How much generator do I need?

[malcolmjwhitaker]

My wife and I are going on a three week road trip in our travel trailer. We will not have access to 120 v shore power. We have two 12 volt batteries size 24 that easily give us 3 to 4 days of power. We don't need to run ac's, tv's or microwaves. How large of a generator do we need to recharge the batteries? Would a Ryobi 900 w propane generator be enough to recharge the batteries? How long would it take to recharge batteries that are half discharge? They are both 690 amp each.

[llr]

what size converter do you have? that will be the limiting factor on how fast they can charge.

I doubt if and TT comes stock with a converter that would need more then that generator

[malcolmjwhitaker]

llr; My converter is a WF89PEC, converter output 12 amp, 950 w. Also says output 55 amp charging and load. Wouldn't I be limited by the generator output; 900 w peak, 700 w continuous? Trailer came with a 30 amp extension cord.

[rsdata]

batteries take time to recharge using the stock converter in the trailer, even longer since you have two 12 V in parallel...

you could start with that genny, but I would buy a separate 8 amp smart battery charger and hook the output of the genny to the batteries via the charger...

Personally I would get the Predator HF 2000 watt genny for about $450 on sale. It may be even quieter then what you are looking at meaning you could be running it overnight to get fully recharged because it is not loud at all.

[malcolmjwhitaker]

rsdata; Thanks for the reply. Today I looked at the predator genny at Harbor Freight today. I've heard good stories about it. It's also big, heavy and requires packing gasoline. I can carry up 80 # of propane (2 @ 30# and and 1 @ 20#) so I would like to stick with propane. I like the idea of a separate 8 amp charger to bypass the trailer converter. I think the 700 watt Ryobi is only capable of 5.8 amps anyway.

[My17Ram]

Originally Posted by malcolmjwhitaker

rsdata; Thanks for the reply. Today I looked at the predator genny at Harbor Freight today. I've heard good stories about it. It's also big, heavy and requires packing gasoline. I can carry up 80 # of propane (2 @ 30# and and 1 @ 20#) so I would like to stick with propane. I like the idea of a separate 8 amp charger to bypass the trailer converter. I think the 700 watt Ryobi is only capable of 5.8 amps anyway.

The Predator 2000 is big and heavy? It’s 55lbs full of fuel, and will run 8 hours on a full tank. No need to pack much spare gasoline.

[rsdata]

I think I am correct in saying that a 20# propane cylinder only gives about an 8 hour run-time... about the same as about 1.5 gallons of gas, and that propane does not give full output as the BTU or energy in propane is less than gas...

I think a full 20# cylinder is about 4.7 gallons of LP... those Blu-Rhino cylinders you return are even less...

I think the illustration I found below should rate the propane at 3.44 POUNDS per hour not GALLONS... but I do believe the 8 hr ( give or take an hour) per 20# tank is correct...

[rk06382]

Originally Posted by malcolmjwhitaker

My wife and I are going on a three week road trip in our travel trailer. We will not have access to 120 v shore power. We have two 12 volt batteries size 24 that easily give us 3 to 4 days of power. We don't need to run ac's, tv's or microwaves. How large of a generator do we need to recharge the batteries? Would a Ryobi 900 w propane generator be enough to recharge the batteries? How long would it take to recharge batteries that are half discharge? They are both 690 amp each.

Originally Posted by malcolmjwhitaker

rsdata; Thanks for the reply. Today I looked at the predator genny at Harbor Freight today. I've heard good stories about it. It's also big, heavy and requires packing gasoline. I can carry up 80 # of propane (2 @ 30# and and 1 @ 20#) so I would like to stick with propane. I like the idea of a separate 8 amp charger to bypass the trailer converter. I think the 700 watt Ryobi is only capable of 5.8 amps anyway.

You should check into a solar panel on your roof. One or two 100 watt panels would recharge your batteries without fuel or noise & produce 5-10 amps all day. You do not need a large solar system if have low power needs. You can also deduct 30% of solar cost off your taxes for 2018. My solar panels generate power even when it is raining.

Original question: Yes. The 700 watt Ryobi should be large enough. Your 24 batteries are 690 Cranking Amps with 140 Amp Hour Reserve Capacity. At 50% you would have 70 Amp hr per battery left.
Interstate Batteries: SRM-24

[malcolmjwhitaker]

rsdata; 20# propane = 366,000 btu. 1 1/2 gal gasoline = 171,00 btu. Therefore, 20 # propane = 3.2 gal gasoline. Home Depot claims 700 watts Ryobi will go for 15 hours on 20 # propane.

[malcolmjwhitaker]

rfk06382; I agree that solar panels on the roof would be the ideal solution. My trailer is pre-wired for Zamp solar panels but these can only be used while stationary. I am considering this avenue. Not ready to make holes in the roof for permanently mounted panels.

[rsdata]

20# propane = 366,000 btu. 1 1/2 gal gasoline = 171,00 btu. Therefore, 20 # propane = 3.2 gal gasoline. Home Depot claims 700 watts Ryobi will go for 15 hours on 20 # propane.

I don't dispute your numbers but I was referring to equal 2Kw gennys...

a 700 watt running LP and a 2 Kw running gasoline, I believe you will find the gas genny more efficient at producing watts... and hauling less total fuel weight considering the metal tank tare weight of the propane never gets used...

not to mention fuel cost... $12 to $20 for a tank of propane (up to 15 hours) and $15-$20 for 5 gallons of gas ( usually 6+ hours/gallon) or 30 hours run time with more energy produced

and while 700 watt genny will recharge your batteries, I believe it will take longer and use more fuel than running a 2Kw with a larger capacity 8 amp smart charger connected to the batteries...

BUT when all is said and done... the smaller genny is cheaper and sounds like you already have the propane tank capacity... Invest another $$ into a solar panel charger and do some research on your next trip...
good luck

[mwdilday]

Originally Posted by malcolmjwhitaker

rfk06382; I agree that solar panels on the roof would be the ideal solution. My trailer is pre-wired for Zamp solar panels but these can only be used while stationary. I am considering this avenue. Not ready to make holes in the roof for permanently mounted panels.

They can be used stationary or on the road. Any time there is sun.

[rsdata]

get a folding suitcase style solar panel and a cheap controller and clip directly to your batteries when you are stationary... that way you can "follow the sun" so to speak with the panel... I got the controller below and it works great for one small panel I own...

[chroniekon]

Isn't there a way that your tow vehicle can charge the trailer batteries while you're going to your next destination?

[rsdata]

Isn't there a way that your tow vehicle can charge the trailer batteries while you're going to your next destination?

YOU could put in larger gauge fused wires for less voltage drop, something on the order of 8 ga and have enough hi-output on your alternator to do the job, but most TV are not wired from the factory to give anything more than a trickle charge to the TT battery

There is quite a bit of info on etrailer dot com...

this is one resource...

https://www.etrailer.com/question-277094.html

[mwdilday]

Originally Posted by chroniekon

Isn't there a way that your tow vehicle can charge the trailer batteries while you're going to your next destination?

Yes there is a pin on the 7 pin connector for charging the trailer batteries. If your tow vehicle is wired for it you can do it. Some vehicles are and some are not. If not there may be a fuse or something that will enable it or you can have it wired. You must have a charger inline either in the tow vehicle or the trailer that will control the rate of charge so it doesn't draw too much current or damage the batteries.

[mwdilday]

Originally Posted by rsdata

YOU could put in larger gauge fused wires for less voltage drop, something on the order of 8 ga and have enough hi-output on your alternator to do the job, but most TV are not wired from the factory to give anything more than a trickle charge to the TT battery

There is quite a bit of info on etrailer dot com...

this is one resource...

https://www.etrailer.com/question-277094.html

My F-350 charges at 30 amps. You can buy after market chargers up to 25 amps or more.

[malcolmjwhitaker]

Thank you everyone for for your thoughtful responses. I will start out with the 700 w propane Ryobi and later upgrade to the solar panels, leaving the Ryobi as the backup unit.

[Bluepill]

In cooler weather, I just run regular jumper cables from the car battery to the camper battery. With the car at idle, it will supply up to 35 amps of charging current if no extra electrical loads (A/C, Heater/Defroster, headlights) are switched on. 2 to 3 hours of run time is enough to recharge my 2 battery bank on the camper from 50 to 60 percent state of charge. No extra fuel or generator or solar panels needed.

[HONDAMAN174]

Side note...

Blue pill- it’s good to see that you have a plan b. Unfortunately, many of the newer vehicles will only put out serious ampere on deceleration. It’s a problem we are seeing as car makers are trying to make mileage numbers. And short trips and congestion are killing vehicle batteries quickly.

At least in my world...