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I’m building Tw200 Yamaha with a 15-20 hp motor and would like about 30 mile range on a 72 volt system can anybody recommend what and how many cells On a vruzened 2.1
 

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Afaik, the Vruzend kits are meant for 18650 cells (and are not ideal for high current draw applications as they have fairly vibration sensitive connections to the battery cells...)

I don't know of any manufacturer making LiFePO4 cells in the 18650 format...

If you want to use LiFePO4 cells, you might want to take a look at the Headway 38120 cells? They might be a little large, not sure.
 

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Could I get 30-50 mile range on a 38120 pack at 72 volts. I would need over 23 cells, correct.
I'm running these numbers rough. 38120's nominally operate at 3.3V. So 22 to 23 cells are needed for 72V nominal. Capacity is 9.8 Ah minimum each. So 9.8 Ah * 23 * 3.3V cells gives a capacity of 743.8 WH.


Here's a paper that discusses the numbers for a Kawasaki Ninja 250R which has a similar weight.

http://www.asee.org/documents/zones/zone1/2014/Student/PDFs/127.pdf

They computed a pack capacity of 1024 WH for their 51.2V 20 lead acid pack. Factoring in Peukert factor for lead acid of 1.3 gives an effective pack capacity of 788 WH. That's close to the 38120 pack.

Now the Ninja got 25 miles with that pack. So the answer to your question is a no. However, there are 40152 cells with 15 Ah capacity which would add 50% to your pack capacity and 50% to your range. That would get you to 37.5 miles which is smack in the middle of your request.

One question: is speed a factor? At 72V your top end is going to be limited. Probably the best way to improve your range and your top speed is to upgrade to a 96V motor. A 96V pack with 40152 (30 cells) would give you 50 miles of range and a higher top end.

ga2500ev
 
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