Friday, Nov 15, 2013 at 09:36
Your right I do not understand how the Sprinter regulator works and I was unaware that there is a regulator with a separate output live only when charging, after the initial high voltage had settled. I am yet to confirm this.
We used to use the oil pressure switch to achieve the no load start.
I do accept your point of view, as I have had this discussion with many sparkies that disagreed with the design on various boats and Bosch did not encompass multiple source battery charging.
I do accept your explanation that the ECU raises the output at start time to 15v and then steps down to 13.6v as the batteries charge. I monitor this now on a regular basis. Without sensing current or battery temp this must just be time based in the ECU.
I have done 100's of boat wiring schematics over the years, my technical grounding began in the 60's installing battery systems for remote telephone exchanges including "non electronic no break systems", army signal corps telegraphs, mini computers for 16 years with UPS systems, V8 supercar electrics and telemetry, in later years on boats, plus remote marine radio repeaters both solar and wind powered.
One bareboat company had all its fleet worldwide setup with ignition switched relays often experiencing 90amp relay failures and I believe still does, whilst most in the Whitsundays have diodes or VSR controlled charging systems.
I do understand how my Sprinter is connected and the way I have it is identical to the way the information sheet says to connect it with the exception that I have a bidirectional VSR that switches when either the alternator or solar regulator reach 13.4v instead of only when the alternator produces voltage on the D+ output. I have installed a manual switch to disconnect my relay when I wish thus removing the 1.8mA standby current drain. The BEP 125a DVSR is a relay not a transistor switch so there is no voltage drop across it.
I consider this is superior to the D+ driven relay approach, with multiple source charging, as it allows the use of standard electrics when the motor is not running, knowing the solar or shore charger will charge the start battery, yet disconnect the start battery when the house battery gets below 12.8v. Commonly on boats auto bilge pumps are on the start battery.
The problem I had with the solar regulator was accepted as a design fault and corrected by un upgrade in firmware.
Kevin H
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