, probably change the motor etc.
Ultimate goal is to make a bike with comparable specs as a basic 400-600cc engine.

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Just want to know how much fase amps are you pulling? And whats the max faseamps that a unlocked 72150 can handle?

bionicon said:

Just want to know how much fase amps are you pulling? And whats the max faseamps that a unlocked 72150 can handle?

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I need to check again but it should be around 400-450 amps if I remember correctly

Ok so I finally moved on and ordered my battery and BMS.

For the Battery, it will be a 23S 2P (72V 40Ah). For now I just bought one, but I'll add another if it turns out to work as intended. Cost is 450 USD:

https://item.taobao.com/item.htm?spm=a230r.1.14.257.66e453eeOo1uaW&id=561625349656&ns=1&abbucket=6#detail

For the BMS, I'll go with this 300A one, including the screen and Bluetooth, for 80 bucks:
https://item.taobao.com/item.htm?spm=a230r.1.14.173.63171b15B1wGxT&id=554867081787&ns=1&abbucket=6#detail

I should receive everything in a couple of weeks. Also need some little hardware, like anderson connectors, main switch, current sensor and stuff like that.

BTW, for those of you who need big, thick cables, here is my tip: Purchase some battery jumpers cables.
-They are super cheap
-They can handle a lot of current without heating
-They are already red and black
-They exist in various thicknesses and various insulator material

Stuff like that, you end up with 4 meters of super thick cable for 13 USD, enough to make several builds:
https://item.taobao.com/item.htm?id=13402953458&ali_refid=a3_430582_1006:1103458179:N:%E6%B1%BD%E8%BD%A6%E7%94%B5%E7%93%B6%E8%BF%9E%E6%8E%A5%E7%BA%BF:738858e26b1a9e7b797c3779a38651bb&ali_trackid=1_738858e26b1a9e7b797c3779a38651bb&spm=a230r.1.14.6#detail

Dui said:

BTW, for those of you who need big, thick cables, here is my tip: Purchase some battery jumpers cables.
-They are super cheap
-They can handle a lot of current without heating
-They are already red and black
-They exist in various thicknesses and various insulator material

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Unfortunately it is a worst choice in some location.
Here, it is 12AWG packaged in 1.5cmD insulator and mostly aluminium clad or iron clad crap. Welding wire is only way to go.

parabellum said:

Unfortunately it is a worst choice in some location.
Here, it is 12AWG packaged in 1.5cmD insulator and mostly aluminium clad or iron clad crap. Welding wire is only way to go.

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I don't know where you live so that might be a possibility.
You might want to check with truck parts and accessories companies, they will use thicker gauge for sure.
Welding wire is OK but it's hard to find them color coded. Personnally I prefer to have an obvious color scheme to avoid any stupid mistake.

Well I just received my new battery, YAY!

But unfortunately, those delivery morons kinda destroyed it...
It arrived pretty badly warped, I guess they just threw it on the floor.















I managed to get it better using my giant vice:








It's about 26 kilos, I quicly checked cells voltage and they all seem to be fine.



Now I need to wire my smart BMS and power lines, hopefully I'll be able to finish the install of the first battery this week.

FWIW, if it were packed correctly, that wouldn't have happened without pretty thorough destruction of the packaging. :/

Probalby could've been built stronger, too, but since it's designed to go into an enclosure on the vehicle that would do that job, it wouldn't have to be strong outside of that; it just has to depend on whatever packing or enclosure it is in to keep it intact.


FWIW, it's fortunate that it didn't warp more; it might've cut or torn tabs or balance wires and shorted cells out.

amberwolf said:

FWIW, it's fortunate that it didn't warp more; it might've cut or torn tabs or balance wires and shorted cells out.

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Yeah, that was very close!
Some of the tabs were less than 0.1mm apart from each other. A tiny bit more and they would have been shorted, I don't think that would have ended up pretty in the express company warehouse...

A little update after using this battery for about 5 months: it is awesome.
Runs perfectly fine, doesn't heat, stays in balance, announced capacity seems to be there no matter how hard I ride it, it delivers any amount of current you might need with very little voltage sag... So far I have absolutely nothing to complain about, so if you have the opportunity to buy those kind of cells, don't hesitate for a second.