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Adding DIY battery to Bluetti AC300

You can also hook up panels to each B300 / B300s battery - there's a 200w MPPT in each. It's poorly documented, but I have shown it works. I had space left for exactly 2 200w panels on my garage (Calpha Solar 12v panel - sold out, but refer for specs). I put them in series to hopefully keep the voltages higher, but not sure if that's best or not. They were cheap to add (just the cost of panels - had mounts etc already)

Currently my lower panels are getting major shade this time of year (wasn't counting on that!), greatly reducing my production.
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So are you getting 370W into the 200w MPPT on the B300's (which of course would be intriguing)? Or is that just combination of all DC inputs on the AC300 and B300?
 
So are you getting 370W into the 200w MPPT on the B300's (which of course would be intriguing)? Or is that just combination of all DC inputs on the AC300 and B300?
In that picture, I was getting 371*2 into the AC300's MPPT pair, and 85w into the B300's MPPT directly. Basically, for each B300, you get a 'free' 200w MPPT that most people don't use. How much it helps, I dunno, but I had all but the panels laying around.

What I did was take my 2 3-panel series strings (I had 2 cables coming off my garage), and combined them in parallel to 2 string (still under amperage, voltage stayed the same ~ 95v). Then, when it entered my house, I then split the line and fed it into both solar inputs on my AC300, *AND* turned on the PV Parallel Enable in the AC300. I assume you need to do this so the system knows not to compete with itself - I really don't know how an MPPT works, and don't really care to learn right now 😉. It just works.

There appears to be no communication from the B300's MPPT to the AC300 - so I wasn't even sure if it was working until I put that power meter in-line. When we hit sun again, I hope I consistently max out that 200w MPPT with 400w of panels - basically it's a micro overpanel.
 
So, can we ponder battery leveling on these hacks a bit?

My setup (1 B300, 2 Vatrer) tends to "drain" the B300 quicker than the Vatrer - I don't reach 100% often, and will have my B300 at 5% and Vatrer at 40% frequently. I have *ASSUMED* that was mainly because the 2 different BMS's have different LiFePO4 curves, but chatting with adirondack_wanderer made me want to ask the hive mind.

Could it be cable lengths?

In other words, now much does cable length come into play? For reference, I have my B300 going into port 2 of my AC300, and my Vatrer's going into port 1. The hacked cable + extension + lugs feels about the same as a single Bluetti cable. I could understand if the cable difference was 10' vs 100', but say 5' vs 6'? I don't know the cable

Is the AC300 preferentially draining the B300? Even just a little bit, over time, could lead to...

crap. Maybe it is cable length - just looked at a photo during hacking, and I probably added 3' to the standard cable.

Is there any easy way to figure this out?
 
So, after reading the above, is there a resource that talks about cable length and drain equalization definitively?

Something I was pondering was cutting the B300's cable, and making it the same length as the Vatrer (while preserving the data connection), hooking everyone to a bus bar, and then tapping directly from the bus bar.

Thoughts?

(I mostly want to cycle the batteries evenly and don't want to leave "energy on the table", so to speak. And, it's a learning opportunity!)
 
In that picture, I was getting 371*2 into the AC300's MPPT pair, and 85w into the B300's MPPT directly. Basically, for each B300, you get a 'free' 200w MPPT that most people don't use. How much it helps, I dunno, but I had all but the panels laying around.

What I did was take my 2 3-panel series strings (I had 2 cables coming off my garage), and combined them in parallel to 2 string (still under amperage, voltage stayed the same ~ 95v). Then, when it entered my house, I then split the line and fed it into both solar inputs on my AC300, *AND* turned on the PV Parallel Enable in the AC300. I assume you need to do this so the system knows not to compete with itself - I really don't know how an MPPT works, and don't really care to learn right now 😉. It just works.

There appears to be no communication from the B300's MPPT to the AC300 - so I wasn't even sure if it was working until I put that power meter in-line. When we hit sun again, I hope I consistently max out that 200w MPPT with 400w of panels - basically it's a micro overpanel.
85W into the B300 MPPT makes sense. I've never had on the PV parallel enable as it dropped my solar input significantly. With max sun I'm able to draw 3kW split between the two inputs so that works for me. I'll be experimenting with the B300 MPPT. My observation has been that if the B300 charges up before the external DIY battery bank is fully charged then the AC300 decreases the solar input as it has no communication with the external DIY battery bank. I only came across this situation once so I'll try to replicate this situation within a few weeks depending on weather. If I add another solar input to the B300 MPPT then I'm thinking it'll charge up the B300 instead of sharing charge with the external DIY battery bank - but we'll see. You'd think it'd just redistribute but this is all unsupported usage.

So, after reading the above, is there a resource that talks about cable length and drain equalization definitively?

Something I was pondering was cutting the B300's cable, and making it the same length as the Vatrer (while preserving the data connection), hooking everyone to a bus bar, and then tapping directly from the bus bar.

Thoughts?

(I mostly want to cycle the batteries evenly and don't want to leave "energy on the table", so to speak. And, it's a learning opportunity!)
In my scenario I have 6xVatrer's and they're connected to bus bars with 1/0 cable. The conductors are roughly the same round-trip length per suggestion from @robbob2112 in https://diysolarforum.com/threads/looking-for-bus-bar-suggestions.93028/ Post #31. Under this configuration the Vatrer's generally stay close in charge although for some reason the far left battery has a slightly higher charge than the rest. For example if all the other batteries are at 75% the one on the far left will be somewhere at or between 77 - 80%. I think maybe the conductors may be slightly unequal due to various factors or the position on the bus bar - not sure but will revisit this at some point in the future.

I still have the stock P150D to P90D cable which uses (I believe) 6 AWG and is not rated for 150A @ 48V so I am cognizantt not to push the AC500 to far. At some point I'll be cutting open one of the extra cables I have to see if the 6 AWG can be replaced and still maintain the AC500 connector form factor.
 
Get YR-1035 meter and you can meassure the impedance of each set of cables. If the one leading/lagging is slightly higher than the others either take it apart and clean and bolt back down ...or cut the cable end off and put a new one on.... sounds like you have it very much under control though so I am not sure I would fiddle much.
 
My setup (1 B300, 2 Vatrer) tends to "drain" the B300 quicker than the Vatrer - I don't reach 100% often, and will have my B300 at 5% and Vatrer at 40% frequently.
With these percentages, are these the device reported state-of-charge percentages, or are you reporting the voltage on a voltage-charge curve? I never got out the multimeter, but noticed that the bluetooth reported battery voltages for my two B300s were usually nearly the same, even when the state-of-charge was reported differently for both.

Here’s an example of them reporting identical voltages over bluetooth, but claiming wildly different states of charge:

1734796111701.jpeg

I’m definitely not a battery expert, so I could be mistaken, but my understanding is that if the voltages are the same you’re probably fine?
 
I'm reading this and I'm getting very excited but I want to make sure I'm not reading into anything and need clarification. I have a completely "maxed out" bluetti ac300 setup. 2 ac300s connected in split phase and each ac300 has 4 b300s for a total of 8 b300s. I also have 2400 Watts of solar for each ac300 for a total of 4800 Watts.

So my first question is this. Can I connect other 48v batteries directly to the b300s to surpass the 4 max supported 12kWh for each ac300? I've read that someone tried to connect a 5th b300 and basically nothing happens. If I connected more 48v batteries directly to the b300s could I surpass the 12kWh capacity of each ac300? Would they charge and discharge? If so is there a limit to capacity?

Second question. If I'm reading correctly, I can connect an additional 200 Watts of pv input directly to each b300, effectively increasing my max solar input from 4800 Watts by an additional 1600 Watts by adding 200 Watts of pv input to each of the 8 b300s.

Am I correct or am I mistaken?
 
I'm reading this and I'm getting very excited but I want to make sure I'm not reading into anything and need clarification. I have a completely "maxed out" bluetti ac300 setup. 2 ac300s connected in split phase and each ac300 has 4 b300s for a total of 8 b300s. I also have 2400 Watts of solar for each ac300 for a total of 4800 Watts.

So my first question is this. Can I connect other 48v batteries directly to the b300s to surpass the 4 max supported b300s which is 12kWh for each ac300? I've read that someone tried to connect a 5th b300 and basically nothing happens. If I connected additional 48v batteries directly to the b300s could I surpass the 12kWh capacity of each ac300? Would they charge and discharge? If so is there a limit to total capacity?

Second question. If I'm reading correctly, I can connect an additional 200 Watts of pv input directly to each b300, effectively increasing my max solar input from 4800 Watts for both ac300s by an additional 1600 Watts by adding 200 Watts of pv input to each of the 8 b300s.

Am I correct or am I mistaken? On both questions?
 
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I'm reading this and I'm getting very excited but I want to make sure I'm not reading into anything and need clarification. I have a completely "maxed out" bluetti ac300 setup. 2 ac300s connected in split phase and each ac300 has 4 b300s for a total of 8 b300s. I also have 2400 Watts of solar for each ac300 for a total of 4800 Watts.

So my first question is this. Can I connect other 48v batteries directly to the b300s to surpass the 4 max supported 12kWh for each ac300? I've read that someone tried to connect a 5th b300 and basically nothing happens. If I connected more 48v batteries directly to the b300s could I surpass the 12kWh capacity of each ac300? Would they charge and discharge? If so is there a limit to capacity?

Second question. If I'm reading correctly, I can connect an additional 200 Watts of pv input directly to each b300, effectively increasing my max solar input from 4800 Watts by an additional 1600 Watts by adding 200 Watts of pv input to each of the 8 b300s.

Am I correct or am I mistaken?

I haven't tried it with all four b300s attached to one inverter unit, but I suspect it would work and you could expand the capacity as you suspected however it would not be detected on the AC300 unit and there's a little bit of guessing. I've been doing this for a few months now using one b300 as Kremer originally stated and I have six Vatrer batteries connected. The charging and discharging is not distributed evenly from my experience. Sometimes the b300 will charge up before the external batteries will charge and because the inverter unit detects that the b300 is full it will start to throttle down how much solar charging it will accept because it does not know the capacity of the external batteries. Overall the discharge does not appear congruent across all batteries (including the B300) and I have everything connected to bus bars so I'm not sure if I don't have it configured properly or that's just the behavior of using unsupported, external batteries. Maybe one of these days I can YouTube my findings.

It's still plenty more battery capacity at a lower cost per Ah while getting the same functionality of the AC300/500 units. You may be able to order additional external batteries and attach them as described in this thread and do some tests to see if you're reaching the expected capacity well beyond the 12 kWh that is offered using the 4*b300. If you're not seeing the expected output then you can just return the batteries.
 
Anybody have extra P090D they want to sell? I have the AC200Max and one B300. Would like to connect them together and add a few custom batteries to the system. Any help would be great. Thanks in advanced.
 
Do you still have the P90D cables?
Yes I do - 2 of them.

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