batteries discharge whist driving

We hav just purchased a 2013 Dorset. I noticed the vehicle battery showed 50% charge on the panel and did not charge over two 80 mile trips. The leisure battery di not charge either.
Been back to dealer who said vehicle batterry was no good and they replaced it. Both batteries charged on mains leisure sowed all light on panel and vehicle one green light.
After a 4 hour drive home, fridge on 12v and a break of around 1 hour fior lunch both batteris now show only 2 orange lights 50% charge.
1) could this be the split charge relay faulty so fridge is drawing from batteries?
2) is it a problem with the vehicle charge circiuts
3) is it a problem with the van charge curcuitry?

I am ringing dealer tomorrow but would like to be armed with a few ideas?
Thanks
Steve

PS we are new to campervan but have had caravans fir over 40 years and never had a problem

G8UZQ wrote:
1) could this be the split charge relay faulty so fridge is drawing from batteries?

If the split charge is working correctly, it ~should~ connect the two batteries together when the engine is running. The thing that stops the fridge drawing from both batteries is the fact that the alternator output is a higher voltage than both of the batteries.

So it may suggest that the alternator is not (for whatever reason) providing sufficient output.

Another possibility is a problem with the fridge relay, so that it is drawing current when the engine is not running (though you would expect eventually to end up with major flat battery issues in that case). Or possibly the control panel is not actually showing you an accurate reflection of actual battery charge levels.

We can speculate, but it really needs a methodical test process to work out what's happening.

Thank mojo, the fridge relay is possible as it was standing for I hour with 12v still selected. If it was the control panel not reflecting the actual charge I would still expect the levels to be the same if not higher after driving for 4 hours? When asking the dealer technician about solar panels when we collected the campervan he said just run the engin for 20mins and it will recharge the battery, I know this sounds opptermistic but if the caravan batterry was very low when on a rally we could connect to the car and run the engine to top up (pre solar panel days).

Appologies for spelling typing on ipad !

G8UZQ wrote:he said just run the engin for 20mins and it will recharge the battery,

I don't think he was speaking from experience there! In most conversions this is pretty much impossible, because the cable run from the alternator to the leisure battery is too long and too thin a gauge to fast charge the battery. Running for 20 mins should top up a depleted leisure battery a bit, but it certainly won't recharge it fully.

but would you expect the vehicle battery to be charged after a 31/2 hour drive?

G8UZQ wrote:but would you expect the vehicle battery to be charged after a 31/2 hour drive?

Yes, I would.