Charging question

[MNtraveler]

On the MBS 2401 as with several other FR models, it appears that the engine alternator charges the coach batteries and in fact is said to be more powerful at that job. So here's my question: assuming one has enough diesel fuel, why use the generator at all? The engine is quieter and the fuel tank is large.

Thanks for your thoughts.


Land of 10,000 Lakes
2016 Forester MBS 2401R

[JLeising]

Not sure, but I don't think long periods of idling are good for the vehicle. Believe there are diesel particulate filter issues. Also, of course, the generator gives you 110 volts for microwave and AC, engine alternator does not.
If you are driving the vehicle, agree - the engine alternator will recharge the house batteries - no need to run the generator to recharge the house batteries while driving the vehicle.

[Witch Doctor]

You do not want your diesel engine to just sit and idling, it is bad for it and you would create a big repair bill. Even doing short trips are not very good. Diesels need to work and get hot. It is only recommended to let a diesel idle to cool the turbo before shutting down and that's only minutes.

[MNtraveler]

Originally Posted by JLeising

Not sure, but I don't think long periods of idling are good for the vehicle. Believe there are diesel particulate filter issues. Also, of course, the generator gives you 110 volts for microwave and AC, engine alternator does not.
If you are driving the vehicle, agree - the engine alternator will recharge the house batteries - no need to run the generator to recharge the house batteries while driving the vehicle.

You are quite right about the AC of course! glj agrees with you on the engine concern...

Originally Posted by gljurczyk

You do not want your diesel engine to just sit and idling, it is bad for it and you would create a big repair bill. Even doing short trips are not very good. Diesels need to work and get hot. It is only recommended to let a diesel idle to cool the turbo before shutting down and that's only minutes.

Makes sense - so you are saying don't emulate truck drivers who leave theirs to idle all night while resting?

[Witch Doctor]

Originally Posted by MNtraveler

You are quite right about the AC of course! glj agrees with you on the engine concern...



Makes sense - so you are saying don't emulate truck drivers who leave theirs to idle all night while resting?

Yes, there engines are not the same as yours. Short trips and not getting the engine hot enough and excessive idling is a killer to a engine. Just idle enough to cool the turbo down that's about 3 to 5 mins per my Ford dealership. Also read the thread going about diesel exhaust filter cleaning here on the forum If you have not yet. important information....

[Too Tall]

Diesel engine combustion temps at idle are low and cause formation of varnish like deposits on in the combustion chamber, injectors, valves etc... Over time, it will reduce the life of your engine.

You can usually tell a truck driver who owns his rig and the ones that are driving for a company. The owner/ operators shut down. Additionally, it waste fuel and DPF filters, EGR don't like idling.

Cummins says don't idle more than 15 minutes. Some trucks have fast idle features that allows for toggling the throttle up to increase combustion temps.

[Appalachian Ed]

In addition to the engine issues, your alternator in your truck is not designed for efficient recharging. It is a constant charge (low amperage) charger as it is designed to recharge a battery that only uses 5% of it's amp hours to start the truck. The charger in your RV is a three stage charger that will charge much quicker during the first bulk charging stage until the battery is around 70-80% charged by supplying a much higher amperage than your alternator in your truck. It is then smart enough by measuring the battery voltage and temperature to cut back the amperage and voltage so as to not overheat the battery. Your alternator is not able to sense this and must use the lower amperage and voltage all along taking many more hours to fully recharge a deep cycle battery.

[WolfWhistle]

Running a generator using the factory charger / converter... or your engine to charge batteries is far too expensive in more ways than one. Even if money is no object.

If you want to use your generator, get a good (high capacity) charger (IOTA makes them) and don't rely on the factory charger, like I said.

These factory Converter / chargers go into float mode way, way too early (at too low of a voltage) and will take days rather than hours to FULLY charge the house batteries.

If you want to do it right, add a solar panel (or two if they will fit), a good solar controller / charger, and a good Inverter charger. There are charger controllers that will charge both the chassis and the house batteries. The quiet will be deafening.
WW

[MNtraveler]

Good points all, thanks!

Since we plan to boon it at least some of the time, solar panels are definitely in the future plans.


Land of 10,000 Lakes
2016 Forester MBS 2401R

[ScottBrownstein]

I gave looked at this on my 435DS with a residential refrigerator. The alternator puts out 175 amps (well can) and the converter puts out 70 amps. On the face of it the engine wins, but it isn't that simple. My reefer is about 900 watts which will draw about 85 amps from the inverter. When running the generator, those 900 watts come out of the genny and the full 75 amps is simultaneously available from the converter. That is equivalent to 75 plus 85 or 160 amps, assuming full power from everything, which pretty well matches a fully loaded alternator.

However, as others have noted, the alternator won't put out full capacity at idle...and idle is not good for the engine. The engine in the generator is designed for constant RPM and will love to run for hours on end.

Bottom line, use the genny.