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Old 05-07-2016, 10:46 AM   #1
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What size generator do I need?

I am sure this question will draw some attention.

I own this battery charger.

http://www.harborfreight.com/10250-amp-12v-manual-charger-with-engine-start-60653.html

I want to use it to keep my batteries charged when boon docking. Will run my batteries to about 50% charge then bring them back up to full charge using this charger.

My question is what size generator will I need and roughly how long will it take to bring the batteries back to full charge? Will a 1000 watt generator work alright using this?

Jim
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Old 05-07-2016, 11:31 AM   #2
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That generator would be large enough. Why not use the charger built into your camper? The charge you linked to will probably charge at a slower rate than the one in you trailer. If you want to use an external charger try to find a 3 or 4 stage unit.
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Old 05-07-2016, 12:58 PM   #3
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FYI: Before my amputation I use to fish using a deep cycle battery and electric motor on my boat. I used this charger and this inverterhttp://www.harborfreight.com/750-watt-continuous-1500-watt-peak-power-inverter-66817.html to charge the battery in the evening. I would hook the inverter up to my truck when I came back to my camp site. It worked OK but don't think it would work too well on my two trailer batteries except for an emergency case.
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Old 05-07-2016, 02:00 PM   #4
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If you don't plan on running the microwave and just want it to recharge the battery, then a 1000w will be fine.

Unless you've got and older trailer, not sure why you just don't plug the trailer's shore cord into the generator.

That's what we've been doing with our '07 Roo and Honda 2000i, for nearly 10 years and works great.
Don't have to haul around a separate charger.
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Old 05-07-2016, 02:50 PM   #5
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That generator would be large enough. Why not use the charger built into your camper? The charge you linked to will probably charge at a slower rate than the one in you trailer. If you want to use an external charger try to find a 3 or 4 stage unit.
You are right, it would be foolish not to just use the existing converter. I just researched it and it will charge up to 55 amps when nothing is running. If I was running a few LED lights and my LED TV that charge rate might drop down to 45 amps, maybe 40 amps? I didn't realize it had that high of a charge rate. I knew it had a 55 amp output but didn't think it would use all of it for charging. Today is not a wasted day, I learned something! Will still keep my charger, worked good for my boat. Might need it someday to start my truck but not for a while. Recently had it checked so know its in good shape.

Now, if I am thinking right (I admit I am going brain dead!) a 1000 watt generator is only going to supply about 28% of what my 30 amp converter is capable of using? So at 28% times 55 amps means the converter would supply a charge rate of around 15.4 amps. I am sure someone will argue with me on my thinking. A 30 amp converter could utilize 3600 watts and a 1000 watts is roughly 28% of that, so its output would be limited to 28% of its 55 amp charging capability? That would be 15.4 amps, right?

Now, am I overthinking this whole thing, LOL?

Jim
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Old 05-07-2016, 03:17 PM   #6
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Y
Now, if I am thinking right (I admit I am going brain dead!) a 1000 watt generator is only going to supply about 28% of what my 30 amp converter is capable of using?...
No, I think you have that wrong. Let's say you have a 55 amp converter and it is trying to charge your batteries at full current and let's say that would be at a voltage of 14 volts. 55 amps x 14 volts = 770 watts. Remember the 55 amps is at 14 volts, not 120 volts. Now there are efficiencies in the converter to consider, but a 1000 watt generator will handle that fine and have a little left over for other things.

Now for the hard part. If you really get 55 amps, for each hour you run you will put 55 AH back in your batteries. But you won't get 55 amps for that long and it will take quite a while to get back 100 AH, say conservatively about 3 hours of generator time.
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Old 05-07-2016, 03:58 PM   #7
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Thing is that it usually only costs a little more for a 2000w unit.
Personally, it's not worth buying a 1000w unit, since the 2000w units are so close in price.
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Old 05-08-2016, 09:03 AM   #8
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No, I think you have that wrong. Let's say you have a 55 amp converter and it is trying to charge your batteries at full current and let's say that would be at a voltage of 14 volts. 55 amps x 14 volts = 770 watts. Remember the 55 amps is at 14 volts, not 120 volts. Now there are efficiencies in the converter to consider, but a 1000 watt generator will handle that fine and have a little left over for other things.
You could be right but got to think about it a little. It is true the converter is capable of putting out 55 amps at 14.X DC volts, or roughly 770 watts as you state. but doesn't it require 30 amps at 120 volts AC in order to do so? Or roughly 3600 watts? So wouldn't the DC wattage output lower as the AC input lowers?

Jim
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Old 05-08-2016, 09:47 AM   #9
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You could be right but got to think about it a little. It is true the converter is capable of putting out 55 amps at 14.X DC volts, or roughly 770 watts as you state. but doesn't it require 30 amps at 120 volts AC in order to do so? Or roughly 3600 watts? So wouldn't the DC wattage output lower as the AC input lowers?

Jim
Nope, Progressive Dynamics rates their 60 amp converter as 60 amps at 13.5 volts which is 810 watts. Their spec for the unit is 1,000 watts which I am sure is conservative on their part. My experience is that the converter will almost never stay at nameplate current for very long. You may be confusing the WFCO 55 amps converter which also includes an AC power distribution panel. The panel can accommodate 5 ac circuits and is rated for 30 amps. The converter doesn't use anything like that.

1,000 watts will do fine with only the converter running.
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Old 05-08-2016, 09:47 AM   #10
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Thing is that it usually only costs a little more for a 2000w unit.
Personally, it's not worth buying a 1000w unit, since the 2000w units are so close in price.
You may be right, I haven't priced generators in a while. Last one I priced was a 3000 watt Honda, which I own, but am trying not to carry any more weight than necessary.

I do know I can get a 2200 watt generator for $530.00 that has a Sound Level at 23 feet, 50% load 64 dB. Sound level and weight are important to me. Just looked at Hondas 1000 and 2000 watt units and they are about $200.00 in difference so you are right about the prices.
Jim

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Old 05-08-2016, 02:09 PM   #11
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While a converter may be capable of supplying 55 amps, a battery will not normally accept that amperage from the converter for very long. The charging current to a discharged battery may initially be rather high, that charging current quickly drops as the battery charges. Charging a battery from 50% discharge to 90% discharge will take a few hours but charging that same battery to a 100% charge will take days.

I would expect a 1 KW generator to successfully charge your batteries and be an efficient source for running a TV and other small power 120 VAC appliances once the batteries were partially charged. However, a 2 KW generator will also power your microwave, something I find handy.

Generator size can become a slippery slope, as you may want to run you’re air conditioner too. Now, a pair of 2 KW generators would be rather handy. However, that is a different discussion.

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Old 05-08-2016, 03:39 PM   #12
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You are right, it would be foolish not to just use the existing converter. I just researched it and it will charge up to 55 amps when nothing is running. If I was running a few LED lights and my LED TV that charge rate might drop down to 45 amps, maybe 40 amps? I didn't realize it had that high of a charge rate. I knew it had a 55 amp output but didn't think it would use all of it for charging. Today is not a wasted day, I learned something! Will still keep my charger, worked good for my boat. Might need it someday to start my truck but not for a while. Recently had it checked so know its in good shape.

Now, if I am thinking right (I admit I am going brain dead!) a 1000 watt generator is only going to supply about 28% of what my 30 amp converter is capable of using? So at 28% times 55 amps means the converter would supply a charge rate of around 15.4 amps. I am sure someone will argue with me on my thinking. A 30 amp converter could utilize 3600 watts and a 1000 watts is roughly 28% of that, so its output would be limited to 28% of its 55 amp charging capability? That would be 15.4 amps, right?

Now, am I overthinking this whole thing, LOL?

Jim
You are probably over thinking things. The 30 amp is how much 120 you would have. In a perfect world with no loss, that would translate to about 200 amp of 12 v. If nothing but a few led lights and occasionally your water pump cycles on 1000 watts of 120v will allow the converter to charge at about its full rate. Now my calcs are approximate and I AM ABOUT HALF BRAIN DEAD, but your biggest problem will be noise level for the hours it will take for a full chsrge
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Old 05-08-2016, 04:31 PM   #13
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If it helps, Costco has Honda 2000 on sale for 899 shipped


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Old 05-08-2016, 09:56 PM   #14
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If it helps, Costco has Honda 2000 on sale for 899 shipped


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In the stores or online?
Never seen the Honda 2000i at any West Coast Costco.
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Old 05-09-2016, 07:44 AM   #15
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Sorry about that- it was sams club and it was online.


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Old 05-09-2016, 08:09 AM   #16
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Replace all of your light bulbs with LED's then the only current draw you will have is the water pump which is intermitent and the draw for the refig which is min. but I would suggest a 3000 watt gen to run the AC and microwave.
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Old 05-09-2016, 09:00 AM   #17
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You could be right but got to think about it a little. It is true the converter is capable of putting out 55 amps at 14.X DC volts, or roughly 770 watts as you state. but doesn't it require 30 amps at 120 volts AC in order to do so? Or roughly 3600 watts? So wouldn't the DC wattage output lower as the AC input lowers?

Jim
Watts is watts (other than some loss in the conversion process). 770 watts at 12V is still 770 watts at 120v, not accounting for the losses, but those are minimal. Even if it was 800 watts, you are still well under the 1000 watts the generator claims it will supply. The 30 amps is the MAXIMUM that charger will ever take, but not unless you are using the full 3600 watts, which you are not.
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Old 05-09-2016, 09:08 AM   #18
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Cabela's has the Champions 2000i for 499 right now. The nice thing about 2000 watts is if you start losing power due to higher elevations, you will still be able to recharge everything.
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Old 05-09-2016, 10:04 AM   #19
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Replace all of your light bulbs with LED's then the only current draw you will have is the water pump which is intermitent and the draw for the refig which is min. but I would suggest a 3000 watt gen to run the AC and microwave.
All bulbs are led and tv is an led unit. Problem is sense I had my amputation I have trouble lifting what it weighs. I bought it so I can run my AC all day when I am out for the day and need to run the AC all day for my dog. I also use it for emergencies during a power outage. It works great for that! I installed a rack on the back bumper of my Signature Ultra Light but have been told it weighs too much to do that safely. I haven't been able to put it thru a test to find out because of my surgery. See photo below. This is what I did.




However I was sent these links to help me:

We Discover Canada And Beyond: Extending the Bumper on 5th Wheel Trailer

We Discover Canada And Beyond: Custom Made Generator Box For Our RV

Same 5er and weighs more than what I did.

But back to this question. I just want a light weight generator I can use when boon docking. Something I can pick up with no trouble Something I can toss into the back of my truck and keep my batteries charged. Being able to run the microwave and coffee pot would be nice but can live without the AC for a day or two if need be.

Just did some checking.

Honda 1000 watt $879.00 29 pounds

Honda 2000 watt $1149.00 46 pounds

Storm Cat 700 watt $125.00

Pedator 2200 watts $500.00 64 pounds Getting a little heavy but could handle it.

All with-in my price range. Weight are doable. All have do-able noise levels for camping. I like the price and 2200 running watts the best but I have never heard of a Predator generator before. Has anyone heard of them? I know Honda are very reliable. Love the one I have. I just wish it was lighter in weight and a little smaller! I know I could handle the Honda 2000 watts weight. Could easily put on a carrier rack behind my truck, which I own, or easily put in my truck bed.

Looking like the Honda 2000 watt might be a winner. Should handle everything but the air conditioner.

Jim
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Old 05-10-2016, 11:04 AM   #20
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I learned something new today. I didn't know that Yamaha makes a 2400 Watt is generator. It weighs 75 pounds so it is pushing my weight limit however it will fit in the back of my truck with the 5er hooked up and it will run my 13500 btu AC unit. A 2000 watt generator will not do that! You need to double up the 2000 watt generators to do that. This is the reason I went to a 3000 watt generator. A 3000 watt is too heavy for me to handle and too heavy for my 5er though. It is 2 inches to high for the bed of my truck also, but the 2400 watt fits in the bed of my truck with the 5er hooked up which is what I need! I could run my AC for my dog when I am not there. I now won't have to worry about adding weight to the rear bumper so won't have to worry about damaging the frame on my Ultra light 5er!

When I spoke to FR they said the reason the did not recommend adding anything to the rear bumper on an Ultra Light was because of vibration caused by the added weight hanging off the bumper. I think their reasoning is stupid considering they add a spare tire carrier that shook like hell with the weight of a spare tire on it though! I eliminated that problem by taking the carrier off though! I just toss the spare tire in the back of my truck.

I will keep the 3000 watt Honda generator for emergencies at the house for when I lose power in the winter, big enough to run my gas furnace and house fridge at the same time. Using the 2400 watt I will be good to go in the summer time. And the 2400 watt will cover me for when I have the dog with me, YEA! Or when boon docking. Was going to get another generator for boon docking just the 2400 is a little bigger than I had planned. But for an extra $500.00 I can cover things I hadn't planned on.

Jim
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