jimmy_the_builder
Well-Known Member
Well, with apologies for all the helpful contributions, latest info is that the existing charger (I was going to say current charger, but I don't know if bjb is here to tell me off or not) is actually ok.
After a lot of digging around, the evidence is that the batteries have good capacity (they are only six months old), the charger is delivering 13.7V, but the domestic panel is showing a voltage that varies between 13.7V and about 12V depending on load.
The domestic panel is powered from the a heavy duty 12V switch box, which in turn is powered from the batteries.
Having checked all the voltages with a meter, it seems that voltage is being lost in the HD box, which looks like this:
You can see the domestic contactor clearly labelled; the bus bar it is connected to is fed from an isolation switch at the bottom of the box (you can see the two heavyish red cables and the two connecting studs). The other side of this switch is connected to the left busbar, which is connected to the batteries.
I found a voltage drop of about 1V across that isolation switch; I exercised it a few times and the voltage drop reduces to something less than 0.1V. (I tried shorting the switch out with a screwdriver and got the same tiny voltage drop, so that last <0.1V must be a loss somewhere else).
Here's a better view of the isolator switch:
And from the outside:
In practice this switch never gets switched off; it serves to disconnect the domestic and non-essential circuits from the service batteries, I guess so you can still use them to start the port engine in the event of some complex fault. However, I can't believe that this prob will solve itself so I need to replace it.
Apologies again for the slight timewastery elements of this thread. However, I do at least know what charger to buy when the time does eventually come.
After a lot of digging around, the evidence is that the batteries have good capacity (they are only six months old), the charger is delivering 13.7V, but the domestic panel is showing a voltage that varies between 13.7V and about 12V depending on load.
The domestic panel is powered from the a heavy duty 12V switch box, which in turn is powered from the batteries.
Having checked all the voltages with a meter, it seems that voltage is being lost in the HD box, which looks like this:
You can see the domestic contactor clearly labelled; the bus bar it is connected to is fed from an isolation switch at the bottom of the box (you can see the two heavyish red cables and the two connecting studs). The other side of this switch is connected to the left busbar, which is connected to the batteries.
I found a voltage drop of about 1V across that isolation switch; I exercised it a few times and the voltage drop reduces to something less than 0.1V. (I tried shorting the switch out with a screwdriver and got the same tiny voltage drop, so that last <0.1V must be a loss somewhere else).
Here's a better view of the isolator switch:
And from the outside:
In practice this switch never gets switched off; it serves to disconnect the domestic and non-essential circuits from the service batteries, I guess so you can still use them to start the port engine in the event of some complex fault. However, I can't believe that this prob will solve itself so I need to replace it.
Apologies again for the slight timewastery elements of this thread. However, I do at least know what charger to buy when the time does eventually come.
