Battery linking

Always pays to check first. See if they will take it back and get one the same as the one you have then hook em up

Wet cell and Gel use different charge settings on your battery charger !!

I also would return it and get another AGM replacement (NOT Gel)

Maybe get a refund and go to a decent "battery place" for correct information!

Mainey . . .

I would get another Gel battery to parallel with the one in the van because the reason that they used that type in the first place is that they are a "deep cycle" battery that can supply a decent current flow to power the vans electricals for longer than a lead acid (wet) battery and the gel battery can do this right up until it is discharged. In comparison a wet battery gradually puts out less current flow over time as it goes from fully charged to discharged and is designed more for situations where it is being charged at the same time it is powering appliances such as in a car, boat, etc. Re the charging settings speak to good auto lekky or look on some websites for batteries or maybe do a Googler search. Both types of batteries can be charged by your car but if not set up properly one may become charged more than the otherbeacuse electrical current flow is just like water flow in that it takes the line of least resistance