Low PV input limit to charge AC300 expansion batteries?

I have an AC300 with 4 expansion batteries. I have 3 PV350 solar panels connected. It is an overcast day, but the panels are producing 120W. The problem is, all the batteries show standby. Why aren’t they charging? Thanks in advance.

Now 220W and still no charging. I feel like I am wasting power.

Hello Amy, Have you enabled DC1 input to PV?

What do you see when tapping on PV INPUT?


Yes, DC inputs are set to PV. To be clear, it charges fine with solar, just not when the panels have low output, such as a cloudy day or at the end of the day. Not sure exactly when charging kicks in, but somewhere in the 300-400W range. I am just wondering why they don’t charge with lower solar power. On a cloudy day, the PV were producing 200W, but no charging. Seems like a waste.

It seems to depend on what is drawing power as well as the level of input. If you check the batteries they have a status of charging, standby and discharging. When running our fridge freezer on ac roughly under 200w Solar input means no charging. If dc and ac are off it charges at under 200w Solar input.

Yes, I noticed what you are saying when also drawing power. However, mine does not charge under 300-400W PV with AC and DC off. In other words, drawing no power. I don’t get why.

Do you know a minimum? I was thinking around 50 watts should work. If not that is not good.

I have not had the chance to sit and watch it, but I believe it is somewhere between 300 & 400W. For sure at 220W, the batteries were all in standby. I was getting up early to set up my panels and waiting until dusk to take them down, but given they don’t charge at low wattage, I don’t do that any more. Literally, if I had a few 100W panels, I could not charge the ac300.

Mine do not charge at under 200w with ac and dc off. They are in standby.

MPPT charge controllers start on a minimum volt/current level. In the solar world it depends on what size charge controller you buy, 12VDC to 48 VDC is typical and the cable is sized according to voltage drop and disance, <2%. Check the voltage at the end of the cable at the battery several times during your locations peak sun. The charge controller most likely turns on at 12 Volts. You’ll alse see the real voltage drop with this test.

Any updates on this topic? I’m experiencing something similar with the AC200Max with 2xB230s. The AC200Max alone (w/o) the extension batteries connected seems to charge at a lower wattage. On the display I sometimes read >70V input from solar and still all three batteries (main unit + ext. batteries) stay on standby. @Chorlton: I have a similar setup with a fridge freezer but I do not understand why the output should influence the threshold for charging?! Maybe @BLUETTI can comment?

This gives some background. My understanding is the input charges the batteries based on what is left over from the AC output in my case. If output is greater than input it also drains the batteries.

Okay, but despite there is only a small consumption (low wattage) from AC in my case, and PV is > 200W, the batteries remains on standby and do not switch to the charging state. For example, with 200W solar input and 10W ac output, I would have expected that the difference (190W) is fed into the battery.

The B230 extension batteries will only charge if their state of charge is less than or equal to the charge of your AC200Max. If the state of the charge of your AC200Max internal battery is lower than the batteries, then only your AC200Max internal battery will charge.

Hi @greeny_germ , Our machine charging power greater than a certain value will show charging. Less than this value will show standby.
The actual charging wattage displayed will prevail. Low wattage can also be charged to the battery. The threshold value is about 100W.

@bxm6306: This is true, but the AC200Max is always discharging the attached batteries first and hence the situation you are explaining never occurs. @BLUETTI: Thanks for your answer. Does this mean that any input PV wattage is fed to the battery no matter that for low wattage the display shows “standby”? That means it still charges in standby?

Hi @greeny_germ , Yes, it will show standby if the charge does not exceed 100W.
Actually the PV is in charging.