How do you know when your parallel battery has a problem?

[danlhayes]

I am considering installing two parallel Redodo 12V 410AH batteries in my RV, along with a Victron Multiplus, current shunt, etc. These batteries have BMS's but do not communicate to the outside world.
I am concerned with what will happen if one of the batteries has a problem. Specifically, if one battery's BMS shuts it down for some reason. How would I even know this had happened? It seems to me that I might go a long time without noticing anything unless I were to go below 50% SOC, which with only one live battery would result in a dead battery and a problem that might be hard to diagnose. And then, even if you were able to determine that one battery was dead, you wouldn't really know why, right?
Is this a realistic scenario? It seems like people commonly use configurations like this, so it must not be a likely issue?

 

[RCinFLA]

It is good to put a current shunt on each battery to check current sharing between batteries.

If you have an overall common monitor you can just put simple current measurement shunts on each battery.

 

[TacomaJoe]

I have 3 in parallel but in my case I have Bluetooth communication with each of the BMSs. To your question, you don't know if one of your batteries fell off the earth. I like the idea of shunt on each of them, nothing expensive, a couple of $40 shunts will give you simple feedback.