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Hello. I just bought my first motor, just to start somewhere but the motor I bought is a K11" dual R20-32078 84,2KW, 5500rpm´s and 400VDC.. bought it used from a guy that gave up on making his EV..

I like the headway batteries, 16ah 3,2V
http://currentevtech.com/Lithium-Batteries/Headway/Headway-40160S-16ah-cell-LiFePO4-p42.html

because they are so small and I can fit them where I want..

but the problem is i´m not sure how many i need.. is there some one here that can help me?

lets say I want to go 50 miles on the charge and the car is 1300kg if that helps you answering my question..

best Regents Ragnar...
 

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About the best you can do is guestimate. Figure 250-300 W/h per mile depending on speed and your aerodynamics. Each of those cells have 51.2 W/h's and about 80% of that is what you'll actually want to safely use so 40.96 W/h's. For each mile traveled you'll need 7.3 of those at 300 W/h a mile. So for 50 miles you'll need 365 of those batteries in a series/parallel configuration that will make your controller happy voltage wise.

There are also a couple range calculators linked to on this site in various posts. just search for range calculators.
 

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That's quite a bit of motor for a 1300lb car, should be fun!
I'm not sure the best way to deal with the 400v rating, but a Soliton1 / Soliton Jr or Zilla 1k-hv / 1k-ehv should give you pretty good performance.

And based on those controllers you are looking for a 300+ volt pack, pretty much as high as the controller will handle to get good high RPM performance from the motors.

Based on the weight 300wh/mi should be a safe estimate as long as it doesn't have the aerodynamics of a truck.
300wh/mi x 50mi = 15kwh (this would be a drop dead 100% discharge for 50 miles)
15kwh x 1.2 = 18kwh (this keeps your discharge to 80%)
18kwh / 300V = 60AH pack
300V / 3.2V per cell = 93.75 (94 series cells)
60AH / 16AH = 3.75cells (4 parallel cells)
94series x 4parallel = 376 cells

This is just to get you started. When you choose a controller, I would optimise the series cell count to be just under the max voltage at full charge. The formulas are simple, you should be able to modify the numbers if you have a different preference for voltage etc.

Good luck.
 

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Discussion Starter · #5 ·
94series x 4parallel = 376 cells
.
wow.. thank you I must have misunderstood this all.. I thought because my motor is 84,2kw I would meed a battery pack og 84,2kw.. that is 1684 batteries.. but i only need 376 batteries so that´s a saving of 38000$ because i was worrying about that i´d have to by 1684 batteries.. i´m a noob.. sorry haha but thinke's
 

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Hi Ragnar

Kw - kilowatt - is a measure of power

Kwhrs - kilowatt hours - is a measure of energy

Treat it as water
Kw,s - are flow - gallons/min
Kwhr,s - are amount - gallons


1 Kilowatt hour is enough energy to have 1 kilowatt of power for 1 hour

3 Kwhrs will run a 3Kw heater for one hour
 

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rwaudio
That was 1300Kg, weight. Do your figures still work for that load ???
Yep, 1300Kg is just a bit lighter than my Porsche will be when it's done (1300kg is 2860lbs, I'm guessing my Porsche will be about 3000lbs)

wow.. thank you I must have misunderstood this all.. I thought because my motor is 84,2kw I would meed a battery pack og 84,2kw.. that is 1684 batteries.. but i only need 376 batteries so that´s a saving of 38000$ because i was worrying about that i´d have to by 1684 batteries.. i´m a noob.. sorry haha but thinke's
As far as peak power goes, you will have more than 84,2kw those headway cells can do 5-10C easily which would be 96kw - 192kw (assuming your controller is capable)

But yes 376 is way better than 1684! However 1684 would give you 200-250miles, and 860kw of battery power (1155hp)
 

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Hi Ragnar

Each cell is 3.2volts and 16 amphours = 51 watt hours - energy

Each cell can deliver 3.2v x 16Ah x 5C = 256 watts of power

5C continous means that the cell can deliver 5 times its one hour rate (16amps)-80 amps - until the cells are empty

10C burst means that the cell can deliver 10 times its one hour rate (16amps) 160amps - for a short period - 10 second? then the cells will overheat

1684 cell contain 1684 x 51 watt hours = 85.8 Kwhours of energy

1684 cells can deliver 1684 x 256 watts [h1] 429 Kw [/h1] 572hp of power (for 12 minutes then the cells will be empty)

1684 cells can deliver 1684 x 510 watts [h1] 858 Kw [/h1] 1144hp of power (for a few seconds)

Power x time = Energy
 

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Is it 5C continuous or 10C. It seems like half of the places that sell them say 5C continuious the other half says 10C continuous.
 

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Is it 5C continuous or 10C. It seems like half of the places that sell them say 5C continuious the other half says 10C continuous.
The info I got from Headway directly indicated 5C continuous and 10C burst for the 16ah cells. They didn't give an exact time frame for burst but it was referenced in a different section as X number of seconds and was related to cell temperature.

The 38120S was 10C continuous 15C burst
I didn't request info on the 38120P but it was listed as 20C burst on one of the other documents.
 

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You will see a lower capacity when cold , also the series resistance of the battery increases.


Just like most things do when their cold. They work a notch slower.
 

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Hi Ragnar

Insulate the battery box,

Good insulation plus heating when charging should fix most temperature issues
The only problem would be if you had to leave the car somewhere without power (for battery heaters) for a long time
 

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Keep in mind that your current vehicle weight will likely increase, requiring more power, which requires more weight in batteries...

With that motor you are best off using a higher voltage pack and an IGBT based controller. A Soliton seems to be the best commercial choice.

You will definitely need to derate the pack capacity when cold. Driving very gently until the pack warms up will help.
 

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but here is another question.. I live in Iceland and this year has been -15°C max how does the headway batteries work in this condition?

can the give me the energy that i need from them in this head/cold..?
I'm in the not always so warm climate of Canada so I had the same concerns.

Please see the attached zip file of an excel sheet for the cold weather performance, but also note the reason the test was done at such a low C rate is because anything higher and the cells will start to heat themselves and provide better performance.

So as mentioned before, after driving for a bit the batteries will warm up and provide more capacity. But unless you have nice boxes kept at 25Deg you will lose some capacity in the cold.

**forgot to mention, the scale at the bottom of the graph in the excel sheet is a bit odd. It is in AH without the decimal, IE 946 at the bottom right represents 9.46AH
 

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Well, you're gonna need a hundred and change of those batts. just to get up to the required voltage, if im not mistaken. Have ya thought about locating a wrecked Prius & gettin your mitts on it's battery pack?
 
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