Greetings Helpful R-Podders,

I am looking at ways to decrease power usage when on battery with my 2011 R-176.  One thing I have noticed is that every time I connect the battery I get a fairly large spark from the wire/terminal.  I've tried removing all the fuses before connecting the battery and still get a spark, so obviously there is a significant current drain on the battery, the question is, what is causing the drain and is there anything I can do to eliminate the it?  

Many thanks,

Tim

p.s. There is probably a post on this subject already, but I searched and couldn't find it, please forgive me for that.

Thanks for the response.  I suppose my thinking is that an RV electrical system should operate much like a house:  When the main breaker is in the off position, you aren't going to have power anywhere in the house, but obviously that is not the case with an RV.  I do have a battery disconnect switch, just haven't installed it yet.  I've been taking the battery inside the garage when the R-Pod is not in use for more than a week or so just so the battery isn't baking in the summer or freezing in the winter.  

I'd like to be able to run the furnace off the battery while boondocking, but given the current draw I have doubts as to just how long I could get away with that without drawing the battery down too low.  Naturally I could use a generator or photovoltaic system to charge the battery but would like to avoid that because I'd rather not shell out the money for something that would only be of use a few days out of the year.

As far as boondocking a couple times a year, and wanting to get by without a large investment to accommodate you 12v needs, surely as a truck owner, you carry a good set of jumper cables, right?

In case of an emergency where you need to pump a few gajjillion electrons into your Pod battery, turn your truck around, hook up jumper cabled to your Pod battery, start truck, idle for 20 minutes.

It's hard to say how long you can stay out with a single group 24 battery before you need to top off the batteries, because only you know what all you are going to need/want to run. The wife and I and 2 golden retrievers did a 3 day weekend in Nov here once, on a single G24. Had to do the jumper cable trick Sunday morning to get the slide in. We doubled our battery bank the next week, and 4 years later switched to dual GC2's. We never needed to do the jumper cables again, and stayed out as long as 8 days off grid.

When I measured my current draws I didn't see a significant current with all the appliances turned off, maybe a few hundred milliamps at most. That really shouldn't be drawing your battery down much, only a few amphours per day. If you've checked everything is off and are confident your battery isn't really just tired, then you might want to consider buying a multimeter with a clamp on dc current probe.  They're really cheap these days. You can use that to determine what your real parasitic losses are and which circuits are causing them. 

The problem with a battery disconnect is that you do still need to keep the battery on float charge, which the pod charger does for you as long as the batt is connected, so personally I don't see the benefit from having one. That's me.  I just leave our trailer plugged in when at home. 

PV modules are dirt cheap these days and idling a tow vehicle engine or running a genny is expensive and inefficient so I wouldn't hesitate to buy one even for a few days a year, as long as your campsites have good solar access. By all means do also retain the capability to charge from a fossil fuel (TV or genny) source when you run into series of cloudy days.  

1.  We replaced all the interior lights with LED (I was going to replace the outside light that we almost never use anyway, but inadvertently got the wrong bulb - hardly worth the effort).  

2.  We run the refer on gas when not connected to AC, which is almost all the time b/c we dry camp.

3.  We keep the batteries fully charged with our 100A solar panel.

4  We minimize the use of the heater weather permitting.

4.  We don't use much of any other appliances or electronics, except keeping the cell phones & macbook charged.

5.  We try to pay attention to energy use and turn stuff off when not needed.

With these simple things, we really have no issues with running low on DC power.

If you want to use things like the AC, micro's, and other high AC powered appliances, your only realistic option is to either go to a camping place that offers AC power or use a generator to run them.

Others have commented on the high power consumption of the furnace fan and we've had the same experience.  That's why we try to run it only for a little bit in the morning - good blankets are cheap and cozy - and we can recover the loss of those electrons by recapturing some from the good old sun with our solar panel.

The biggest problem for us when dry camping is the fresh water and gray water tank capacity.  It's easy to use more than you should and run out of water or space for gray water.  Again, being conscious of it makes you use less.

A good quality deep cycle battery or, better yet - in the view of many - a pair of 6v golf cart batteries will give you all the electricity you need if you combine it with a solar panel and try to conserve energy.

Many thanks for all the feedback.

I've already replaced all the incandescent bulbs with LEDs.  As an aside, my external power meter indicates that one two-bulb light fixture with incandescent bulbs uses 46 watts, while the same fixture with LEDs uses 3 watts. Quite a difference especially if you have several fixtures on simultaneously.

We never use the fridge as we use a five day cooler that does the job just fine.  The only thing I'm really concerned about is heat during cold weather, which, if we use the jumper cables from the truck method it seems like that should work just fine for a few days.  It does make me wonder about putting the extra load on the alternator while out in the boonies, though.

IMHO, generators stink.  Add the gasoline, noise, yet another thing to maintain, and more weight.  Maybe I should just go ahead and get the lobotomy now.  Nothing ruins the moment like somebody nearby running a generator so they can watch Gilligan's Island reruns or whatever while we're trying to get some sleep before climbing a 14er the following day. 

Going solar sounds like a great idea, but there are so many options my head started hurting trying to figure out the most reliable and cost effective way to go about it.  Is a 100 watt panel really enough to charge a deep cycle battery in one day if the battery is at about 50% charge?  I saw an Airstream a while back and the top was completely covered by flexible solar panels.  Obviously they are doing more than just charging a battery...

Happy camping to all.

As for generators, yes the noise is awful.  You can get duel fuel inverter generators that run just fine on propane.  The only problem is there are less electrons in the propane than gasoline so when  you convert the fuel to electricity you get less.  [For those who take that literally, I'm not serious.  I know that the electrons in propane and gas molecules don't get sent into the generator.  It's just that there is less energy in the combustion of propane that there is in gasoline.]

I never let our batteries get fully discharged as you suggest.  It's not good for their longevity.  When you camp with a solar system, set it up when you arrive and take it down when you leave and you should have electrons enough to lend to your neighbors.

50% discharge on a 12V 100AH battery is roughly 600 watt-hours. On a good summer day below the 40th parallel you should get 6-8 hours of sunshine (no clouds). I generally expect roughly 80% on our panels (we're at 37 degrees north), and we rarely have clouds in the summer. So, 80% at 7 hours gets you a bit over 560 watt hours with a 100 watt panel.

Figure out how many watt-hours you use in a day, and see if that is close. Even if it's not quite enough, it could take weeks to add up to a problem.

It's a question of how much power you are consuming and how balance consumption with recharging.  If you use 1000 watt-hours a day, then you'll need a solar (or other charging) system that has that capacity.    

Thanks for the insights.  Which charge controller are you using?

I expect that we will be setting the thermostat at about 50 degrees (during the night only in weather averaging mid-40s during the day, low 20s at night.  Reading all the responses thus far, I'm leaning toward buying a PV charging system.

Yes, with that cold, you're going to need some power to run the furnace.  We've had temps in the 20's on some mornings with frost on the meadow grass, and it was no problem getting the pod up to a comfortable temperature pretty quickly.  Taking a leak in the night, on the other hand, is a little chilly, but with a warm bed and blankets, you recover quickly.

So start by estimating how many amphours a day you need. You need to know the current draw on each item and the daily hours of operation for each. Multiply then add. It sounds hard but its actually pretty easy.  Here is an example showing my summertime use. Lots of amhours for fans because its hot in NC in the summer. In the cooler months fans will be off but heater will be on so it works out to be a bit less but similar. Lights are really a minimal part of the load. I have a 12V TV which is why I've included that. Easy mod if you want to watch TV in the pod off grid and save lots of energy. 

Next, battery capacity. You can see that I have a total of about 75 amphours per day. As we don't want to bring our batteries below about 50%, I need a minimum of 150 amphours to get through one day without charging. If you want to go 100% solar and never charge from your vehicle or a generator, you will need about 2-4 days storage in summer depending on where you live. While you never get a day with zero solar output, this 2-4 days gets you through longer periods of cloudy or stormy weather. I have 220Ah battery storage (dual 6V GC2's) for 110AH useable and so expect to need to use my genny fairly frequently in cloudy weather. 

On to solar sizing. A 100 watt module will not be the right answer for everyone. Your mileage will vary. The variation depends on several factors. Besides your actual loads as above, it depends on the time of year, the region you live in, whether you camp under trees or not, and whether you are manually moving around a portable solar module and keeping it pointing at the sun all day or (if you're lazy like me) have them permanently mounted to the trailer roof. 

You can figure that a 100 watt solar module will deliver about 6-7Ah for your loads from an hour of full direct (perpendicular) sunshine.  This is not 100 watts/12 volts=8.3A because of the way solar modules are rated and the charge/discharge losses in the battery.  So if you have a perfectly clear cloudless day, no tree or other shading and keep your module tilted toward the sun, moving it from east to west over the course of the day, you might get 50 amp hours from it. Where I live in the mid atlantic with solar flat on the roof I get about 30 amphours on a good summer day from 100 watts. If I'm not under trees (which I often am). So, I plan on installing a 350 watt module on the roof of my rPod, which should give my about 100 amphours a day in summer when not under the tree canopy. You can get a 350 watt module for under $200 now so why not?  I'll revert to the genny or TV charging when forest camping as needed. 

To mitigate the genny noise and smell you can get a nice 2kw inverter-generator which runs very quietly, convert it to propane, and put it  and a 20lb tank far from your campsite on a 100 ft extension cord.  That's what I do, no stink of gasoline, and I can barely hear it. Running it once a day in late afternoon/early evening when everyone is making noise and cooking helps as well.  I don't fell bad about running mine, its a lot quieter compared to the family in the next campsite with the shrieking kids and barking dogs 

I don't know if this apply's to other models. But I discovered that on my 189 if I pull the lowest green 30a fuze I have no 12v to anything. Makes a quick easy way to pull power when your going to want it back on shortly.

I have used it a few times when wiring new 12v/USB plugin's in our pod.

Originally posted by offgrid All, the best way to do your energy budget for off grid solar is in amphours. It is misleading to do it in watt hours because a 100 watt solar module for example does not produce 100 watts for a 100 watt load in one hour of sunshine. its much less.

I disagree. I convert everything to watts and watt-hours because it represents POWER. Amps and volts are variable. The battery is never 12 volts, but always something between 12 and 14.5 volts, and the amps vary accordingly.

Once you convert everything to watts, then you understand how much POWER you need. You don't need to think about whether you have 6 volt, 12 volt or 2 volt batteries, you can treat each battery as a bucket full of watts. Much simpler to convert to watts and work accordingly. Sure panels don't put out 100 watts, but we often see 80% of that on our solar installations. When the sun isn't ideal, maybe between 50 and 80 percent, but still it's power.

That's why appliances, lights, and generators are all sized in terms of watts. Watts rule.

I've been sizing off grid PV systems professionally for going on 40 years so I think I know a little about it. 

The reason for sizing battery based systems using amp hours is because batteries do not charge and discharge at the same voltage. If you calculate watt hours in and expect to get the same watt hours out of a battery you will be overestimating your system performance substantially. In other words, it is exactly because voltages vary throughout the charge/discharge cycle that watthours are not the way to do the sizing calcs when batteries are involved.  

But one thing that I've found turns people off to trying solar or really any other new (to them) technology, is if they feel they are being oversold on it. Nothing in life is that simple, and everyone's situation is a little different.

So consider your actual needs, expectations, and situation, then make the choice that's right for you. For some it will be solar only, others generator or TV charging only, and yet others (like me) will be best off with a hybrid solution. 

Speaking of solar, here in NV we have a ballot measure that, if it passes, will require 50 of our energy from renewable sources, in effect solar, by 2030.  There are already discussions of setting up monster solar arrays in our desert which they claim can generate huge amounts of watts or amps (?).  Or, in my book, sending "gazillions" of sparky electrons scurrying all over NV, including to the 30 amp plug at my house where our Pod is plugged in at the moment.  

Then we will have to agree to disagree offgrid. I have over a decade sizing, building, and using solar systems, and I always work in watts. This is precisely because of the reasons you mention. Because the voltage varies, the amp-hours also vary. Voltage goes down, amps go up (or the voltage goes up, and the amps go down), but the watts used and the watts required will stay the same. I go for simple, and the simplest way for me to plan and use is by using watts.

Amp-hours gives you no clue about the power because it is only a measure of electron flow. It's meaningless unless you know the voltage.

If you spent your decade designing grid tie PV systems than watts are the way to go. But if you are designing battery based systems, amp hours works better and is much simpler. The nominal voltage is known and is established by the battery, so there is no reason for confusion on that.

If you do use watts and are doing it correctly,  and I certainly agree that can be done, then you must use derates for battery round trip efficiency and PV module temperature. I expect that if you take a look at those derates you will find that they match up very closely with the amp hour approach. If you are not derating when working in watts and watt hours then you will be overestimating system performance. 

We use telemetry on our solar installations. We monitor both voltage and current, and our usage graphs display in watts in vs watts out. Ohm's law rules!

Batteries are the core energy storage element of any off grid power system. Batteries rule, voltage is established by the battery. Everything else is either a load drawing current from or a source feeding current into that energy storage element. The source could be (and in the case of our trailers, is frequently a hybrid of all three) a battery charger, an alternator, or a PV module. It's all about the amp hours clocking in and out. 

So, in order to use amp hours to size the battery but watt hours for the loads and power generation sources you have to use I=P/V to convert units at some point into amps and amp hours so you know what your battery state of charge is.  And you have to know the battery voltage to do that if you work in watts and watt hours. That voltage is not the same during charge and discharge cycles. You don't need to worry about that if you're working in amps and amp hours. Takes care of itself. 

In case you're wondering, my degree is in physics, which means I know just enough to be dangerous in all kinds of areas. 

One other important concept to remember is that your batteries are being recharged by the solar input.  so you are using X amount of power and putting Y amount back in from the solar panel.  Even though x may be bigger than Y, as long as you keep your batteries above 50% discharge, you are still good. For example, At the beginning of the trip you are at 100%,. Day 1 you use 20% and recharge 15%, so you are only down 5%. The next day is the same-now you are down a total of 10%. Using this example of losing only 5% daily , you can theoretically go for 10 days losing 5% and still be at 50% charged.

Batteries are made to be discharged and then recharged. They don't have to be 100% to be usable.

Vann

One thing you should consider is how to keep your battery charged while your rig is in storage.  I see from earlier in the thread that you bring your battery home if its going to be more than about a week before you use it again. That's good, because lead acid batteries shouldn't go more than about a week without being charged.  I'd suggest you also consider getting a battery charger and keeping it on float charge while you have it at home.

Alternatively, if you can keep the trailer on ac power or install a small solar charger so it was being charged at your storage site you wouldn't need to remove the battery.