July 22, 201114 yr I had to answer one of our customers question about LifePo4 battery conditioning and usage,the answer may be useful to others. Our LifePo4 supplier has no specific conditioning instructions but has recommended that for optimum battery life they should be stored between 30% and 80%,it should be avoided to leave fully charged or empty for lengthy periods. the un loaded loss rate is very low,only 2% per month so if leaving for a long period it is recommended to charge to about 80%. In practice this probably means fully charging then use the bike to empty a bit from the battery. If using on a daily basis you can fully charge because you will soon reduce the percentage. These batteries are much less sensitive to temperature but extremes of heat (above 30C or below freezing should be avoided. I used LifePo4 because they are less fragile than the LiMn types,but we did experiment with a 16Ah battery on one of the prototypes and it was really too heavy so we are sticking with our limit of 10Ah,but you guys are getting good range from the !0Ah so a bigger battery would not seem necessary for most people. On balance,especially with the lower cost our choice of LifePo4 would seem to be a good one the slightly additional weight seems acceptable-in a conversation with a leading retailer who was selling a bike with a replacement battery cost of over £500,his comment was that if his customers could afford a Range Rover then they could afford batteries every 2 years of £500-this is exactly the opposite attitude of Kudos,who are determined to bring these costs down. Dave Kudos Cycles
July 22, 201114 yr He does kind of have a point though; people baulk at the cost of a battery but the reality for me at least is that even if I half the quoted 2000 charge cycle life of my LiFePo battery (around £300 inc. delivery) that still equates to a petrol saving of around £8500 for my commute. This is based on a single charge per return journey, £8.50 petrol cost per day (I have a daft car which is somewhat inefficient over the 2x9 mile runs). So while some are probably working harder than others to bring the cost down, genuinely massive savings are achievable even now and when put in context the battery cost isn't as bad as it might first seem.
August 1, 201114 yr Dave, Having just purchased a King which I hope to receive later this week have you any advice about the initial discharging and recharging of the battery. For some it appears that a full discharge cycle is desirable, but I wonder if thiis is necessary with the LifePo4 battery. cheers, Alan
August 1, 201114 yr Over 400 charge cycles, 2000 miles plus on my homemade LifePo4 pack and still going strong http://farm5.static.flickr.com/4058/4272164656_9a3caf6b15.jpg In terms of initial charging, I think for the first ten or so charges I never drained it more down to more than 40%. Now though it gets drained often depending on if I can be bothered to charge it at work or not. I use it pretty much every day unless the temp goes below 3 degress when I use my car. In all that time I have had to balance it once when I first made it and it has remained balanced with no BMS ever since. Note mine is only a small series packs though 6s1p * 2 in series and made from A123 cells. Total 36v, 2.3Ah. I have a second packs if I need to go further. http://farm3.static.flickr.com/2632/4143431063_536415b261.jpg Regards Jerry Edited August 1, 201114 yr by jerrysimon
August 1, 201114 yr A123 have the flexibility of having a huge C rating though allowing you to have the flexibility to have a small pack and draw alot of amps from it. Good though its now what I'm looking into and LIPO for smaller light battery packs. Most of the companies offering Lifepo4 tend to be cheaper cells with poor C rates.
August 1, 201114 yr Agreed the A123 cells certainly are robust, but as you say best suited to smaller packs like mine and in my application of a 10 mile round commute a perfect fit Regards Jerry
August 2, 201114 yr Agreed the A123 cells certainly are robust, but as you say best suited to smaller packs like mine and in my application of a 10 mile round commute a perfect fit Regards Jerry Hi Jerry. I'm in the process of building up a Trek FX 7.5 with a 190rpm Tongxin in a 700cc wheel. I'm using a lyen controller limited to 15a but I haven't yet decided on a battery. Does that 36v 2.3ah pack do your whole 10mile commute then? How mch pedalling do you do on that commute? I have a 19 round trip commute on very flat land (Blackpool prom) and I'm trying to size an appropriate battery pack. What
August 2, 201114 yr Hi Buy one off these battery's cost delivered £170 You have an electric bike NOT a remote controlled toy car If you don't want to rack mount on the bike put it in a back pack 36V9.5Ah LiFePO4 Alloy Shell EBike Battery Pack - BMSBATTERY Frank
August 2, 201114 yr I was looking at 36V 15Ah Li-Ion Shrink Tube EBike Battery Pack - BMSBATTERY Should fit this with a little persuasion. Bit concerned about the effects of bulk charging a NiCoMn pack all the time.
August 2, 201114 yr Please note the shrink wrap versions dont come with a charger. An to buyone in the uk is quite pricey! RC LIPO can work fine for small robust packs. Its just you need more care when charging and discharging them as you do not have a BMS doing all its wonderful trickery...
August 2, 201114 yr Hi Yes the 15 ah is fine It will Just give more range and is is complete with 180 watt charger look at the picture and read the description Frank
August 2, 201114 yr Please note the shrink wrap versions dont come with a charger. An to buyone in the uk is quite pricey! RC LIPO can work fine for small robust packs. Its just you need more care when charging and discharging them as you do not have a BMS doing all its wonderful trickery... Hi Scottyf, in my members kits spreadsheet I have a column for BMS size. I have no idea why! ... Do you think it is of value to have a column or columns relating to the BMS.. BMS: Y/N, BMS_SIZE: small/medium/large! ... etc ...
August 2, 201114 yr Please note the shrink wrap versions dont come with a charger. An to buyone in the uk is quite pricey! RC LIPO can work fine for small robust packs. Its just you need more care when charging and discharging them as you do not have a BMS doing all its wonderful trickery... It says a charger is included. I don't think the pack I linked is the stuff they use in RC Lipos - it's really only rated at 1c discharge and the cheapest RC lipos are rated 15c (I was thinking og using two 6s 8000mah lipos as wel - swings and roundabouts atm). The BMS battery I linked states it has a BMS - does that just protect for high and low voltage cutoff (not that I intend on testing it) or does it take care of the balancing duties as well?
August 2, 201114 yr Thatnks very much for the info Frank. looks like that's my budget, lighweight and discrete build finalised then! Roll on payday!
August 2, 201114 yr Hi please have fun on your new Electric bike Conversion and welcome to the world of E biking Its Great FUN gets you fit and saves you Money Please allow Up to 6 weeks for delivery from BMS can be as quick as 2 weeks but some times 6 depends how busy they and there suppers are pay by paypal to protect your payment Frank
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