Best Battery Charger

[chad]

Here's the CTEK reply:

"HI

It’s always better to have one charger on each battery. Every time you charge the service battery through the relay from the starter battery, the two batteries will even out and the better charged battery will be “quick emptied” to the same level as the less charged battery.

The charger will not see this as two separate batteries. It’s the connection and disconnection that will harm the batteries in the long run.

I hope this will help"

I always thought that the leisure battery could not drain the starter battery - I think that I maybe should have explained the set up in more detail - sorry

 

[rlepecha]

That will happen anyway; as soon as the alternator kicks in and the voltage sensing relay closes the circuit when the voltage is above 13.3 volts the batteries will equalize.

It will not switch back until one of the battery voltages drops below 12.8v, hence both batteries would have balanced to 12.8v anyway because they have been connected together.
The only instance where this is not the case is when a large load is applied to one battery significantly reducing its voltage in a short period of time, I.e. the starter motor. The relay breaks the connection early enough to avoid discharging or pulling excessive current from the leisure battery.

If you have the simpler style of charge relay then this will not happen as long as the alternator can supply sufficient power to keep both batteries charged whilst running, if not both batteries will end up at a reduced state of charge/voltage.

My voltage sensing relay works both ways, so will close the circuit if the leisure battery reaches 13.3v and charge both batteries.
If one battery is significantly flat then the charger will build up the voltage in a special manner to try and restore the battery to its original state without loss of capacity. This will usually be at voltages less than 13.3 volts and therefore the relay will not complete the circuit until the battery is in the bulk or absorption charge cycle where it will absorb as much of the energy it can from the chargers output, I do not think it is relevant whether there are two batteries or one, they will only charge up to a certain point (i.e once at 14.4v they are pretty much 100%, and will only use the current/amps required to keep it there).. If two batteries are connected together all you have to do is ensure the charger is capable of supplying sufficient power to keep both batteries topped up, so say two batteries 50ah and 110ah; make sure the charger can adequately charge and maintain 160ah of capacity.
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