more power for climbing hills

[dogman dan]

Hey, just saying what he could do, some of them are not great ideas, but they could do it. lots of options for him, good or bad. The goal is simple, more watts.

So lets repeat the most sensible option, his best bet is a new 48v controller, a 40 amps one. Then he can parallel another 10ah 48v lifepo4 pack with it, and he'll have 2000w to get up that hill. It should be enough, unless he happens to weigh 400 pounds.

He can parallel something else with it, but then he's got to pay attention to the 100% discharged voltage of both types, and stop when the first pack is done, the one that is done at a higher voltage.

Cheapest thing he could do is a poor idea, but he could parallel 5 ah of lipo with the lifepo4. He could do that only when he comes to the hill, if he wants.

If his new controller has a three speed switch, then he can just ride at lower power till he plugs in the additional pack, then flick the switch, climb the hill, then unplug the boost pack and put the switch back to middle power.

 

[teklektik]

Ya - sadly, the images for the similar-sounding SunThing pack that wes pointed out shows a Ping-style battery fabrication (not A123 prismatic) that looks like a 2C situation:

If this is the battery pack you have, it looks like it's rated for 30A continuous and 50A max,...
http://www.ebay.com/itm/48v-20ah-LiFePO4-Battery-5A-Charger-BMS-Ebike-Powerful-Rechargeable-USE-1000W-/131548396564

• 

This is a budget pack and I'd guess that it will supply 40A continuous but that will eat into it's longevity. That said, the motor is so starved for amps that even a jump to 35A improves hill-climbing considerably:


Your suggestion to mod the shunt is directly in line with my post on the previous page to buy a basic CA-compatible 40A controller. If the OP can handle a mod, the shunt change is the way to go. Since he has a CA V2 to tweak in the limiting, a sloppy/over-zealous mod will be okay, since he can crank it back down with the CA.

Depending on skills, either approach is a fair first step so he can try the 35A or 40A solution without springing for a new battery. With the Vector frame, fitting a second booster pack and working out the in-situ charging (and chargers) may take some fiddling to work out - the controller upgrade is quick and almost immediately gets the bike at least working better. If the solution is inadequate, he could move on to a booster pack as phase 2. In that case, one option would be a custom 24v 7s8p 25R pack from EM3EV using one of their off-the-shelf 29V chargers - size would be about 6.5x5.5x3" and weigh about 6lbs - but that's a solution that would cost as much as the present SunThing.

Here's what the bike looks like with a 24V booster pack - it will do also about 36mph on the flat (not shown here):


To give some notion of what the motor can do when it's fed better, here it is on 48V 60A (doable by reprogramming the 12FET controller mentioned previously, but an 18 FET would be better):


Buying a second 24V EM3EV pack when it could be afforded and ditching the SunThing would give a premium 48V 100A pack that would deliver the performance above. Here all the improvement is acceleration and hill-climbing - the top speed would not be materially better than it is now - more speed on the flat would require a jump to a higher voltage...

Truth be told, if the present battery held up for a couple of years of being flogged w/o a booster, it would have paid for itself and a proper new replacement battery might then look more reasonably affordable as a major performance upgrade.

 

[dogman dan]

Oh yeah sun thing cells will sag like hell past 1c. So at least 30 ah of it for a 40 amps controller.

Somehow, he's got to throw some more wattage at that motor. It will cost $$$. So a controller with three speed switch would allow running low amps most of the time, avoiding such a quick battery murder.

I'm in the same boat in a way, with a 48v 20 ah el cheapo 18650 pack. To run my powerful bike, (40 amps) I need to parallel in another 13 ah pack. So that bike always has to carry 33 ah, or have the CA limit to 25 amps.

 

[Vincenzo]

This is a relatively old but good discussion and it is the only thing I found that is (probably remotely) related to a question I have, even though some of the replies here are very ignorant when they use the capacity of a battery (in AmpHours or Ah) which has nothing to do for the power capability (in Watts or Amps if voltage is known) of the battery which is very important to climbing steep hills.

My question is, if you have two identical bicycles, with identical motors (lets say, 1500 Watt hub motors, what I have), identical motor drives (aka controllers) that are more than enough to handle the motors may be to 50% higher than what the motors can do (in amps, or watts), and batteries that give the same voltage (lets say 14s 18650's or 52v). The only difference is that one bicycle has a battery that is made using cells that are modem cells (enough parallel to run the motor), while the other is made from tool battery with much higher discharge current capability. Which bicycle may perform better in a steep uphill?

 

[lnanek]

Tool batteries aren't high discharge. Typically something like 20A. My cheapest ebike battery made with a bunch of Samsung 35e cells can do 35A. Ebike batteries tend to be much bigger than tool batteries, so you can have a lot more cells in parallel, so can handle higher discharge rates.

 

[eMark]

(lets say 14s 18650's or 52v) ... The only difference is that one bicycle has a battery that is made using cells that are modem cells (enough parallel to run the motor), while the other is made from tool battery with much higher discharge current capability. Which bicycle may perform better in a steep uphill?

... generally the more cells in parallel (discharge rating) the longer the motor output with higher continuous discharge rating ...

Let's assume the Continuous Discharge rating is the same for both batteries. Say both have a 35A discharge rating for the two 14S batteries. To know for sure the temperature of each 35A battery would reach 100°F at approx the same time (distance and speed) along the upward hill climb.

Lets say each battery uses the same Samsung 18650 cells with a continuous discharge rating of 10amps. However, one battery has more Ah capacity (cells in parallel - 20Ah vs only 10Ah). The 20Ah battery should get you considerably further up the hill at the same speed taking longer before these same cells reach, say 100°F.

One 14s battery has 18650 A-grade Samsung 35e 3.5Ah cells rated at 8amps continuous discharge (9 in parallel). The other 14s battery has 18650 A-grade Samsung 30q6T 3.0Ah cells rated at 15amps continuous discharge (5 in parallel). Which 14s battery would you build using the same quality 50amp BMS with Controller cut-off set at 40amp? Assume ebike riding conditions (speed & power requirements) are the same using same setup with either battery (35e-14s9p or 30q6T-14s5p).

35e - 14 x 9 x $4.50 = $567 for 126 35e cells
30q6T - 14 x 5 x $$5.25 = $368 for 70 30q6T cells

 

[Vincenzo]

Tool batteries aren't high discharge. Typically something like 20A. My cheapest ebike battery made with a bunch of Samsung 35e cells can do 35A. Ebike batteries tend to be much bigger than tool batteries, so you can have a lot more cells in parallel, so can handle higher discharge rates.

Can you please reword your statement comparing cell to cell instead of comparing whole batteries? So you made a bicycle battery from a type of samsung cells that give 35 A/cell or 35a from a number of them in parallel?

thanks

 

[Vincenzo]

... generally the more cells in parallel (discharge rating) the longer the motor output with higher continuous discharge rating ...

Let's assume the Continuous Discharge rating is the same for both batteries. Say both have a 35A discharge rating for the two 14S batteries. To know for sure the temperature of each 35A battery would reach 100°F at approx the same time (distance and speed) along the upward hill climb.

Lets say each battery uses the same Samsung 18650 cells with a continuous discharge rating of 10amps. However, one battery has more Ah capacity (cells in parallel - 20Ah vs only 10Ah). The 20Ah battery should get you considerably further up the hill at the same speed taking longer before these same cells reach, say 100°F.

One 14s battery has 18650 A-grade Samsung 35e 3.5Ah cells rated at 8amps continuous discharge (9 in parallel). The other 14s battery has 18650 A-grade Samsung 30q6T 3.0Ah cells rated at 15amps continuous discharge (5 in parallel). Which 14s battery would you build using the same quality 50amp BMS with Controller cut-off set at 40amp? Assume ebike riding conditions (speed & power requirements) are the same using same setup with either battery (35e-14s9p or 30q6T-14s5p).

35e - 14 x 9 x $4.50 = $567 for 126 35e cells
30q6T - 14 x 5 x $$5.25 = $368 for 70 30q6T cells

I have not a clue what you are talking about!!!!!

My question has nothing to do with range and Ah's...I specifically complained about unrelated content in this thread.

I don't do the so-called "BMS" because they don't make sense to me, so assume that they do not exist, just a simple battery-controller-motor.

It's simple,
2 batteries,
both have the same maximum current (e.g. one has 3p of 10A max cells, while the other has 10p 3A cells, making both capable of supplying 30A max),
both on identical bicycles ,
both climbing the same steep hill
both will probably slow down a little because the hill is very steep
the question is:
Will there be a difference in the slowing down (or deceleration, or -ive acceleration), or will they slow down the same way?

concentrate with me please, I don't care one bit about how long the two last before getting depleted, and I do not care about watt-hours or amp-hours, ...etc, because that has nothing to do with the slowing down on the hill. Try to review the (usually) first chapter in any physics textbook for kids that is usually called "dimensional analysis", if needed.

 

[amberwolf]

If the total capability of the paralleled cells is the same, it doens't matter how you get it, the result would be the same.

If there are differences in the total characteristics of the paralleled cells, there will be differences in the results.

 

[eMark]

My question has nothing to do with range and Ah's...I specifically complained about unrelated content in this thread.

I don't do the so-called "BMS" because they don't make sense to me, so assume that they do not exist, just a simple battery-controller-motor.

concentrate with me please, I don't care one bit about how long the two last before getting depleted, and I do not care about watt-hours or amp-hours, ...etc, because that has nothing to do with the slowing down on the hill. Try to review the (usually) first chapter in any physics textbook for kids that is usually called "dimensional analysis", if needed.

YES y,our exmple is correct in scientific theory, but how practical for a DIY ebike battery build when camparing salvaged modem cells with salvaged tool cells. So lets get more realistic ...

With respect to - "more power climbing hills" - a 25Ah 18650 battery will perform better than a 12.5Ah 18650 battery using the same A-grade cells (2500mAh 10A). One is an 10p14s (25Ah) with a continuous discharge rating of 100amps. The other is a 5p14s (12.5Ah) with a continuous discharge rating of 50amps.

The 25Ah battery can make use of an 80amp Controller; whereas the 12.5Ah battery uses a 40amp Controller. The advantage of the 25Ah 10p14s (80A Controller) over the 12.5Ah 5p14s (40A Controller) is more power/speed when needed like going all the way up a "steep uphill" with more power in less time.

YES, You are correct that salvaged usable tool cells (e.g. 25r 2.5Ah 20A) have a considerably higher discharge rate than salvaged usable modem cells.

 

[Vincenzo]

If the total capability of the paralleled cells is the same, it doens't matter how you get it, the result would be the same.

If there are differences in the total characteristics of the paralleled cells, there will be differences in the results.

in theory, it makes sense, but have you done anything close to this kid of comparison in real life? i just have a feeling that high discharge cells would be easier when going up a steep hill (something about their discharge curve?)

 

[Vincenzo]

YES y,our exmple is correct in scientific theory, but how practical for a DIY ebike battery build when camparing salvaged modem cells with salvaged tool cells. So lets get more realistic ...

With respect to - "more power climbing hills" - a 25Ah 18650 battery will perform better than a 12.5Ah 18650 battery using the same A-grade cells (2500mAh 10A). One is an 10p14s (25Ah) with a continuous discharge rating of 100amps. The other is a 5p14s (12.5Ah) with a continuous discharge rating of 50amps.

The 25Ah battery can make use of an 80amp Controller; whereas the 12.5Ah battery uses a 40amp Controller. The advantage of the 25Ah 10p14s (80A Controller) over the 12.5Ah 5p14s (40A Controller) is more power/speed when needed like going all the way up a "steep uphill" with more power in less time.

YES, You are correct that salvaged usable tool cells (e.g. 25r 2.5Ah 20A) have a considerably higher discharge rate than salvaged usable modem cells.

I was wondering...how hard is it to understand What I'm saying?

 

[Chalo]

in theory, it makes sense, but have you done anything close to this kid of comparison in real life? i just have a feeling that high discharge cells would be easier when going up a steep hill (something about their discharge curve?)

If you max out or exceed the amp rating of your cells, their voltage will sag more deeply than if you use them at a fraction of their rated current. But they'll still sag, and the resistance of your cables, plugs, controller etc. will still drop voltage before it can serve the motor.

I think the main reason to have a surplus of battery current capacity is for battery lifespan and health, rather than small improvements in performance that you may never even notice.

 

[E-HP]

in theory, it makes sense, but have you done anything close to this kid of comparison in real life? i just have a feeling that high discharge cells would be easier when going up a steep hill (something about their discharge curve?)

amberwolf is right, and you are wrong.

 

[calab]

Take a look at the graphs for cell testing on this random 25r 18650

Test of Samsung INR18650-25R 2500mAh (Cyan)

You put more in parallel to lessen the stress so it lasts longer. The pack gets bigger and heavier the more you add and costs more.

 

[amberwolf]

i just have a feeling that high discharge cells would be easier when going up a steep hill (something about their discharge curve?)

Sounds like you are just going to have to do the experiment both ways and see what happens, given that you won't accept what anyone else says. I wish you good luck with your project and hope it turns out well.

 

[Vincenzo]

amberwolf is right, and you are wrong.

have you done it?

 

[Vincenzo]

Sounds like you are just going to have to do the experiment both ways and see what happens, given that you won't accept what anyone else says. I wish you good luck with your project and hope it turns out well.

I'm about to place an order of high discharge cells to conduct the experiment for my new backup bicycle build as it looks like no one has done anything similar so far. I was curious and wanted to know if it's worth it (a $40 vs $65 kind of cost difference for a 20 mile battery). If the higher discharge cells let me get over this 2 mile long assent, that will change my commute from 20 miles to 12! another issue is if I may make it smaller (e.g. 8p to 6p) or two 6p batteries (2nd in back pack just in case)

 

[Vincenzo]

Take a look at the graphs for cell testing on this random 25r 18650

Test of Samsung INR18650-25R 2500mAh (Cyan)

You put more in parallel to lessen the stress so it lasts longer. The pack gets bigger and heavier the more you add and costs more.

those curves are volt-time for one kind of low-discharge kind. Those have nothing to do with my decision between low/high discharge cells. thanks

 

[E-HP]

I have not a clue what you are talking about!!!!!

My question has nothing to do with range and Ah's...I specifically complained about unrelated content in this thread.

I don't do the so-called "BMS" because they don't make sense to me, so assume that they do not exist, just a simple battery-controller-motor.

It's nice that you are open about your ignorance about these things, but no real need to showcase it here. I think folks have figured it out already.

 

[calab]

There is a great video on the explanation of efficiency/speed on hills in one of Justins presentation videos.
I believe its this video titled
Deep Dive into Ebike Motor and System Efficiency

 

[richj8990]

16% serious, but we still have no clue what weight you are going up it, you, the bike, the motor, the battery, any cargo.

But one thing for sure, you'd have to be very heavy to not make it, if you just give the thing more amps. Up to 400 pounds should be possible. (with 3000 w) Despite the motor being big, it really needs more amps to do that grade, at any weight over 250. If your battery can stand it, you need at least a 40 amps controller. Your motor is huge, and your controller is tiny by comparison.

I don't think you need a second motor, you just need to give your current motor some real juice. It can take 3000w easy, possibly a lot more, and you are giving it 1200w. At the very least, give it 2000w, with a 40 amps controller.

BTW, with a controller that can take a direct plug in Cycle Analyst, it would be possible to set a lower amps most of the time, only giving the motor higher amps on that hill. Or, just a simple three speed switch.

Even a 500W rated hub motor (geared) can climb a 16% grade. Putting in about 800-1000W for a minute or two. Combined weight maybe 210 lbs. 500W would do it at maybe 5-6 MPH, but it will 100% for sure be able to do it.