Trickle charge from solar/battery pack?

In my box trailer i have:
1 x 100w solar panel charging a bank of 4 x 80amp hr batterys (sealed deep cyc).
1 x 80a/h Waeco thumper pack charging as well.

All this runs 12v fridge, accessories, and lighting. It also has an inverter and generator for emergencies.

Hypothetical question. (Pro's and cons please)

Where the bikes sit in the trailer I am thinking of running a maintenance trickle charge points from above to the bike batterys.

Can I run directly in parallel to the battery bank or thumper pack?

Is it better to run from the solar regulator outlet through the fuse panel utilising the existing light circuits?

Do I need a proper battery charging unit?

Dedicated 10w panel/reg?

Thanks

If you've got the room, install a second solar panel (20 watt) and run it through it's own reg. as you said. Then just parallel the bike batteries whenever they need charging. This way both systems are completely isolated from each other. The existing solar panel has already got a lot to do, especially if your using the fridge, accessories etc...a fair bit. You don't want to load it up further. Otherwise there are auxillary charging devices( VSR's and the like) on the market that you can tie the two banks together with, but these can slow charging times and cause other problems and also, you don't want to tie different types of batteries and different ages of batteries together for prolonged periods.

Thanks Craig.

20w setup will cost little, even cheaper than a good charger I suspect.
Yeah 2 different types of batterys was my concern, this way will be safer.