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Author Topic: What size generator do I need for re-charging the batterys?  (Read 4077 times)

More D

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What size generator do I need for re-charging the batterys?
« on: September 01, 2006, 12:02:13 PM »
This is my first post but I have been reading the EXCELLENT forum for months now in preparation for our first TT purchase.

We will be doing mostly dry camping and in the cooler months. I have looked at the Honda generators and although the cost is a bit high I think it will be the best for us. I plan on purchasing the EU2000, one at first then a second later to run the A/C if needed.

We will be using it in Nov in the AZ high contry and the heater usually drains the battery's after the first day. So now my question. How long of a run time will the one Honda 2000W generator need to run to completely re-charge the 2 battery's? The TT is a new  2007 and we just bought it last month in Aug.

Thanks in advance for your responces and for all the great information I have been getting since I found this wonderfull site!!

More D

JohnSandyWhite

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Re: What size generator do I need for re-charging the batterys?
« Reply #1 on: September 01, 2006, 12:39:59 PM »
 :) Hi More D. It's not how big your generator is (power wise that is). It's more a matter of how much does your charger put out? A 50KW generator will not charge your batteries any faster than a 900 watt generator.  ;D If you are referring to the shore hook-up and the on-board converter/charger? Then I would say anything between 4 and 6 hours. Happy charging and RV'ing.  ;)
Been there, done that. But I never stop learning

Gary RV Roamer

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Re: What size generator do I need for re-charging the batterys?
« Reply #2 on: September 01, 2006, 03:56:17 PM »
As the Whites said, its the size of the charger, not the size of the generator that counts.  The EU2000 itself can put out 8 amps at 12+ volts, but that isn't really intended as  a charger.  You will do beter charging via your trailers own converter/charger, which probably puts out at least 30A at full charge.  You need to find out the converter/charger make and model to find out for sure - there should be a manual for it in the package of stuff that came with the trailer.

Two size 24 batteries (typical for your type of trailer) have a capacity of about 160-170 amp-hours and are probably 60-70% depleted if completely run down. That means you have to put back in .70 x 170 = 119 amp hours.  If you could charge ata 30A rate, that would mean about 4 hours, but the charge rate will decrease substantially once the battery reaches about 75% of full charge.   It takes many hours to get that last 20-25% into the batteries, so you would have to run for 8-10 hours to get close to 100%.  It's more practical to stop at the 80% level and simply recharge more often.  I's also better for the batteries to begin to recharge when they reach the 50% level, rather than drawing them further down.

If that's not enough power for you, I suggest adding a another battery, even if you just hook it in temporarily with jumper cables. More batteries will increase the amount of power available between the 50% and 80% charge levels and more batteries will charge faster than fewer will. Each battery can absorb some of the available charging current in parallel with the others, so you get typically better use of the available charging capacity.
Gary
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Gary Brinck
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2007 GMC Acadia
Homebase: Ocala National Forest, FL

Jeff

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Re: What size generator do I need for re-charging the batterys?
« Reply #3 on: September 01, 2006, 07:06:25 PM »
I have considered buying  1000 watt Honda to have a quiet means of recharging our batteries when boondocking in quiet areas. Our diesel generator gets used fairly regularly but is a little noisy around 7:00PM in a quiet campground.

The 1000 watt Honda can put put a continuous 800 watts or so that would provide just enough to run our Freedom 2000 that puts out 50 amps of charge.

Having gasoline on board is probably the single largest obstacle I haven't talked myself over yet.

Lou Schneider

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Re: What size generator do I need for re-charging the batterys?
« Reply #4 on: September 02, 2006, 03:19:54 PM »
Quote
The 1000 watt Honda can put put a continuous 800 watts or so that would provide just enough to run our Freedom 2000 that puts out 50 amps of charge.
Make sure you have an opportunity to try it with a set of discharged batteries before you buy.  While 50 amps x 14 volts = 700 watts there are several factors that may or may not let this combination work.

It's possible your converter may have a starting surge that will overload the Honda when you first plug in the converter.  Or the converter's Power Factor may not be exactly unity.  A 0.8 power factor will increase the apparent power draw at maximum charge to 875 watts, beyond the Honda's capacity.

John From Detroit

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Re: What size generator do I need for re-charging the batterys?
« Reply #5 on: September 02, 2006, 05:04:17 PM »
My house has an 80 amp Intella Charger, originally breakered at 20 amps (I think I wound putting it on a 15 amp breaker, which it has tripped, once or twice)

Batteries so dead that you could not see a light, no hope in Heaven of starting the generator and my kilowatt Genrac did not even sweat, Of course a kilowatt generac, which is  a traditional generator, can put out a fairly heafty surge if it's short enough (and electronic surges are on the order of 1/30 secnod) where as the same surge can kill the inverter alternator packages like Honda nad Kipor   Still I think a kilowatt box should power it nicely
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Jeff

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Re: What size generator do I need for re-charging the batterys?
« Reply #6 on: September 02, 2006, 08:18:56 PM »
Make sure you have an opportunity to try it with a set of discharged batteries before you buy.  While 50 amps x 14 volts = 700 watts there are several factors that may or may not let this combination work.

It's possible your converter may have a starting surge that will overload the Honda when you first plug in the converter.  Or the converter's Power Factor may not be exactly unity.  A 0.8 power factor will increase the apparent power draw at maximum charge to 875 watts, beyond the Honda's capacity.

Lou:

I haven't got there yet but the Freedom 2000 allows you to pre-select the charging current from 5-50 amps.

JohnSandyWhite

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Re: What size generator do I need for re-charging the batterys?
« Reply #7 on: September 03, 2006, 05:14:30 AM »
 ;D I have a cheapo Chinese/Taiwanese 900 watt genny that I used on our old Coachmen that had a Truecharge 40. We used to charge the batteries, watch Satellite TV and at times boil a 600 watt kettle. It used to trip out on the ODD occasion.  ;D
Been there, done that. But I never stop learning

More D

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Re: What size generator do I need for re-charging the batterys?
« Reply #8 on: September 04, 2006, 06:53:06 AM »
Thanks to all who replied!

Looking thru my packet of manuals the only thing I find on the converter/charger is the warrenty information but not the manuel itself. I will contact the manufacturer and the dealer for it. Right now all I know is that the brand name is WFCO. Is this an good brand at least?

If we plan on doing 80% of dry camping should I consider an upgraded charger for my TT? I don't imagine that the one that came on my TT is very good one or at least one geared to my needs.

With the recommendation so far I will put in a 2nd and 3rd battery. The TT only came with one.


Thanks again!!

More D

Gary RV Roamer

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Re: What size generator do I need for re-charging the batterys?
« Reply #9 on: September 04, 2006, 01:13:22 PM »
Are you also aware that the generator won't run if the fuel level gets below about 1/4 tank? That's a safety feature, so you won't run the motorhome out of fuel using the genset and get stranded out in the boondocks somewhere. When he fuel level gets near the minimum for genset operation, it may cut off but then be able tore-start and run for a bit before cutting off again. 
Gary
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Gary Brinck
2004 American Tradition
2007 GMC Acadia
Homebase: Ocala National Forest, FL