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jeffwi avatar image
jeffwi asked

2 MPPT controllers into 3 batteries in parallel

I have 2x 150x45 MPPT controllers connected to my 3x24V Batteries wired in parallel. I had this done for me, and since I'm about to replace the batteries I'm looking at the wiring and it does not look correct. I would have expected the MPPT connections to both be wired to the shunt....but they are not they are wired directly to the batteries with the positive and negative connections spread across the 3 battery sets. Is this correct? Why are they not wired to the shunts?

MPPT Controllers
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seb71 avatar image
seb71 answered ·

You are right, from your description the wiring is not correct.

But to be sure, make a wiring diagram or some photos.

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jeffwi avatar image jeffwi commented ·

mppt-connections.jpg

Hope this makes sense. Why are the MPPTs not going right to the shunt connections at the top?

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mppt-connections.jpg (30.7 KiB)
Michelle Konzack avatar image Michelle Konzack jeffwi commented ·
If they are connected this way, you can get a nice imbalance in the batteries, especially with the high current from the MPPTs


The MPPTs should be connected to the shunt and alo the eires from the batteries to the shunt should have the same lenght.


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jeffwi avatar image jeffwi Michelle Konzack commented ·
I suspected that. I recall the installer said something about having a problem when they connected themn to the shunt and were told to do them this way......could this have something to do with the chargers conflicting with each other?
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Michelle Konzack avatar image Michelle Konzack jeffwi commented ·
Since you have not the CAN version of the MPPTs, which syncronise the output voltage, it minght be, that in absorbtion, just before the batteries are full, one charger switch to float while the second is still charging in absorbtion.


But i think, this is only a minor issue


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seb71 avatar image
seb71 answered ·

Use busbars. One positive busbars and two negative busbars (one for battery negative and one for MPPTs, inverter, loads). The shunt will be placed between the two negative busbars.



Positive busbar:


 MPPT1 (+)   MPPT2 (+)
   |           |
  FUSE        FUSE
___|___________|______________________________________________________  ( + )
       |                |             |             |
      FUSE             FUSE         FUSE           FUSE
       |                |             |             |
     SHUNT (+)       BATTERY1 (+)  BATTERY2 (+)  BATTERY3 (+)


You can add battery disconnect switches.

Or, if using NH fuses for the battery fuses, there are NH fuse holders which also double as a disconnect switch.



Negative busbars:


MPPT1 (-)   MPPT2 (-)
___|_________|_________ SHUNT__________________________________________  ( - )
                                 |               |              |
                              BATTERY3 (-)    BATTERY2 (-)   BATTERY1 (-)


Connect each battery to the busbar, using a fuse on each positive wire.

All battery positive wires should be equal length.

All negative battery wires should be equal length.

If you only have one battery, you don't need the second negative busbar. You connect the negative wire from the battery dirrectly to the SmartShunt (on "Battery" side).


Connect all MPPT, inverters, any other loads to the positive busbar using fuses and to the second negative busbar (the one on the "System"/ "load" side of the SmartShunt).


All wires should be the sized for the maximum current they are supposed to carry.

All fuses should be sized to protect that wire (so the fuse should burn before the current is too high for that wire).

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seb71 avatar image
seb71 answered ·

Also, if those MPPTs are SmartSolar (with buit-in Bluetooth), you can use VE.Smart Networking for the 2 MPPTs and the SmartShunt.

Details here:
https://www.victronenergy.com/media/pg/VE.Smart_Networking/en/index-en.html

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jeffwi avatar image jeffwi commented ·
That is excellent! They are already networked together. I will connect to the shunt. Thanks so much.

Jeff

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