Squeezing out range ... questions about voltage and amperage

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kbarrett   10 kW

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Squeezing out range ... questions about voltage and amperage

Post by kbarrett » Dec 10 2007 5:09pm

I am currently using a clyte 405 and a 35a 36-72V controller. I'm using 48v SLA ... and should have five dewalt packs to disassemble today or tomorrow.

I would like to bump my range up ... I really don't need to go all that fast.



Would I be better off dropping to 36V? Or increasing Voltage and then using a Cycle-Analyst to limit speed?

Would dumping down to a 20a controller help?
Sun EZ-1 recumbent, Heinzmann 450W, 36V16A Ping "Duct Tape" LiFePO4
Evil Smoker ( Schwinn beach cruiser with 49cc two stroke, and a one gallon gas tank )

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BiGH   100 kW

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Post by BiGH » Dec 10 2007 6:52pm

is it the newer style controller? or old? if its the newer i'd say run the higher voltage 2s2p or whatever. You'll get faster acceleration using the higher voltage too.

the older controllers had a lot of issues with being fried at 72v with only normal usage, but you could always get a new one with a plugin CA. :)

either way it just doesn't really matter, if the CA is limiting then there much of a muchness :)
Bike / Motor: Electric specalized rock hopper with Crystalyte 504 / 26"
Batt: Yesa 72v (36v*2) (getting 6.7ah) LiFEPO4 in a Topeak bag. OR 1x eMTB 48v 20ah pack (straps to frame) -depending on range requirements.
Controller: Unmodified 48a digital with 4110 Fets
Current Prob: Bike is in parts getting painted / drying / testing replacement BMS
Trail of Dead Parts:Avanti Frame, 408 motor *melted*, 35a controller - i broke by trying to mod it 2nd controller - blew it up.
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Post by kbarrett » Dec 10 2007 7:42pm

I bought the controller last month from poweridestore.com here in the US.

It has a 6 pin "cruise control" plug on it, as well as brake, throttle, battery, motor, and hall cotroller plugs, if that means anything.

Does anyone know if this 6 pin plug is the same one the CA controller attaches to?
Sun EZ-1 recumbent, Heinzmann 450W, 36V16A Ping "Duct Tape" LiFePO4
Evil Smoker ( Schwinn beach cruiser with 49cc two stroke, and a one gallon gas tank )

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Post by Drunkskunk » Dec 10 2007 8:50pm

Nope, its not the same 6 pin. thats the cruise controll If I remHember right. Mine had it, but I removed it early on. the 6 pin on the Ebike.ca is something Justin adds just for his CA.

Save that 6 pin, though. IRRC you can cut it off your controller and solder it back in the locations indicated on Ebike.ca's website to use the CA fully.

As for voltage VS amperage, it doesn't really mater. V x A = Watts, and it really doesn't matter how you arange your batteries, they will always end up with the same wattage, and therefor, the same range.

More voltage will give you better acceleration, but will also mean you can use more amperage while accelerating, and therefor decrease your range.
Less voltage means you're running higher amps forthe same wattage output, and the higher amperage can heat some componants.. probably not a problem on your controller.. But it also means that you'll be putting less strain on your battery. a battery configured for more amps and less voltage will have a higher C rating because of more parrallel cells... again, not really a problem for you with Dewalt A123 cells.


So what it really means it doesn't matter. find the voltage that gives you the highest speed you think you'll ever use, then build from there.
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Post by kbarrett » Dec 10 2007 9:05pm

OK ... it's looking like it's going to be 36 volts.

At 48v with a 20" 405, I can't keep up with the motor on a flat, even pedaling like a madman ... part of the reason for this is exercize.

So down to 36v I go ... if I want faster, I'll just have to start sweating.
Sun EZ-1 recumbent, Heinzmann 450W, 36V16A Ping "Duct Tape" LiFePO4
Evil Smoker ( Schwinn beach cruiser with 49cc two stroke, and a one gallon gas tank )

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Post by BiGH » Dec 10 2007 9:38pm

yeah 405 is wound for high speed. you might find if you move to a different motor (after ur current one has paid for itsself) you will get better range. if you moved to a 406 or 407 it would lower your top speed at a given voltage, but improve your range bigtime. its hard to comprehend how much of an issue it is.

What is your no load wheel speed on the 405?
Bike / Motor: Electric specalized rock hopper with Crystalyte 504 / 26"
Batt: Yesa 72v (36v*2) (getting 6.7ah) LiFEPO4 in a Topeak bag. OR 1x eMTB 48v 20ah pack (straps to frame) -depending on range requirements.
Controller: Unmodified 48a digital with 4110 Fets
Current Prob: Bike is in parts getting painted / drying / testing replacement BMS
Trail of Dead Parts:Avanti Frame, 408 motor *melted*, 35a controller - i broke by trying to mod it 2nd controller - blew it up.
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Post by kbarrett » Dec 10 2007 10:53pm

On a flat, with my fat ass on the bike, about 25-27MPH with fully charged 48v SLAs.

( no clue what the free spinning speed is )

Way too fast for what I need.
Sun EZ-1 recumbent, Heinzmann 450W, 36V16A Ping "Duct Tape" LiFePO4
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BiGH   100 kW

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Post by BiGH » Dec 10 2007 11:19pm

try and work out what the free spinning speed is - get a speedo and calibrate it.

I think that you'd definately be better off going for a higher wound motor. my 408 on 36v in a 26" wheel did around 18-20mph on the flat and could pull up hills at 15mph.

I really REALLY think you've got the wrong motor for what you want.

efficieny is a function of speed - as the motor gets closer to the free spinning speed the efficiency goes up. if your freewheel speed is 40mph, and you're riding it at 20mph, then your efficiency will be lower than a motor that's freewheel speed is 25mph and you're riding at 20mph... if that makes sense.

on 36v 10ah would get you about 30km = 18mi for a 408 on 26" wheel.
Bike / Motor: Electric specalized rock hopper with Crystalyte 504 / 26"
Batt: Yesa 72v (36v*2) (getting 6.7ah) LiFEPO4 in a Topeak bag. OR 1x eMTB 48v 20ah pack (straps to frame) -depending on range requirements.
Controller: Unmodified 48a digital with 4110 Fets
Current Prob: Bike is in parts getting painted / drying / testing replacement BMS
Trail of Dead Parts:Avanti Frame, 408 motor *melted*, 35a controller - i broke by trying to mod it 2nd controller - blew it up.
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Post by recumbent » Dec 11 2007 2:50am

BiGH wrote: efficieny is a function of speed - as the motor gets closer to the free spinning speed the efficiency goes up. if your freewheel speed is 40mph, and you're riding it at 20mph, then your efficiency will be lower than a motor that's freewheel speed is 25mph and you're riding at 20mph... if that makes sense.
That makes very good sense, and answers my dilema on which motor to get for my 20" front wheel. Justin recomended the 406 motor for 48 volts, but I thought the 405 looked better on the simulator.
Obviosly I'm wrong and you guys are right, thanks BiGH for clearing that up. 8)
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max speed: 52 km/h (30 mph),
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Post by BiGH » Dec 11 2007 7:02am

no problemo :)

it took quite a lot to actually work out how to best explain the efficiency, buteventually got it down :)

almost hit a kangeroo today! :(:(
Bike / Motor: Electric specalized rock hopper with Crystalyte 504 / 26"
Batt: Yesa 72v (36v*2) (getting 6.7ah) LiFEPO4 in a Topeak bag. OR 1x eMTB 48v 20ah pack (straps to frame) -depending on range requirements.
Controller: Unmodified 48a digital with 4110 Fets
Current Prob: Bike is in parts getting painted / drying / testing replacement BMS
Trail of Dead Parts:Avanti Frame, 408 motor *melted*, 35a controller - i broke by trying to mod it 2nd controller - blew it up.
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Post by fechter » Dec 11 2007 9:36am

For a given motor setup, range will be very dependent on speed. Wind resistance increases dramatically above around 20mph, so if you go faster than this, the range will really start to drop.

It might be easier to maintain the desired speed at the lower voltage. If you run the higher voltage, but keep the speed down to the same level, the range would be nearly the same (slightl less).

I find that it's nearly impossible to resist using full throttle, so using the lower voltage would guarantee a better range for me.

You might be able to do a series/parallel switching arrangement on the batteries to allow either mode. Sometimes a burst of speed is a good thing.
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Post by deardancer3 » Dec 11 2007 9:52am

Excuse me for jumping in here, but have questions on the EZ-1 assist:

Are you going to drop to 36v with SLA's? that is going to seriously decrease your range if you do because 1- carrying less battery energy, and 2-higher current draw for hill climbing to get same wattage assist which decreases number of AH availlable from SLA's.

Or am I getting something wrong here? maybe?


another question, what is your high gear ratio; ie big chainring in the front and small in the back? (We all have problems getting high enough speed out of 20" wheels with reasonably priced drive chains)

If you are running an 11 tooth rear and a 50 tooth front, that is a 91 inch gear, but at 100 crank rpm would give you 27mph on leg power, 90rpm= 24mph, per http://www.sheldonbrown.com/gears/.

I would consider staying at 48v on sla and getting a bigger top end gear, which of course may mean new derailers, but, would give more exercise. And just stay out of the throttle at speed, or use a C/A.

anyway, just my thoughts.

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Post by GGoodrum » Dec 11 2007 11:28am

I think he's talking about switching to an a123-based setup, not SLAs.

One thing to keep in mind that a 10-cell DeWalt pack really is 33V, not 36V. Each a123 cell has a nominal voltage of 3.3V per cell.

How much capacity does your 48V SLA setup have now? What knd of range are you geting? What kind of range are you looking for?

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Post by recumbent » Dec 11 2007 2:46pm

edit: oops posted in wrong place, still this has 20" fr wheel.
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Ebike in use:
LWB Recumbent bike, Sram i-9 internal gears.
Power: 58V, 16 amp/hr, lipo batteries.
max speed: 52 km/h (30 mph),
max range: 40 km's, incl stop&go few times, minimal pedaling.
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Post by TylerDurden » Dec 11 2007 2:46pm

As for higher-voltage, lower-throttle efficiency, compared to lower-voltage, full throttle:

We don't have validated proof yet, but initial tests have shown possible significant losses during partial-throttle use.

Further testing is needed to confirm/refute the initial findings.

Offhand, I'd say that the pack, controller and motor should be matched to provide the highest efficiency at full throttle, wherever the majority of the use is centered: flats hills, loads, etc. A boost-pack could be switched in or out for periodic peaks.
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Post by BiGH » Dec 11 2007 7:54pm

i've tried both - 36v vs 72v and i have to agree, you definately get further on 36v. It feels more efficient, but being that it also feels slower :P

i run 72v daily now.
Bike / Motor: Electric specalized rock hopper with Crystalyte 504 / 26"
Batt: Yesa 72v (36v*2) (getting 6.7ah) LiFEPO4 in a Topeak bag. OR 1x eMTB 48v 20ah pack (straps to frame) -depending on range requirements.
Controller: Unmodified 48a digital with 4110 Fets
Current Prob: Bike is in parts getting painted / drying / testing replacement BMS
Trail of Dead Parts:Avanti Frame, 408 motor *melted*, 35a controller - i broke by trying to mod it 2nd controller - blew it up.
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Post by Beagle123 » Dec 12 2007 5:02am

I've read many posts on this subject, but I never really understood how electric motors use energy until I connected an ampmeter to my bike. We've all grown-up around gas engines that function poorly when at high rpms. For example, if you drove in 1st gear all the time in a car, you'd get horrible gas mileage. Our ebikes are the opposite. When I drive my scooter in 1st gear, it humms along using very few amps. I can get approximately the same range in 1st gear as 4th (I think).

The worst waste of energy occurs at low rpms when acclelerating, or when going up hills. I beleive that most people using hub motors would benefit from a smaller wheel (lower gear). If you downsize your wheel (or voltage) so your top speed while driving is approximately equal to your no load speed, then your bike will be optimized.

It sounds like that in your case, if you made a smaller wheel so your "no load" speed was 25mph, and when you rode your bike you spent lots of time going 22-25mph, you'd get much more range.

According to the simulator, your top speed is 40mph+. I bet you spend 90% of your time at speeds below 25mph when riding which means you may only be getting about 55% efficiency.

The idea is to find a "comfort speed" for the bike, and drive at approximately that speed. Then your motor will humm along using very few amps.

When I ride my scooter I can easily feel when the motor hits the "no load" type rpm. It almost feels like its coasting, and the amps go way down. However, if your bike's "no load" speed is 40+ mph, you may not be able to experience it reaching this zone because wind resistance may prevent you from reaching 40+ mph.

xyster just downsized his back wheel and lost nothing in the process. Look for his thread.

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Post by kbarrett » Dec 13 2007 1:48pm

I am using a rear wheel hub assist ... already at 20". Can't make it much smaller without getting silly.

I think I will need to go to a lower voltage and a less extreme winding. I am using 8 12v 8a SLAs, 4c2p ... 48v 16a. With the 405 hub, I run out of juice really fast ... and it goes really fast.

I am building an a123 39.6v 12c6p pack right now. Not sure if that is going to be my final configuration, I am open to suggestions.


Apparently my 405 hub is best for suited for a speed freak.
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Post by vanilla ice » Dec 13 2007 1:53pm

18s4p! Nah.... nm

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Post by kbarrett » Dec 13 2007 1:55pm

vanilla ice wrote:18s4p! Nah.... nm
Bloody lunatics .... I'm surprised no one suggested bigger fets and 120v.

Any suggestions for a better hub winding?

40x? 50xx?
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Post by Beagle123 » Dec 13 2007 2:49pm


The simulator says your top speed will be around 25mph with a 20 inch wheel @ 36v and 20 amps. That seems pretty good to me. You should get really good range with the a123s because they can use almost all of their energy. With SLAs, you can only really use about half of their energy, or they start to degrade. My SLAs are already losing their mojo after 4 months.

Your 12s 6p pack will be about 15 ah, I'd guess that be good for a range of about 20 miles.

The best thing about having a "lower geared" set-up is that you'll run your hub more efficiently. The simulator shows that you get about 70% efficiency at 15mph, so as soon as you reach 15mph, you'll be getting 70% and as you go fasster it will reach about 80%. This could save you significant battery power.

So the a123s will increase your total available energy by about 30%, the more efficient speed/voltage should increase your range by about 15%, and the efficiency gains from driving slightly slower (wind resistance) will likely be about 10% (guess). So, I"d guess you'll get about 60% more range.

Also, I bet your SLA aren't nearly performing like new. They go bad fast.

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Post by BiGH » Dec 13 2007 6:06pm

kbarrett wrote:
vanilla ice wrote:18s4p! Nah.... nm
Bloody lunatics .... I'm surprised no one suggested bigger fets and 120v.

Any suggestions for a better hub winding?

40x? 50xx?
you need to spec your motor and voltage to fit in with two parts of the ebikes site.

The first thing i do is get a rough estimate of speed from their "purchase online page" ie 0.93 kph/V for a 405 in a 20" rim. and match what you want your top speed to be.
ie you said 25-27mph with 48v which is 25mph-27mph = 40kph -43kph

I just noticed that only the 405 is listed :(

anyways

.93 x 36v = 33.48kph = 20mph
.93 x 48v = 44kph = 27mph (too fast)

so you either need to drop your voltage or increase the windings amount. I'm guessing actually that a 406 or 407 in a 20" rim would suit you better! (at 48v)

and confirm this on the simulator - look at the graph for a 405 on a 20" rim and see the point of the graph where it is 44kph - now change the parameters around until you get that point to line up with your desired maximum speed - which would be about 33kph yes? (or 20mph). make sure you give yourself a little headroom to go faster as u get more into riding and power assist;)

doing this for you (i was having breaky and looking it up) - a 407 at 48v in a 20" rim seems perfect in terms of maximum speed. This would give you very good acceleration and good efficiency with a top speed of around 33kph (~20.5mph) or so.
Bike / Motor: Electric specalized rock hopper with Crystalyte 504 / 26"
Batt: Yesa 72v (36v*2) (getting 6.7ah) LiFEPO4 in a Topeak bag. OR 1x eMTB 48v 20ah pack (straps to frame) -depending on range requirements.
Controller: Unmodified 48a digital with 4110 Fets
Current Prob: Bike is in parts getting painted / drying / testing replacement BMS
Trail of Dead Parts:Avanti Frame, 408 motor *melted*, 35a controller - i broke by trying to mod it 2nd controller - blew it up.
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Post by monster » Dec 13 2007 6:22pm

what simulator is this Beagle? the normal bicycle speed and power calculator doesn't give % efficiency of hub motors?

thanks for pointing out the smaller wheel thing -i might try that because my range is poor, only 7-10miles on 72v 7ah and i have a X503 in 26" wheel. only problem is it would mess with my rear brakes.

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Post by BiGH » Dec 13 2007 6:35pm

monster wrote:what simulator is this Beagle? the normal bicycle speed and power calculator doesn't give % efficiency of hub motors?

thanks for pointing out the smaller wheel thing -i might try that because my range is poor, only 7-10miles on 72v 7ah and i have a X503 in 26" wheel. only problem is it would mess with my rear brakes.
ebikes.ca simulator has an efficiency curve!
Bike / Motor: Electric specalized rock hopper with Crystalyte 504 / 26"
Batt: Yesa 72v (36v*2) (getting 6.7ah) LiFEPO4 in a Topeak bag. OR 1x eMTB 48v 20ah pack (straps to frame) -depending on range requirements.
Controller: Unmodified 48a digital with 4110 Fets
Current Prob: Bike is in parts getting painted / drying / testing replacement BMS
Trail of Dead Parts:Avanti Frame, 408 motor *melted*, 35a controller - i broke by trying to mod it 2nd controller - blew it up.
My Ride

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Post by TylerDurden » Dec 13 2007 7:03pm

Have a Nice Day,

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