Generator vs Power Inverter - Fiberglass RV


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Old 09-01-2006, 05:07 PM   #1
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I'm at a decision crossroads...trying to decide which way to go. I wish to add a auxillary power source to my 13' Scamp, and I have two options.

I've figured out that most of my everyday 110vac. power needs, if having go without shore power, would accumulate at most to around 2500 watts. I figured into account a 400 watt refer, two 100 watt radios, a laptop computer that would draw 60-80 watts, lighting for the camper 100 watts, a floor fan 50 watts, and a pelonis ceramic heater 1500 watts. I didn't figure in the A/C. My actual power needs would be much less...only the refer would be a continuous draw...the fan or heater, only seasonal, and the application very sporadic...limited emergency field use only.

My two choices for auxillary power is a 3000 watt inverter with 4 200mAh deep cycle batteries, or a 3000 watt gas generator. I'm looking for any observations or advise, past experiences, comments or fresh ideas... it's brainstorming time! I'm considering cost, flexibility, fuel/recharge issues, noise, maintenence, ease of use, ect.

Please don't be shy...speak yer piece!

Thanks,
ConwayBob
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Old 09-01-2006, 06:00 PM   #2
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just because you want to use an electric heater a generator is need a battery will not last a night
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Old 09-01-2006, 06:28 PM   #3
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What type of refrigerator do you have. Can it run on propane? That will really cut down on your electrical consumption.

My second thought is to get a Mr. Heater, catalytic heater or something like that for your winter heating needs. They also run off propane.

Third, convert your lighting to Cold Cathode Lights. I paid $4.95 per pair. They use very little power.

This brings your generator needs way down. You could get a 2000 watt or maybe even a 1000 watt Honda or Kipor.

So I guess what Iím thinking is you could attack your needs from multiple options and meet your needs. Learning how to conserve has been my biggest challenge.

I hope this helps.
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PS: FYI - The links are for information only. May not be the best price.
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Old 09-01-2006, 06:28 PM   #4
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I would consider a third option of using a propane heater or furnace instead of the electric one, and a corresponding smaller inverter/battery setup. Okay, I would really use this option instead of planning to use an electric heater supplied by the battery, even briefly.

Bob, you've described your power needs, but not your energy needs: how much energy do you expect to use each day, and for how many days? Energy is (power x time), or (current x time) if you do everything in amps and amp-hours at 12V. For the battery setup, this is crucial because the batteries need to store all of the energy (or charge); in the generator setup it matters, too, because it determines how long a given size of generator will need to run each day.

In considering requirements for battery size, the 12V loads need to be considered as well, assuming that the same battery set would feed the inverter and directly supply the 12V stuff, unless the assumption is that everything is AC-powered.

Edit note: Mike and I were typing at the same time, and it seems like we're also saying the same thing!
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Old 09-02-2006, 12:04 PM   #5
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I would consider a third option of using a propane [b]heater or furnace instead of the electric one, and a corresponding smaller inverter/battery setup...

Edit note: Mike and I were typing at the same time, and it seems like we're also saying the same thing!
Thanks for the replies, I do see that both are are aimed along the same theme, and I had completely forgot the propane furnace in the Scamp , I would be using it instead of the electric heater.

My '83 Scamp came with only the minimun of 110v accessories; a single 15 amp circuit breaker pnl, one florescent light fixture and one ac outlet next to the heater thremostat. The only 12v dc needs the trailer has currently are two lights at each side of the kitchen cabnets and the starter for the heater.

As for my energy needs there is not anything that is in the extreme while on shore power, I've added a 5000 BTU AC, thats the single big energy hog and would not be used without shore power. Aside from that, and a small 1100 watt microwave that is seldom used, the only other AC energy requirements is the small 1.5CF AC powered fridge, my computer & radio gear.

I should clarify what I'd be doing with my auxilary power. My Scamp is my Ham Radio Shack. In the event of a emergency that would require me to operate in field conditions with out shore power, I would need a power source necessary to provide lights & power for one laptop, two 100 watt radios minimum for sustained operation of at least 8-12 hours.
The fridge could even be taken out of the circuit. I'm estimating around 600-700 watts sustained with 1000 watt capacity for the fridge start, (I think this is a very liberal estimate).

I'm well aware that a small gas generator can easily handle this load, but I really want to explore other options. I am not pleased with the noise and service issues with a generator, and the added fuel requirement. I'm currently selling off a 5000 watt (POS)generator that is WAY too noisy and is extremely hard to start. A power inverter is being considered since I have access to some very large capacity(200 Ah) 12 volt batteries at a very low price, the unit would be quiet and low maintenence, and since my truck has a heavy duty alternator, recharging a portable bank of deep cycle batteries is already possible.

As I figure it, a 1200Ah bank (200Ahx6) would give 7 1/2 hours of service @ 650 watts before requiring a recharge. Again, my actual wattage use would probably be much less. The Inverter and Battery Bank could remain on the back of my truck in a vented enclosure, with a charging circuit to my trucks alternator.

I may be all wet with all this but that's why I'm posting this topic, there's a great braintrust here in this forum. Thanks again for the replies.
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Old 09-02-2006, 02:44 PM   #6
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Bob

I too use my egg as a shack and if you give it a little thought....we don't need anything that is other than 12 volt D.C. really.

I have made every electric item in my egg run from 12 volt other than the battery chargers and inverter for those things A.C. and I dare you to tell of a HAM device that needs A.C that you would use like here?

This allows me to run 100 watt H.F. rigs and 50 watt Mobiles and H.T.'s all from 12 volts.

I use a large battery for my lighting and fans and non-ham gear and I have two banks of 2-12v 75ah gels for the gear.

I can switch between them so that one is charging under no load while the other is in use.
I use a small 1000w generator and solar to charge when not connected to shore power.
While connected to shore power my power converter/power supply charges and can run the gear at the same time.

It can be as simple as one of the West Mountain Powergate devices or as I do get a high quality marine charger designed to supply its full rated output continously while charging.

I have used this setup for two Field Days and many other times and never been without "Juice".

I would be happy to talk about it with you further.
PM me your number and I will gladly call.

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DE KC0UKR
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Old 09-02-2006, 07:01 PM   #7
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I'm at a decision crossroads...trying to decide which way to go. I wish to add a auxillary power source to my 13' Scamp, and I have two options.
I too am at that same place ... I think it comes down to 'horses for courses' ...

We live in Florida and only use our camper between April and October so that means air conditioning, swimming pools and real showers ... i.e. full service campgrounds ... but we still need to power the fridge on the road ... simple right?

Well, the fridge only needs 140 watts of A/C power ... no problem ... one 100 amp hour battery and a 300 watt inverter ought to do the trick? Wrongo, bright one ... the fridge compressor over-heats when supplied with less than pure sine wave 60 cycle 110v current. My 300 watt inverter is a 'modified sine wave' (read cheap) variety.

So the problem isn't simply a matter of watts used vs watts available ... it matters what kind of watts ...

Just be sure that all of the appliances you need to run off the inverter can live with 'modified sine wave' (which really means pulsed) current.

As far as I know, generators produce the pure sine wave variety common to household circuits but pure sine wave inverters are quite a bit more expensive than the usual off the shelf versions.

Most small appliances such as computers, battery chargers for cordless appliances, LCD TVs, and the like that use step down transformers will run just fine off the modified sine wave type inverters. That's because the transformers convert the stuff back to one voltage or another of DC current anyway so the current issue gets cleaned up along the way. Even my Dremel tool and corded power drill run fine on the stuff but the fridge refuses. It just overheats like it was getting low voltage.

So IMHO it matters how you use the camper ... if you spend a lot of time off the grid maybe the genset makes more sense ... but if you're really adverse to all the fuel and maintenance ... then a pure sine wave inverter, lots of battery capacity and lots of solar cells might answer ... with a genset for recharging on rainy days.

Consider too the type of battery and the recharging system. Wet cell batteries can only be discharged to about 50% of capacity before recharging without much damage. Regular discharges below that level shorten battery life a lot. Other types such as Gel or AGM batteries can sustain deeper discharges and can be charged back quicker...

On my boat (our other camper) for example, we consistently run a deficit of 50 amp hours per day on our 200 amp hours of Gel cell batteries. That's net after our 120 watt solar panel does what it can during the day. We can recover that deficit in about an hour of running time on our main engine because we have a heavy duty alternator and a 3 stage regulator that optimizes recharging ... also the Gel cells have an acceptance rate that approaches 70% of battery capacity. AGMs have even higher acceptance rates. Of course, our wiring and stuff is more than adequate for the job.

I'd be interested in what you finally decide ...
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Old 09-03-2006, 08:34 AM   #8
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I'm at a decision crossroads...trying to decide which way to go. I wish to add a auxillary power source to my 13' Scamp, and I have two options.

I've figured out that most of my everyday 110vac. power needs, if having go without shore power, would accumulate at most to around 2500 watts. I figured into account a 400 watt refer, two 100 watt radios, a laptop computer that would draw 60-80 watts, lighting for the camper 100 watts, a floor fan 50 watts, and a pelonis ceramic heater 1500 watts. I didn't figure in the A/C. My actual power needs would be much less...only the refer would be a continuous draw...the fan or heater, only seasonal, and the application very sporadic...limited emergency field use only.

My two choices for auxillary power is a 3000 watt inverter with 4 200mAh deep cycle batteries, or a 3000 watt gas generator. I'm looking for any observations or advise, past experiences, comments or fresh ideas... it's brainstorming time! I'm considering cost, flexibility, fuel/recharge issues, noise, maintenence, ease of use, ect.

Please don't be shy...speak yer piece!

Thanks,
ConwayBob
Hi Bob; by seasonal emergency use meaning hurricane season? There is a fellow in the North East (Vermont?) using a 13 Scamp for the same purpose (not hurricanes tho). I seem to recall that he used a generator but I hope someone can put you in touch with him. The use of a combination of battery/solar would really keep you off the grid and you could be on the road within minutes in an emergency. Even with just a single deep-cycle battery you can get along for a surprisingly long time (my wife and I camped in a primitive campground this March for five days... a little TV for news, the furnice on for a short time in the mornings to get the chill off and a Coleman lantern for most of the light).

I assume you don't have a gas fridge?
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Old 09-03-2006, 09:36 AM   #9
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ConwayBob,

Just my 2 cents here.........................

I'm building a trailer that we'll be using mostly off-grid. I have two Group 27 batteries to power what we need................which includes two C-pap machines. After much study and asking lots of questions of experienced off-grid campers, I've decided to go with a quiet Honda generater (probably the 2000). I'll only be running it during the daytime. It will be used with a 3-stage automatic charger to keep the batteries up and running. Then, while on the road, a line from the tow vehicle battery to an inverter to the charger will keep the batteries topped off. (charging from the tow vehicle's charging system will only charge batteries to 70% capacity) I can't speak from personal experience that this will work, but based on what I've learned from those who do this regularly, it should be just fine. Once again, this is just my opinion.
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Old 09-03-2006, 10:20 AM   #10
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I was in Wally world the other day and saw their best battery advertised as 100% replacement in the first 3 years and then prorated after that for a total period of 7 years.

I'm thinking it might be cost effective to purchase the highest amp battery they have and donít worry about abusing the thing and if it goes bad as most on this site predict will happen by the constant discharging Ė charging take the chance that it will crap out within the first 3 years.

Any thoughts on the life of a camper battery?
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Old 09-03-2006, 05:07 PM   #11
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I was in Wally world the other day and saw their best battery advertised as 100% replacement in the first 3 years and then prorated after that for a total period of 7 years.

I'm thinking it might be cost effective to purchase the highest amp battery they have and donít worry about abusing the thing and if it goes bad as most on this site predict will happen by the constant discharging Ė charging take the chance that it will crap out within the first 3 years.

Any thoughts on the life of a camper battery?
The life of deep cycle batteries is usually quoted in cycles ... that is number of discharges and recharges ... assuming discharge no deeper than 50% and proper maintenance/recharge ... standard deep cycle 12 volt marine/RV batteries typically get somewhere around 500 to 700 cycles ... golf cart batteries often get up to 1000 cycles ... so do Gel Cells and AGMs ... Rolls battery says their wet cell batteries will get 1000 cycles and I think Trojan quotes similar numbers. The best dollar cost averaging is with golf cart batteries ... they are cheap and last well ... again assuming they are maintained and charged properly.

If you tend to neglect batteries, the Gel Cells and AGM may be better buys because they will take deeper discharges, and have low self discharge rates and need no water level maintenance ... just keep the charging voltage to 14.1 or lower ...

The main killer of wet cell batteries is failing to maintain the fluid level. Charging at volatges over 14.1 causes outgassing ... essentially boiling the battery causing fluid levels to decline ... most wet cell chargers use 14.3 volts ... considered to be optimum ... unfortunately this causes the fluid to boil off. If you charge Gel cells or AGMs at any voltage above 14.1 the same thing happens but you can't replace the electrolyte ... at least with wet cells you can add water.
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Old 09-03-2006, 05:57 PM   #12
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ConwayBob,

Just my 2 cents here.........................

I'm building a trailer that we'll be using mostly off-grid. I have two Group 27 batteries to power what we need................which includes two C-pap machines. After much study and asking lots of questions of experienced off-grid campers, I've decided to go with a quiet Honda generater (probably the 2000). I'll only be running it during the daytime. It will be used with a 3-stage automatic charger to keep the batteries up and running. Then, while on the road, a line from the tow vehicle battery to an inverter to the charger will keep the batteries topped off. (charging from the tow vehicle's charging system will only charge batteries to 70% capacity) I can't speak from personal experience that this will work, but based on what I've learned from those who do this regularly, it should be just fine. Once again, this is just my opinion.
Chris,
I'd give the inverter/charger thing another walk through ... like this ...

Your TV alternator will give you about 14.3- 14.5 volts DC for about 10 minutes ... after that it drops to 13.6-13.8 volts because its charging job ... namely replacing the starting current used ... is over and it just needs to maintain the TV battery, so 13.8 is what 'they' set the trickle charge voltage at.

Now suppose you have a heavy duty wire running the 25ft or more back to the trailer say size 12 (most are even smaller). I doubt if that size wire can deliver more than 15 amps over that distance at an initial voltage of 13.8 without serious overheating ... hence it is likely protected by a 15 amp fuse ...OK so now maybe you can get 13.5 x 15 amps back to the trailer or about 200 watts ...

Now the inverter is about 80% efficient so maybe the charger gets 160 watts but it bumps the voltage back to 14.3 or so that means the battery, not counting charger losses gets about 160 watts/ 14.3 or about 10 amps maybe 11 amps ... 10 to keep the math simple.

If the Trailer battery bank is 200 amp hours (two group 31s say) and it was discharged to 50% of capacity then you need to replace 100 amp hours ... at 10 amps you'll need to be on the road for 10 hours to recharge ... not allowing for inefficiency in the charger or the acceptance rate of the batteries (which declines with age)

If you just connect the alternator wire from the TV to the battery you'll get 15 amps maybe ... the problem is the charging voltage is only trickle charge rates or about 13.8 volts not allowing for the drop over 25ft of size 12.

A bigger inverter won't work ... it'll just blow fuses unless you also increase the wire sizes and fusing. Also look at the inverter wiring instructions for some insight into wire sizes. I have a 2000 watt inverter in my boat (our other camper) but it must be wired with 2/0 AGC battery cable directly to the battery in a run of no more than 6 ft ... that's some heavy duty wiring. Even so we pass the positive cable through a 150 amp breaker just to be on the safe side.

Hence the dillemma ...

A generator powering the charger however might offer the ability to deliver all the power the charger wants ... and therefore get the trailer batteries back up in a couple of hours ... I'm just not sure how to rig a genset for running while you're running down the road. Haven't tried this either but ...

Maybe someone out there has a rig set-up like this and could contribute?
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Old 09-03-2006, 10:07 PM   #13
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Ron, I don't think you mentioned that the TV charging system is seeing some composite of both the trailer battery (needing charge) and the TV battery (almost charged after starting), so the charging voltage will be lower than optimal -- One way around this would be to install a 1-2-Both switch, but it has to be the right kind or it may damage the TV alternator diodes when swithed -- Another way ($$) is to install a dual-output alternator to charge each battery at its best rate.

One fellow I know in a Class B (van-based) camper just assumes his El Cheapo deep-cycle batteries will only last two years before needing replacement and budgets for that -- If they last longer with no special care, that's good -- At $50 at Wally, that's $25 per year and he doesn't sweat the maintenance.
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Old 09-03-2006, 10:26 PM   #14
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...Well, the fridge only needs 140 watts of A/C power ... no problem ... one 100 amp hour battery and a 300 watt inverter ought to do the trick? Wrongo, bright one ... the fridge compressor over-heats when supplied with less than pure sine wave 60 cycle 110v current. My 300 watt inverter is a 'modified sine wave' (read cheap) variety.

So the problem isn't simply a matter of watts used vs watts available ... it matters what kind of watts ...

...As far as I know, generators produce the pure sine wave variety common to household circuits but pure sine wave inverters are quite a bit more expensive than the usual off the shelf versions.
Capt. Ron, thanks for the insight in modified sine waves and their effects on motors. I hadn't figured on that, and I'm not happy with the prospect. A pure sine wave producing inverter is too costly for me, (as yet) but I would really rather have a aux power source that would be motor safe. I guess this is a plus mark in the gas generator column.

But about this Propane/LP Gas conversion for gasoline running electrical generators, am I understanding correctly that a 20# LP tank is only equivelent to 5 gallons of gas? Wouldn't that put me into collecting and keeping filled, a large bunch of tanks to keep me on the air?
Thanks again,
C.B.
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