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Old 08-04-2013, 02:51 PM   #1
zuley
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Using a generator

Well, I have become what I swore I would never be; someone who uses a generator while camping. We just returned from 23 days in one of Ontario's provincial parks with our Elite 23RB. We have always chose the non electrical section of the park. Lasted 10 days, power wise, being very conservative using 2 group 27 batteries. Using a 30 watt panel I was hoping to be able to go the distance as we have previous years before jumping to the dark side. I had brought my Coleman Sport 1800 watt generator, for nothing else to be able to get the slide and awning in if we went dry prior to leaving. This thing sounds like a lawn mower running and is certainly not very quiet. I ended up having to run it for about 45 minutes every third day to get some juice back into the batteries. As it turned out there were a couple of others in our area who did the same. However, my little Coleman was certainly the loudest. One neighbor joked that he would wait until I started mine so that no one could here his running. We head back to the park a month from now for another 23 days. Two part question if I may... What is the minimum watt generator I could use for nothing else other than to give the batteries a quick boost every couple of days and what is the most quiet gen that would suit my needs? I'm certainly not interested in running anything else other than my charger off of it.
Thanks.
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Old 08-04-2013, 03:09 PM   #2
Festus2
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Oh boy, here we go again!

If your looking for a small, quiet generator to do nothing else than to top up your batteries, then you might consider a 1000W. You don't need an 1800W generator just to charge batteries! OR you can upgrade your solar panels to something larger --- say 85W - 100W. Having to rely on a 30W solar panel is cutting it too close - especially in cloudy conditions. Solar is quiet so your neighbor won't be bugging you about the noise.


You'll get all sorts of responses about which generator to buy. We have a thread that has been running for quite some time about that very topic so I'm not about to get into that. It's been thoroughly discussed on the forum both currently and previously. You might want to read the 6 pages of posts in response to skenney's thread question, "What kind of generator to buy?" which can be found in the Repair and Maintenance section of the forum.

If you are on a tight budget, there are generators that are available in the 1000w range that are quite quiet and reliable. If you want to spend more $$$ then there are others that are known to be quieter. You probably know which one(s) I am referring to. You can spend $400 or $1000 ---- you be the judge of what is the best value for the money.

OR you could install 2 6v golf cart batteries which will give you more amp hours than the 2 group 27 12's that you currently have but this probably isn't a practical solution to your problem at this point. However, if you do a lot of dry camping, 6v's are the way to go and when the time comes to replace your 12V's, it is something to consider.
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Old 08-04-2013, 04:25 PM   #3
diugo
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First, thank you for recognizing that your generator should only be used to charge batteries or briefly run high-current devices. Recently stayed in a BLM campground in Nevada where some ******* ran his genny from 7am to 9pm every day.

The answer to your question is that the generator, charger, and batteries should be well matched. Batteries generally require 14 volts to fully charge. If your generator puts out 1800W, that's 129 amperes at 14V (129=1800/14).

Batteries are sized in ampere-hours, ranging from about 50Ah for small 12V sizes up to 300Ah for the larger common 6V sizes. The amp-hour rating is often denoted as C, for capacity. So a single 50Ah 12V battery has C=50. Two of them in parallel, C=100. Two 225Ah 6V Trojans wired in series have C=225 for the pair.

Batteries are either flooded or sealed. Flooded batteries can be charged faster than sealed ones. The GENERAL guideline is, the maximum charge current for flooded batteries is 0.5C for a one-hour charge (0.3C for sealed batteries). Consult with your battery manufacturer for their recommended rate---some high-quality AGMs can be charged at the full C rate!

So at a rate of 0.5C, a 50Ah flooded battery should not be charged at more than 25 amperes (25A). Your 1800W generator can put out 129A, which is way too much for a single 50Ah battery (129 > 25). But it's just right if you have five 50Ah batteries in parallel (because 25*5 ~ 129). On the other hand, the ideal generator size for two 225Ah 6V Trojans is 1575W (1575=0.5*C*14=0.5*225*14) so 1800W is pretty close.

Remember, all this assumes charging for one hour with the battery depleted to 50% of its capacity. The less you deplete the battery, the less time you need to run the generator. In other words, if you only deplete to 75%, you only need to run the generator for a half hour.

It also assumes the charger is rated higher than the generator. Don't use a dinky charger, or it will become the bottleneck! For example, a 100A charger is too small for an 1800W generator (because 1800/14=129 > 100).

There's a lot to digest here, but if you piece it all together, it should answer your question.

ETA: The aforementioned describes the BULK charge phase only. Leave your 30W solar panel connected to ensure the batteries get their full absorption phase as well.
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Old 08-04-2013, 04:47 PM   #4
Festus2
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The OP did not specify the Ah for his Group27 12v batteries and since he does not have any 6v's which might require more wattage to charge, I suggested that a 1000w generator would probably do what he wants to do: maintain or top up his 2 Group 27 12v's. I am assuming that he would use the 12v DC charge from the generator and not have to plug in separate battery charger to do the job.

We have no way of knowing how depleted his batteries become - 50%, 60% or ?? so it is difficult to say with any certainty that he needs "X" hours of charging at "Y" rate to bring them up to being fully charged. While having a 1750w, 1800w or 2000w generator may be ideal, it may not be necessary in his situation.

I think the OP is looking for a quiet generator and one that will keep his batteries "up". If he is worried about bringing his slides in and out or using the landing gear or stabilizers, he can always plug into truck with engine running to help give the battery a "boost" for these two chores.
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Old 08-04-2013, 05:15 PM   #5
zuley
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Thank you for the replies. I just had a look at the batteries I am using. They are Interstate SRM-27, 600 CCA, 750 MCA. There is no indication of AHs stamped on them. Once the onboard power indicated one third power remaining, or 12.2 volts by a test meter I fired the gen. 45 minutes would bring them up to two thirds power on the indicator or 12.6 volts on my meter. As I stated earlier I am against running a generator in a camp ground so I was very causious of the run time. Also, I was not charging directly from the gen. I ran the shore power cord to the generator and plugged in using the adapter from 30 amp to 15 amp.
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Old 08-04-2013, 05:35 PM   #6
diugo
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Group 27s are typically rated around 100Ah, so two in parallel would make C=200 and thus 1400W the ideal generator size. Smack dab between 1800W and 1000W! The only drawback to a 1000W is a longer charge time, that's all.

OP has a good handle as to how to measure the depletion level---resting voltage. 12.2V generally corresponds to about 60% of full charge, so the RV's energy gauge is quite conservative if it claims 33%.

You mentioned 12.6V as the generator cutoff; that's fine as long as the batteries eventually reach ~14V by the end of the day via solar charging or using the RV's converter-charger. Otherwise you will be shortening their longevity.
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Old 08-19-2013, 03:11 AM   #7
zuley
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Further to my original posts... Brought home from work a Midtronics battery load tester and load tested both batteries after charging at 2 amps for two days and letting sit for a day prior to testing. Battery one tested 100 percent good. Second battery load tested at only 525 CCA and 50% of life remaining. Stopped in at the Interstate depot on Friday afternoon. Told them what the load ratings were on the battery and how old the batteries were. No questions asked; did not even ask for paperwork. Walked out with a new grp 27 battery. Hopefully this will correct any short comings we experienced.
I'm thinking next spring I will clear the wallet of moths and spring for the Honda 2000.
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Old 08-24-2013, 08:49 AM   #8
christopherglenn
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The size of generator has more to do with the charger / converter then the batteries. A 50 amp charger will happily run on a 1000 watt generator. A 100 amp charger will overload the 1000 watt generator. Once the batteries are partially recharged the chargers are running a fraction of their rating - but when first energized they *should* be 90%+ of their rating - if even for a few seconds when the batteries are down - like after being run for several days without charging. From AC to DC there are 10-15% losses, 1000 watts at 120 volts is closer to 850-900 watts at 14.4 volts.
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Old 08-24-2013, 11:02 AM   #9
Bluewater
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Zuley. You will really enjoy a Honda 2000...very quiet and durable..well worth the money.
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Old 08-25-2013, 05:37 PM   #10
dacar
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2nd the Honda callout- running 3000I Handi - receive nothing but compliments how quiet it is
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Old 08-26-2013, 01:25 PM   #11
macattack
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Any reason you don't just recharge from your tow vehicle? It's there anyway, and you wouldn't have to lug around a generator just for a quick charge.
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