Elec help!

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
A

AmeDeBoheme

Guest
I have posted a couple times on some other issues, but my partner, our dog and cat and I are preparing for a year or so of fulltime RV living where it is our hopes to be boondocking as much as possible. Living off the grid and not in parks is very appealing to us.

For the last 4 or 5 days (pretty much non stop) I have been trying to wrap my brain around the RV elec system. I have read countless blogs, books, forums, posts, and watched dozens of hours of videos....literally anything I can find. And I must say I think I am more confused than ever LOL!

Allow me to explain my current setup and then I shall ask my burning question.

We have an 84 Pace Arrow.

The current converter (pd764q located under the bed in the rear) is currently not charging the batteries/I only get power when connected to shore power or the 6.5onan gen is chugging away eating all my gas and being louder than the chevy 454 motor. The prev owner mentioned he had to change the pc board in the converter twice during his ownership and that the LED light was dead again and he suspected that needed changing again.

After speaking with the super helpful Bob (formerly of Progressive Dynamics converter company) we thought it best to upgrade my converter to a newer 45amp PD9145 (which is in the mail and on it's way to me and will be put in this weekend)

I also understand thru my researching that when boondocking and running off the house bats, I can not run things off my outlets (laptop, lamp, wifi router etc) or my A/C without the use of an inverter - so I purchased a 5000w inverter from ebay for 200 bucks and that is on it's way to me (hopefully being installed this weekend as well while I am grunting sweating, contorting and wrestling with wires, breakers and trying to solve this elec mess)

MY BURNING QUESTION(s): Firstly...did I buy too big of an inverter for the setup I have? Secondly...I currently have two deep cycle house bats in addition to the chassis bat...how many more batteries should I be getting to run this inverter I so overzealously purchased ignorantly thinking a larger Wat rateing gave me more power longer? And thirdly, where I am running 2 laptops, a record player, charging 2 cell phones, a wifi router, a table lamp or two and the reg house lights, water pump etc (and sometimes the A/C on desperate days) how long should I expect to be able to live off of the battery juices and (as of now the budget sets back the solar panel purchase a couple months so it's just us and the genny) how longish would it take the Gen to charge it all back up?

please be gentle (yet generous) with your responses....I am very much a newbie, confused, excited and prob making stupid mistakes in my overzealous excitement...I just gotta wrap my head around all this stuff and set it up right. Am I on the right track? Am I totally off base? AM I EVEN ASKING THE RIGHT QUESTIONS?! HELP!!!! 

Thanks again for all your help gang!
 
The first answer to your question about inverter size is yes, it is probably way too big for your batteries AND charging capability. With a 100 amp charger and 2000 watt inverter we use four 260 amp 6 volt batteries. With your 45 amp charger you would need a lot of charge time to recharge batteries with 500 watts of storage.


If you ever put a 5000 watt load on the normal marine/RV 12 volt batteries your Pace Arrow has you would run them dead in 20-30 minutes. A 500 watt inverter would run the electronics you mentioned, a 1000 watt would give you some reserve and a 1500 watt would let you make coffee, etc but would also drain your batteries pretty quickly.


Without knowing specifically what you have for batteries I would guess you have a total of 200 watts of capacity and we usually recommend running the batteries down to no  lower than a 50% charge to conserve their life.  That means 100 amp/ hours of available power that run a 85-90% efficient inverter or a net of 90 amp/hrs. A couple of 12 volt lights, a charge for your phone, and running your laptop for a few hours will pretty much use that up. Forget the air conditioner, none of us have the battery capacity to run those off inverters.
 
Jeff,

thanks for getting back to my question. I will now go bang my head against a wall. And then see if I can return this 5000w Inverter. What size Inverter would you recommend for my setup/usage needs? 3000w? 2000w? Should I also get another battery or two? to add to the two I already have?

More answers seem to lead me to more questions. gosh.
 
The best bang for the buck and weight are 6 volt wet cell golf cart batteries, four of those provide 450 ah of 12 volts at 20 amps an hour, or 225 amps at 50 per cent charge. Keep in mind that your 45 amp charger will probably need six hours or more of generator run time to fully recharge that 225 ah. (The charge is tapered, not a full 45  amps). If I was installing batteries, converter, and inverter I would consider a 2000 water inverter/charger combo plus four 6 volt batteries. On your 84 Pace that would present a real space challenge because the batteries and inverter need to be in separate compartments with the batteries in a vented area unless you use glass mat sealed (expensive) batts.
 
I use a 400W inverter for the computers and CPAP.  It plugs into a regular auto 12VDC receptacle.  Use this for the CPAC when boondocking and for the computers on the road.  Normally hookup to SP or use the Generator for AC otherwise.  Found we could live OK if prudently used the DC lighting and water pump - turning the pump off after use and minimizing the number of lights used in the evening (turned off several locally that are on a master switch).  I have 2 285AH 6V batteries.  Been able to make it over night running the furnace and the CPAP in 10 o F weather and be able to start the 5500 Onan.  Hope this helps.  JM2?...
 
I do a lot of dry camping at the sand dunes, desert and mountains.  I have a 2000w inverter/charger and have upgraded the original three 12v bat to four 6v Trojan golf cart bat.  I like my satellite TV and that is a power hog that is on from 8 am to 11 pm and records our tv shows & sports.

When I dry camp for more than 2 days I use my little Honda 650 portable generator to charge the bat during the day.  It will run about 6 hrs on 1/2 gal of gas.  It is quiet and I put it on a 50ft extension cord so it is some distance from the patio.  I use the little Honda to run this very efficient 40 amp Black&Decker charger: http://www.amazon.com/Black-Decker-VEC1093DBD-Battery-Charger/dp/B000EJQJ1G/ref=sr_1_1?ie=UTF8&qid=1375813759&sr=8-1&keywords=VEC1093DBD

When we need to microwave or a/c, we run the Onan 7.5.  Since it consumes about 0.7 to 1 gal per hour, we don't usually chose to camp in the heat where we need much a/c.

You can go the solar panel route or the really small generator for max efficiency for dry camping.

Enjoy the ride....
Bill
 
AmeDeBoheme said:
I have posted a couple times on some other issues, but my partner, our dog and cat and I are preparing for a year or so of fulltime RV living where it is our hopes to be boondocking as much as possible. Living off the grid and not in parks is very appealing to us.

For the last 4 or 5 days (pretty much non stop) I have been trying to wrap my brain around the RV elec system. I have read countless blogs, books, forums, posts, and watched dozens of hours of videos....literally anything I can find. And I must say I think I am more confused than ever LOL!

Allow me to explain my current setup and then I shall ask my burning question.

We have an 84 Pace Arrow.

The current converter (pd764q located under the bed in the rear) is currently not charging the batteries/I only get power when connected to shore power or the 6.5onan gen is chugging away eating all my gas and being louder than the chevy 454 motor. The prev owner mentioned he had to change the pc board in the converter twice during his ownership and that the LED light was dead again and he suspected that needed changing again.

After speaking with the super helpful Bob (formerly of Progressive Dynamics converter company) we thought it best to upgrade my converter to a newer 45amp PD9145 (which is in the mail and on it's way to me and will be put in this weekend)

I also understand thru my researching that when boondocking and running off the house bats, I can not run things off my outlets (laptop, lamp, wifi router etc) or my A/C without the use of an inverter - so I purchased a 5000w inverter from ebay for 200 bucks and that is on it's way to me (hopefully being installed this weekend as well while I am grunting sweating, contorting and wrestling with wires, breakers and trying to solve this elec mess)

MY BURNING QUESTION(s): Firstly...did I buy too big of an inverter for the setup I have?YES!  Way too big.  A 100 watt will work just fine for watching a little TVSecondly...I currently have two deep cycle house bats in addition to the chassis bat...how many more batteries should I be getting to run this inverter I so overzealously purchased ignorantly thinking a larger Wat rateing gave me more power longer?Depending on what you want to run and for how long.  More the better if your boondocking a lot And thirdly, where I am running 2 laptops, a record player, charging 2 cell phones, a wifi router, a table lamp or two and the reg house lights, water pump etc (and sometimes the A/C on desperate days) how long should I expect to be able to live off of the battery juices and (as of now the budget sets back the solar panel purchase a couple months so it's just us and the genny) how longish would it take the Gen to charge it all back up? About 30 seconds trying to run the AC

please be gentle (yet generous) with your responses....I am very much a newbie, confused, excited and prob making stupid mistakes in my overzealous excitement...I just gotta wrap my head around all this stuff and set it up right. Am I on the right track? Am I totally off base? AM I EVEN ASKING THE RIGHT QUESTIONS?! HELP!!!! 

Thanks again for all your help gang!
Click to expand...
 
I'm not sure there is a downside to a too-large inverter. You simply can't use anywhere near its full capacity, but then you probably don't have 5000 watts worth of electric appliances anyway. Heck, your entire coach is probably running on less than 3600 watts when plugged to shore power (3600 watts is the max a 30A shore power cord can provide).

In any case, you are going to have to learn to budget your electric power use to the amount your batteries can provide between charges. Watts themselves are not the issue so much as watt-hours, i.e. the number of watts used times the number of hours.  The two 6v batteries that Jeff mentioned can provide about 225 amp-hours at 12v, which is about 2700 watt-hours. Half that, the practical working amount from the battery, is 1350 watt-hours, so that's 1350 watts for one hour or 100 watts for 13.5 hours. Anything that makes heat, e.g. a hair dryer or toaster oven, uses a lot of watts, often in the 1000-2000 range. Computers and phone chargers, on the other hand, use much smaller amounts, in the range of 5-75 watts.
 
Re read Gary's post, it is exactly what you need to know.  But I'll reiterate some of his points.
No shuch thing as too big of an inverter, however you simply do not have the battery capacity to use any where near its capacity. The TV and perhaps one other outlet is are the only things most likely connected to the inverter.
You A/C is not, or should not, be connected to your inverter circuit. Donn mentioned 30 seconds, I think he is being generous.
If you boondock a lot you need to look at adding an additional two 6 volt batteries, still no A/C. I was trying to figure out how many batteries you would need to run the A/C for 10 hours but my calculator ran out of digits.
 
Gary RV Roamer said:
I'm not sure there is a downside to a too-large inverter. You simply can't use anywhere near its full capacity, but then you probably don't have 5000 watts worth of electric appliances anyway. Heck, your entire coach is probably running on less than 3600 watts when plugged to shore power (3600 watts is the max a 30A shore power cord can provide).
Click to expand...

The only down side to large inverters that I can think of would be the idle current as it tends to grow with the size of the inverter.
 
The downside to too large an inverter (there are 3)

1: Cost
2: "Overhead" the larger the inverter the larger the overhead, (That is the stand by battery drain and the drain needed to operate the device)
3: Poor regulation at low loads.
 
Well, they ask for the downsides.. And yes, already OWNING the big  box. is a major factor in the decision.. Now the question is "Spend money/Don't spend money" and that is a very easy one.
 
Another plus of your 5kw inverter is that it should be able to handle a substantial amount of surge current from smaller loads that surge a lot - yes, your big inverter will probably trip out for low voltage in short order if you try to get continuous 5kw out of it, but there are some gadgets and motors that have a huge surge for the first second that smaller units can't handle, but then settle down to a more reasonable load - my 1950's drill press for instance.

And, there is no reason you cannot have multiple inverters hooked up at the same time, and just turn on the ones you are actually needing.  If an inverter is hooked up but turned off it should be using nothing at all.

So if I were you and the 5kw inverter was working fine and paid for, I'd keep it and acquire a smaller pure sine wave inverter like the Xantrex Prowatt 600 for under $200, that produces utility grade power and will not cause any issues with any fancy electronics you might plug into it.

I'd have them both wired up and ready to go, and I'd invest in extra battery capacity and solar panels for charging.

With energy saving strategies such as propane fridge or newer super efficient electric fridge (don't run a propane/electric fridge on electric), LED lights, solar oven for much cooking, laptops instead of desktop pc's, elimination of 'vampire' power drains, and a properly installed and calibrated battery monitor, you may be able to boondock for extensive periods without running a generator at all, assuming you have some solar charging set up.
 
One possible downside is a 5000 watt inverter efficiency may be rather poor when running at light loads say 50- 200 watts, which might be typical load.  That's only 1-4% of rated capacity.  I think max efficiency of inverters is up around 80-90% of full load.  So running at just a few percent of rating, you may be loosing half your power in the inverter.  Not many of the low cost MSW inverters will provide specs with charts for efficiency over zero to full load.  The specs I've seen show efficiency trailing off as the load decreases.
 
Thanks for your feedback and advice all - I was able to return the 5k watt inverter and now have a more sensible 2500watt. Before installing the new converter/charger and the new inverter. I am trying to identify why I can not run on 12v power. Everything is fine with SP and the genny, but the batteries will not power the house. All checks out at the bats and the fuse boxes and the multimeters read as they should, the battery sensor on the dash tells me the charge is in the green and good, other than a kill switch under the stearing collum which shuts off the chassis batt to the dash and ignition switch I can not seem to find any sort of battery disconnect switch that others in similar troubleshooting posts have mentioned...I have chased wires as best I can and tried to find fuses or sneaky inline fuses that may be blown....I am at my wits end and on top of not wanting to pay some guy 85 bucks an hour to chase down the issue...I really want to tackle this myself - any other suggestions or ideas on where I might look/what the problem may be?  Could it be the converter? Would swapping out the new one solve my problem? Is there something else that could be wrong somewhere? Why is the world round?! why is the sky blue?!?!?!? WHERE ARE ALL THE BEES GOING?!?! So many questions and so much confusion...HELP!
 
"Why" may have to do with the way the old converter or inverter was wired into the 12V system. We recently had a system described here where the battery 12V output wiring went through a converter relay before actually reaching the house. A search may reveal it, but my memory won't give up the details...
 
I reread this discussion and did not find any mention of the battery shut off switch that was located in the compartment over the entry door in our 83 Pace Arrow. If it is off or not working properly you would pretty much have the condition you describe with the 12 volt system.
 
If there isn't a house battery disconnect where Jeff described, you will just have to start at the house batteries and follow the cables, usin a voltmeter along the way to determine where the voltage stops. There is almost surely a house disconnect relay, triggered by a remote switch, and it is probably open. Could be simply that you haven't found the remote switch, or could be the relay isn't working. Not hard to diagnose, repair or replace once you find it.

Sometimes it just takes elbow grease rather than science.
 
You must log in or register to reply here.

Latest posts

Members online

Total: 1,170 (members: 25, guests: 1,145)

Forum statistics

Threads
131,932
Posts
1,387,726
Members
137,682
Latest member
duckyw7528
Back
Top Bottom