Yes this is a viable option while waiting for (or avoiding) the 30A 240 cable.
Keep in mind that input is limited to 30A total between the two AC300s in split phase.
Not 30A each. So there really is no need for two 30A 120v circuits.
You could do 29A and 1A, but why?
Do you have a reference for that (documentation, spec page, etc.)? The plug on the new split phase charging cable is rated at 30A at 240V. The cable splits that out into 120V for each of the two AC300s (one AC300 gets one hot leg rated for 30A and the other AC300 gets the other hot leg rated for 30A, both AC300s get neutral and ground). So it is limited to 30A total, but that’s at 240V. That should equate to 120V at 30A x 2.
A quick experiment… My 2 AC300s are running in split phase mode. I just tried and it let me set the charging limit to 30A on each of them at the same time (requiring the password that anybody can get from Bluetti support). I didn’t try having them both actually draw 30A because the wiring from my panel is not yet sufficient, but I’d be surprised if it lets me set things there and then draws less. I’m talking about this screen:
I’m hoping this works because winter storms can cause me to lose power for a week or two with the power coming on for an hour or two each day near the end of the outage - I want to get as much energy into the batteries as possible during those short windows. That’s why I’m running a new 240V 30A line to the room with the batteries.
Great description of your creative methods of dealing with load imbalances. I wonder if there’s an adjustable charger that would allow you to set the charging amps to approximately the difference in the two units’ loads so that you wouldn’t have to check so often to see that the B300’s were in balance.
And that’s a clever way to use your small generator during long outages.
Interesting about your ½-HP motor but unfortunately that doesn’t have much relevance for my situation. My ¾-HP 240V well pump draws almost three times what your motor draws - 9A steady and 38A surge.
Thanks for your informative post.
I’m using adjustable constant voltage / adjustable constant current power supplies (the closest thing I know to what you’re suggesting). They’re made for powering LED lighting installations, but they work for charging, too. On the ones I picked, you can adjust voltage anywhere between about 46V and 57V. I set mine to the top. Then there’s also an adjustable current cap that goes from about 4.5A to 9A. It maintains the set voltage until you hit the current cap and then it starts dropping the voltage (to as low as 27V), expecting the load to drop its current draw in response. This interacts with the AC300’s MPPT algorithm in a way that makes adjustment pretty finicky, but you can eventually find something that works pretty well. So I adjust them to keep them around 10% under their rated power output (i.e., ~430W out of 480W each) in hopes of delaying any heat induced demise. So far I’ve found switching them back and forth easiest. But if the usage imbalance is pretty static, finding balanced settings could work well.
I’m using Mean Well HLG-480H-54A LED Drivers. They are out of stock everywhere I normally look, but in February one or two would come back in stock at Mouser every week (despite them showing long lead times). I haven’t seen them in stock at all at Digi-Key or Amazon. I put Anderson Powerpole Connectors on them and on my AC300 DC input cables to make switching easy. My units are indoors where I don’t need to keep water out with MC4 connectors.
I got that from Bluetti support after asking the question.
- *The pass code of adjusting the charging current between 10-30A is *****. Also 30A is total charging current for your units.
- Kind Regards
- Apple
However I tried this from my own split phase set up with two 15a cables (before 30A cable) and w/o password. Hooked up to out of phase outlets.
I set both units to 15A and it failed. Set both to 9A and it failed. Set both to 7A and it worked.
When I say failed it means lot of errors on AC input side etc. this suggest that it was set to 15A max input combined between two units
Let us know if it works for you. I did just send one unit in for RMA, so who knows if was the issue.
This is almost identical to the cable assembly I built, down to the blue SP29 aviation connectors. But that assembly molded the two cables to the L14-30 plug which makes it safer. I paid less than $90 for all the materials so if you order the Bluetti preassembled cable you will be better off than me.
Remember that the cable is rated for 30 A but the two AC300 units only supply 25 A on each phase, and that is the 240 x 25 = 6000 watts of continuous power. I know that it cannot supply 30 A because my setup did a shutdown and the error log had the infamous 008 OCP code, due to my wife starting up our 30 A clothes dryer accidentally. Shutting it all down and restarting solved the problem.
I’ve been searching for a 2nd TT-30 cable, but there’s none available. Instead of getting the twist-lock cable and wiring up that, you’re photos showed me how to disassemble the 15A cable and allow me to get a 10 gage cable/TT-30 on there instead. Wish I could just buy the cable, but this is the 2nd best case. Thanks for taking the time to document this!