Can someone explain the proper way to charge a battery using your auxiliary diesel engine? Seeing diesels like to run at high rpm with a big load on them, what is the proper way to run a diesel if you are at a dock or sailing in a race where it is against the rules to use the engine to turn the prop? My alternator would use about 1/2 hp to charge and the engine is 20 hp. So I am using a small fraction of full load on the engine. Does charging in this way damage the engine?
This topic always gives me a chuckle especially when I work on so many engines with 10,000+ hours of "light loading".
#1 If you need to charge and have no other means then by all means RUN THE MOTOR.
#2 There is no need to race it beyond where the alt makes about 80-90% of the alts rating. Figure out where this is, often just a fast idle, and run it there.
#3 The next time you run the motor, run it hard. Once she is warmed up run at wide open for two to four minutes then back her down to 80%..
#4 The idea that you will fully recharge a lead acid battery AGM, GEL or Flooded is fools gold unless you sit there and run it for ten + hours. "Charging" by alternator is what trawlers do, not sailboats...
We restore energy in bits and pieces and hope to get back to full at a dock or via solar, wind etc. on the hook..
#5 Run the motor only until the batteries hit absorption voltage and perhaps just a bit longer while current is still pretty high in early absorption
. Anything more is inefficient charging and wasteful..
#6 Motor charging is best used for bulk charging unless you are motoring for a long distance with no wind or are motor sailing.
#7 I work on piles of motors with thousands of hours of idle running. These motors purr perfectly, burn no oil and have not had any shorter life. These owners simply know how and when to run it and what to do after you run it with minimal load... Our own engine is one of them.. We have engine driven refrigeration so a lot of the engine running has been lightly loaded
. I would not trade our 4000+ hour engine for a 200 hour engine owned by an in and out
of the harbor guy.
*Change the oil regularly
*Run it hard when you run it
*Stop worrying about putting some energy back into the bank
* Stop charging when you attain absorption, if running only for charging purposes