@user-xv5iw5zh4m6 месяцев назад +4
I am a home brew battery specialist. If you intend to charge the cells to 4.2V, then there is no problem to charge them to 4.22V. They won't explode, leak, catch fire or have a 2x shorter life span or something. If you, for some reason, are concerned about cycle life, then you shouldn't be. The cells will degrade much faster due to age in an EUC, than to being charged to a higher voltage, unless you are a courier and cycle the battery 3 times a day. 99.99% the wheel will be long gone until noticeable battery degradation will kick in.
@grb19696 месяцев назад +1
This is only true for battery cells that can charge to 4.22 volts and hold that charge for at least 5 hours. As battery packs degrade over time, cells that cannot maintain charge will lower the total system voltage slightly, and continuously attempting to overcharge degraded cells will accelerate damage.
This s why EVERY wheel owner should have cell monitors and the lowest fully charged voltage in the group should be the maximum voltage output of the charger. This is why BOB YAN developed the PIDzoom ‘Charger Enhancer’ (announced last week).
Ideally we would get reading for individual cell RESISTANCE in addition to voltage. Dendritic decay is the main reason why thermal overload occurs, and cell resistance is a good indicator of pack health.
As a hobbyist, I’m sure you resistance “match” cells to ensure a safe pack. Even degraded cells are fine to use as long as matching is done and park charge voltage is reduced appropriately.
Please let me know if this doesn’t jive with your experience.@user-xv5iw5zh4m6 месяцев назад +3
@@grb1969 First of all - the recommended charge voltage by manufacturers is usually 4.2V per cell with some sort of a current cutoff, so it's not even a true 4.2v charge. Second - the charge voltage is specified by the manufacturer as 4.2+/-0.05V... That means that the manufacturer says that it's OK to charge the cells up to 4.25V. Third - a BMS is not a measurement instrument: if it shows 4.2V it doesn't mean that it's actually 4.2V, it can be 3.5V, 5V or who knows how much, unless the BMS is somewhat calibrated. Most run of the mill multimeters have +/-1% accuracy, and that's +/-0.042V (doesn't that sound familiar to 0.05V?), and that's a measurement instrument, not some toy that can display some numbers. So, If the BMS shows less then 4.25V per cell - I don't see a problem. Fourth - dendrite growth is not the sole reason for battery degradation. Those dendrites can grow all they want, unless they get too big as to pierce through the insulator - that's when you start to get problems. But you should be aware that dendrite growth is influenced not only by voltage, but also by current and temperature. If you charge a cell to 4.25V at 25C with 0.3C current - then the dendrite growth will be waaaay less compared to charging the same cell to say 4.2V at 15C but 3C current (that is what exactly happens when you break in moderately cold weather). And charging (breaking) at any sub-zero temps is almost a death sentence. So to me it sounds hypocritical that charging to 4.25V is a problem coming from a man who charges his EUCs at sub-zero temps (winter driving) with high currents on a daily basis (breaking). Like I said - I wouldn't wory at all about that slightly elevated voltage. And IMO any technical stuff including voltages should be shown only to power users - people who can correctly interpret the information.
@grb19696 месяцев назад
@@user-xv5iw5zh4m I agree. The problem for the casual user is that they have little control over over-current abuse of their batteries, whereas over the lifespan of the batteries, over-voltage conditions can cumulatively creep unnoticed by users and prematurely degrade performance. As cells degrade below 4.2V yet the charger remains at 4.25V, the gap accelerating cumulative damage and eventually risks thermal runaway. If we’re specifically looking at increasing battery lifespan, why not lower the charge voltage (or use the PIDzoom Charger Enhancer) to limit the additional stress on the anode?
The are structural changes in design that could increase over-current damages (besides switching to LiFePo4) but these options have yet to be implemented on EUC vehicles.
Are you suggesting that over-voltage charging has negligible effect on overall lifetime and battery safety? If so, then do you see Bob Yan’s charge cut-off device as superfluous? Similarly, why not charge to 4.25V and store your batteries indefinitely until use? I’ve been of the opinion that 20% low-80%high is my preferred range for intermittent use and only charge to 100% if I’m going to be using my vehicles within a few hours of reaching 100% SOC: I know this subject is controversial but I would like to hear other opinions.
Related to this topic, what recommendations do you have for MSP owners with LG M50T cells who would like to keep riding and charging worry-free? Wouldn’t reducing charge voltage make sense to prevent home fires?
Anecdotally, my 12 years old electric car still has 85% total charge capacity which is about 10-25% higher than similar vintage vehicles. I attribute this to a slower charging rate, slow acceleration/top speeds and very conservative driving style. (Granted, it’s a Gen1 battery and newer designs can handle more abuse.)
I’m genuinely curious as a hobbyist. Thanks for your reply.
