aerickse said:
Pictures will be posted soon! I'm in the middle of moving so it's all totes untill the 1st. Also finals haha so alot of studying right now.
Can you explain amperage and how putting more cells in parallel correlate, my book doesn't describe the correlation if there is one.
One million thank yous
My pleasure
I'll try to explain but it's not super easy, you might want to browse the forum a bit, some might have done a better job at explaining than me.
Basically, lets say that your controller needs 80 amps.
Your battery is 6P, which means 6 cells in parallel. Let's assume each cell has a capacity of 2000 mAh (so 2Ah). In your case it's more around 2.2Ah but let's keep the example as simple as possible, you can redo the calculations yourself with the correct figures.
So your total battery capacity is 6cells x 2Ah = 12Ah. It means that if you want to discharge completely your battery in exactly one hour, you will have to draw 12Amps from it continuously. Discharge rate is what is generally called C-rating. If you discharge it in one hour at 12 Amps, the C-rating is 1.
So, let's assume your controller only needs 12Amps: then you are drawing 1C from the battery.
Now, if your controller needs 24Amps with the same condition: you are now drawing 2C from the battery.
So, instead of discharging your battery in one hour, it will discharge at 1hour / 2C = 1/2hour =30 minutes.
If your controller is drawing 36Amps: then it's 3C, so 20 minutes, etc.
In your case, if the controller needs 80 amps, then it will be 80A / 12Ah = 6.6C = 9 minutes or so.
Which means that your battery will be fully discharged in 9 minutes, which is pretty fast, the battery won't like it.
In real life of course it will be more than 9 minutes, because your controller won't use 100% of the power all the time, so that's just theoretical. But it gives an idea of what to expect if you ride at full blast.
Now, let's look at the spec sheet of your cells.
From what I remember reading yesterday, your cells are rated like that (you might want to find ant have a look at the datasheet yourself to make sure my figures are correct, just type the cell reference in google):
0.5A continuous discharge
5A maximum discharge
Generally speaking, you want to use your cells close to the "continuous discharge" rating, because they are designed not to heat as long as you stay under this figure.
The "maximum discharge" means that the cell can take this rating as a maximum for a short amount of time (this time is rarely defined by manufacturers, so it can be anything between 10 seconds or one minute).
Your controller is rated at 40A continuous and 80A peak (peak=maximum discharge). So your cells need to be able to provide that. In this example I'll only consider the maximum discharge figures, but the same calculations apply to the continuous ratings.
You have 6 cells in parallel, so you add up the output of each: 6cells x 5A = 30A. Your controller needs 80A so the battery is only able to produce 37% of that power requirement (80/30 = 37). That's the absolute maximum your cells should be able to deliver. Anything above that might damage them. Maybe not kill them instantly (but maybe yes), but at least reduce drastically their lifetime.
The other way of calculating would be to use C-ratings. In this case, you can determine the C-rating of your cells: they are rated for a 2Ah, supposedly at 1C. Since according to the specs they can deliver a maximum of 5A, they are capable of 5A/2Ah = 2.5C. We determined earlier that you need 6.6C, so, here again 6.6/2.5 = 37% of what you need. Which is coherent with the previous calculation. Tadaaaa.
You can use any of those two methods,depending whichever you prefer or whatever data you have to start with.
So, your cells can only deliver 37% of your needs (according to this basic example at least, in your case it's a bit more since your cells are not 2Ah but 2.2). You have only two options there: either find better cells, capable of a higher discharge rate, or add more cells in parallel. The ideal would be a combination of both. Don't forget also that in this example we used the "maximum rating" of your cells, you want to use your cells at their "continuous discharge" ratings... and in your case that rating is 10 times lower while the controller needs are only half lower (40A)! So... well I guess these cells kinda suck.
Hope it is clear enough, I tried to keep it simple and some stuff is a bit inaccurate for clarity purposes but that's the idea.
