Tawpie Posted February 8, 2021 Share Posted February 8, 2021 (edited) Various internet sources and battery gurus say that you can extend the usable cycle count of a Li Ion battery by only charging to 80%. Being able to have something last longer is always tempting even if it's silly**. But, charge to 80% of what? a) 80% of the terminal charge voltage? b) 80% of the difference between terminal charge and 'walk' voltage? c) 80% of the difference between terminal charge and cell shutdown voltage? Does anybody know? For my 84V KS wheel these would be: a) 84 * .8 = 67.6 b) ((84 - 63) * .8) +63 = 79.8 c) ((84 - 50) * .8) +50 = 77.2 "a" seems like I wouldn't ride anywhere for long but both b and c are over 90% of the terminal voltage so that seems like more than 80% state of charge. **it's a silly question because assuming I get 100km from a full charge on my wheel, and full-charging every time (max life reduction) gives me 300 full cycles (it's probably more like 500 but this is an example). That's 30k kilometers before the pack is permanently degraded to 80 km/charge. I personally don't have the kind of time it takes to ride the wheel 30k km much less some multiple of that. Edited February 8, 2021 by Tawpie 1 Quote Link to comment Share on other sites More sharing options...
Tawpie Posted February 8, 2021 Author Share Posted February 8, 2021 Personally, I think the answer is 67.6V is the mythical 80% mark, which is not useful in this application. If this is true and we're already over the 80% SOC mark just to be useful, that begs a second question: is it better to go 100% with balancing every time than it is to stop in the 90% range? Quote Link to comment Share on other sites More sharing options...
Popular Post meepmeepmayer Posted February 8, 2021 Popular Post Share Posted February 8, 2021 15 minutes ago, Tawpie said: Various internet sources and battery gurus say that you can extend the usable cycle count of a Li Ion battery by only charging to 80%. No. You need to regularly charge to 100% for the cell balancing to happen. Otherwise the battery will die much faster because some cells are always more stressed than the others and fail first. Store at 80%, maybe. But that really only applies to long term storage (weeks and months). And then it doesn't have to be 80%. It should not be close to 100% (full) or too empty so the voltage might drop too low from some vampire drain or whatever. It's not an exact number. "80%" merely means "not too full, not too empty" because apparently that's what stresses the battery over long time spans. And I guess you can charge to 80% most of the time. But so far nobody has seen any battery degradation, even if regularly charging to 100% (and even storing there). So not sure if the effort is worth it. I'd rather have less mental hassle, the range guarantee, and more safety from charging to full when I might need it. - 80% would be 80% battery voltage. What that exactly is depends on the used 100% and 0% voltages, so you already see it's not exact because manufacturers can use different numbers there. E.g. 16X: min voltage is 20*3.15V = 63V, max voltage is 84V, so 80% would be 63V + 0.8 * (84V-63V) = 79.8V. If you're wondering, I stopped riding over the winter and my ACM was somewhere around 70% battery after the last ride. That's how it has been since then. Didn't bother with anything but "not full, not too empty". 9 Quote Link to comment Share on other sites More sharing options...
Popular Post PLEASE_DELETE Posted February 8, 2021 Popular Post Share Posted February 8, 2021 (edited) Deleted. Edited March 18 by PLEASE_DELETE 4 Quote Link to comment Share on other sites More sharing options...
Planemo Posted February 8, 2021 Share Posted February 8, 2021 14 minutes ago, /Dev/Null said: Agreed with null. I charge to 100%, use within 12-24 hours & get it back down to 45-55% and then they stay there (store) until I charge them again. Seems to work well. This is absolutely the best thing to do with li-on cells. 1 Quote Link to comment Share on other sites More sharing options...
Tawpie Posted February 8, 2021 Author Share Posted February 8, 2021 (edited) Kinda what I thought. A person like me that rides for entertainment would be best served by: ride on return, don't plug the wheel in (to allow the batteries to come back to room temperature) next morning if it looks like a day for riding, plug it in (be mindful that if yesterday was a long hard ride this could take a while) unplug and power cycle when KS gives me 7 slow beeps (KS16X firmware 2.0.2) Seems like a good task for IFTTT or Alexa. Edited February 8, 2021 by Tawpie forgot I have a slow charger! 1 Quote Link to comment Share on other sites More sharing options...
Rich Sam Posted February 8, 2021 Share Posted February 8, 2021 16 minutes ago, Tawpie said: Kinda what I thought. A person like me that rides for entertainment would be best served by: ride on return, don't plug the wheel in (to allow the batteries to come back to room temperature) next morning if it looks like a day for riding, plug it in (be mindful that if yesterday was a long hard ride this could take a while) unplug and power cycle when KS gives me 7 slow beeps (KS16X firmware 2.0.2) Seems like a good task for IFTTT or Alexa. Sounds like good advice to me! I purchased a fast charger from Ewheels but only use the "Fast" part when I have a back to back ride opportunity [only once have I done a 5 amp charge]. In Seattle you have to take advantage of good weather when you have it! Mostly though, I use the "Fast" charger to actually charge slow. I charge at the slowest speed [lowest amps] for the required result to be ultra safe. Quote Link to comment Share on other sites More sharing options...
Popular Post Rawnei Posted February 8, 2021 Popular Post Share Posted February 8, 2021 2 hours ago, Tawpie said: Kinda what I thought. A person like me that rides for entertainment would be best served by: ride on return, don't plug the wheel in (to allow the batteries to come back to room temperature) next morning if it looks like a day for riding, plug it in (be mindful that if yesterday was a long hard ride this could take a while) unplug and power cycle when KS gives me 7 slow beeps (KS16X firmware 2.0.2) Seems like a good task for IFTTT or Alexa. Honestly, ride, charge it to 100%, don't overthink it, adjust your charging to fit when you want to ride. 7 Quote Link to comment Share on other sites More sharing options...
Tawpie Posted February 8, 2021 Author Share Posted February 8, 2021 2 minutes ago, Rawnei said: don't overthink it you are 100% correct, but I do ride in the cold and don't want to be charging a wheel until it's finished developing dew on the inside and has dried out any dew that did form, so there is that to overthink. Besides, making IFTTT do the work would be a worthless-to-the-good-of-humankind but entertaining diversion! Quote Link to comment Share on other sites More sharing options...
HarpMudd Posted February 8, 2021 Share Posted February 8, 2021 I treat my battery the same way. Just charge it up before I ride. If I get back and have a low battery, I charge up to just 70% and let it sit. I never let my wheel sit around that long at 100%. With the newer 16X firmware, I turn down my eWheels chager to 4A so I can avoid most of the annoying beeps! Quote Link to comment Share on other sites More sharing options...
Skecys Posted February 9, 2021 Share Posted February 9, 2021 Just enjoy riding and don't worry so much . Unless there is something inherently wrong with your battery pack, you will have other critical problems (mechanical, motherboard, etc.) loooooong before you would notice loss of range due to battery life. Even if you recharge to 100% every night. I'm not saying people are wrong when they say what to do and what not to, but don't sweat it. 1 Quote Link to comment Share on other sites More sharing options...
Popular Post Seba Posted February 9, 2021 Popular Post Share Posted February 9, 2021 Short - by regularly charging battery to anything less than 100 % will greatly increase a risk of single cell failure. And single cell failure is something that will make your entire battery useless, including elevated risk of cell thermal runaway and battery catching in fire. More, ocassional 100 % charging won't help. Why? Because most of our EUCs are equipped with bleeding balancer, which only works for cells that reach full charge voltage. So balancer won't work below 100 %. For new battery this is not a problem, but with each charge/discharge cycle battery cells will get more and more unbalanced. At some point of time, some cells will go higher in voltage than others, tripping overvoltage protection that will disconnect charging circuit etc. To get benefit from extended battery life by partial charging you need a smart BMS equipped with enhanced balancer that works also when cells are partially charged. Not the one built into KS batteries. 14 Quote Link to comment Share on other sites More sharing options...
alcatraz Posted February 9, 2021 Share Posted February 9, 2021 (edited) As your pack ages you might want to increase the time spent at 100% to give the balancing more time. If only we could monitor individual voltages so we wouldn't have to rely on guesswork. 80% or 90% refers to the charge level. 90% of a 4.2v cell is usually around 4.1v. 80% is a bit extreme for euc use as the packs don't cost a fortune, but on cars 80% is likely very real. Charging to 80-90% increases the amount of cycles drastically. If 100% offers 1000 cycles before the effective capacity declines to 80% of new, charging to 80/90% increases that tenfold. The jump from 100 to 90 is big, the jump from 90 to 80 is smaller. I saw a paper on the subject. The numbers were like 1000 - 8000 - 20000 (cycles) or something of the sort. Another interesting discovery was that even with 100% charging, after the cell being tested (NCR18650B) reached 80% of original capacity, it basically stopped deteriorating and stayed over 75% capacity for thousands of cycles. So they come to 80% rather quickly but after that they stay there for a loooong time. The deterioration tapers off and flattens out. The problem is that the bms essentially kills the cells as the imbalances become too great to handle. It's not the fault of the cell. With stronger balancing your battery pack could outlive you and still have 75% of original capacity. Edited February 9, 2021 by alcatraz 1 Quote Link to comment Share on other sites More sharing options...
Rich Sam Posted February 9, 2021 Share Posted February 9, 2021 3 hours ago, Seba said: To get benefit from extended battery life by partial charging you need a smart BMS equipped with enhanced balancer that works also when cells are partially charged. Not the one built into KS batteries. Do you know of any EUC manufacturer using smart BMS? Or heard rumors of brand adoption? Quote Link to comment Share on other sites More sharing options...
Chriull Posted February 9, 2021 Share Posted February 9, 2021 9 minutes ago, Rich Sam said: Do you know of any EUC manufacturer using smart BMS? Or heard rumors of brand adoption? Some call there BMS smart but none support partial charging. 1 Quote Link to comment Share on other sites More sharing options...
Rich Sam Posted February 9, 2021 Share Posted February 9, 2021 Excellent battery discussion guys. Just to be clear and spell it out for me, the balancing we are talking about is when the battery reaches 100% and the charger still shows red [under load], or is it the period after the charger goes green [no load] that the balancing occurs? Quote Link to comment Share on other sites More sharing options...
Popular Post mrelwood Posted February 9, 2021 Popular Post Share Posted February 9, 2021 17 minutes ago, Rich Sam said: Excellent battery discussion guys. Just to be clear and spell it out for me, the balancing we are talking about is when the battery reaches 100% and the charger still shows red [under load], or is it the period after the charger goes green [no load] that the balancing occurs? Balancing starts when the first cell reaches 4.2V. With a perfectly balanced pack that would be when the pack reaches full voltage and enters the CV phase. In practice a bit earlier. Balancing never actually stops on EUCs, the balancing current just decreases enough to be meaningless. The charger turns green somewhere in the middle. (Usually at 300-700mA total charging current.) Your calculation about reaching 30k km before the pack gets notably deteriorated is the most important one. If you look for topics titled “won’t charge past...”, you’ll see that without sufficient balancing the packs can fail as soon as 2k km. So an actual failure roughly 10 times sooner than 100% charging gives you some degradation. Pick your poison... Yet I wasn’t able to convince eWheels to fix the disastrous 80% charging recommendations from their shop’s fast charger product descriptions. 12 Quote Link to comment Share on other sites More sharing options...
Popular Post PLEASE_DELETE Posted February 9, 2021 Popular Post Share Posted February 9, 2021 (edited) Deleted. Edited March 18 by PLEASE_DELETE 5 Quote Link to comment Share on other sites More sharing options...
Rich Sam Posted February 9, 2021 Share Posted February 9, 2021 4 minutes ago, mrelwood said: Yet I wasn’t able to convince eWheels to fix the disastrous 80% charging recommendations from their shop’s fast charger product descriptions. Thanks @mrelwood, yeah that is how they sold me a fast charger! hehe. But after some extended research into the topic I quickly learned about balancing and how it may not be the best choice to not charge to 100%. Ultimately I'm not salty about the purchase of the charger as I still have a fast charger, and I can also take one to work and one at home. I feel this info should be stickied somewhere in a maintenance section! Quote Link to comment Share on other sites More sharing options...
Tawpie Posted February 9, 2021 Author Share Posted February 9, 2021 (edited) For my KS on 16XS v2.0.2 firmware, it beeps slowly 7 6 times long after (hours after) the charger has gone green and the reported voltage is well full... it is believed (I possess no facts to back this up) that the 7 6 slow beeps means the wheel has decided that it has finished balancing. I have a slow charger, but during balancing that doesn't matter as the current drawn during balancing is very tiny. Edited February 9, 2021 by Tawpie only beeps six times, not seven 1 Quote Link to comment Share on other sites More sharing options...
Rich Sam Posted February 9, 2021 Share Posted February 9, 2021 1 minute ago, Tawpie said: For my KS on 16XS v2.0.2 firmware, it beeps slowly 7 times long after (hours after) the charger has gone green and the reported voltage is well full... it is believed (I possess no facts to back this up) that the 7 slow beeps means the wheel has decided that it has finished balancing. I have a slow charger, but during balancing that doesn't matter as the current drawn during balancing is very tiny. I'm going to perk my ears up on my next charge cycle and see if I hear some cool sounds when my V11 is done charging. It makes kind of a Jaws [Da Duh] kind of sound when it starts charging. Problem is my fast charger is kind of Loud to have it in my home office, I wish the fan on this thing was thermal triggered and not always max fan speed. Need to pull in quieter charger inside next time. 2 Quote Link to comment Share on other sites More sharing options...
Rawnei Posted February 10, 2021 Share Posted February 10, 2021 11 hours ago, Rich Sam said: I'm going to perk my ears up on my next charge cycle and see if I hear some cool sounds when my V11 is done charging. It makes kind of a Jaws [Da Duh] kind of sound when it starts charging. Problem is my fast charger is kind of Loud to have it in my home office, I wish the fan on this thing was thermal triggered and not always max fan speed. Need to pull in quieter charger inside next time. Same here, on my Gotway I have a fast charger (5/7/9, always charge at 5A) where the fan is always full on and kinda loud. On the V11 I use dual stock chargers which will also give 5A combined and those are totally quiet which are super nice. Quote Link to comment Share on other sites More sharing options...
Seba Posted February 10, 2021 Share Posted February 10, 2021 12 hours ago, Rich Sam said: Problem is my fast charger is kind of Loud to have it in my home office, I wish the fan on this thing was thermal triggered and not always max fan speed. Need to pull in quieter charger inside next time. It's very easy to replace fan to a silent one: 2 Quote Link to comment Share on other sites More sharing options...
..... Posted February 10, 2021 Share Posted February 10, 2021 (edited) 20 hours ago, Rich Sam said: Thanks @mrelwood, yeah that is how they sold me a fast charger! hehe. But after some extended research into the topic I quickly learned about balancing and how it may not be the best choice to not charge to 100%. Ultimately I'm not salty about the purchase of the charger as I still have a fast charger, and I can also take one to work and one at home. I feel this info should be stickied somewhere in a maintenance section! My wheels and scooter have e-wheels fast chargers. I could see how the 80% could be useful if a person was charging with intent to store them. I got mine so I could use the FAST section of it IF need be. I typically charge on a cooled battery and slowly. Im guilty of keeping my wheels fully charged so I can grab and go at any time. Hell, if i cant be bothered to grab safety gear, I sure as hell wont remember to charge BEFORE every ride. Oddly enough, the ewheels charger seems to taper off and stop BEFORE my wheels reach 100%. I asked about it, and was told it was safer to be just under max, than over. Be that as it may, I still use my factory chargers every 3-4 charges, and let them sit at green for hours to balance. Looking at the fast charger, it seems like it stops altogether, but the factory chargers trickle forever(dont quote me on that). I did notice ONCE on the factory charger, my scooter had that wonderful smell of batteries cooking. 15 miles on the scooter even now. Meh, it still fully charges and who knows what damage may or may not have been done. I do know the e-wheels charger doesnt cook it tho. There's tons of threads on batteries. I simply charge mine full and monitor it while it charges. Light goes greeen and done. Every handfull of charges, let it stay green. I have better things to obsess over, and Im pretty sure if my batteries last even close to 1000 cycles, its a miracle. 1000 cycles = 30,000 miles on the 18L, 65,000 miles on the sherman and hell if I know on the mten. Something will be destroyed, the wheel will simply wear out, or a random cheap part will fail, LONG before I can be blamed that I shortened a battery's life. Charge it, ride it, set it free!!! Edited February 10, 2021 by ShanesPlanet 3 Quote Link to comment Share on other sites More sharing options...
Rich Sam Posted February 10, 2021 Share Posted February 10, 2021 9 hours ago, Seba said: It's very easy to replace fan to a silent one: Fantastic thanks Seba! Great find on that fan as well, I looked up similar fans in the 60x60x25 range and the specs are hard to beat on that one. Quote Link to comment Share on other sites More sharing options...
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