Building a high Amp output battery question

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maarkmohamed

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Hello guys, I was suggested to come over here from another forum I was told you guys would be about to help me figure out my problem. I am currently in the process of building a complete electric dirt bike and I'm just about to start with the battery portion. However the problem I've been thinking about is, I'm looking to make a total of 35-45kw of power and I'm most likely going to be drawing from the battery around 500+ amps. Now my battery configuration is going to be something like a 28s 11p setup. Now when the battery is all done and I need to connect the positive and negative lead from the battery, how do I do this in a way which will allow me to safely draw 500-600 amps? Now obviously I'm going to have to go with some very thick gauge wire and you wouldn't be soldering something like that. And so I'm most likely going to have to use bus bars connecting the whole thing. And from the bus bar in going to connect the positive and negative leads. But how thick of a bus bar do I need, and how exactly should this be done? Hope my question is clear.

Thank you in advance for your help.
 
You need to check your math here...500-600amps on an 11p battery? Dood..thats like 54amps per cell... You need to revisit this... That much power would nearly be equivalent to a Tesla...they just run 300+ volts... But 500amps??? Really?? 500?? Your talking some 0000 gauge wire...let's see here. McMaster Carr has some 500mcm wire that's 1.13 diameter thats rated for 380 amps... At $30/ft...

I hope your building a car...
 
No Philaphlous it can make sense.
Maarkmohamed, you say you want to power a dirt bike with 40kW max power. I assume max, as i can't think of a bike taking 40kW sustained ;) You're talking about 28s battery. Let's assume Lipo/LiCo and not LiFePo4 we're talking 3.65V nominal, so ~100V. So that's 400A peak battery.
If you say 11p, than this should be high-c capable RC-LiPo. If those are 5Ah cells, it's 35A per cell, or 7C. This is doable. Battery will be depleted in under 10min. But i don't know your demands.
For battery connections you may use stubs that are crimped. This is industry standard. Something like this https://www.amazon.com/Pico-Battery-Tubular-Terminals-Package/dp/B00030CXZM
I don't know where you want install bus bars, but bus bars are basically copper bars that are VERY capable current wise. A 10x5mm copper bar can candle crazy ammounts of current.
Another question is: What wires will your controller use to bring the power to the motor. Normally these wires need to handle a multitude of battery current. So choose the same wire for your battery <-> controller connnection and you should be fine.
 
I did make a silly mistake with my math. Thank you philaphlous for correcting me. However i will be using 0000 gauge wire, and its good to know that copper of that thickness will handle high currents.
 
maarkmohamed said:
i plan on using either samsung 20s cells or lg HG2 but im still choosing.
Click to expand...

You won't be able to get that much current from those cells with 11p.
 
Yes sorry for not specifying where my calculations went wrong. I improperly calculated the cdr with my desired battery configuration. On a side note, i was looking at the imren high drain cells which are in the link below, anyone have any experience with them? I can imagine they put out good numbers but wont last as long as your well known name brand cells. Those cells have a max discharge rate of 40 as per there specifications. If i change my battery configuration to 26s 14p, that would put me at 96.2v nominal and at 40 a maximum discharge that would be 560a. Which would put me in the ball park of where i wanted to be. However i understand id rather not pull its max amp unless its for a short time, and instead pull something like 30a from each cell. Another cell option is the mxjo imr 18650 high drain, with 35a max discharge link below. Wondering if anyone has experience with these cells, and whether i should avoid them or not.




https://www.amazon.com/3000mAh-Rechargeable-Protection-BD-Electronics/dp/B0768FWTBZ/ref=sr_1_2_s_it?s=hpc&ie=UTF8&qid=1547149918&sr=1-2-spons&keywords=imren+18650&psc=1


https://www.amazon.com/Force-18650-3000MAH-TYPE-2-rechargeable/dp/B076J47RZ1/ref=as_li_ss_tl?ie=UTF8&qid=1536448478&sr=8-1&keywords=MXJO+IMR+18650&linkCode=sl1&tag=powergenix-20&linkId=887c1a68e742aff12fbcecc40b1206ad&language=en_US
 
NO WAY. There is no 3000mAh 18650 cell with 40A discharge. This is 99% fake data.
Known good high discharge cells like the Sony VTC4 can do 30A but have only 2100mAh.
If something like a high capacity high discharge cell really existed this forum would go nuts - rest assured! ;)

See http://www.candlepowerforums.com/vb/showthread.php?415345-Test-Review-of-Imren-IMR18650-3000mAh-(Purple)
 
Yea i think it might be better to stick with name brand cells. And also that 35 - 40 a discharge rating there giving is a pulse discharge, which means it could do it for about 30 sec. But as the tests shown they get rather hot/unsafe at those levels. Its better to stick with the cdr (continual discharge rate).
 
If you really want a high current output battery, I recommend looking into used / salvaged large-EV pouch or prismatic cells, like those from the Leaf, etc.

I'm using old 20Ah EIG NMC cells (easy to bolt together in any configuration), whcih are capable of 5C continuous, 10C bursts, so 1p gets you up to 100A continuous, 200A for at least several seconds at a time. 2p = 200A, 4p = 400A, etc.

The disadvantage is they aren't as energy-dense, and they're big flat cells, so you can't just configure them into as many shapes of pack as 18650s, and require more volume for the same energy.

But for a motorcycle, they could be easier to manage and build into a pack than the 18650s. Zero Motorcycles used them at one point, though they have also used packs made from 18650s.
 
amberwolf said:
If you really want a high current output battery, I recommend looking into used / salvaged large-EV pouch or prismatic cells, like those from the Leaf, etc.

I'm using old 20Ah EIG NMC cells (easy to bolt together in any configuration), whcih are capable of 5C continuous, 10C bursts, so 1p gets you up to 100A continuous, 200A for at least several seconds at a time. 2p = 200A, 4p = 400A, etc.

The disadvantage is they aren't as energy-dense, and they're big flat cells, so you can't just configure them into as many shapes of pack as 18650s, and require more volume for the same energy.

But for a motorcycle, they could be easier to manage and build into a pack than the 18650s. Zero Motorcycles used them at one point, though they have also used packs made from 18650s.
Click to expand...

Appreciate the advice, im going to look into them.
 
High amps current output is one thing.

But don't lose sight of AH capacity required.

No point going faster than sh1t through a goose but for 20min only
 
LiPo pouches might be the best compromise for you then - 30C continuous and still ~158 Wh/kg.
 
jonescg said:
LiPo pouches might be the best compromise for you then - 30C continuous and still ~158 Wh/kg.
Click to expand...
Why am i not surprised to see this suggestion from you ;) Master of RC-Lipo ...
maarkmohamed you shoiuld look through jonescg's threads to see how high quality big lipos packs are built!
 
Izeman, I looked at those batteries you just suggested the a123 and they look neat, they look ok but bulky but not too bad. The only reason why I'm not willing to use other batteries besides the 18650 is because I know how to assemble and work with 18650 cells, theres countless videos on them which makes it easy for me. If there was a tutorial video on how to assemble that and install bms, I would appreciate it. However I just can't seem to imagine that theres a better cell option than 18650 cells considering companies like zero and ktm electric dirt bike use 18650 cells. I know zero used other than 18650 for a certain time but now use 18650. That's my two cents.
 
The AMP20 batteries are by far the most easiest to assemble. It's just 20+ cells in ONE string. One after the other.
And the BMS' balance wires go from one end to the next interconnection, and the next etc ... until the last cell. Super easy.
And there are connector sets where you just slide in the cell's tab, fold it down, put two screws on, and you're done. No welding or soldering involved. The cell's are a bit lower Wh/weight wise, compared to Lipo, but very easy to handle and SUPER capable current wise. Search the forum for it, and you will find a lot of threads about them.
There is a simple reasone why ppl choose 18650 nowadays (me included). They are widely available, have a high energy density and the biggest pro is, that you can build any shape with them and fill any open space. But if your space is more or less rectangular, nothing beats the simplicity of those big pouch cells. And btw: They (or similar cells) are quite commonly used by electric car companies. 18650 is more or less a TESLA (and motorbike) phaenomen.
 
If you are looking in to car batterys, I think vw hybrids is worth looking at. I have made some measurements, but I don´t remember exacly.. But I think they are about 145mm wide and 100mm high. I don´t know how thick, maby about 15-20mm. They are in 12s1p modules, I think they are 25Ah. This was from a passat hybrid, but others are simular from what I have seen.
 
Ok im going to have to take a bit of time searching up these other options and figuring out whats going to work best.
 
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