Monday, November 30, 2020

How to turn a 3 hour job into a 3 day one - upgrading the Battery compartment wiring.

With the main domestic batteries requiring replacement (explained in the previous post here) I decided that it would be a good opportunity to tidy up the main power distribution system which had grown by stages with items scattered around the battery areas, often in inconvenient places. Also the new batteries are shallower than the previous ones so that the already slightly dodgy and difficult to fit strong-back over them would no longer work.

During the round GB trip I only spent a limited time in marinas but destroyed 2 shaft anodes and an anode on the P bracket (on the A9m the P bracket is not electrically bonded to the engine etc. an anode is therefore a good idea). That was more erosion than I used to get from a year at Haslar Marina so clearly something was not right with the electrical system at one of the marinas and / or on nearby boats. I therefor decided to fit a Sterling Galvanic Isolator (AKA a Zinc saver), for a good description of the problem and solution see the Sterling Power website here (other suppliers also supply appropriate hardware). 

Of course on a boat things are never as simple as you would like and what I estimated as a 2 day job ended up taking three and my elegantly simple wiring scheme had to be abandoned when I found that the domestic main switch would only just take a single heavy duty flexible cable to each of the terminals, two was impossible. But finally it was finished and with the addition of 3 lashing points, extra wood battens, and a new shelf in the compartment, the batteries are more secure than ever.  

The re-done main battery compartment with the new galvanic isolator
(AKA a zinc saver) top right to protect the boat from Galvanic action
when connected to shore power. Below it are the shunts for the
battery monitors, to the left switched and non switched bus bars
and master fuses - The second battery bank has its own master fuse
close to it. (Updated Feb 2022 after minor changes).
This post shows how effective the galvanic isolator is.

Shore power circuitry (click for a larger view), 2 pole circuit
beakers should be used rather than single as sometime found.
Naturally I found more work to do, in this case replacing the bilge pump switch that one or more previous owners had rewired multiple times leaving it damaged and with the built in fuse bypassed, not expensive but annoying.
Power distribution and control (updated Feb 2022). For reasons
explained elsewhere I have 2 domestic battery banks so charging
management and switching is more complicated than usual.

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