I’d suggest you install a smart shunt from Victron Energy first so you know how much power your new system is going to draw before doing anything with your “current” battery set up. Anything else is a guess and would most likely end up wasting money.
For example, your dealer is telling you to go with three group 31 batteries, one of the batteries is a dedicated start battery and is isolated by the factory installed BEP marine battery switch. A group 24 start battery is more than sufficient for starting these boats engines, in the PWC these engines are started by a much smaller battery.
A quick explanation of the DVSR. When you start the boat and the start and house battery voltages are less than 12.7 volts the DVSR is not active, the DVSR switch is open isolating the start and house batteries. When you start the engines, the alternator outputs from the engines are tied to the start batteries and when the battery voltage comes up to 13.2 volts the DVSR switch will close, the little red light will come on, paralleling the start and house batteries and the start battery will start charging. After you are floating and the battery voltage decay to 12.7 volts the DVSR switch will open isolating the start and house batteries there by making sure your start battery is fully charged and ready to do its job, starting the engines.
That leaves the house batteries that will be powering your new zoot sound system and the MFD / chart plotter as well as the oem accessories. You’ve got quite the forecasted load with all of that sound equipment, but again, I think you need to measure how much load and load you are going to need to support your sound system as well as the rest of your systems and the only way to accurately measure that is with a smart shunt, they’re about $135 and super easy to install. The victron app is free and works with all of Victrons various equipment.
The SmartShunt is an all-in-one battery monitor, only without a display. Your phone acts as the display. The SmartShunt connects via Bluetooth to the...
www.victronenergy.com
For sure you need an onboard charger. NOCO is the most popular brand on this site and they seem very reliable, you need to get at least a 10A per battery charger, so for a two bank charger you’d need a 20A charger. Lead acid batteries require 10-13% of the their Ah in charging amperage to charge properly, those group 24’s you have are probably 70-75Ah batteries. Flooded lead acid batteries are tough and work well, but you have to charge them properly and individually if possible. And you need to maintain them, which is a simple process of checking the specific gravity of the cells once a month and running an equalizing charge.
I have used two types of chargers, Minnkota precision chargers which are a lot like the NOCO chargers and the Victron IP 67 chargers. The Victron chargers are more money but are well worth the extra cost, and they are Bluetooth capable through the app, these chargers have pre installed charging profiles for all of the battery chemistries as well as user defined charging profiles, they have charge rates from 3A up to 25A.
The Blue Smart IP67 Waterproof Charger is the new professional battery charger with built-in bluetooth. Find a Victron Energy dealer near you.
www.victronenergy.com
In the drawing above you can see a reference about cutting the red wire to change how the DVSR operates. This is something that needs to be done to allow your start and house batteries to charge properly, mainly the house battery since it will be discharged to a much deeper level than the start battery. There are threads on that here on the site and many of us have done this different ways that have all worked out well.
Once you know your system demand you can then make an educated decision about the batteries and the amount of capacity you will need for a typical day on the water. Something to keep in mind about lead acid batteries is that they can only deliver 50% of their capacity without dramatically reducing their life cycles typically 500 cycles, where as LFP batteries can deliver 90% of their capacity without decreasing their life cycles typically 5000 cycles.
Note: If you are not willing to spend the money on a quality LFP battery, Battle Born, ReLion, Dakota Lithium, then stick with lead acid batteries.
You can save yourself a lot of money by doing most of this work yourself, for example, you can save yourself $398 just buy installing the onboard battery charger yourself, there several threads here about how people have done that to their boats.
a) Is the battery charger a good idea? If so, is the proposed NOCO Gen Prox2 a good solution?
Yes as long as it is at least 10A per battery
b) Is the upgrade from the two stock group 24 batteries necessary?
Probably but not yet.
c) If so, is the proposed three group 31 batteries plan the way to go?
Not necessarily, that is a lot of weight and you may or may not need that many batteries.
d) How reasonable in your opinion are the labor quotes?
Too high, you can do the work yourself.
e) If I'm having an audio dealer install the audio system, should I have the audio guy also do a battery upgrade, or leave it to the marine dealer?
Between the two, the dealer you bought the boat from but best to do it yourself with the sites help.
Remember, you are in the early days of doing this set up, take your time and do it right methodically and you will have a great set up that will serve you well with no muss no fuss. There is tons of information here, use the search function and you will be amazed at how much information there is. You’re putting in a very expensive sound system, don’t skimp on the battery set up.
