January 17, 20179 yr Author Hi Andy, Your battery is OK. The range of battery voltage is 10V (from full to empty), you use roughly 53% of your 12AH capacity for 15 miles, 19.3WH per mile. That's normal for a direct drive motor. It is unpleasant to ride on a more than half empty battery when you may be pressed for time but I am pretty sure you can squeeze 3 more miles out of it without needing to buy a new battery. Thats good to know, thanks very much...it has confused me a bit though...if its used 53%...doesnt that mean I could get another 47% out of it?
January 17, 20179 yr yes, but you have to reduce the current draw to avoid low voltage cutout. That means go slow. The last 15%-20% will almost be unusable on a high current controller.
January 17, 20179 yr As the voltage goes down peak power available goes down too assisting you less. Simples. A real world example, my battery at assistance level 5 and me just turning the pedals so not adding (m)any man Watts: 41.5 x 15 Amps = 622.5 Watts 36.5 x 15 Amps = 547.5 Watts A difference of top end power of 75 Watts - that is roughly the Watts needed to compensate for the extra weight of the motor and battery on the bike.
January 17, 20179 yr No, not go slow, go as fast as yo can on level one. The faster you go, the higher the efficiency. You could try switching your controller over to speed control rather than current control. It's in the settings, so look in the manual how to do it. You could run on level 1 all the time then. It would be interesting to see the difference in efficiency. My prediction is that it would be more efficient.
January 17, 20179 yr No, not go slow, go as fast as yo can on level one. The faster you go, the higher the efficiency. . Don't you mean pedaling harder on level one? Should increase in air resistance more than eat away increase in motor yield?
January 17, 20179 yr Author Now i really am getting confused....Im pretty good with mechanical stuff. can even rebuild a car engine, but when it comes to electrics, I am at a loss. Ill have a google later, see if i can get my head round it all, appreciate the advice though
January 17, 20179 yr Now i really am getting confused....Im pretty good with mechanical stuff. can even rebuild a car engine, but when it comes to electrics, I am at a loss. Ill have a google later, see if i can get my head round it all, appreciate the advice though Stick a WATT meter between your battery and controller and you will see what the amps/watts are doing in relation to your speed on different power levels. http://www.ebay.co.uk/itm/DC-LCD-Monitor-Energy-Volt-Watt-Meter-RC-Battery-Power-Analyzer-60V-100A-UK-/252242300442?hash=item3abad00e1a:g:SrsAAOSwa~BYTkKu
January 21, 20179 yr Author Hi Andy, Your battery is OK. The range of battery voltage is 10V (from full to empty), you use roughly 53% of your 12AH capacity for 15 miles, 19.3WH per mile. That's normal for a direct drive motor. It is unpleasant to ride on a more than half empty battery when you may be pressed for time but I am pretty sure you can squeeze 3 more miles out of it without needing to buy a new battery. Sorry to drag this up again, but after reading another thread about battery levels, it looks like a voltage drop of 1 volt is 10% of capacity gone....in which case, why dont these LCD's have a half decent "range left" display on them? It cant be that hard surely? Maybe there is a way to DIY one. All this has helped me though, I think im riding my bike in a different way now, and getting more out of it, but still not killing myself on the way to work. Ive been using it on level 1 assist for most of the journey now, 2 in a few places, and knowing I should have a burst of speed left at the end of the journey if I want it. And I can still do it in jsut under an hour which is my target really.
January 21, 20179 yr that is because the voltage also sags when the controller pulls more current. You will see the battery level on the LCD losing a bar or two when you climb a hill. If you stop the bike for a minute to let the battery recover then the LCD shows pretty much the remaining capacity.
January 21, 20179 yr Author Im sure I read somewhere that the stealth meter for some reason doesnt show that...it shows how much drain you are putting on the battery based on your current load.....which is totally pointless really. My old greenedge CS2 was much better at indicating what was left, and did work like you say.
January 21, 20179 yr I have an excellent new power meter APP on my nexus 7 tablet and even that isn't capable of calculating what I have left in the battery (LiPo 3.8 V, 3950 mAh) despite it being a rather powerful little computer. Using a tablet doesn't involve head winds, hills, road condition... so you can imagine the added difficulty involved in calculating remaining range. Experience and a Watt meter are the best tools to guess how much further you can go on a charge. My 20 month old Li-ion battery is completely unpredictable because it sags so much now. On the other hand my LiPo battery doesn't sag on the hills so it is very easy to guess how many km are left in it just from reading the remaining volts on the LCD.
January 22, 20179 yr Hi Andy, Your battery is OK. The range of battery voltage is 10V (from full to empty), you use roughly 53% of your 12AH capacity for 15 miles, 19.3WH per mile. That's normal for a direct drive motor. It is unpleasant to ride on a more than half empty battery when you may be pressed for time but I am pretty sure you can squeeze 3 more miles out of it without needing to buy a new battery. Perhaps I'm getting confused, but I thought Andy said he could only just about get to work on a single charge - he mentioned taking the charger to work. In other words, his range is 15 miles, which equates to 39wh per mile. Surely that's very high, suggesting the battery has nowhere near its theoretical capacity of 48v x 12ah = 576wh.
January 22, 20179 yr Author Yes, its a 15 mile run, I charge every day when i get to work. Occasionally I have ran out of juice on the way in and had to do all the work for the last mile.
January 22, 20179 yr Perhaps I'm getting confused, but I thought Andy said he could only just about get to work on a single charge - he mentioned taking the charger to work. In other words, his range is 15 miles, which equates to 39wh per mile. Surely that's very high, suggesting the battery has nowhere near its theoretical capacity of 48v x 12ah = 576wh. In his earlier posts, he said he rides at arounnd 17-20mph. You can extrapolate that he pulls about 400W from his battery, or 8.3A, 8.3A * 0.3 Ohms internal resistance for this type of battery = 2.5V voltage sag. That means that he can't really use the last 25% reserve at that sort of speed. His trip uses 53%, he has 22% charge at easy going voltage before he hits the bottom 25%. He said he could do 3 more miles, I reckon he can do so about 6.5 miles rather than 3. After that, he'll have to reduce assist level and pedal more. Commuters on this sort of distance would do a lot better on a lightweight, light assist, rear hub bike like the Karoo.
January 22, 20179 yr Author In his earlier posts, he said he rides at arounnd 17-20mph. You can extrapolate that he pulls about 400W from his battery, or 8.3A, 8.3A * 0.3 Ohms internal resistance for this type of battery = 2.5V voltage sag. That means that he can't really use the last 25% reserve at that sort of speed. His trip uses 53%, he has 22% charge at easy going voltage before he hits the bottom 25%. He said he could do 3 more miles, I reckon he can do so about 6.5 miles rather than 3. After that, he'll have to reduce assist level and pedal more. Commuters on this sort of distance would do a lot better on a lightweight, light assist, rear hub bike like the Karoo. Would probably take me 30 minutes longer to get to work though
January 22, 20179 yr I would say not as much as that, may be 5 more minutes. Select assist mode 0, that will let you use the bike in throttle mode. That mode will let the throttle push the bike efficiently to 16mph legally. Then your legs can hit much higher speed as the road allows without the motor drag while remaining totally legal. Most commuters who bought the Karoo reported about 75 miles with the13AH battery, no need to buy the 15AH.
January 22, 20179 yr Author I would say not as much as that, may be 5 more minutes. Select assist mode 0, that will let you use the bike in throttle mode. That mode will let the throttle push the bike efficiently to 16mph legally. Then your legs can hit much higher speed as the road allows without the motor drag while remaining totally legal. Most commuters who bought the Karoo reported about 75 miles with the13AH battery, no need to buy the 15AH. Ok, thanks for the info. Might be something for me to consider at next C2W scheme in a few months. I think the problem i have is finding one that can also stand up to the route I do. Others have commented greatly in the past that its quite a punishing route for the bike. Bumpy canal towpaths, muddy trails, and potholed roads....so quite a mixture
January 22, 20179 yr Some rated battery capacities must be nominal, as in you can't use all the watt hours stamped on the label. However, I did London to Brighton at an average 16.5mph for 45-odd miles on one and a half/threequarters Bosch 400wh batteries. This suggests about 15wh a mile, which sounds about right. The pace was a gnat's chuff away from what Andy does, I weigh more than he does, and while the route only undulates, it does include a couple of decent climbs, including Ditchling Beacon. All of which suggests to me Andy would get his 30-mile return trip to work at very close to his current speed from a Bosch 500wh battery bike. Which is very different to his present bike which supposedly has a 576wh battery but will only get him half way. Is the Bosch system magic and/or am I Superman? No and definitely not, which suggests some manufacturers are more honest than others when it comes to battery labelling. Or Andy's battery is faulty, which the experts on here tell me it's not. The only sensible conclusion is the best bike for Andy's job is a 500wh Bosch one. Apart from getting him there and back on one charge, it would be most unlikely to suffer from all the typically Chinese breakdowns which he's now had on two Chinese ebikes. Buying another really would be a triumph of hope over expectation. Edited January 23, 20179 yr by RobF
January 23, 20179 yr Author Thanks Rob, that's a very informative post. Its been a big learning curve for my first 9 months or so in the world of e-bikes, or the first time back on any type bike in anger in over 20 years. I'm actually on my 4th bike now, the first being a standard bike, which to be honest only lasted a few weeks as there was no way I was goign to stick with it when I looked into ebikes. The stealth is definitely the most suitable of these for what I need so far, just the range issues. I've seen loads of bikes linked on the forum that look the dogs gonads, and I'm sure they would be THE best for my needs, but I guess the price of them is there for a reason. Bit out of my range for a while at least, but who knows for the future. What I do know is, I couldn't go back to commuting in the car on a regular basis now! What would be nice is if you could trial bikes from dealers before you commit to buy, even the cheapest ones aren't cheap to everyone, and committing yourself to it for a year if going by C2W scheme, it would be nice to know its good for your needs based on experience. I've learnt that the hard way
January 23, 20179 yr If someone could devise a trial scheme for commuters, Woosh will certainly support it. Lending demo bikes for a day or low cost a week rental is not a problem for suppliers like ourselves, we can always refund the rental if it leads to a sale. The transportation cost is prohibitive if the potential customers can't come to us.
February 2, 20179 yr I also have a 1000w Stealth and I would say that my range experience is similar to Andys. I've had mine for 3 months and haven't used it that much yet so I'm sure there's nothing wrong with Andys battery.
February 2, 20179 yr I'm sure there's nothing wrong with Andys battery. Agreed. Motor efficiency (the ratio of kinetic energy output / battery energy input) is zero when stalling, then gradually increases with RPM then decreases past the peak back to zero again. Andy's and RobH's kits have a direct drive motor, they don't have internal gearbox so the yield remains low under 11mph, reaching optimal around 25mph, but then air resistance becomes the dominant factor from 15mph up. Depending on traffic, if you have a lot of starts/stops, you may see your range reduced substantially. If you have long stretches of empty roads, direct drive motor is a good choice. This is a typical graph, taken from ES, the green plot is the efficiency, the motor is a Golden 500W DD
February 4, 20179 yr Author Thanks whoosh...that was really informative. I was wondering...if I was to turn my stealth power to 250 watts, put it on lowest assist and use the throttle at 16mph without pedalling....would that go 15 miles or is that way off the mark? I only ask as riding home Thursday into gale force winds, I tried the last couple of miles doing that and it got me home. Seems I'm putting a lot of effort into getting to work in under an hour but maybe there's a way to do it with a lot less effort but not a lot longer in time Sent from my iPad using Tapatalk
Join the conversation
You are posting as a guest. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.