Saturday, October 10, 2015

Power Pointing part one

Before we start the wall insulation and finish up the ceiling insulation and bead board, I want to get the electrics installed. Mainly because it is easier to snake and run lines without all the insulation getting in the way. I decided to start with the charging system, then add all the distributed power points.

The charging system consists of an AC inverter/charger, a solar controller, and a house/car battery interface. (Not to mention the batteries and solar panels that are already installed.)
In this chapter, we'll get the inverter/charger and solar controller hooked up.

The AC system will charge the batteries from an external shore source, or use the batteries to provide AC for things like a microwave or electric toothbrush. The idea is to avoid needing a generator.

If we want to plug in shore AC, we need a plug. And that means a hole.

Now that we find we have a have a hole, we need to plug the hole with our plug. Otherwise, air, and nighttime darkness might leak in.

 I'm using a 30Amp bulkhead plug. It has no darkness leakage specification, but it is theoretically waterproof.
It comes with a rubber grommet, but since Annie's wall is slightly curved,  I also added some caulk strip.

The plug is a nice shiny white. The aesthetics committee convened an emergency session, and concluded that the plug must match Annie's skin color. So we painted it.


The AC wiring will be made up of 12 gauge exterior grade extension cord. This gives us a stranded, flexible cable with a strong abrasion resistant outside sheath. The hole edges are also painted, and the plug is caulked from the inside as well.

I also made a 30A->20A adapter plug using the male end of the extension cord.

Next I mounted and wired up the solar controller. I probably don't need my scrawled reminder any more.

Then the catastrophe fuse, the current monitor shunt, and the battery temperature sensor. These are all on the batteries or the battery tray.

The next step is mounting the MS2012 inverter/charger. It goes on a wood panel that's mounted to the floor in a similar manner to the battery slide. The MS2012 gets bolted to that wood panel with 1/4-20 bolts and t-nuts.


Then wire it all together. I built the DC cables myself to keep the cabling as short as practical, using 2AWG stranded. The cables to the battery tray are long enough to allow full extension of the tray.

The MS2012 can theoretically draw up to 267A, which exceeds the rated current carrying capacity of any 2AWG cable. 2AWG is rated as OK up to 200A, IF it uses 105degC rated insulation. Since 200A is somewhat more than the maximum current I ever expect to draw from the batteries,  the catastrophe fuse is being replaced with a 200A breaker.
I'm not using the 2/0 wire that the MS2012 nominally needs at full load since 2AWG is MUCH less expensive and is much easier to fit and route. The 200A breaker makes this an acceptable choice.



 A test of the system with a ~1000W AC load (a pair of halogen work lamps) results in a total .1V drop between the batteries and the MS2012, at a measured battery discharge current of about 78A.

That's about it to this point. Next power system steps are to install the car/house battery VSR interface, and hook up the house AC/DC distribution panel. Then tuck in all the wiring neatly.

Here is a rough block of the wiring setup. Note that the battery monitor (ME-BMK) is not shown connected to the shunt.
Also note the slightly unorthodox fuse hookup. This was done for convenience, since the MPPT 60A fuse assembly came with extremely short leads.