48V batts with a 72V controller?

[praskal]

I've decided to go down from 72V SLA to 48V because the weight keeps breaking spokes. I also have an X5 motor. I am wondering if anyone thinks that my 72V 40amp crystalyte controller would be able to work with 48V SLA? I don't want to have to buy a 48V controller if I can somehow get the 72V one to work with this new settup. Any guesses??

 

[Zoot Katz]

I'm running 48 volts of NiMH into a Xlyte digital controller rated as 72V 48A on my 5304.
No problem.

 

[praskal]

Hmm. Mine works with 72V batts, but not 48V. I turned the CA low Voltage cutoff down to 35V and everything. And still it does not work with 48V.

 

[Zoot Katz]

Hmm. Mine works with 72V batts, but not 48V. I turned the CA low Voltage cutoff down to 35V and everything. And still it does not work with 48V.

Quoting: http://www.ebikes.ca/store/store_controllers.php

Voltage Rating
If you are using a battery that is nominally 48V or lower, then you should get the lower voltage 24-28V motor controllers. There is no advantage to having a higher voltage rating on the controller unless you are actually using a battery that is higher than 48V nominal.

Current Limit
For the 400 series hub motors, the 20A motor controllers are generally a good match. It is no problem to find a battery pack that can deliver 20A of continuous current, and the power output is pretty decent. However, if more torque is required, then you can upgrade to a higher current 35A controller. This is especially true with the lower winding count and lower resistance motors like the 20" 405 and 26" 406. For a high winding count motor like the 4011, there is little benefit in using the 35 amp model.

For the 5300 series hub motors, you need the 35 amp controllers in order take advantage of the higher weight, higher powered motor. In the majority of cases the 24-72V 35A analog controller will be a perfect match. However, if you are running a lower winding count motor like the 5303, or you are running at voltages above 72V, then it may be better to use the 36-72V digital controller with IRFB4110 mosfets.

My new controller is rated as 36-72 volts, 48 amps. The analog one was 36-72V, 35A and it worked at 48 volts too.
As far as troubleshooting it is concerned, you'll probably get a guru jumping in soon enough.

 

[Takemehome]

Hmm. Mine works with 72V batts, but not 48V. I turned the CA low Voltage cutoff down to 35V and everything. And still it does not work with 48V.

The low voltage cutoff need to be modified in your controller.

 

[praskal]

I have already set the CycleAnalyst low voltage cutoff down to 35V. Is there some other way to re-program the controller?

 

[dnmun]

weight of extra battery is not breaking your spokes. go read holmes' bafang build thread in selling. rebuild the wheel correctly so the spoke heads don't flex so much and you could go with 14G spokes too. if you can charge 72V then keep it intact. imo, BOL

 

[ejonesss]

well it depends on several factors.

if you are using full sized car batteries then you are riding close to or on the edge of the spoke breakage point with the weight of 72 volts.

if you are using electric on racing wheels (thin and very few spokes) .

potholes at high speed.

i may be wrong but in my opinion for electric it is better to use 12g or thicker spokes and wider rim that is used on mountain bike and very good knowledge on how to lace up a wheel.

weight of extra battery is not breaking your spokes. go read holmes' bafang build thread in selling. rebuild the wheel correctly so the spoke heads don't flex so much and you could go with 14G spokes too. if you can charge 72V then keep it intact. imo, BOL

 

[praskal]

I figured there would be many different theories on spoke breakage. I am not a wheel-builder, so I am dependent on local bike shop dudes. Most of them hate electric bikers, so I must say it is really difficult to get anyone of expertise to build the wheel. I feel like the last build was done very well actually. I was surprised to get spoke breaks this time. I think they are 14 gauge though. My sense is that next time I want 12 gauge, and I want a bike with full suspension (because in my mind the suspension will even out the constant bumps. I may be wrong, but this seems intuitive). Also, the X5 motor is too fricking big, in my opinion after having it for a few years. It also sucks up too much juice. If I was to do it again I would get a smaller motor and put it on the front. But since I already have the rear X5, this is what I am stuck with.

The first issue, however, is to try to get the 72V 40A controller to work with 48V batts. As I stated earlier, I have already set the CycleAnalyst's low voltage cutoff to 35amps. Does anyone know of another way to reprogram the controller and lower this cutoff voltage???

 

[dnmun]

it is a big motor, you lucky dog! but from what i have read, the spoke breakage at the head is because the spoke can flex at the bend if it is unsupported, when it goes through each leading trailing cycle and under load most likely even more so. with each flexure adding to stress cracks inside the spoke.

that's why i recommended reading holmes' thread
http://www.endless-sphere.com/forums/viewtopic.php?f=9&t=6388&st=0&sk=t&sd=a&start=15
the pedelec.uk article is worth reading, and holmes can give you private advice too i bet on how to solve the spoke breakage problem, his don't break.

 

[praskal]

I decided to go to http://www.electricrider.com/ and order the 26 inch rim and 12 gauge spokes made specifically for the X5 phoenix motor. I found a local bike shop willing to build the wheel. I think it will work this time...

 

[rkosiorek]

I have already set the CycleAnalyst low voltage cutoff down to 35V. Is there some other way to re-program the controller?

no, the controller also has a low voltage cut-off independant of the CA. changing the one on the CA will have no effect if the controller LVC cuts off at a much higher value.

the LVC setting varies by the distributor that you bought it from and wheter it is the newer digital V2 Crystalyte controller or the older V1 analog controller. changing the value requires soldering and exchanging a resistor on the board.

details on which resistor to change including pretty pictures are in the stickied threads at the top of the Ebike Technical forum.

i would be willing to bet that you have the newer V2 controller as almost all of the older V1 controllers had the internal LVC set for 29V. so check out the
rick

 

[praskal]

Yow. I don't think I'll get into soldering semiconductors in and out...

Maybe I'll just go back to 72V SLA.

Thanks.

 

[dnmun]

it really is best for you to run with 72V if you can. less heating in the motor and controller, better performance in spite of the weight, and your spoke problems will disappear once the wheel is laced up with the twist of the spokes against each other. i would recommend you take the holmes build thread to your bike shop where they laced up your hub and let them read through it including the pedelec article. i think after that, they will rebuild the wheel properly and you should never have problems after that. plus they will learn enuff to do it right the next time someone brings a hub motor in to be laced up. tell them single cross with a twist. you could pm holmes too and ask his advice too.

 

[Ypedal]

I'm not convinced that the " twist " has that much effect on the durability of the wheel, when considering an X5, with 12 gauge spokes, laced on a Heavy Duty rim !

The least amount of dish possible ( 3 speed freewheel is plenty imo ), again with a strong rim, 1 cross pattern is likely all that will be possible with the standard clyte spokes.. couple that with a fat/high pressure tire and a thick tube and life should be good.

14g spokes are much more flexible and the over/under lacing works well, but with 12g the spokes have to be bent to reach the nipples and the rim has to be drilled/reamed to match the angle of the spokes so that when you start to tighten the thing the rim stays true.