Out of the 2000 watt battery of the AC200P, how much of that is usable? 80%? In other words, does the system automatically prevent you from charging more than 90% or less than 10%? Or can one use all 2000 watts? (drawn down to zero). Thank you very much.
You can drain down to 0. When you measure actual watt hours produced however you will see 80 to 85 percent of advertised spec due to efficiency losses with the inverter or regulated high amp DC circuits.
Thank you for your response. I assume when you state “you will see 80 to 85 percent of advertised spec” means one will have 80-85% usable wattage, or 80-85% of 2000 watts (in case of AC200P). Is this correct?
Yes, usable wattage is what the 85% refers to
When you say “You can drain down to 0” does this mean:
- The “0%” is actually 10% above zero as the Battery Mgmt. System (BMS) only lets you go down to an actual 10% battery drain, which means zero percent of USABLE watts left? OR does it mean you literally can totally drain the battery to zero, period?
If you drain LiFePO4 cells down to 0% (zero volts), you can severely damage them. And they are more than happy to give up every last drop of energy. That’s what the BMS takes care of. So 0% on the display doesn’t mean the cells are empty.
“0%” on the display is about 10% (200Wh) reserved on the AC200P to prevent damage. In some cases if you’ve left the AC200P deeply discharged at 0% for a while and it self-discharges below 10%, you’ll see the screen stay at 0% a bit longer until the charge is brought up above 10% actual.
Mark:
Thank you very much for your response. So, if I understand you correctly, when the display says 0% the BMS is really saying “you are at 10% and thou shall go no further.” Conversely, when the display says 100%, the BMS is really saying “you are at 90% and you shall go no further.” And it is the BMS that automatically takes care of this; it is not the user who has to consistently monitor the readout and manually shut the thing off at the appropriate discharge and fully charge levels. Am I correct? Thanks.
John
I’m not sure of the exact % numbers Bluetti has programmed their BMS, but essentially yes that’s how it works. Though I think the top number would be 100%. These unit are designed to where you don’t have to worry about things and try to micro-manage it all the time. The BMS, cooling fans, etc make sure it runs safely. Just use it.
Thank you for responding. Does the same logic apply to the 100% charging issue; i.e., “100% on the display is really 90% charged with 10% (200 Wh) reserved on the AC200P to prevent damage.” Appreciate your response.
John
AFAIK, 100% is actually 100%. The BMS displays a linear ratio of 0% to 100% for the actual 90% (10%-100%) that’s useable.
For example: If the BLUETTI displays 80%.
(Display % * 90% Useable Capacity) + 10% Reserve = Actual Battery Level
(0.80 * 0.90) + .10 = 82% Actual Battery State-of-Charge
Dan:
Thank you for your response. Probably my fault, but I do not understand all of what you are saying. So, please indulge me here: When the display says “100%” doesn’t that mean that one has charged it to 90% with the system not permitting the user more than that, and therefore the readout says “100%”. When the display says (0%) does it really mean that the battery has 10% charge left with the system not permitting the user to discharge more than that, and therefore the readout says “0%”.
No, it means that the system is charged to 100%. You will not “damage” the battery by charging it to 100%. If you want to maximise battery life you can manually charge up to a desired percentage, say 80%. But I have said in the past and still maintain, that at the rate of innovation and new technology being developed, you will want to upgrade to the latest tech long before your battery life is no longer usable. Use the product as you see fit by allowing the built in BMS do its thing and you will be fine.
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So is the Bluetti BMS calibrated pretty much the same across it’s product line? If I have an EB240, the BMS will cut off the charging at 100% (5 bars in my case) and also limit the discharge to not go below 10%??
Thanks
I’m guessing yes. I have an AC200P, EB150, EB70 and AC50s and they all produce about 80% of their rated power which would make sense if they have a 10% reserve and use another 10% for power conversion.
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So, are you saying that the BMS allows one to:
- charge the unit to an actual full 100% (not 90%), and the display says 100% only at that 100% point
- discharge the unit to an actual 10% wherein the display will display “0%”?
Correct. It’s to prevent extended self deep-discharge which will cause a reduction in battery capacity cycle life.
Bingo! That is correct.
So, that means the BMS protects the battery at the “low-end” but not at the “high-end” (full charge). I have heard to fully charge at 100% is not good for the battery. It is concerning that the BMS does not protect the battery from being literally 100% charged.
The specifications on cycle-life (to 80% usable), implies you’re charging to 100%, or a full charge. There is exponentially more damage done to lithium when deep-discharged vs. being charged to 100%. One of the BMS’s main purposes is to make sure it isn’t overcharged.
In the end, although it’s nice to know how the technical and internal guts work, all the BLUETTI products are designed to be “plug-n-play” without having to worry about it. The BMS protects the batteries so you don’t have to.
The ONLY thing that most solar generator (power station) companies do state is if you’re not planning to use your unit for more than say 6 months, you can discharge the unit down between 60-80%. It’s NOT a must-do, but it does put less stress of the batteries holding such a high-charge for an extended amount of time. Then if you have a storm coming up which you know might disrupt power, or a trip you’re about to take to go off-grid, you quickly charge it back up to 100%.
Long story short, don’t worry. Let the BMS take care of the unit and you’ll be fine! Hope this helps.