Generator vs. chassis alternator to charge house batteries

[Ronscomm]

While dry camping, what is the most efficient way to charge the house batteries - run the generator or run the engine?

[RetiredLEO]

Run the gen. It's good for a gen to get exercised anyway and it will be a lot faster than the engine.

[WinnieView]

x2

It can be real detrimental to idle the engine for extended periods.
Engine while moving, generator while stopped.

[RoyBraddy]

This is what PROGRESSIVE Dynamics states in their operating manuals on how long it takes to charge a battery using the DC VOLTAGEs listed below: "Progressive Dynamics ran this test on the amount of time it took a PD9155 (55-amp) converter/charger set to three different output voltages to recharge a 125 AH (Amp Hour) battery after it was fully discharged to 10.5-volts.

14.4-VOLTS (Boost Mode) – Returned the battery to 90% of full charge in approximately 3-hours. The battery reached full charge in approximately 11 hours.

13.6-VOLTS (Normal Mode) – Required 40-hours to return the battery to 90% of full charge and 78-hours to reach full charge.

13.2-VOLTS (Storage Mode) – Required 60-hours to return the battery to 90% of full charge and 100-hours to reach full charge."

This is based on having 17-20AMPS DC current available to be absorbed for 'each' battery in your battery bank... NOTE That Progressive Dynamics doesn't even list using DC Charge Voltages around the 12.0VC range as this would take alot more than 100 hours to achieve a 90% or 100% charge state.

It has been my experience that just charging for an hour or so usually destroys my battery. I have to get to at least the 90% charge state before getting somewhat full performance out of my batteries again. If I am camping OFF-GRID I have found I can only do some 10 or 12 90% charge state recharges and then I have to do a full 100% recharge otherwise I will start doing harm to the batteries. A FULL 100% charge will literally take a day to finish so I want to do that when I get back home if possible.

I just watch my DC VOLTMETER and when it gets down to around 12.0VDC I know this is somewhere around the 90% charge rate. If I can't run my trailer charger for a three hours charge period than I just stop using the batteries until I can...

This is what works for me at least...

My goal is to have my 1-2 AMPS DC parasitic drin 24/7 and then be able to run my home entertainment and some other items between 6PM and 10PM each evening and not get my battery bank below 12.0VDC by the next morning. Then I will run my small 2KW generator connected to my on-board battery charger for three hours when allowed and this will get the batteries back up to their 90% charge state. Then I am good for the next day/night run off the batteries until the next morning... This is my daily routine when camping off-grid...

You should be able to experiment with a similar routine that works for your setup...

On my new battery bank I am wanting to do the same routine but only run my generator for around one hour time to get the batteries past their high DC Current absorb time and then I can use a couple of solar panels in the high sun to get them to their 90% charge state before I loose the high sun...

Can't just show up and it works for you haha...

Roy Ken

[JimD]

I dry camp in my 2017 Greyhawk 29W in the sand dunes of Southern California most of the time. Using the coach generator to keep the batteries charged is better than the chassis alternator. The unfortunate side effect is a lot of hours being logged on a big generator (mine is 4K) for something that doesn't need big power.

I added a couple of solar panels which helps but if the TV is going all day, the charge goes down and then after an overnight of no charge, the batteries need charging in the morning. I am running 2 Costco 12 volt batteries.

A couple of my friends bought the Ryobi RYI2300BTA portable generator which is a 2300 watt unit. It has a great feature of bluetooth control where you can monitor fuel, run time, etc. PLUS shut the unit off remotely with your cell phone.

OUTSTANDING unit! A lot quieter than the 4K Onan and can run all day, depending on load, on a gallon of gas. I still fire up the Onan for air conditioning and microwave and to keep it operational. With the Ryobi plugged into the shore power cord, it feeds the coach just like you are plugged in. When you fire up the Onan it will automatically override the shore power connection and run everything I want. Turning off the Onan will revert the 120 power to the shore power which is the Ryobi.

Instead of using my power hungry inverter to run the Direct TV when I go to bed, I run the little Ryobi and then when I am done I use my phone to shut it down. Yeah, lazy I know. I once tried leaving the inverter on overnight with the TVs off but it dropped my batteries to 11.9 volts.

I feel it will be less expensive doing maintenance on the little Ryobi rather than the big Onan. I still keep the Onan happy by running it once a month under a good load.

The Ryobi generator is available many places including Home Depot. I researched and found brand new units on EBay for $479. which is what I paid. This is one of my better purchases.