Connections Between House and Starter Batteries?

Question:

We have three supposedly separate battery banks on our catamaran. One house and two starting. Why is it that I can connect a load to a starter battery positive and the house battery negative and it works? Aren't these two different power sources? Which battery bank would be getting discharged? - Ray

Answer:

Great question, it's absolutely normal for all battery negatives to be common and non-isolated. The behavior you indicated below is to be expected.- Jeff

House Battery + Starter Battery + 2 Battery Monitor Shunts?

Video
House Battery + Starter Battery + 2 Battery Monitor Shunts?

I Am Adding a Second Battery, Should I Use a Battery Combiner or a Battery Isolator?

Video
I Am Adding a Second Battery, Should I Use a Battery Combiner or a Battery Isolator?

Battery Charging Redundancy with a Battery Isolator

Video
Battery Charging Redundancy with a Battery Isolator

If I Have Three Battery Banks Do I Need Three Battery Monitors?

Video
If I Have Three Battery Banks Do I Need Three Battery Monitors?

My Battery Charger Has Three Outputs, Can I Connect Them All to One Battery to Charge Faster?

Video
My Battery Charger Has Three Outputs, Can I Connect Them All to One Battery to Charge Faster?

Can I Use One Alternator to Charge an Flooded Lead Acid Starter Battery and an AGM House Battery?

Video
Can I Use One Alternator to Charge an Flooded Lead Acid Starter Battery and an AGM House Battery?

How to Charge a Lithium Battery House Bank and an AGM Starter Battery at the Same Time?

Video
How to Charge a Lithium Battery House Bank and an AGM Starter Battery at the Same Time?

Why You Can't Use a Starter Battery as a Deep Cycle House Battery?

Video
Why You Can't Use a Starter Battery as a Deep Cycle House Battery?

Can You Explain Battery Capacity and Battery Voltage?

Video
Can You Explain Battery Capacity and Battery Voltage?

The Role of a BMS (Battery Management System) in A Lithium Battery Bank On My Boat

Video
The Role of a BMS (Battery Management System) in A Lithium Battery Bank On My Boat

Should My Battery Isolator Have Diodes or FETS?

Video
Should My Battery Isolator Have Diodes or FETS?

How Do I Charge The Generator Battery on My Boat?

Video
How Do I Charge The Generator Battery on My Boat?

What Is the SI Post for on an SI-ACR Battery Combiner?

Video
What Is the SI Post for on an SI-ACR Battery Combiner?

IT ISN'T BROKEN! Why Your Battery Monitor Is Not Wrong! PYS Tech Talk

Video
IT ISN'T BROKEN! Why Your Battery Monitor Is Not Wrong! PYS Tech Talk

How Do I Charge a Lithium House Bank and a Lead Acid Starter Battery With My Alternator?

Video
How Do I Charge a Lithium House Bank and a Lead Acid Starter Battery With My Alternator?

Using A Battery Switch While the Boat is Running - Good or Bad?

Video
Using A Battery Switch While the Boat is Running - Good or Bad?

How to Monitor Lithium Battery State of Charge Without Bluetooth

Video
How to Monitor Lithium Battery State of Charge Without Bluetooth

Does a Battery Combiner Draw Current When No Charge Is Present?

Video
Does a Battery Combiner Draw Current When No Charge Is Present?

What Is the Depth of Discharge for My AGM Battery?

Video
What Is the Depth of Discharge for My AGM Battery?

I Purchased a 3-Output Battery Isolator but I Only Need 2 Outputs - Can I Leave One Unwired?

Video
I Purchased a 3-Output Battery Isolator but I Only Need 2 Outputs - Can I Leave One Unwired?