vsr with mains charging

[JimC]

When a vsr is used to direct the alternator's output, is it customary to also feed the output of an inbuilt mains charger via the vsr? On my boat when I replaced the diode splitter with a vsr I left the two output leads of the mains charger going straight to their respective batteries. They are separated by diodes within the body of the charger.

 

[RAI]

Depends on if you want to follow the vsr purpose of first charging one battery fast and then switching to all. So how long has the mains charger got and how many Amps can it provide compared to the batteries capacity?

 

[JimC]

The engine and domestic batteries are 55 and 125 a/h respectively. The mains charger is a Dolphin 10 amp "intelligent" charger. My purpose in having separate direct leads to the batteries was to make it easy to take the engine battery off charge when we are living aboard at the pontoon for days at a stretch. The domestic battery is getting heavily used with heater, lights etc. and the charger is working hard to supply it, but the engine battery is doing nothing.

 

[PaulRainbow]

The VSR is connect to each battery bank, it will close when the voltage of either bank reaches the setpoint of the VSR. Doesn't matter what the charging source is. So if you disconnect the mains charger from the engine battery the VSR will sense the voltage from the charger at the domestic bank and close, charging the engine battery too.

Unless the domestic bank are using a charging regime/voltages that would be too high for the engine battery there is no point in disconnecting it. It will sit at the same voltage as the domestic bank, but won't actually take any charge, unless it needs to do so. Just because you are living aboard and using powerwe it doesn't automatically mean that the charger will be charging the domestic bank either. The domestic bank can go into float and the charger can power the domestic loads, depending on the charger.

 

[PaulRainbow]

Depends on if you want to follow the vsr purpose of first charging one battery fast and then switching to all. So how long has the mains charger got and how many Amps can it provide compared to the batteries capacity?

That's not how a VSR works. It's a Voltage Sensing Relay, it will close when the voltage of either bank (assuming dual sensing) reaches the set point of the VSR. THis will usually be shortly after the charging source is present, not when one bank has been fully charged or fast charged.

 

[halcyon]

That's not how a VSR works. It's a Voltage Sensing Relay, it will close when the voltage of either bank (assuming dual sensing) reaches the set point of the VSR. THis will usually be shortly after the charging source is present, not when one bank has been fully charged or fast charged.

The last few years we have measured both the current and the voltage to decide when to close or open the relay. Back in 1985 we integrated with mains charger with the VSR, only put the engine battery on charge when the service battery charge was complete, and we call this progress ?

Brian

 

[Gixer]

If I understand what you’re asking correctly, I’ve just done this.
I have two batteries, engine and domestic. I have the alternator going to the engine and my 240v charger going to my domestic battery. They are both connected at the isolators by a VSR, seems to work perfectly.

 

[RAI]

The engine and domestic batteries are 55 and 125 a/h respectively. The mains charger is a Dolphin 10 amp "intelligent" charger. My purpose in having separate direct leads to the batteries was to make it easy to take the engine battery off charge when we are living aboard at the pontoon for days at a stretch. The domestic battery is getting heavily used with heater, lights etc. and the charger is working hard to supply it, but the engine battery is doing nothing.

Some chargers have separate outputs for engine and domestic batteries, which would be better than a vsr in your case.
Your 10 amp charger is not much for keeping up with live aboard domestic loads these days, so I can see that the domestic battery could be pulled down during the day and recharged at night.
Do you know at what voltage your vsr switches? If it's at 13.6 volts, it will switch when the directly connected battery is fairly full.
If that is your domestic battery, in your situation, the engine battery would be isolated from the domestic by the vsr if the charger can't keep up with load.
Do you have volt meters on your batteries or can you take voltage measurements during the daily cycle?