Battery and 12V DC Upgrade

This project began in the Fall of 2014 and turned into an almost complete upgrade and update of the 12 Volt DC system

First a little background

As far as I can tell, the boat came from the factory with 3 – 8D batteries located between the stringers centred in the lazzerette. One 8D was wired just for the port engine (starting)  the other 2 were wired for the starboard start and house bank. We had a house bank of about 650ah or so and yes we did drain that down while anchored last year.
It was then I started to seriously think about a new set up


Charging these 8D’s (while cruising) came from both engines wired to an old charging combiner and then to each battery. This seemed to work OK but I do not think the batteries were ever fully charged with this method.


last 8D in place. There were 2 more in front of this


At some point the previous owner added a Xantrex Prosine inverter/charger and powered this with 4 – 6V Golf Cart batteries. These were located between the outside stringers, 2 on each side.
This was wired as a complete seperate battery bank dedicated to the inverter only and only charged by the Xantrex.

Nov 8 (8)

Old Location for GC 6V batteries. 2 on each side


Everything seemed to work OK   but we lacked the ability to charge the Golf Cart batteries with the engine alternators (remember we don’t have a generator) and we lacked the ability to properly monitor either battery bank. Another issue was we could not completely isolate the “House” bank from the “Start” bank.

The 8-D’s were 8 years old and were on the list to be replaced, so this all led to a re-design and upgrade of the entire system.

I started thinking that if we combined the inverter batteries and the  existing”house bank” and added a separate stand alone “start” battery that would be better. One huge benefit will be that the new combined house bank can now be charged from the alternator while underway.  I had recently changed the 4 Golf Cart Batteries and my supplier felt that adding an additional 4 so soon was no problem.( Usually you would not want to combine new and old batteries but these should be just fine.)

None of the cables or wires connected to the batteries were labelled or marked, so the first step was to trace them all back and mark them. That took longer than I had expected but I was then able to see how the boat was wired and I ended up changing the main power switches to dedicate one as the “House Bank” and one as the “Start Bank”

By increasing the new “house bank” to 8 – 6Volts this will give us just over 900ah of standby power, should be plenty!

This new combined House Bank will use the inverter/charger for AC charging and I could eliminate the OLD – GIANT – NOISY pro mariner.  Some people call these old chargers “battery cookers” because they are single 60 amp chargers that just BLAST a charge at the batteries. More modern chargers are 3 stage and will make batteries last longer.
Well, we have one of those, so why not use it !


Old Pro Mariner Battery Charger


Next I thought If I could move the location of these batteries, 4 on each side, to the outside stringer space this would free up a huge amount of storage space where the 8D’s were.
I constructed heavy duty plywood shelves to fit the batteries on . The shelves are fixed and are quite solid. The batteries in their boxes slide in place from the lazzerette and are held in with cleats and nylon tie downs.

Nov 8 (6)

Testing out the new loaction

Nov 8 (5)

Batteries in place ready for cables


I wanted to isolate the entire house bank circuits, dedicate a new, larger alternator for the new house bank , add new wiring with the proper fuses and at the same time add a
Blue Sea ACR. This will combine and then isolate the Start Battery from the new House Bank. I found and removed a few wires that were unused and a added few runs that needed an upgrade. I was able to re-use most of the heavier cables by shortening them and crimping new lug terminals. Shrink tube was used on all cables and wires. I did increase the size of the main house bank alternator and it’s cable. I added fuses where there were none to bring the wiring up to today’s standards.

November 14 (3)

Wiring Begins

Jan 2 (8)

Almost Finished. That’s a Group 31 Start Battery in the box.








Battery Boxes

Battery Boxes

Battery Boxes (1)

Nylon Strap Tie Downs


Jan 2 (9)

Wiring Almost Complete



As usual, there were a few more things to add.

To be able to monitor the House Bank I added a Xantrex Link-Pro. This will give us all the information we need to properly keep track of our usage and battery level. It even monitors the Start Battery Voltage.

Link Pro (6)

Link Pro Battery Monitor

Dec 14 (13)

Wiring showing the Xantrex Shunt



One thing leads to another……..

Unlike many other models of Tollycraft, our 34 did not have a separate 12V distribution panel. Many of the circuits were simply fused from a main fuse panel. Some had single switches but many were not switched at all.

I wanted to clean this up and be able to switch circuits, so I added a Blue Sea 8023 panel.

Jan 2 (16)

New DC panel and LinkPro mounted

New distribution panel

New 12Volt Distribution Panel


To make room for the new panel I removed the old water tank level gauge (it never worked) and re-located the Espar Thermostat  Control.
While identifying and changing circuits over to the distribution panel I tested each device and circuit. I found that the LP Gas sensor was not working correctly. We’ve had several false alarms and I suspected that the solenoid was not closing properly.


I installed a new LP gas sensor and solenoid control and relocated it from the cabinet wall in the head to a more convenient location easily reached while in the galley. This solves 2 issues and updates the solenoid and alarm! Perfect !


New propane switch and alarm panel added

Jan 17 (5)

New Propane Switch and Alarm



Of course this left a huge hole in the vanity cabinet in the head….


Giant hole and old switches to fix


So………………. I made a custom aluminium panel.  This houses the VacuFlush control, a switch for the shower light, the shower drain pump and I  added a “night light”.

It covered the hole nicely .



New Control Panel

New Vacuflush panel

New Vacuflush Panel covers the giant hole




“Well, you’ve got the whole boat ripped apart and tools everywhere… you might as well keep going. This project is taking a long time”…….



I thought it would be nice to have a working monitor for the Water Tank so…. I found a company that makes a sensor and panel system that gets great reviews.
Ferriello make these sensors under private label but sell for a few dollars less on their website.


Solo Tank Level Monitor Panel


This panel reads the tank level from a sensor mounted on the outside of the poly water tank. 2 strips of aluminium are attached vertically spaced 3″ apart and 2 copper contacts are adhered to the strips.

External sensor

External Sensor Kit


Sensor Installation Drawing



Sensors attached to water tank








New Control Panels

New Control Panels

I have a feeling that this project is not over just yet but that’s it for now at least.

Check back in a few weeks and see if I have added anything else….. you never know what I might find at the BOAT SHOW !!!!!!


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6 Responses to Battery and 12V DC Upgrade

  1. Peggy says:

    My you have been busy

  2. Darin Sims says:

    Just read up on your electrical update. Awesome! Loved reading it. I want to do a smaller version of updates on my 30′ sport. I also dont have a 12v DC panel and I hate that. So i have a question….. Why did you need to install a propane alarm? Do you use propane on the boat for cooking or something? Thanks for sharing your upgrades.Your giving me some new ideas too.

  3. Wyatt says:

    Great post. After owning our boat for a year and a half (it took me this long to figure out our electrical system) I’m about ready to make some upgrades. We have two engines, four banks (start, house, inverter, generator start), and a generator. Our house bank is an under-powered 8D (240 Ah) and our inverter bank is four overpowered golf cart batteries (840 Ah). I think I am going to follow your approach and consolidate the house and inverter banks into one big bank. Back when the old owners watched big screen TVs and cooked with a George Foreman grill, all that AC power made sense. In the age of 2.1-2.4 amp USB devices it’s kind of a waste – and I’d like all that extra DC power for my fridge. Thanks for the inspiration and ideas.

  4. Pingback: Going Solar | MV Tolly Roger's Blog

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