Quick battery wiring question please

[Yeoman_24]

So, 3 batteries now for my boat. Battery 1 is starter battery.
I have wired my 2 new house batteries in parallel with the positive load (and alternator) on battery 2 and negative load (and alternator) on battery 3.
My question is, does it matter which of the house battery negatives my starter battery negative connects to?
Thanks

 

[VicS]

The same as the load and alternator negatives are connected to. ie battery 3

 

[Rhylsailer99]

I'm no expert but doesn't battery 1 need an alternator to charge the battery as it would eventually run flat.

 

[VicS]

More usual to connect the alternator to the starter battery and charge the house battery via a VSR or other similar split charge device

 

[ghostlymoron]

You need some way of isolating the two banks whilst allowing charging when necessary - either a manual switch or a relay.

 

[CapPugwash]

Your alternator and starter motor are probably connected together I expect? I think that's normal. Assuming it is then those connections, both positive and negative should connect to the stater battery. You would then have all the negatives connected together. All the positives on your house bank should be connected together. To charge your house bank from the alternator you need a switch (manual or VSR) to connect the positives of your house bank and starter battery. This also allows you to use your house bank to emergency start should your starter battery die. I recently fitted a Victron Cyrix-ct 12v / 24v 120A Voltage Sensitive Relay (Batt Combiner) to this end. You could use an isolation switch though.

So…

• Connect Alternator/Starter to starter battery (positive and negative)
• Connect all the negatives together
• Connect the House Bank positives together
• Fit a VSR/Isolation Switch between the House Bank and Starter positive terminals

Hope that helps

 

[Yeoman_24]

Thanks everyone