Might just be a mismatch between what the solar controller leaves the batteries at and what the mains charger sees when first turned on. I don't see much of a problem if the mains charger only goes in Boost mode for long enough to resolve the difference between the battery resting voltage and charger output voltage. It is normal operation for a charger to end absorption at about 13.8 volts and for the battery to drop back to around 12.6/8 after resting for a few hours. Have you measured the battery voltage before turning the mains charger to On?

If you do want to use the batteries when out on the road, you could consider more solar, at least another 200 Watt panel. It takes quite a lot to pump up a 260 Ah battery bank that has been drawn down a fair bit.

Iza

Thanks for the reply I will test the batts next time before turning the charger. I have another 80 at and will set that up as well. May get another 200 to mount as well. Should just have enough room. Did not think when a small amount is drawn a boost for 3 hours would be required Showing 1.7 Amp Input from monitor in van .charging 13. 7 volts. Bill

Trouble is sun is not out all day . So you need almost 100% more than you think to charge batteries . As said depends on 240v charger ? One of mine does that for a few minutes, assume after measuring volts , battery. condition it sets itself . Note it seems to do it more when fridge or some load .