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Dc step up

Jake8890

Aug 17, 2023
1
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Aug 17, 2023
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Hi forum,

A Friend of mine gave me a 3000watt 230VAC (Growatt SPF3000) island inverter with a lion 4kwh battery. I mounted this set into my rv.
This inverter has 2 mppt inputs. To one of these inputs i connected 4pc 420wp solar panels
and on the other input i try to connect the rv's alternator who can supply 14VDC/120A so that the battery charges whils driving even if there is no sunlight.

The mppt requires a 75voc to start (datasheet says 65v but i think that is 65vcc) Now i am trying to boost up the 14vdc alternator voltage to 75vdc in order to feed the mppt with 5amps/375watt, this will draw 30amps at the dc step up IN. Offcourse i dont want to blow up the dc step up's capacitors due to time constant mppt v/s capacitors and also the mosfets becouse of the high current draw.

But maybe i see it wrong and there is a better solution. I was thinking about 2 dc step ups wired parallel to curb the currents.
 

kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
Is this a 24V or 48V unit? Sounds like the 48V version going by your figures????

In which case this might sound daft but you should just use an ordinary inverter on your alternator/RV battery and apply the AC output to the 'grid' input of the Growatt unit.

But if you do this you already have an inverter - so do away with the Growatt unit....... and use an MPPT charger for your solar-to-battery!

The fact that the unit you have is meant to be used with a 24/48V battery bank is the 'killer' - making the interfacing of it too complicated or, at least, more troublesome than using a straight inverter and separate MPPT unit.

There are such things as 'boost converters' though but these tend to be limited in capacity to around 500W (pushed to their limit and I wouldn't trust them at that level anyway - stick to <300W max)
 

Bluejets

Oct 5, 2014
7,043
Joined
Oct 5, 2014
Messages
7,043
datasheet says 65v b
Can you supply the data sheet you refer to and a wiring diagram of your setup.
We do not have a need to go searching all over for it or second guessing how you want to connect everything.
 
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