How does the leisure battery charge through alternator

[sharkjazz]

Have tried to find this information through search but couldn't find anything.

Van is 1988 Westfalia, no zig unit as I have seen mentioned in over threads, just a black box under the rear seat.

When I am driving, the alternator goes to the relay thing and then charges up the batteries. Will this top up the leisure and starter battery to full power, i.e. does it know how drained the batteries are and charges accordingly. Or will it only charge the batteries up, if power is being taken from them at that time? i.e. stereo on, so alternator puts the charge back in the stereo took out, but it will not put back the power the stereo took whilst the van was parked up?

Thus, eventually after a while, the batteries may be very empty and will need to be plugged into a charger overnight? If this is the case, is there anything I can buy / modify that will allow the lesiure battery to take additional charge whilst driving?

[kevtherev]

The battery with the least power will get the most amps when the engine is turned back on. All to do with the laws of electricity.
Once running the alternator powers all things in the van, not the battery.
Your starter batt will be isolated from the leisure loom, though I think westys have lighting on the starter (there's a fix for that), as soon as the engine stops

[Red Westie]

Once running the alternator powers all things in the van, not the battery

Well both.......which means there might not be much 'OVER' to charge the batteries (depending on the alternater fitted ie: 45/60 or if you're lucky 90 amp/hour).

Martin