48v 20Ah lifepo4 -vs- 72v 15Ah lifepo4

danjpendleton

danjpendleton

100 W
Joined
Dec 4, 2013
Messages
252
Location
Hudson, New Hampshire USA
im trying to decide between 72v or 48v for the bike i am building and with so many battery options, im having a hard time making a good decision.

The commute- one way- 14 miles, overall pretty flat.

I can charge the bike at work all day

Then 14 miles back on a full charge.

Need a steady cruising speed of 35 mph. Yes i know its fast, but i have my reasons and overall im the one on the bike.

the bike is relatively light, id say around 250 lbs.

havent chosen a motor or controller to match the battery, obviously..... Because i havent chosen a battery.
 
what about 60v 15ah? 20 of the headway lifepo4 batteries will get you there... i like the way they hook up, and even if they are a bit bulky, they hold their power throughout discharge, and charging is very safe...the 60v will get you up and going pretty fast... what type of motor are you driving?
 
http://www.battery-matrix.com/DIY-60V15Ah-20S1P-LiFePO4-HEADWAY-BATTERY-PACK-KIT-40152S-cell-40152-cells-headway-lithium-battery-40152-headway-lifepo4.html



This would be a 60v 20Ah headway battery - 20s1p

I know theyd need to be wired in series but could i arrange them in various ways to fit a certain enclosure?

Oh and if my controller is rated at 50amps max then whats the benefit of the higher c-rate(10) with the headway cells as opposed to the standard lifepo4 stuff with discharge rates of around (3)?
 
For starters, you think of those headways as being a 5 c cell, in real world use. Then, the more c rate the better.

Then, you never choose the battery first. You have your requirements, then choose a motor and controller that will reliably do your requirements, or adjust requirements. Then and only then can you even think about the battery that can handle that motor and controller, and even then more requirements adjustments may be needed when you see how hard it will be to carry a gigantic battery.

48v won't get you the speed you want. But it might get you 30 mph, with the right motor.

For commuter reliability though, I'd forget a 50 amps controller. Use it, and most cheap dd motors will melt on down by mile 10. But I am only assuming you will use the typical cheap 28mm dd motor.

Cheap dd motor, and 72v 20 amps will get you your 35 mph cruise. And the lower amps will keep you from melting the cheap motor. It won't fly away from a stop light, but it will not make you pedal to get going. It's about reliability, you don't want to pedal home broken many times.

Ignore all this about the controller and meltng the motor, if you are planning on an expensive monster motor.

The ideal setup could be exactly what I have on my cargo bike, but you can't buy a 5304 motor anymore. I get reliability at 40 amps, and 33 mph max speed on 48v. 15 mile range at 30 mph is possible on 48v 20 ah.
 
im on the fence about whether the new hs3540 will be up to the task, because the 5304 is no longer available.

or just spend the money and get a cromotor....

i just read that post you participated in about sony's konion cells in comparison to lifepo4 and lico.

Unless im building a pack, i think the a123 packs that cellman sells will fit the bill just fine.

Dogman, i had no intention of cheaping out on the motor, or controller.
 
Welcome to ES****Do this before your first post or now (it's retroactive)*****
Please go to the User Control Panel, select Profile, and then enter your city, state/province, and country into the Location field (country minimum) and save it. This will help people help you. Example: Wylie, TX, USA. or just USA, but country as a minimum, and country is the most important. There are many cities with the same name all over the world. Without knowing what country you are in it's hard to make any recommendations. Thank you.
Pretty much any 1000W motor will do what want on 72V. 48v*20ah=960wh. 72v*15ah=1080wh, so more capacity with it.
 
danjpendleton said:
im on the fence about whether the new hs3540 will be up to the task, because the 5304 is no longer available.

or just spend the money and get a cromotor....

i just read that post you participated in about sony's konion cells in comparison to lifepo4 and lico.

Unless im building a pack, i think the a123 packs that cellman sells will fit the bill just fine.

Dogman, i had no intention of cheaping out on the motor, or controller.
Click to expand...


I have an HS3540 on 48 volts with a 40-amp controller. It gets me pretty close to 35 mph on flats. Unless you absolutely have to exceed 35 mph, it is a lot cheaper setup than 72 volts.
 
jimw1960 said:
danjpendleton said:
im on the fence about whether the new hs3540 will be up to the task, because the 5304 is no longer available.

or just spend the money and get a cromotor....

i just read that post you participated in about sony's konion cells in comparison to lifepo4 and lico.

Unless im building a pack, i think the a123 packs that cellman sells will fit the bill just fine.

Dogman, i had no intention of cheaping out on the motor, or controller.
Click to expand...


I have an HS3540 on 48 volts with a 40-amp controller. It gets me pretty close to 35 mph on flats. Unless you absolutely have to exceed 35 mph, it is a lot cheaper setup than 72 volts.
Click to expand...

Im assuming u run 26" wheels. What controller and battery are u running? If u dont mind sharing
 
danjpendleton said:
Im assuming u run 26" wheels. What controller and battery are u running? If u dont mind sharing
Click to expand...

It is just a stock Crystalite 40-amp controller. I built my own 48v 10Ah battery using 26700 cells from OSN (no longer available) and an 80-amp BMS. Yes on the 26" wheels.
 
I like a123 cells with match cells the battery should be a lasting battery. More than 30 amps and hills makes heat to melt. 30 mph is fine over 30 takes a lot more of everthing. Like problems.
 
danjpendleton said:
http://www.battery-matrix.com/DIY-60V15Ah-20S1P-LiFePO4-HEADWAY-BATTERY-PACK-KIT-40152S-cell-40152-cells-headway-lithium-battery-40152-headway-lifepo4.html

Click to expand...

Kit looks very nice for a nice price.
Any experience with this shop?

THX
 
2000w is enough to get you the speed you need, and the current clytes should handle that wattage for long rides.

I'm assuming any steep hills you have will be short compared to the rocky mountains I ride in.

But if you want 3000+ watts, then I would say just go for the monster motor.

60v with a 30 amps controller sounds like a good plan if a bit more reliability is wanted. Still won't see much over 2000w max, but will feel better off the stop sign than 72v 20 amps.

But I think those HS motors can take 60v with a 40 amps controller. Whatever your top speed is, limiting speed to about 35 mph cruising will limit motor heating, since it will be well under 2000w at 35 mph.

It's' the cheaper ebay motors of the 9 continent type 28mm rotor that melt easy if you push them past 35 mph. The clytes are slightly bigger, and take a bit more to melt them. But unfortunately, they don't equal a 5000 series motor if you have need for one, such as my cargo bike in the rockies.
 
I cant say i have had any experience with battery-matrix. definitely a decent price though.

Im almost positive ill be using a clyte hs3540 with an infineon 40amp controller.


according to my calculations, 48v 20Ah was doable....cellman(em3ev) wants $775 for his 50v 20Ah a123 pack. a little pricey considering his 72v 20Ah pack is only $275 more.

so i was thinking maybe something around 60v, 15-20Ah and came across this >>>>60v15Ah $559 and uses headway 40152 cells which have a decent c-rate of around 5c(real world)(thats 75amps) ....which should be enough with a 40amp limited controller at 60v i believe.

http://www.bmsbattery.com/packs/535-48v-10ah-38120-lifepo4-battery-16-cells-ebike-battery-pack.html


ive heard pretty good reviews about bmsbattery.com, so i emailed them about the dimensions of the battery pack^^

there are 2 different bms options 30-60A or 50-100A though, if im running a 40 amp controller, i should probably stick with the 30-60A bms right??

thanks for all the input guys. now that im honing down on my choice of setup im starting to get really excited about this project. with so many vendors and so many different variations and choices its hard to figure out exactly what your needs will be.
 
I see brief spikes of at least 70 amps with my 40 amps controller. They are too short to show on the display of my CA, but they do record on the max amps readout.

Not sure if they will be long enough to trip a 60 amps bms though. Ask others about that specifically, I'm just running no bms with RC batteries now.
 
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