Generator charging questions

[treedoc]

I have questions concerning dry camping & generators. First, I have 2 2000w Honda generators which I can tie together to create 30amps. If I am using 30 amp plug to help maintain battery charge, I do realize I may not keep battery charge full due to the amount of power I would be using, and battery charge drops enough for auto gen to start, what will happen next? Can or should both generators run at the same time? At what battery charge (storage) precent will auto gen start? For those of you who dry camp what do you do to maintain battery storage? If battery storage was say 25 percent how long would it take to fully charge batteries? FYI my batteries are 2 years old and my generator is 20 kw. Rick

[ajducote]

Rick,

I do not have a Liberty so my answers may not be 100% correct.

1. For those of you who dry camp what do you do to maintain battery storage?
Run the built in 17.5 generator as much as needed. Usually in the morning to make coffee and top off the batteries. And again at supper time until bed time.


2. Can or should both generators run at the same time?
If you are using your shore power cord to plug into the little Honda's, when the big genny starts the transfer switch in the coach will disconnect shore power and run from the internal generator. At least on my Royale that is how it works.

3. If battery storage was say 25 percent how long would it take to fully charge batteries?
You should start a recharge at 50% discharge, that will make your batteries last a lot longer. Charge time is something you will have to time on your bus. Number and size of batteries, inverter setup have a lot to do with charge times. From 90% to 100% charge does take a fair amount of time.

Do not be afraid to use the 20KW generator. The more you use it, the better. The enemy of generators is under use.



I have questions concerning dry camping & generators. First, I have 2 2000w Honda generators which I can tie together to create 30amps. If I am using 30 amp plug to help maintain battery charge, I do realize I may not keep battery charge full due to the amount of power I would be using, and battery charge drops enough for auto gen to start, what will happen next? Can or should both generators run at the same time? At what battery charge (storage) precent will auto gen start? For those of you who dry camp what do you do to maintain battery storage? If battery storage was say 25 percent how long would it take to fully charge batteries? FYI my batteries are 2 years old and my generator is 20 kw. Rick

[jack14r]

With the 2 Honda generators producing 30 amps I don't think that you will draw the batteries low enough for the auto start to engage,but lets say it does,then it would be just like you were plugged into 50 amp shore cord,in a Liberty when the generator is producing power the generator contactor is made and the coach only knows that the generator is the power source,if the generator stops and you are still plugged in to shore then the shore contactor is made and the shore is the primary source.

[truk4u]

Rick,

Why would you want to do this instead of running your gen? It's designed to run for 30,000 hours and uses minimal fuel. Your batteries will quickly become toast running them down to 25%. Like Andre said, 50% or somewhere close to 12v will give you the most service life. I could tell you more, but would violate the rules here. Contact me off line for more battery information.

[Jon Wehrenberg]

I want to emphasize what Tom said. Perhaps Jack can share information about how he modified his auto start voltage to avoid the deep draw Truk mentions. The important thing to remember about our house batteries is they benefit highly from being recharged at a higher voltage than the Liberty Watchdog is set at. Jack has added a resistor to trigger the autostart at that higher voltage.

But the real message I would like to convery is to use the on-board generator. Use it often and use it hard. I ran mine from about 6:00 AM to about 10:00 PM for a week or more in the hot summer days and left the AC units on so I would never have to come into a warm coach. I also had the HW tank, and numerous other devices on such as the dryer when needed to dry bath towels. I did not load the generator as much as I would have liked but it still was running under loads which probably averaged about 35 to 45 amps. For that entire period my fuel usage was about .4 GPH. At less than 1/2 GPH it might not be as cheap to run as the Hondas, but I also did not have to mess around with gasoline. And our generators are not going to be worn out by us. They typically run in excess of 30,000 hours on entertainer coaches and they thrive on frequent use. They suffer from light loads or rare use.

[jack14r]

What Jon is referring to is I added a resistor to the watchdog because Liberty draws the batteries down to around 21.8 volts before the auto start activates,I found that a 13.8 k ohm resistor will activate the auto start around 23.8 volts,I know that this is below 50% but I am always running at least 1 cruise air and that load is 12-13 amps AC and if the load were removed the batterier will show 24.2 which is aabout 50%.I added the resistor on the 24 volt wire that activates the auto start,to find it I turned on the auto start found 24V on the watch dog with a VOM and then removed the wire from the terminal and the auto start will activate in about 30 seconds.I then added the resistor,I cannot tell any difference in charging or run time for the generator but the auto start will activate at the correct voltage,I have about 10 resistor packs of different values that I made up and I recorded the voltages that the auto start would activate with each pack so if I want to change it I can.Why Liberty and others want to destroy batteries makes no sense to me.

[BoaterAl]

Last summer when faced with plugging into a power source with enough electric lines at a Texas marina that looked like trouble in the making we ran the generator for 71 hours straight. At over 100 deg temp using 3 A/C during the day and 2 at night.

The only time I was shaken up was hearing the OMG hair dryer go on. They seem to really test electrical systems when they are used.

[Jon Wehrenberg]

This may be different on other Liberty coaches, but in my Liberty the wire Jack refers to is on a multi fuse holder in the electric bay. It is a 24 volt circuit and has a 1 amp fuse. I am not aware of any other 24 volt circuits with a one amp fuse. If the Liberty is a Classic, not an Elegant Lady, it is likely a 12 volt circuit.

If I remember correctly from what Jack posted a while back the sense wire is used by the watchdog to detect the low battery voltage and what Jack has done is trick it into seeing a lower than actual voltage so the generator starts at a higher voltage than the Watchdog is originally set to initiate the start. It does not sense the battery voltage for shutting down the generator, but is programmed to run a specific time after start prior to shutdown.