I have 3 x Hubble am2 batteries.

Obviously 1 is set as the master and has the main comms to the Sunsynk inverter (8kw) and the other 2 batteries are connected via comms cables to each other.Now I dont expect the inverter to be able to read all the info from all 3 batteries.When I switch the the 2 slave batteries off then I get full comms and data from the master such as temp and accurate soc and voltages.

The issue I am finding is that the 3rd battery is discharging way quicker than the other 2 and when it got to the set shut down limit of 12%, it shutdown as it should BUT the other 2 batteries still had about 50% left but the whole system shut down.

Clearly the bms of the battery that shut down is doing its job which is good but I dont want my system to shutdown when i have plenty of juice left in the other 2 batteries.

I was wondering if I unplugged the comms cable from the battery that shutdown would it the isolate that low power state from the system, shutdown as per settings (bms doing its job correctly)and the other 2 batteries continue to supply power as they were at about the same soc/Voltage.The 3rd battery that shutdown first is the newest one and has had about a month to balance out.I dont see the harm in cutting comms from that battery as its bms will look after it and as long as the other 2 continue to supply power its fine.

Any thoughts?

2 minutes ago, Nicholas Strachan said:

Any thoughts?

Are the positive and negative paths of all three batteries to the inverter the same length?

12 minutes ago, frivan said:

Are the positive and negative paths of all three batteries to the inverter the same length?

Here is a pic of my set up.The battery  I am pointing at is the one that discharged first to the low state.It doesnt seem too far away.

Have you considered running a test where you make this new battery the master?

 

1 minute ago, Nicholas Strachan said:

Here is a pic of my set up.The battery  I am pointing at is the one that discharged first to the low state.It doesnt seem too far away.

Physical distance is not as important as the length of conductor and size of conductor that current has to flow through. As example, if one battery sees 1V more than the battery next door due to volt drop, there could be a 20% difference in SOC. Open up the conduit, draw and measure each battery cable.

2 minutes ago, zsde said:

Have you considered running a test where you make this new battery the master?

 

You mean by physically moving to where the master is now which is the one closest to the inverter or by simply connecting the  can etc cables to this one ,hence making it the master? I didnt think that this distance would make such a difference.I have switched off the other 2 batteries,unplugged the comms cable from the low state one which is now charging nicely off Eskom.

7 minutes ago, Nicholas Strachan said:

You mean by physically moving to where the master is now which is the one closest to the inverter or by simply connecting the  can etc cables

Perhaps do a test first where you just do the comms cable connections and dipswitch settings to make it the master and see if that makes a difference.

 

I think there might be a comms cable issue.

The main yellow can comm cable from the master to inverter was plugged in as were all the grey comms cables.I am using grid to charge the batteries and battery 2 and 3 were charging nicely but as soon as I switched on battery 1 (master) the charge rate dropped off dramatically.I then unplugged ALL comms cables and all 3 batteries charging fine.I am going to let the bms of all 3 batteries manage the charging.I have set a conservative 60 amp grid charge spread across all 3 batteries, let them fully charge up and then plug comms cables back in and see but I suspect its a comm cable issue.The bms of all should manage the charge etc.

So I did a test while the 3 batteries comms cables are all unplugged and grid charging at 60 amps.I plugged the yellow can bus cable back into the master and the telemetry was good.It showed that the master was being charged at 20 amps which makes sense as the 60 amp grid charge is spread across the 3 batteries. Interesting stuff.

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Edited May 1, 20233 yr by Bobster.