Adding DIY battery to Bluetti AC300

Hey guys I have been looking into adding an additional pack to a Bluetti but they make it hard and seem to want you to buy theirs for some reason haha.

I don't own it but my grandfather in California bought one for all the brown out and grid outages they've have in recent years. I live across the country so I've been researching it on my own and can't seem to find much on anyone adding their own batteries to them. Which makes sense, if you could build the battery you could build the all in one equivalent.

My main hang up is the connectors. The AC300 is 48V so I figure I can tie the battery in through the P090D connector (two in right side of picture) that the Bluetti batteries plug into. Problem is that appears to be a fancy overpriced cable that a P090D to XT90 goes for $100 and is really right at the edge of supporting the 4000W continuous the unit can draw. I probably wouldn't be able to get it to talk to the Bluetti using that pre made cable and with a Bluetooth BMS I'm not worried about that. Just need to get the juice into the unit.

My other option is to tie in through the PV input as the input voltage can be 35-110V (middle plug on left side of picture). That appears to be a more standard plug and while it can only input like 2000W that should be more than enough to support his minimal loads in a blackout.

I thought the one unit could do split phase and it can, if you buy a second but he's on a limited budget to pull this off so I'm looking into an autotransformer next but should figure out how to hook up the batteries that I'm trying to buy right now first haha.

TLDR Has anyone bought a Bluetti but made a battery and have links to the cables? My grandfather is measuring things for me but didn't have calipers.

Thank you guys for the knowledge that got me this far!

I Been wanting to do the same thing.

I'm really close to trying the same thing. The ports are clearly straight DC bus voltage. My plan is to buy a factory battery cable, cut it in half and extend to a 100ah rackmount pack.

Kremer said:

I'm really close to trying the same thing. The ports are clearly straight DC bus voltage. My plan is to buy a factory battery cable, cut it in half and extend to a 100ah rackmount pack.

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So I just did this last night... It WORKS PERFECTLY! It charges and discharges with the main unit and shares draw and charge amps in parallel with the OEM battery, just like you would think it should. You just need to have at least one B300 attached so the head unit has a BMS to talk to and keep happy. Same thing should work just fine with the AC500 also.

Kremer said:

So I just did this last night... It WORKS PERFECTLY! It charges and discharges with the main unit and shares draw and charge amps in parallel with the OEM battery, just like you would think it should. You just need to have at least one B300 attached so the head unit has a BMS to talk to and keep happy. Same thing should work just fine with the AC500 also.

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Nice! Any pics/vid of the process?

Kremer said:

So I just did this last night... It WORKS PERFECTLY! It charges and discharges with the main unit and shares draw and charge amps in parallel with the OEM battery, just like you would think it should. You just need to have at least one B300 attached so the head unit has a BMS to talk to and keep happy. Same thing should work just fine with the AC500 also.

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Come on. Don't leave us hanging. Lol..
I would like to do the same thing. I have 2 12v 100ah Hybrid deep cycle gel batteries. Can I do the same or I need LiFePo4 batteries?

Tiger2380 said:

Come on. Don't leave us hanging. Lol..
I would like to do the same thing. I have 2 12v 100ah Hybrid deep cycle gel batteries. Can I do the same or I need LiFePo4 batteries?

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I don't think I would try it with lead acid. It really should be 16S LiFePO4 matching the B300 or B300S OEM battery. I have only tried it so far as a proof of concept, not a permanently wired up thing.

Kremer said:

I don't think I would try it with lead acid. It really should be 16S LiFePO4 matching the B300 or B300S OEM battery. I have only tried it so far as a proof of concept, not a permanently wired up thing.

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I'm a subscriber to your YouTube channel. I would love to see you do a video discussing this in details.

Thanks

Tiger2380 said:

I'm a subscriber to your YouTube channel. I would love to see you do a video discussing this in details.

Thanks

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Thank you for that. They have been pretty good to me so far and I think I would be disowned if I made that video. Maybe in the future.

Kremer said:

I'm really close to trying the same thing. The ports are clearly straight DC bus voltage. My plan is to buy a factory battery cable, cut it in half and extend to a 100ah rackmount pack.

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How did you manage to buy the factory cable? I haven't been able to find it anywhere.

billvon said:

How did you manage to buy the factory cable? I haven't been able to find it anywhere.

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I bought the P90D to P150D adapter cable for my testing. One end connects to the AC300/B300, the other end an AC500/B300S.

Sorry just turned notifications back on after having them off when it was requested before. I see there has been some progress on the front though.

Are you able to ohm out the plug and see which pins corresponds to the positive and negative side of the battery? I'm guessing this plug only uses the two main pins but just did a little more googling and couldn't find any other non OEM sources for the cable. $160 on AliExpress and $100 on Amazon is a little steep but still probably cheaper than buying one of Bluettis prebuilt batteries.

Kremer said:

I don't think I would try it with lead acid. It really should be 16S LiFePO4 matching the B300 or B300S OEM battery. I have only tried it so far as a proof of concept, not a permanently wired up thing.

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I find your your proof of concept very interesting and congrat Kremer! Do you recall if the display/app showing your new connected bat pack with capacity level status?

jtran69 said:

I find your your proof of concept very interesting and congrat Kremer! Do you recall if the display/app showing your new connected bat pack with capacity level status?

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The AC300 does not know the external pack is there, there is no BMS/computer connection, only the power leads. It properly shows the B300 battery, which is same voltage and being augmented with the external in parallel, in theory they are all at the same charge level.

I have the P90D to P150D adapter cable, ECO-Worthy 48V 50AH lifepo4 16S ready to test with my AC300-B300.
@Kremer , Does it matter if the ECO pack is connected to the AC300 or B300?

jtran69 said:

I have the P90D to P150D adapter cable, ECO-Worthy 48V 50AH lifepo4 16S ready to test with my AC300-B300.
@Kremer , Does it matter if the ECO pack is connected to the AC300 or B300?

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No. Make sure the voltages match very closely, like +/- 0.2V. Be EXTREMELY careful, you are dealing with hundreds of amps of available current.

Thank you @Kremer to be first brave man to test if third party battery can work with Bluetti AC300. Now I'm after connecting 5kWh Fogstar battery to my AC300 and looks like this solution working well.

Hi Kremer,
Attached pics are the eco-worthy battery spec and the 4gauge wire crimped to the Bluetti cable, I hope that the max charge/discharge of 50A would work well. Also I have a 200A fuse attached, not sure what is the more proper size for this setup?
Any safety suggestions would be much appreciated! Thank you

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I’ve tested 2 cases in the evening, hence no Solar charging.

Case1. While the AC 300 B300 are OFF, connecting the ECO battery to either battery port would cause the AC 300 to turn itself ON with the beeping alarm msg attached.

Case2. With the ac300 and the b300 idling, connecting the ECO Battery did not cause any alarm. I tested some ac loads without any issue for a few minutes.
I plan to test with daylight next.

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jtran69 said:

I’ve tested 2 cases in the evening, hence no Solar charging.

Case1. While the AC 300 B300 are OFF, connecting the ECO battery to either battery port would cause the AC 300 to turn itself ON with the beeping alarm msg attached.

Case2. With the ac300 and the b300 idling, connecting the ECO Battery did not cause any alarm. I tested some ac loads without any issue for a few minutes.
I plan to test with daylight next.

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Yes, read post 4 of this thread. The AC300 NEEDS a B300 to talk to. The B300 and its BMS aren't an optional accessory, at least one attached is mandatory to have the AC300 work.

Kremer said:

Yes, read post 4 of this thread. The AC300 NEEDS a B300 to talk to. The B300 and its BMS aren't an optional accessory, at least one attached is mandatory to have the AC300 work.

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That really is a bummer, because I found an AC300 on eBay for $750 and I wanted to play around with it but came to that conclusion myself, that you need to have the B300 before it will let you use it at all.

Which makes sense, but I was hoping to trick it to be able to use some of its functionality before I could afford to get the battery that went along with it.

I almost bought it anyways, because that was such a good price.

The AC300 is still sitting there on eBay for sale if anyone wanted to snag it up.

After a few days of running with the added ECO battery, it seems to work very well just like Kremer said. Adding more loads to the AC300 on a good solar day, it can generate more than 15kWh, amazing. I plan to add more ECO LFP and maybe a 2nd AC300 for split phase capability if I see a good deal.

jtran69 said:

After a few days of running with the added ECO battery, it seems to work very well just like Kremer said. Adding more loads to the AC300 on a good solar day, it can generate more than 15kW, amazing.

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It’s a beautiful thing isn’t it. On a good day I can make and store 10kWh with my 1600W of panels.

My set up AC300+B300+Fogstar 5kWh battery working nicely. I had just one unexpected drop from 20% to 0%. Probably Bluetti BMS lost calibration. 8kWh storage is good amount for my conservatory 1.5kW solar panels. No longer worrying if we have enough energy, when cooking dinner or washing clothes.

I am thinking about doing this, but am wondering about the cable. Do I need a P090D To P150D and then I cut the P150D end for connection to a third party battery? What about the locking mechanism on the cable I thought the cable doesn't work without the lock engaged? Are you locking the B300/AC300 side only or are you keeping the connector on and engaging the lock while exposing and rerouting the positive and negative wires to the third party battery.

Is the AC300 able to monitor the capacity of the system using a third party battery? Does it try and guess at a capacity based on the voltage using a profile for the B300 battery? I guess it tries to balance the batteries similarly to how multiple expansion batteries work to keep the voltages similar.

@Zedart I am also in the UK and have been keeping my eye on the Fogstar 48V server rack battery is it working well, and are you able to charge it from the B300 at 10A and discharge at the full 3000 Watts?