I have two MP2 setup as split phase. Also have a cerbo gx, 4 smartshunts of which 3 set up as DC meters and connected to my Solar charge controllers (non-Victron), 1 set up as battery monitor between some loads and battery bank. I always have to manually set the battery monitor to 100% SOC charge. Problem is that the SOC keeps reducing as loads draw on the battery and never goes up or back to 100% even when batteries are fully charged several times over. The reason for this is the requirement for tail current to be at certain level for certain time before a battery monitor synchronization to 100% SOC. However my battery monitor only sees load going through it and not charge current because all charging goes through the other 3 smart-shunts set up as DC meters. I would have thought since they all connected to the cerbo, they should be able to speak to each other and the battery monitor can see charging and tail current from the other shunts set up as DC meters. Unfortunately it wrongly assumes that since it sees no charge current on the battery monitor, only loads, it reduces the SOC continuous based on this load it sees till it gets to zero and the system shuts down from low SOC even with a full battery bank! I have to alway manually set it to 100% to prevent this which is exhausting. Even more surprising is that voltage is read by the same battery monitor to be full at 57.6V but system shuts down regardless from low SOC. I have disabled alarm for SOC on the shunt itself but since battery monitor on remote console is set to automatic, it selects the shunt for this so it still sees the SOC from the shunts and shuts down the system based on low value.
Two questions:
if there a way to tell the cerbo or MP2 (not sure which one does the actual work of shutting down the system) to ignore the SOC from the battery monitor?
Alternatively can how can I get the battery monitor to use the charge or tail current from the other shunts set up as DC meters to synchronize SOc to 100% when battery fully charged.
You can do neither 1 or 2 because your system is set up wrong and not how it is expected. I have all Victron chargers with current monitoring built in but the charge current still goes through the battery monitoring shunt. You must connect the negative leads from your MPPTs to the system negative side of the shunt. See the FAQ I wrote about this.
Thanks a ton for your very clear explanations of what I was doing wrong. Now I understand why the charge current is not coming through. However the recommended solution to run all DC loads and chargers through the battery monitor will just not work for me. My PV array is really large and running all through the battery monitor will mean cable sizing at a scale that is not just easily available and super expensive.
In the meantime I found a workaround by specifying my MP2 as battery monitor which rids it of the SOC from the monitor. And also simply making the measurements from the smart shunt visible in VRM. I see all the parameters I want from the shunt including the SOC but since it’s disabled in the shunt, it longer shuts down my system even when down to 0%.
I will live with this for now. Redesigning to pass all through the monitor would be a humongous and expensive project for me. Nonetheless thanks ever so much for the clarity you brought to bear on this. Extremely useful!!!
Needed cable size is not only a function of maximum current it needs to carry, but also of the length of the cable.
Is your PV array + chargers really able to deliver more A peak (in worst case situation of maximum irradiation and freezing cold) than the SmartShunt can handle?
If not you could simply set up the shunt to the battery negative and the other side of it to a main negative bus bar, with as short as feasible cabling.
Direct consumption would then also flow through this bus bar (as it does now through your common connection point on the battery negative), instead of going through the battery connection point and the SmartShunt.
