Bypassing the OBC on Precedent?

[Colbyntx]

I have a LV4800 automatic 25 amp charger. I bought for my project series cart with no OBC. I would like to try it on my 08 precedent 4X12. On the LVS site they have a 1 wire step for bypassing the OBC for charging. It doesn't state how large (ga) of wire should be used for the bypass. It also states once you splice the neg wire behind the charger recepticle, to run it to the neg post on the furtherest back battery on the drivers side, which I would call bat#2. The setup in the diagranm is a 6 battery system so I wanted to be sure in a 4 battery system. I know that the powerdrive II charge system is a good one but my 4X12's are on their last leg and I can't get a new set right now so I just wanted to see if this 25 amp charger will give my batteries a little more life. Here is the diagram.

Thanks

http://www.lvssales.com/ComputerInstructions.pdf