Does the 80% charging rule apply to BYD LFP blade batteries?

Just charge to 100% without any worries. Actually, you should do it once a week. If you have a slow charger at home (not 11kW), just arrive home, plug it in, unplug in the morning at just forget about it. Just don't forget to at least charge to 100% once a week as I already said.

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Yes 100 percent perfectly fine and follow it once a week as earlier reddit user mentioned. Also to ensure cell balancing at top end which is taken care by weekly full charging, follow the same for the bottom end cell balancing by discharging close to 10 percent and fully charge to 100 percent in one go every 3 to 6 months. This ensures the battery readings on the display stays accurate and gives you close to true readings and estimated mileage remaining from SOC as close as accurate without sudden drop offs say for example from 15 percent to 0 if the readings are way off. Hope this helps and this is the most accurate information and we per guidelines from the BYD official owners manual. This also ensures to retain the battery warranty by following these protocols as byd service centers can check battery health diagnostics.

No. In fact BYD recommends you charge to full weekly.

Not only does BYD recommend it, but I kept it hovering around 80% for two weeks and it works not stop telling me to charge to 100%.

Nope, LFP batteries should be charged to 100% at least once per week

Charge to 100% it’s recommended by the manufacturer.

Once a week was new to me, but I’ll try that

LFP batteries have a very flat voltage curve, so the battery management system cannot read the state of charge by measuring the voltage, but has to measure how much current goes in and out, which gets increasingly inaccurate. The voltage spikes once the battery gets full, so the BMS can reset once it reaches 100%. Every 3 to 6 months discharging to around 10% and then doing a full charge to 100% in one go helps the BMS to measure the full capacity of the battery and more accurately display SoC. Those recommendations are purely for the BMS to calibrate battery reading. LFP degrade much slower than NMC batteries, so charging to 100% is less taxing on the battery, but they still degrades faster than sitting at a lower level. Long term it is better to time charging to 100% before a "longer" trip and keeping it at a lower level of charge when only doing short trips. But given their durability you don't need to worry too much about it. This is probably why most companies don't bother offering a % charging limit on LFP batteries. If you want to charge it but not go to 100%, you can just use scheduled charging with a time limit.

This is by far the best answer. Keeping the battery at lower levels will increase its lifespan significantly. However, you will need to hit 100% more often purely for BMS calibration

Once a week is quite difficult if you are making very short trips. Is like going 85% to 100% every week :). But yes, LFP doesn't have the same issues as NMC and doesn't need to be pampered.

For BMS calibration and from what I've read also cell balancing. But it helps to time the 100% charging to days where you going to use the car more so you don't stay at a high SoC for too long.

no

I own a BYD. The dealer told me that to calibrate the battery, I just need to do a full AC charge to 100% every 2–3 months. It has to be AC charging, not DC fast charging — DC charging won’t calibrate the BMS properly. LFP batteries are actually fine with being fully charged; they’re not like ternary batteries that are sensitive to 100% charge.

Can someone tell me tricks how to discharge hybrid batteries below 10%? I have seal u comfort and with new firmware in eu car doesn’t want go below 20 even on blue ev mode (hold ev switch around 10s)?

Use Sentry mode?

Best advice, don't think about it. 80% charge for LFP is not needed because chemistry is far more forgiving on higher states of charge compared to NMC. Studies suggest still 100% charge on LFP stresses battery and degrades faster but impact is small enough to be able to live your life without too much worry. Additionally given relatively flat voltage curve of LFP chemistry it is recommended to charge 100% (cell balancing & BMS calibration) frequently, some manufacturers say every few weeks, some weekly. What's more important is not charging 100% or 80%, rather how long battery stays at 100%. So if you charge to 100% and let it sit for 12 hours it'll harm much more. Anyway if you don't charge to 100% frequently your car reading of state of charge will go way off. Additionally cell voltage variation increases and during charging (up to 95\~99%) high voltage cells cutoff charging for other cells, and during discharge low voltage cells cut off discharge of nearby cells practically trimming battery capacity from both ends. You may be trying to avoid a problem and end up creating another problem. Almost as if in order to protect the battery you end up never utilising full allowed capacity. Double edged sword. Back to best advice, ignore all this, live your life and use your car as you your lifestyle wants it (rather than changing your lifestyle to suit your car) and do frequent/occasionally 100% (not 99%) charging without guilt. If you have LFP you're already set to worry much less compared to NMC. Enjoy it.

Great points. Thanks bunches!

Always staying at that high level of charge still has a more negative effect. If you only do 15% per week then you don't need to charge to a 100% every week to calibrate since you didn't charge it between.

You should do a 10% to 100% full AC charge every 3-6 Months, a charge to 100% is recommended more often so the BMS can recalibrate to more accurately show the charging state. LFP have a much flatter voltage curve, so higher states of charge are less damaging than for NMC, but LFP still degrade faster at higher SoC especially at 100%. There are studies showing that a LFP battery cycling between 75%-100% degrades faster than a battery cycling between 0-100% (https://iopscience.iop.org/article/10.1149/1945-7111/ad6cbd/meta). Still much slower than NMC batteries so you don't need to mind as much, but I wouldn't recommend letting the car stand for days at or near 100%.

Currently I am leaving it drop below 30% then charge to 100%. This means I charge it once overy 3 - 4 weeks.

Nope, I've been charging mine for 100% for three and a half years.

The manufacturers keep it simple, that recommendation is just to ensure the BMS can reset and determine where 100% is again. But if you don't have any intermittent charging during the week (don't drive that much each week), you don't really need to charge up to 100% each week either. Sitting at or near 100% for longer time still increases battery degredation.

Yeap, this is the answer!

You've already gotten accurate and detailed answers. I just wanted to remind you that no matter what you do, modern batteries (especially BYD Blade) are always going to outlast the lifespan of the vehicle and sometimes even the owner's. Battery longevity is a problem that has already been solved. Development is now focused on solving other problems like cost (sodium batteries) and energy density (solid state batteries) among others.

Usually, when it gets to about 30% I plug it at home, and let it charge overnight to 100%. Dolphin 60kWh battery.