Hello Everybody,
@BLUETTI @Derceto @Raymondjram
I am curious if I can add an MPPT from my solar panels to a B300S?
I am changing things around for my current expansion project and have 2 x 550w in series so my voltage is too high (VOC 97V). Yes, I know I can split the two panels to two B300S and utilize the MPPT built into the B300S, however, I am trying to avoid running additional cables and needing to unscrew and disconnect the 550W panels. If I put in the 3rd party MPPT, I can have the 48V battery out plugged into one B300S and the 8A DC out of the MPPT to another MPPT.
So my question, is it ok to add the 3rd party MPPT inline and will it interfere with the built in MPPT in the B300S?
As long as there is enough solar power, will the max power into the B300S be about 480W (10A x 48V)?
(There is a max DC Load out of the 3rd party mppt which will be 8A x 12VDC (maybe 24VDC) <–need to research.
Thank you,
Will
In theory, yes, you can. A MPPT (maximum power point transfer) is a series voltage regulator and converter, and can boost (increase) or buck (decresase) the output voltages in relation to the input.
So if your 3rd party MPPT can convert the 97 V down to 48 V, give it a try.
Thanks @Raymondjram ,
I just hope that it won’t work against the one built into the B300S, but I guess it wouldn’t be any different than the Bluetti’s D300S but down to 48V. Now to find an economical mppt, wish they had one with 2 battery bank outputs, currently my only choice is the DC load out which is limited to 8 amps (wonder if the mppt DC Load could be at least set to 24VDC out instead of 12V -192W vs 98W). I keep getting incorrect search results (even with AI search) for Dual battery bank outputs.
Will
The B300/B300S 8A DC adapter input is protected by a diode and that only allow energy to flow inward.
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The duty of an MPPT controller is also to regulate DC output based on battery voltage so the controller will not power on if it will not sense a battery. And this cannot work on the DC input of the B300S as it will not provide power to the MPPT controller to be detected. That is because a DC input is not a battery.
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To charge the B300S by using its DC adapter input you should use a power adapter that provides a linear voltage higher than battery voltage. The original adapter provides about 58.8 V DC to make sure energy will flow inward until battery will reach EoC.
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If you would like to make use of your 97 VoC array to charge the B300S your only option would be to use a DC/DC buck converter to lower the voltage to under 60V and then feeding it to the 12-60 V 10 A PV input.
But, as a personal note: this is very inefficient since your PV power will be converted 2 times and will be probably zero on low voltage ranges (since your buck is not a boost). I would go to the roof and rewire the 2 panels in parallel instead or run new wires. 
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As a last note: please consider you should never connect 1 source to 2 batteries since that will create a loop. An MPPT controller can only work being connected to a solar array alone. Two MPPT controllers cannot share the same wires to the same PV array in parallel.
thank you @ndwr,
I thought that there would be a communication mismatch with the inline mppt and the B300 mppt. However, I thought that today’s mppts would be able to be set to provide a constant “set” output IF the battery needed to be charged, and yes a buck converter came to thought and that would be a waste. Just note there is a Victron solar controller that has DUAL battery bank outputs (e.g. for varying battery types) with one solar array input, but unfortunately it’s just 12/24 V batteries not 48V batteries.
I figured that I would need to disconnect the 2 panels, and rewire. So that part will need to wait until the knee injury recovers.
Thank you for the input.
Will
Theoretically it won’t. But the voltage below 30V will limit the current to 8.2A, and the charging power is not that high. It’s better to have the one with 48V output.