Shorepower connected to battery banks

[Gryphon2]

My boat has an engine start battery and a bank of 3 for domestic use. The shorepower unit is connected to both with what looks like a voltage sensitive relay between them.
Is this a normal way to wire things up? I don't much like the 2 being joined together and have routed the charger so it only charges the domestic batteries on the basis that the engine battery will get enough charge from starting the engine occasionally.Advice welcomed!

 

[ShinyShoe]

I'm no expert on normal but I'd say it is abnormal to not want your engine battery to be fully charged at all times. When the brown stuff hits the fan you need the engine to work when you press start not decide the battery is too low...

If the house doesn't work it is unlikely to sink you. If the engine doesn't start just as you are needing it for some tight manoeuvres it might.

The VSR should presumably ensure the engine is topped up and then sort the house? What is not to like?

 

[maby]

The device between the two battery banks is usually a diode splitter and is perfectly safe. It will slightly reduce the maximum charge voltage of the batteries, but the charger/alternator can be configured to compensate for that.

 

[Gryphon2]

Not a diode splitter. I have one of those between the alternator and the batteries but the shorepower goes direct to the batteries.

I have never had starting problems and the shorepower would only help if i was sat in a marina .....so nothing to hit any fans!

 

[PaulRainbow]

The device between the two battery banks is usually a diode splitter and is perfectly safe. It will slightly reduce the maximum charge voltage of the batteries, but the charger/alternator can be configured to compensate for that.

Huh ?

How do you work that out ?

A VSR is connected between the batteries, a diode is connected between the alternator and each battery.

Also, how are you going to configure an alternator to compensate for voltage drop ?

 

[PaulRainbow]

Not a diode splitter. I have one of those between the alternator and the batteries but the shorepower goes direct to the batteries.

I have never had starting problems and the shorepower would only help if i was sat in a marina .....so nothing to hit any fans!

You need to carefully identify what you have and where/how it's wired. If there is a diode and a VSR, you would do well to remove the diode, connect the alternator to the start battery, the mains charger to both banks and leave the VSR in place. This will allow the mains charger to charge all batteries, whilst the alternator also charges all batteries, without the voltage drop from the diode.