I was actually going to clamp around the PV cable to see if it is actually shut off 100% or is it passing through whatever AC Load amount that is being drawn. Of Course, I wouldn’t cut through the Battery sheath.
AC300 can’t be turned on without battery having been connected for a reason.
Additionally it is not good to charge lipo4 chemistry batteries to 100% continually. Would be preferable to charge to 90-95%.
Work around for constant cycling imparted by the design might be to assign one battery to run the system. Then disconnect all other batteries when they are charged. Then only reconnect those batteries to discharge when PV input is less than the demand of all loads.
@stumped, unplugging the batteries daily is unrealistic especially if used daily. I am wondering if other systems work the same, e.g. EcoFlows (and their new Power system, which I almost purchased when it was introduced).
Yeah it is no way a good work around for a system that can cost up to $10K when fully populated with batteries. But is an option to preserve battery life on up to 3 batteries which accounts for $6K of that cost.
I’m not happy especially given the lack of clarity in the documentation.
It would be nice if @BLUETTI could improve this performance via firmware update. But hardware may not support that.
That makes sense. Maybe I will look into installing an inline DC ammeter. It would be interesting to monitor the different arrays. I will have two banks of 3 panels.
That is a bit disappointing news. For me personally i would like load to by pass the battery at all times except when PV isnt adequate to meet load. Even at 100%
The issue once 100% is reached is not optimal at all.
Up until it reaches 100% I think power is not running through the battery as we fear. Only at 100% does the suboptimal issues appear to start. So up to 100% it will hopefully not be placing extra wear on batteries.
On the eb240 the same happens at 100% pv input says 0 and must be zero because the fans switch off. Only after the battery starts being used up will the pv later switch on.
Im not sure but even on a system where you have separate cc then battery and inverter. So just looking you think the energy must always go through the battery first. It think it actually does flow to the inverter first and supplies that before the battery absorbs excess pv energy. Something to do with less resistance towards the inverter load than to charge the battery. So energy will flow to the least resistance first. If say your pv was supplying 500w and you were using 400w only after the 400w was supplied would battery absorb 100w and at that 100w rate the battery level would rise.
If the battery level neither rise or fall i would expect it would count as 0% of a cycle.
An expert on this stuff could probably explain why a battery cant charge and discharge at the same time way better than me.
Bluetti could probably explain why pv has to switch off at 100% and not by pass required energy to ac load direct. It may damage the bluetti more to do this in cloudy days or damage the item it is powering because if clouds come and bluetti has to quickly mix in power from battery to supplement pv on and off lots of times
I know some other hybrids dont need batteries at all and can just go direct to ac load. But i think you have to have a minimum of 240v pv load coming in and bluetti only has 150 voc. Again thats just a speculation on my part.
On super sunny days which are rare i usually just plug in a ac charger to starting filling my car battery banks up so my bluetti never gets to 100%.
For now thats my best solution
Just an update, I have had 6 days straight of rain/overcast and have not charged up the 4 batteries to 100% to test the output on the panels if the batteries are @ 100%, I should reach 100% today or tomorrow as it’s only going to be partly cloudy and will try to test then.
I have had one other situation occur that is frustrating. When my batteries reached 5% the AC300 automatically changed over to grid, which was great, but something happed around 10% and I received a grid relay error (#025 AC Relay Short Circuit & 026 AC Relay Open Circuit) alarm code which I could not clear from the app and needed to wait until I got home to clear it and then it worked properly (I will probably open a new forum topic on this issue). The AC300 shut off both the AC in AND the PV in, AND disabled the AC OUT, however DC OUT worked. I don’t know what caused the error.
Anyhow, back the main topic. Battery Wear. I have been reading more on other MPPT+ inverter combos and they typically to not work like the AC300 where the battery is always being drained (at 100%) and is usually PV pass-through as long as the PV in is greater than the AC Load. (typically referred to as “opportunity” loads).
What is likely going on, and I say likely because we have no insight to the underlying system engineering of the AC300 charge controller. But what is likely going on is that Bluetti has chosen a charge profile where the bulk/absorption and float voltages are set far apart. We can theorize this because the same behavior can be observed with other brand charge controllers where these settings can be manually adjusted.
I am betting that somewhere along the line that the engineering department decided they wanted to prioritize charging speed over the ability to power loads FIRST via PV in, then battery. And this makes sense for most solar generators given they are meant to be mobile. To speed up charging speed the charge controllers bulk/absorption voltage is increased several volts above the batteries resting voltage. The caveat is that the higher the bulk/absorption setting is the wider the disparity with the float voltage becomes. So you get this period where when the bulk/absorption voltage is reached and the charge controller must be shut off until the battery discharges below the float voltage.
The AC300 given its substantial PV input capacity and size of it batteries is not nearly as mobile as its earlier cousins. It has become a platform where users want to install it primarily at home to leverage the UPS functionality AND also power as many loads as possible by solar without going to the batteries except when there is say an inrush load of current that PV can’t completely power.
Maybe Bluetii can provide via a future firmware update an advanced option that lets the user select between two charge profiles. One charge profile being similar to the existing that prioritizes charging speed, and another charge profile where the bulk/absorption and float voltages are closer together so that attached loads can be powered by available PV input 1st, and then battery second.
@BLUETTI is the above suggestion something you could take back to engineering teams? I believe if something like this could be integrated it would be a big selling point for the larger Bluetti systems.
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I don’t think they (Bluetti) want(s) to comment on this subject because they don’t want to discuss that the batteries are constantly being used and goes against a comment that they made, earlier. Yes, it would be nice to allow us utilize a firmware update to allow a sort of PV passthrough. However, they are taking their time to allow us an option to reset our AC300’s remotely when an error occurs (such as error 25/26), so I don’t think this firmware update would happen for quite awhile.
Ugh. I’m using my AC200Maxs and solar to lower my electric consumption and support power outages. I am probably losing battery life like crazy. I can’t believe nobody discussed this in any of the reviews.
Because my unit is mostly used for SHFT disaster prep, I keep my AC300+2*B300 in PV priority mode at 90%. (I know that may slightly reduce battery longevity compared to, say, 50-70% but I need this full or close to full if the Big One hits here.) In my testing, I’ve used a ~900-1000W space heater. When my battery is at 88% after being off for a month, for example, when I turn it on, the unit will take about 1250 watts of AC (I have charge set to 11A) and the output to the heater is about 930W. So slowly the battery charges up to 90% with roughly 300W going into the battery, and at 90% SoC the AC input drops to around 945W. I assume the 15 watt difference is the unit being on and the inverter being on in standby, and just overhead used by the unit’s operation.
I don’t know the exact workings of this. But I hope in this configuration the inverter is on but not actively working (it has to be on to produce any AC out, I think, and to be ready in UPS mode), and that all that wattage is simply passing through from wall to the heater and not doing much at all to the batteries.