February 17, 201016 yr Yes, they are certainly advancing and are nearly at the point of more widespread acceptance, one e-bike manufacturer dipped their toe in the water last year and now eZee have an option arriving. E-bike makers are being extra careful ever since the debacles of the earlier lithium variants, the fires in cobalt cathode batteries, the current delivery failures of manganese cathode ones and the short lived premature failures of so many. One can hardly blame them for being cautious, since those events proved very expensive. In the case of eZee, they tipped them from the top of the market to near the bottom and cost them well over 1000 free replacement batteries. .
February 18, 201016 yr We, after careful thought, are sticking with Li-Ion. Our latest is 37V 17.4Ah and here is a photo. Huge current dumping capbility. Heat sink in a probust Al casing.
February 18, 201016 yr We, after careful thought, are sticking with Li-Ion. Our latest is 37V 17.4Ah and here is a photo. Huge current dumping capbility. Heat sink in a probust Al casing. Wow! A mighty meaty monster! Sounds like a good choice, but I imagine it's fairly heavy, though not as much as the twin batteries some companies and individuals use to gain capacity. .
February 19, 201016 yr Max power I am certainly still learning about batteries, we have for the last 4 weeks been testing a 37V 17.5A Panasonic celled power pack in NZ, to my astonishment is it being out performed on range and power by our current 36V 14A Li Po battery. Does anyone know why this should be the case? On top of this; The Panasonic has looses 25% of it's power after 500 cycles and then goes into free fall loosing another 20% in the next 50 charges. Where as the Li Po lasts for nearly twice as long loosing 25% after a massive 900 full cycles and the next 20% after another 600. I was looking forward to advertising a new 600Wh battery but it seems we can save our money and stick to what we have! All the best David
February 19, 201016 yr I am certainly still learning about batteries, we have for the last 4 weeks been testing a 37V 17.5A Panasonic celled power pack in NZ, to my astonishment is it being out performed on range and power by our current 36V 14A Li Po battery. Does anyone know why this should be the case? Very high densities within cells that are necessary to increase capacity can result in reductions in discharge rate due to raised internal resistance. Fine on a lower powered motor where the additional capacity is translated into extra range but not with a powerful motor which can be starved of adequate current. The cell chemical stresses that result from a powerful motor draining a battery that's unable to deliver adequately shorten the cell life. Those account for the two phenomena you've seen and highlight the importance of correctly matching a battery and it's capabilities to the motor power intended. .
February 19, 201016 yr Electric Guru It's like consulting a oracle! Flecc you should set up in Tibet, dress in yellow robes and have people walk up mountains for days on end to ask a single question! Many thanks, I was disbelieving the results! Kindest regards David
February 21, 201016 yr I agree 100% with Flecc. The issue is current dumping capability. Out new battery can chuck out current like there is no tomorrow. This is to do with the physical geometry of the internal design - how much conductive stripping is used and how configured and how big the heat sinking. Our beast works not because only of the number of cells. Also Lion seems to work better han LiPO at the high end....
February 21, 201016 yr Dump Are you using a 250W motor? If so what does the motor need to have dumped from the battery to run at it's highest efficiency? There is only so much a 250W motor needs to maximise range and power. I would be interested to learn what technology you are using and what the battery chemistry is. We have found a battery of exactly the same size as the one you are talking about very disappointing compared to the 14A Li Po we are currently using. Flecc has explained why the 17.5A batteries are not as good as the slightly smaller ones on 250W electric bikes. It would be interesting to hear if you have managed to overcome these problems. If you are using Panasonic cells you may need to reconsider. All the best David PS we have used both Li Po an Li Ion over the last 5 years, the difference in life and reliability is massively in favour of Li Po in our experience. Edited February 21, 201016 yr by Wisper Bikes
February 21, 201016 yr The latest generation of hard case li-ions can produce very high discharge rates, certainly if cell densities are not too high. Of four lithium types used on my eZee bikes, original 10 Ah li-ion, new generation 10 Ah li-ion (never introduced for sale to customers) and new generation 10 Ah and 14 Ah li-poly, the "never introduced" li-ion that I've run during testing for over two years now, comfortably out performed the others. However, the downside is that at 342 charges it's almost at the end of it's life, probably explaining why eZee didn't introduce it. .
February 22, 201016 yr The latest generation of hard case li-ions can produce very high discharge rates, certainly if cell densities are not too high. Of four lithium types used on my eZee bikes, original 10 Ah li-ion, new generation 10 Ah li-ion (never introduced for sale to customers) and new generation 10 Ah and 14 Ah li-poly, the "never introduced" li-ion that I've run during testing for over two years now, comfortably out performed the others. However, the downside is that at 342 charges it's almost at the end of it's life, probably explaining why eZee didn't introduce it. . Panasonic are quoting 500 charges so under normal usage your 342 seems more likely Flecc, this is the reason we decided to stick with our tried and tested Li Po. All the best David
February 22, 201016 yr BUT if the battery is £300 what do you think then....... Hi Eddie By the time the cells have been put into a decent case (not the cheap aluminium type) and have a high quality BMS installed, I would think £300 is unlikely unless the cells are the low grade variety available in China. Even the Panasonic cells would make the battery more expensive. When we tested similar set ups recently, Porta Power weren't overly confident regarding the use of 70 x 0.245 cells as the chances of cell and connection problems were multiplied. Although as a matter of interest I thought the construction looked pretty good. According to Advanced Energy, (for the size of our large battery case) the state of the art currently for 250W electric bike motors is a 36V 15.5A Li Po power pack. If we were to have a larger battery pack made they could increase this, however IMO the 55 to 85 mile range in urban conditions this battery is capable of is probably about the right balance between battery volume and performance. And of course we can confidently give a 2 year new for old warranty, in the knowledge that this battery would comfortably take a full charge / discharge cycle every day for two years without loosing 25% of it's original capacity. All the best David
February 22, 201016 yr BUT if the battery is £300 what do you think then....... Yes, it'd be interesting to have some real world stats as the received wisdom is to not fully discharge your battery between charges. So if you're using a huge Li-ion battery for runs well within its range, the capacity degradation may not affect you until it's significantly advanced, and at 1/2 the price (approx) of a Li-Po with a similar starting capacity, it may make economic (if not environmental) sense to go with the cheaper option. Perhaps manufacturers should offer their customers the choice (expensive in terms of stock, I realise), explaining the facts about each option, as this may vary with regard to the intended use of the machine.
February 22, 201016 yr Real world I think Flecc's figures were real world, my worry is that even Panasonic are saying only 500 charges and then a massive drop over the next 50. In the real world I would expect the figures to be more like Flecc's . I would really love to use a cheaper battery, we would no doubt sell more bikes! However according to all our road tests we would have to reduce our warranty period back to a year. Judging by past experiences with Li Ion, I don't think it would be wise to go down that rout again on our longer legged bikes. Li Ion on folding bikes is much more acceptable as they are not used for long distance riding. All the best David
February 22, 201016 yr Maybe Flecc could answer as to whether the charge cycles he quoted were full discharge, for the purposes of the experiment, or partial as most of us do?
February 22, 201016 yr The life cycle vs discharge of Lithium has been known for a while. If you continue to charge to 100% and discharge to <10% then the life is shortened considerably. By capping the charge to say 95% and making sure DOD goes no lower than 20% the life is extended considerably. Good BMS configuration limiting cell voltage to 4.10~4.15 max charge and cut off at 3.10~3.00 volts or higher will achieve 800+ cycles.
February 22, 201016 yr Maybe Flecc could answer as to whether the charge cycles he quoted were full discharge, for the purposes of the experiment, or partial as most of us do? The first 208 charges were between 80% charge and full charge, a spare battery being carried on the runs to take over whenever the test battery was emptied, and the current drain usage conditions were severe with the motor forced to do all the work to it's limits before assistance with pedalling. The remaining 134 charges have been between 30% and 50% of charge with more normal and moderate usage conditions. I don't think the life would have been materially different with different usage since that battery was very willing to give all the current the motor could demand without impeding performance. The impression I had was that the passage of time was an important factor in its life, just as it was in the former incarnations of this li-ion battery. I agree with David, li-polymer compound cathode batteries are the way to go at present for the optimum of number of charges life with adequate performance. On a separate subject, I'm now far from convinced that frequent part charging is advantageous for long life since an accumulation of evidence over the last four years appears to show no gain, even the opposite to some extent. It's something I'll probably post separately on at some time. .
February 22, 201016 yr Sorry, have been busy hence tardy reply. "Are you using a 250W motor? If so what does the motor need to have dumped from the battery to run at it's highest efficiency? There is only so much a 250W motor needs to maximise range and power." Yes, 250W. The issue is the instantaneous power demand, especially if using throttle only on a hill start. We find that nominal voltage is only one part of the equation. "I would be interested to learn what technology you are using and what the battery chemistry is. " Lithium Ion is all I am able to say. It is a slight variant on the conventional chemistry, but with very substantial connectors..... "We have found a battery of exactly the same size as the one you are talking about very disappointing compared to the 14A Li Po we are currently using." We have measured in excess of 600Wh and real world performance in terms of acceleration (power) and longevity (endurance) in excess of the LiPo's so far realeased on the market. "Flecc has explained why the 17.5A batteries are not as good as the slightly smaller ones on 250W electric bikes. It would be interesting to hear if you have managed to overcome these problems." I believe we have overcome them, but an independent test of the two battery set ups on competitor bikes would be fun
February 25, 201016 yr Hi Bruce I have just found out who you are and have had a good look at one of your bikes today. Bruce, Who are you ? Give us a link us to your bikes. Herb
February 25, 201016 yr Hi Herb Bear Print Electric Bikes. Bear Print - website under construction All the best David Edited February 25, 201016 yr by Wisper Bikes
February 25, 201016 yr Bear Print Electric Bikes. Bear Print - website under construction They can't be all bad - they were kind enough to give names to their batteries Hector and Gavin - and some of the bike colours were pretty.
February 25, 201016 yr To be fair Bruce has 4 new bikes and only one looks a bit like a wisper....... As blatant as this? "LIFECYCLE MOUNTAIN SPORTS BIKE" http://i46.tinypic.com/2w2muea.jpg
February 25, 201016 yr I do wish companies wouldn't go live with unfinished web sites. If they can't be bothered to finish a web site before publishing it leaves me wondering if they will develop their bikes before selling. One bike shop in London has a site so illiterate I didn't even consider buying from them. Maybe it's only me and maybe it's unfair but I doubt that I'm the ony one.
February 25, 201016 yr I am sure you are right Herb, I just get a little grumpy when I see blatant and quite frankly cheaper copies of my bikes! All the best David Fixed it for you:D Just joking I may want a Wisper one day :o Seriously it must be frustrating but that seems to be how China works.
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