Charging my Kingham batteries

With the onset of cold weather I have decided to boost my Kingham batteries (x2 leisure and the main vehicle)  by plugging in to the house mains for a few hours each evening with nothing else running. The readings  the past day or two have been around 65/70% prior to charging and yet after 6 hours or so charging I only achieve around 88/90%. I would have thought it would have reached the maximum (100%)  in that time...does this appear low or slow to others on here please?

Leave the charger on 24 hrs at least. Assuming it is 'intelligent' three stage charger.

When charging batteries, the charge rate diminishes as the batteries are charged.

So by the time you get to nearly charged the amps going in will be very low.

The last 10% will take a lot longer than the previous 30%

Think of a battery as a bucket that you are filling with a hose and you want to get in as much as possible without it overflowing.
At the beginning you can fill very fast but as the bucket fills you have to reduce the flow until it is almost stopped.

Batteries control charging not chargers.

If you have an ammeter, with batteries on charge, when it reads one percent of the battery capacity and the voltage is at its maximum then the batteries are charged.

or

charge until the amps going in are static (not reducing) for at least one hour.

Amp.hr meter, state of charge meters are totally inaccurate.
Unless re-synced with the batteries actual capacity. Batteries lose capacity as they age and used.

All above is generic and not just specific to your vehicle.

Many many thanks KeithM for your helpful reply