VX20 battery plan AGM starter, LI on dash/electronics.

[boarder1995]

More battery planning talk…

I’ve got a ‘22 Vexus VX20 with the following stock setup:
HB Solix 15” on dash
HB Solix 12” on bow
HB Mega360
MK (non-LI) 4 bank charger
MK Ultrex 36v TM
Stock Group 31 AGM batteries

Bought the new boat in the Fall of ‘22, but the vessel was on the dealer’s lot since April or May rigged and ready. I suspect the stock batteries aren’t fully healthy? When I use run both graphs a fair amount, without a lot of long gas runtime, even just 1/2 day, I get the house battery below 25%, based on the MK charger indicator lights. I’ve had other AGM boats and not nearly the quick drawdown on batteries. Granted that was with Helix units and not Solix.

I’d really like to keep the starter battery a lead acid AGM, per Mercury. One plan or thought is to add a small LI battery dedicated to the dash and graphs, and isolate the AGM to just starting duties. Think this is possible in the Vexus? Keep the large leads from the AGM to the outboard. Run the smaller leads to the Lithium. I haven’t traced out the wiring harness arrangement Vexus uses yet. I think I remember a talk about a master bus bar under/near the dash that distributes power to the bow and dash? Time to go investigate in my boat when I can get to it.

I’d add a dedicated charger for that LI battery as well and tie the AC power lines from the chargers together in the back well and out the port with a single outlet lead. I may also consider going lithium on the TM too (3x12v or 1x36v), and thus a whole new onboard charger - maybe MinnKota 5 bank.

[jhanson1114]

My AGM died within a year. I replaced it with an X2 group 31AGM and that has worked great. This year I am going to add a powerhouse lithium 16v, for in the increased performance. I can't help you with the wiring, since I ran dedicated 8 gauge to all of my units. The added lithium will require another dedicated charger.

[Koma]

I also had to replace the AGM that came in my VX21 shortly after I got it. Just a FYI, Mercury has approved ReLion RB100HP lithium as a cranking battery. I waited to make the change until they released the approval for use but know quite a few guys that are running different brands of lithium's with no issues. I run 2 RB100 HP's, One dedicated to my electronics and the other for cranking and everything else 12V. I ran a sea clear harness for my graphs and use the stock wiring for the rest. I also have three RB75's for the trolling batteries with a power pole charge for the trolling batteries and the cranking battery and added a Minnkota PC110 to charge the house electronics battery. Works perfectly for my needs.