Question about my onboard battery charger?

[Perithead]

The previous owner of my Montgomery 17 installed the ProSport 6 battery charger in the boat and it currently is hooked up to one deep cycle battery.

This particular charger says that it is made to charge one battery only, but I was wondering if I could hook two batteries up parrallel as one bank, having the charger actually hooked to one battery but the batteries be connected together as one?

The ProSport 6 is described as having - 1 output, 12v, 6amp capacity.
Here is a link to it if it helps.
Prosport Battery Chargers 6, 1 Output, 12v, 6a Capacity

I am hoping I can do this to try to avoid having to buy a second charger in the event I decide to install two batteries in the boat.....

[Stu Jackson]

Sure you can.

Two individual batteries connected together = one bank.

[peikenberry]

I agree. You can charge both at the same time if the batteries are paralleled. It will take a lot longer but the charger will automatically adjust the charging rate for the two batteries.

[hellosailor]

"one battery only, but I was wondering if I could hook two batteries up parrallel as one bank,"
Sure you can. Remember, a "battery" is a collection of CELLS. If you combine them in series, parallel, or series-parallel, it is still ONE BATTERY.
A battery bank is simply a collection (an ordered group or array) of cells that have been assembled into "sub" batteries within the bank, but as long as there's one big terminal at each end, that "bank" is still just one battery of cells. Same term, same usage, as a battery of cannon.

At 6A capacity, it may take longer to charge the two batteries. And if the batteries are of different age or condition, you may find one is under/over-charged as compared to the other, unless you charge them separately. But you certainly can try, those issues with combining batteries would apply regardless of the charger you used.

[HPLou]

If you install a second battery, you can also install a battery switch to charge Battery 1, Battery 2 or both batteries as well as for using the batteries separately or together in parallel.

[AJSquaredAway]

In deciding specifically how to hook up a second battery, what do you want it for? Additional overall capacity? Safety of a dedicated starting battery?