Wednesday, 16 March 2016

Fledgling 12v electrical system - job #5 - part 2...

Progress on job #5, installing some electrics, is progressing.. as a reminder first post was here [clicky], but I've set up a blogger label for this series of  posts so just select "12v" (over to the left) and you should get any/all of them as I progress...

So just a recap - basic requirements at this stage is nothing more than:
  1. battery
  2. isolator switch
  3. bus bar
  4. switch panel
  1. Battery

My original idea was to strap the battery box to a sheet of epoxied marine ply bolted to (some) part of the boat, but in the end the solution I used was much simpler - using part of the original idea (to use the lip of the opening under the cockpit sole), I :
  1. trimmed part of the carrying handle on the battery box so that the handle then sat comfortably on the lip,and then 
  2. cut a wooden batten the width of the inside of the box to act a strengthening brace
  3. clamped the whole lot in place - batten inside box to lip
  4. drilled through the lip, box, and batten twice - once at each end to provide lateral bracing
  5. bolted through with M6 stainless bolts/nuts - I used some butterfly nuts to make it easier to remove in future should I need to...
...this shows the spot, and the opening... before...

..and after...  you can just see the hex heads of the M6 bolts behind the cockpit sole...

2. Isolator switch

The master switch to the whole system, if this is off, there's no power to any of the devices in the boat...  still to be fitted (that this weekend hopefully) but it's going here ==>

The jump leads are now attached to the quick release cable clamps - I have copper tube terminals (16mm2 with 10mm and 5mm openings) on order for attaching to the switch (positive) and busbar (negative)...

Next job is to run the cables from the battery up the inside of the bulkhead to the isolator switch, and then along the bottom of the shelf and into the switch box/panel...

3. Bus bar

The supplier for the stainless steel 8 Way Earth Terminal Block has let me down - after three weeks waiting for "re-supply" they have given me a refund but I now need to go and get a replacement - to be honest I'll go to Screwfix and get a nickel plated one - it's inside the boat inside a switch box so it shouldn't have a rust issue....

4. Switch panel


...has become this:

Over the preceding week I gave it two or 3 coats of the same wood preservative I use on the outside of the boat. Once that was done I then made the cut out for the switch panel with a jig saw and mounted the panel - power cables connect at the top of the board which is why it isn't central - I wanted to leave room to route cables...  to the left I have plans for a battery monitor, a cigarette/12v charger socket and/or a USB charger. Inside the box I have a glued a wooden batten on the left to mount the earthing block.

The box now sits on the shelf, in a cut out to the lip (jig saw again), I have two M4 stainless bolts through the bottom of the box and shelf holding it in place (they're 70mm long!).

Next job is to drill a hole (or holes) up into the bottom of the box big enough for cable entries..

Costs so far...
  1. battery - free
  2. battery box - £15.99
  3. jump leads for battery cables - £4.90
  4. isolator switch - £4.99
  5. bus bar - stainless steel 8 Way Earth Terminal Block - £2.27
  6. switch panel - £18.95
  7. wooden "switch" box - £14 
  8. copper tube terminals (5 each of 5mm and 10mm) - £4.50
  9. Nuts/bolts/washers - from the spares box


  1. Really smart job. I would have positioned it exactly where you have it and up the same way - I might have been tempted to sand the edges and corners into a half round as I am the type that ends up banging my head on everything but that's a minor point, great work. Man the costs add up don't they!

    1. Alden - thought about sanding the corners but this is a pre-made box and the outer surfaces are only 4mm ply - not much to sand off.. :o) It only overlaps the shelf by an inch so I think it should be fairly bump proof... the whole lot should all come in with change from £60, not too bad for what I've got at the end.. I hope...!