Bizarre behavior of SOC indicator on my new AC200P

Definitely top marks to you, Midi! I’m very happy to find the hidden screen.

Hopefully your battery is OK. Do the deep cycle and let us know!

Just for the record, when I cycled my battery (which restored the SOC to 100%) I ran the unit down by running a moderate load continuously for a number of hours. When I charged it back up I ran the charger (approx 450 watts) continuously. I was so happy to see the unit charge all the way back up – at least so the SOC indicator says!

If bluetti changes the secret menu and disables that in the next firmware update then it is very telling that there is something to hide, I hope that it doesn’t happen.

1 Like

Hey Midi, how did you find the secret menu screen in the first place? I would never have found it.

The more this becomes known, the harder it will be to “hide” for suspicious reasons from a customer relations point of view.

The total voltage on both of my units is about 53.x. I haven’t always monitored this but I don’t think it’s ever been higher. For whatever reason, Midi, you have higher voltage, but more variation between cells. But since ALL of your cells have high voltage, I’m thinking maybe your battery isn’t bad – only the SOC indicator is off. At least I hope that will turn out to be the case.

I think Bluetti has brilliant designs and is producing a lot of units that have the right features. In other words, they’re very sensitive to what the market wants. But I fault them for two things:

  1. Bad customer service. They are slow to respond by email, no one answers the phone, and finally, when you do get some help, it is cryptic and not very helpful. They need to have someone who really knows the units and speaks good English and is actually available by phone to talk about issues.
  2. Bad quality control. WAAAY too many reports of people having issues with new or relatively new units. These are expensive items that are no picnic to return. In my case, for various logistical reasons, they are effectively impossible to return. Faulty units should be extremely rare, but instead they seem to be quite common.

Ok I cured my stuck at 73% problem by removing ac charger and plugging in solar next day … solar ran trickle charge like it was topping out the battery then it jumped to 100%soc … not only that all the cells went into balance .


Which was a surprise . Strikes me it’s all software related . I have not done any cycle charging from a low soc

Good news! Thank you for the update.

Mine does that all the time, to get the display to read 100% I usually charge through the PV port. Hardly ever use the AC adapter port anymore unless I have 2 chargers going at the same time.

It’s probably given in another post somewhere – can’t find it now – but how do you charge using the AC adapter through the PV port? Obviously different types of input jacks on these two ports, as well as different types on plugs on the AC adapter and typical PV outputs.

One of these XT90 To DC7909 cable – BluettiPower or if you buy a second T500 charger it will come with one.

Thank you eric102. I just ordered the XT90 To DC7909 cable from Bluetti. I do have two T500 chargers, but that is from having two AC200P units, so the adapter cable was not provided. The cable looks like a good thing to have, either for charging from the T500 through just the PV input port, or charging through both ports.

it might actually be a normal protective “feature” of the BMS to shut down charging when one or some of the cells get higher than others. you don’t want to overcharge any individual cell as that will lead to failure of the entire unit. so if they get out of balance, charging will look at the highest cell and protect that one, perhaps leading to not being able to charge the entire thing past 78%, which would be the sum of all the charges in each cell. then when somehow (not sure why solar worked for you, except that it allowed a cell balancing function to work better or for longer) things get balanced again, you are good to 100% charge per specs.

I don’t think that likley as the effect was near instantaneous. The soc didn’t start increasing again once I plugged in solar as though it was charging. It jumped from 73 to 100 in a matter of seconds. Literally the time it took the unit to detect solar input .

I was considering starting a new thread because my issue is on AC200Max (as opposed to AC200P) but it seems similar which leads me to believe the BMS is similar or the same on both models. Either way, today (after using the AC200Max for almost three days straight, charging via PV input (one 305W panel) I noticed the SOC indicator change from 75% TO 100%. AC200Max shut off the solar input (panel no longer charging the unit). I plugged a few electronic devices in to see if I could make the SOC indicator jump down like it jumped up. The SOC indicator did not jump down but (as far as I can tell) dropped at a rate I would normally expect. What I did notice is that the appliance that usually draws 160-167W (according to the AC output indicator) was drawing between 200W and 240W (according to the AC output indicator). This 200W+ drain decreased over the next 20-30 minutes to 177, which is closer but still higher than normal. When I say normal, I mean what the display normally tells me. I only charged the unit once via AC outlet, all other charges have been via PV input. Reading over this post makes me think the issue is not battery related (just my two cents), and for the moment I am leaning toward the 100% SOC being accurate and the 75% (in my case) SOC being inaccurate. I say this because I couldn’t get it to jump back down like it jumped up. But this is just a hunch. Also, I have noticed that the “top half” of the battery drains faster than the “bottom half” (it goes from %100 to %50 faster than from %50 to %18…which is the lowest I have taken the battery down to). I have kept fairly good notes since I pulled it out of the package so if anyone has question, please ask. My guess (as someone else stated above) is that the SOC indicator is cheep and probably a ballpark that errs on the side of safety for the sake of the battery banks. I did look at the BMS cell menu (the secret one) and the only thing I noticed was that the temperatures between the cells (A, B, D, P, I. AC200P does not have “I” cell) vary more and are higher than what others have posted (45, 25, 38, 33, 45). The unit does not feel warm. The fan cycles on and off at a regular interval (I just haven’t noted how often, I can do that for future reference though).

These are just my observations.

The SOC indicator isn’t perfect. It likely uses a number of techniques like monitoring voltage rise over time, absolute voltage, charge counting to estimate SOC. Maybe it was ramping up based on one of the metrics, and then another metric indicate max charge so it jumped to 100%. Try draining it to 10% and then charging back to 100% to see if it would better calibrate.

As for the power output indicator, I have heard that it isn’t too accurate at lower power. We also don’t know whether it is measured before or after the inverter. If it is measured before the inverter, then 10-20% higher would be expected due to inverter overhead.

Can you post or PM me the secret BMS cell voltage menu instructions? It is a shame that they removed it from easy access.

@MontAnna I would recommend running a complete “cycle” on the unit to recalibrate the bms. Charge it to “100% via the AC power brick, then run a consistent load on the unit until it powers off completely. Then charge it back up to 100% with the AC power brick with no loads attached and having both AC & DC outputs off during this recharge. When the unit then hits 100% and the power brick light turns red (or the ac input display shows 0 incoming watts)

This should sort of “reset” things internally. Hope this helps and keep us posted

Just for an update. This only happened two times back to back (same day) and hasn’t happened since. I did notice that when it happened I had both AC and DC loads switched off. I was charging using PV (305W Trina panel). Something else that was strange that hasn’t happened since then was that when I turned the AC Load back on and plugged in a fridge that the AC draw was indicating a fluctuation from 0 watts to 840 watts or so when the compressor was on. This is is quite a deviation from normal (I guess the base line I have established is powering a fridge…). Normal is surging to 400-450 watts for maybe 1-3 seconds then quickly dropping to about 163 watts. After this anomaly everything returned to normal. I don’t know what triggered it and I don’t know what cured it. I can just report what I observed.

I am having the same problem with my AC200MAX, the display jumps when charging from 75% to 100% with only 140w solar going in. I cannot be certain but I think the same may happening when drawing power, a sudden loss.

Bluetti should advise
Is this normal ?

hopefully give a solution

The only thing I have heard from Bluetti is to re-calibrate the SOC indicator. “For voltage jumps, you can discharge the AC200MAX to 0%, then fully charge it to calibrate the SOC.” The email I got from Bluetti didn’t specify whether or not to use the power brick provided with the ac200max (the one you plug into the wall) or via any method (solar, etc). I discharged mine to 0% then charged it up to %100 with nothing drawing on it while charging. So far I haven’t seen another jump in the SOC.
I think someone speculated on another forum that the SOC indicator is just a cheep part and not very accurate. My ultimate concern is not how accurate the SOC indicator is, rather, whether or not I am able to charge and discharge the battery to it’s maximum ability. As far as I can tell, so far, the SOC indicator does not limit how much I can put into and take out of the battery (charge/power wise). I could be wrong, but these are my basic observations, for what it’s worth.

Thank you MontAnna. I will try what you mentioned and thanks for the advice