Dual MPPTs Alternating Charging. Never charge at the same time?

DIY
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1

I have a new RV that came with a Victron 30AMP MPPT and (2) 400watt solar panels. It had prep for (2) more panels, and a second MPPT. I got the dealer to add (2) more 400 watt panels and a second Victron 30AMP MPPT. System totals 800 watts of panels, 400watts through each controller, a Victron Shunt, and 400AH of LIFEPO4 batteries.

No matter what I do (networking the Shunt and 2 MPPTs together or NOT), the system only shows charging from ONE MPPT at a time. It alternates back and forth (around 20 seconds or so I would guess).

The lowest I have drawn the battery bank so far is 83%, and if it is in Bulk or Float (even fully charged) it still alternates between MPPTs.

This just seem wrong to me, and that I am getting zero benefit from buying double the solar that came with the RV, as it is only using 400 watts at a time.

Am I correct in this fear, OR, is this how the system is designed, and I am incorrect?

equip list 85 percent.PNG
equip list 85 percent.PNG1320×2868 268 KB

mppt settings
mppt settings1320×2868 359 KB

shunt settings
shunt settings1320×2868 344 KB

2

Several things spring to mind

  1. Is the charge voltage on the two MPPT different they have to be set exactly the same.
  2. 14.6v is high for LifePo4 should be 14.2v.
  3. Absorption time is to long should be 30mins
3

I believe you have a problem with your wiring from the MPPTs to the battery.

Is it possible that :

  1. The 2 MPPTs share one set of wires to the battery
  2. This wire has too much voltage drop, because too thin, bad contacts, circuit breaker or whatever ?
4

SOLVED! :slight_smile:

I ended up tracing all wiring, running each MPPT sperate with the other unplugged, etc. What I found was that the big solar disconnect switch in the RV, had BOTH sets of panels running through it. Meaning that the (2) 400watt arrays were joined, as well as joining the MPPTs.

I bypassed the switch for one panel array, and direct connected it for now (waiting on a second switch to ship).

Works like I felt it should now, with both MPPTs charging at the same time! :slight_smile: :slight_smile:

Thank you to those that replied.

cheers

5

Hi there Julian, thanks for your reply.

Yes the charge voltage is the same.

The 14.6 is also what Battle Born recommends for their batteries, as well as 30 mins per 100AH of capacity. I am open to changing the settings if there is advantages however. :slight_smile:

On another note, as per the reply to the main thread, I got it sorted. Installer had both arrays conencted through a single disconnect switch.

6

Just as a note, the Battle Born BMS will cut out on high voltage at 14.7, so in practice Battle Born actually recommends 14.4v.

7

Interesting re the voltage, I have always been led to believe that it’s better not to take LifePo4 cells hard up against the disconnect voltage as after a while it causes degradation. The same for the absorption time as once the cells reach 3.6v they are pretty much at 100% so holding them there doesn’t gain anything.
My system in the van is set at 14.2v and if I remember when it’s in storage I turn solar off when it gets to 97% turning it back on when I collect it.