Replacing VP Split Diode with Sterlings Pro Splitter or Smart Bank

[john_morris_uk]

If the sensing wire is connected to the battery side of the diode splitter, rather than to the battery itself, it will ensure that the alternator compensates for the volt drop across the splitter.
Any volts drop in the wiring between there and the battery should be minimised by adequately sized good quality wiring and other components, something which the OP needs to address if his quoted figures are anything to go by

Agreed.

However I took our sense wire straight to the batteries as then the alternator controller makes the alternator work at exactly the right voltage to produce the desired battery voltage. (I put a small inline fuse in the wire as I didn't like the idea of an unfused small current wire that was connected to a large lead acid bank chafing through somewhere and potentially causing problems.)

 

[charles_reed]

Converting the alternator to voltage sensing would be a quick and easy fix which will overcome the voltage drop in your diode splitter.

If you're still tempted to replace the diode splitter, I'd suggest that you spend a few more quid on a Sterling Alternator-to-Battery charger. This will give you a boosted charge voltage, to charge more quickly, plus it will drop to a float voltage when the batteries are charged, to prevent overcharging. It incorporates diodes so effectively replaces the splitter diode.

But you really need to do something about the voltage drops in your system, perhaps by replacing the main switch and using different bolt-on fuses. You've listed the voltage drops and say "and then the same on the negative side", but surely you haven't also got switches and fuses on the negative wires?

I've always been sceptical about the sense of converting a.c to dc (alternator) then back to a.c and into a charger to charge 3 battery banks. Perhaps you could, pvb, persuade me.

Incidentally, in Cediera I came across a British owner of a formerly German owned vessel. He couldn't get his Raymarine pilot to work. On contacting the Srevice Department we worked through all possible faults. Finally we found that, with true Teutonic thoroughness the previous owner (or his electrician) had fitted the wiring to the motor with fuses on both +ve and -ve connections - it was a faulty holder in the -ve section that was the trouble.

 

[charles_reed]

The factory alternator on my Volvo D1-30 has a sense terminal on the back. By default it's connected to the output by a short jumper lead, but converting to battery sense is as simple as swapping over a spade terminal.

What did require soldering onto the brushes was the smart booster - which was definitely worth it as described above.

Pete

I really am not picking on you Pete, but my experience of external smart controllers had a complete popularity reversal after 3 melted alternators.
Admittedly in the Med, where it's a lot hotter than UK waters, and where motoring for long periods is the norm.
I now run on the on-board alternator controller. However it's a modern Bosch (unlike most obsolescent marine gear) which charges @ 14.1v.
A 0.5 volt drop at a splitting diode is quite normal, but so is a drop @ every fuse and join.
Currently terminating volts in my system are 12.8v.
As I've already made the point - increasing complexity will inevitably lead to additional risk of malfunction.
KISS