note.Engine Electrical Harness Revisited

The Engine Electrical Harness

I'm in the process of replacing the Engine Alternator External Regulator. The existing regulated is a dumb backup from the previous system, the new Regulator is a Balmar Max Charge MC-618-H

I'm playing with the idea of keeping the old regulator and all of it's wiring to serve as a backup if the New Regulator fails ( it won't be 'new' for long :)  )

However, a supplemental reason: I'm planning on replacing our 'House' batteries. Currently we have 4 x Trojan T105 225ah 6v Batteries with a total usable 12v of 225Ah( 50% of 450Ah ). The replacement will be a 300Ah 12v LiFePo4 battery which has a usable capacity of 90% or 270Ah at 12v. (Note, the 225Ah  of the current Flooded Lead Acid Batteries is  actually much less because the voltage of the batteries drop significantly as the remaining capacity drops)

Therefore, the Regulator must have a choice of "Lithium" Charging Profile and that means that the backup regulator must also have a "Lithium" option.

With that clearly in mind, I need to address the issue of switching over from the Primary External Regulator to the Backup External Regulator ( using an internal regulator is not an option for the safe operation of LiFePo4 Batteries)

If the backup Regulator was the same as the Primary, the switch over process could be as simple as moving each of the terminal connections from the Primary to the Backup - the Backup being already programmed to the same settings.

There's more complex ways to manage the switch from Primary to Backup regulator, but it's just not worth the effort. I figure that switching over the regulators would take all of 3 or 4 minutes and having to make any moves inside of the engine bay would take a lot more time and involve a lot more steps.

Ok, decision made. I'll remove the old regulator.

All that leaves is the method of connecting in the New Regulator to the Alternator, here's another crest to overcome.

When I rebuilt the engine harness in 2016, was it really that long ago? Yep! Six years ago, there's been a lot of water under the keel since then. Well, in 2016, I built a really nice engine harness and nicely labeled the wires in the engine bay, including transparent heat shrink tubing. Guess what! The labels are unreadable today! Six years being close to the engine heat and dust have made it impossible to even guess what the labels read. 

The original ( to us ) engine harness was wired to a 'chocolate block' type terminal block. The terminations were not done well, the wires were burnt, not the correct colors nor sizes. The new engine harness wires were contiguous from the Engine Control panel to as close to the engine that I could get them, in some cases they went directly to the Alternator.

Now I realize the benefit of a terminal block in the engine bay. The most likely area of wiring failure is very close to the engine, especially for the smaller gauge wires. So I'm going to install a terminal block.

Each wire will be correctly terminated with heat shrink tubing and I'll have a printed image of the terminal block so that wire recognition will be easy.

Then I'll run wires from the terminal block to there destination. That should result in a very clear, clean and with protection from the Vibrating Engine.

OK, decisions made. Now to draw up the wiring schematic.

With the diagram completed, it pretty much matches the diagram from Balmar except that I only show the two connections to the plug on the back of the Alternator, because - I did make the connections for the Internal Regulator. I will add a backup external regulator to use if ever the Balmar fails.

The install went pretty smoothly. The Balmar is installed where the old one was located.

The Wiring harness runs through a grommeted hole in the shelf into the engine bay and is secured to the engine bay aft bulkhead ( I know, there's not really a bulkhead, except on the port side there's a 2" corner of the port side bulkhead.) It's secured with a couple of tiewraps.

The cables for the Battery Temperature Sensor and Battery Voltage Sense were easy to run. The remaining wires are on a terminal block ( I have updated the terminal block in the diagram) 

This has been in place now for two years, working perfectly.

See you on the water.