Solar Trickle Charger & Dead Battery - Fiberglass RV


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Old 03-11-2010, 10:52 AM   #1
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1988 Bigfoot B19 Deluxe, Interstate Marine-RV Deep Cycle Battery (a month old) & SunForce Solar 12V Battery Maintainer rated at 1.8 watts and 125mAmp under "ideal conditions"

We had a credit at Camping World, so I got a little 12 volt solar panel to act as a trickle charger, expecting it to keep the brand new battery charged while the Travel Trailer is not in use. However, we first had to splice the 12V wires to extend them so that they would reach the battery from where we positioned the solar panel (why the solar panel came with such short wires, I don't know). By the time we got it set up (3 weeks later), our new RV battery was dead, and the trickle charger is no help with that, so I am wondering if anyone with deep cycle battery and solar panel experience can clue me in on the following:

1. Will the deep cycle battery get recharged if I plug the travel trailer in to our regular household outlet? (We don't have a special "RV outlet," so I have been scrambling through everything we own to find the adapter -- I am sure we have one -- to plug the travel trailer into a regular outlet). That should start charging up the battery, right? If not, will plugging the TT cord into our truck's outlet while the truck is just sitting there running charge up the battery or do we have to drive around for several hours with the travel trailer hooked up? (We are in the middle of doing modifications to it, so having to hook it up to drive it around for several hours would be a pain). Are there other ways to get the battery recharged?

2. I realize now that the travel trailer probably pulls something from the battery even when nothing is being used (so we should have stored it disconnected while we were setting up the solar panel)... but the only thing I can think of that would be pulling power is the propane/gas alarm, there aren't any lights or anything else that stay on. So, how long should a brand new deep cycle battery hold a charge? Is it normal for it to go totally dead after 3 weeks?

3. How can I tell if the solar panel trickle charger is providing enough juice to keep the battery charged once it is charged up again? The packaging for the panel says it is 1.8 watts and 125mAmp under "ideal conditions." I bought a multimeter and read the instructions and tested the solar panel, but I have no idea what the readings mean. Can anyone help me understand them:

at 9:40 AM in the morning, I put the panel is a somewhat sunny location and following the multimeter instructions, I tested the DC mA side first, and had to put it on the lowest setting .5 mA to get any reading, after which the dial went to just that first bar on the left (with the numbers 50, 10, 20), then I changed it to DC volts and set it to 50, which gave a reading just past the second bar on the left (with the numbers 100, 20, 4). I also removed the 12v extension wire & tested the original wire length to see if having a shorter wire increased the output, but that made absolutely no difference in the multimeter readings.

Then I put the panel in full sun and set the DC mA at 250 mA and got a reading at the first bar on the left (with the numbers 50, 10, 20) . I then set the tester at DC volts to 50 and got a reading of between the 100,20,4 bar and the 150,30,6 bar in the middle of the dial.

I read the WikiHow "How to use and read a Multimeter" but I am still illiterate in this area...

Would be very grateful if those members who are more electrically inclined can illluminate me on how to interpret these readings in light of the "ideal performance" rating of the solar panel.
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Old 03-15-2010, 01:03 PM   #2
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Somewhere I have a chart that tells what the voltage on your meter means coralated to a full or discharged battery. In order to get a true reading though you have to have everything disconnected from the battery. Any charge controller must supply around 14V in order to charge a 12V battery. Most of the inexpensive Solar charge controllers do not have a Diode (Check valve) in them. That means that when the light outside is no longer powerfull enogh for the panals to produce more than say 12V they will actualy become a load and begin to pull power from your battery. You can solve this by installing a diode between the charger and the battery (On the positive side). The other problem with most shelf baught controllers is that they do not invert. That means if your panals are producing 9V at .02 amps your not going to charge batteries. A good controller will take the input power and make it 14V output no matter what. As long as there is enogh "POWER" to do this. So instead of 9V [at] .02 amps you might have 14V [at] .014 Amps. You will actualy be still charging your battery even when the sun is starting to set.

Take your meter and put it on the output wires of the controller. And see what kind of voltage you are getting. If you see 13-14 Volts you should be able to charge a 12V battery. When your Battery is charged it should read around 14V (Not 12) If you battery reads 12V it is either discharged or dead. Remember when you are charging you are applying "Preasure" to the "Preasure" of the output of the battery. Just like inflating a flat tire. In order to inflate the battery, you have to be applying more preasure than it is putting out. And just like a tire, a bateries preasure varies with its state of charge.

As for solar power in general... Volts X Amps = Watts So if your solar panals are say 1.8W you take 1.8 Watts devided by 12 Volts and you will get the amps they will put out 1.8/12= .15 Amps (Or 150 mh Now if your controller is 24V It will still work the same. With a 24V system the line loss is less on the panels, so if your panals are 1.8 Watts 24V and you are converting down to 12V you will still have 1.8W of charge power. Now most RV batteries are rated in AH Amp Hours. There is a calculation that will tell you how many amps it takes to charge a particular battery but I cannot remember it off hand. I have buit remote radio sites that are powered entirely on solar. It is not nearly as easy as it sounds. Here is where it gets kind of "hairy" in the Solar Market. A standard interior RV light is around 40W This means if you wanted to run that 40W bulb for 1 hour at best preformance, you would need to charge your battery 22.2 hours on that solar panel to do so. That being said even the slightest drain on your battery will usualy overcome those "Solar Trickle Chargers". They do however make good power plants in witch to charge batteries for cellphones and Ipods.

Dont feel bad about your purchase. This is one of those Snake Oil products that the Green Energy race has really pushed. I also purchased one as well only to be disapointed in the claims on the package and the salesman at Cabelas. I returned it shortly after testing. Best thing to do for storage is to buy an ATV trickle charger and leave it plugged into your battery when your storing. If you do the math it is better for the enviorment.

In my trailer I installed a power center with smart charging. I just leave it pluged in all the time and it takes good care of the battery for me. There is another issue with those trickle chargers, in that they do not know when the battery is full. They tend to either overcharge, or boil the battery. This will greatly reduce the life of your battery. A smart charger has different charging methods depending on what the battery is doing. They will actualy add life to your battery. I stongly recomend a smart charger system for any trailer. Some manufactures sell the Smart Controller as an option and these usualy work well.


Hope this helps!
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Old 03-15-2010, 03:33 PM   #3
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OK, I'll try answer some of your questions, but I will also ask some questions.

1. Yes the 12V deep cycle Battery will recharge when you connect to your house current (or any other source of 120V current) if the charger side of the trailer converter is working. It would be unusual for it not to work. To charge a dead 12V battery is going to take 120 volts to the trailer or a stand-alone battery charger directly connected to the battery. You would need a large solar array to charge a dead battery. The converter/charger in the trailer should be up to the job, just fine. Do not have the trailer plugged in and the battery connected to the trailer when you are trying to use a stand-alone battery charger. Two chargers trying to charge one battery is a recipe for unhappiness. After you have plugged the trailer into house power you can use the multi-meter (set to measure 20 volts or the lowest number greater than 12 volts) to see how many volts the trailer charger is pushing into the battery.

2. Your guess about the propane alarm is correct. A propane alarm can definitely kill a battery in three weeks or less. I suggest you either disconnect the battery when not using the trailer or install a cut off switch between the battery and the trailer. El-cheapos

3. The solar charger won't keep the battery charged if the amperage rating of the propane detector is larger than the amperage provided by the little solar charger you have. {3a} Do you know how much amperage the propane alarm draws? {3b} What is it's amperage rating? Usually posted on the back or inside, in tiny print that is hard to read. Watts and mAmps are different ways of saying the same thing. You need to compare the mAmps of the solar charger to whatever the propane detector wants. Your meter does not appear to be accurate enough to accurately measure this. I'm not familiar with a multimeter that uses a display such as you have described it. The Wiki shows a digital and analog meter. {3c}Is your meter not one of those types? {3d}How much did you pay for it?

I recommend a digital multi-meter. If your meter could accurately read amps and you can put the meter in series with the detector you can read the Amps the detector is drawing.

The standard power rating for a maintenance charger is usually 2 Amps (Battery Tender). Your solar panel only puts out a very small fraction of that during daylight hours only.

Here are some pages that may help you understand the trailers electrical system.

Batteries and electrical by Phred

RVers corner

The 12 Volt side of life

Battery Stuff

Battery bank wiring
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Old 03-17-2010, 09:39 PM   #4
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Thank you, Curtis and David!

From your helpful and intelligent responses, I gathered that the trickle charger (which should have a label stating "for decorative purposes only") and the multimeter (which looks like the analog one on the Wiki site and was a cheapo) I got are both pretty much junk, so I will start over on the solar panel concept after reading up on it in more detail (thanks for the links to info on the travel trailer electrical system and using solar panels) and will get a digital multimeter. I finally went to Camping World and bought another 30A to 15 A adapter and the travel trailer has been plugged in for several days now, so I will test the battery as suggested in the next few days to see how it's holding its charge. I don't know what a stand-alone battery charger is, but from now on, I will either keep the trailer plugged in to not drain the battery, store the battery disconnected from the trailer, buy the cut-off switch you recommended or at some point get the recommended SmartCharger and higher capacity solar panels.

We do want to be able to dry-dock using solar at some point, but will do a lot more research before we buy anything!

Thanks again for your erudite input!

Val
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Old 03-17-2010, 10:06 PM   #5
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Quote:
I don't know what a stand-alone battery charger is
This is the one I use:

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Sears DieHard 10/2/50 amp Automatic Battery Charger
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Old 03-17-2010, 11:02 PM   #6
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Here's another book that I found useful:

http://www.amazon.com/gp/product/096...ef=oss_product

Or have a look at these postings:

http://www.fiberglassrv.com/board/index.ph...ng+twelve+volts

It does a good job of explaining the whole mystery of 12 volts, including different types of battery chargers.

There are many automatic / microprocessor controlled / three stage stand alone battery chargers on the market these days which might be worth investigating. The best of them say they can recharge a "dead" battery. For example: http://www.xantrex.com/web/id/256/p/1/pt/7/product.asp or
http://www.sears.com/shc/s/p_10153_1...1225000P?mv=rr

Brian
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Old 03-17-2010, 11:25 PM   #7
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Hi Val,

If you remove your battery from your camper you will still need a SmartCharger (or 3-stage) type of charger. A battery that just sits in a garage will drain, too. As the others have said, the right charger will give you longest battery life -- and keeping your battery properly charged is the key.

Also, some converter-charger combinations really don't "charge" your battery, but just "maintain" it -- that is not as good and will shorten your battery life. You might want to learn more about what you have in your camper. Somebody more versed in this than I will need to help you here as my full 12-volt system is still in the planning stage!

Part of my plans include attaching the correct charger to a box that contains my battery (among other electricals). Depending on your converter-charger, you might find it easier to do something similar (along with that cut-off switch); it gets real tiring to lug that heavy battery in and out and constantly connect and disconnect. (Been there, done that.)

The best of luck to you!
Darnelle



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Old 03-18-2010, 10:40 AM   #8
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Hi Frederick, Brian and Darnell,

Thank you for educating me about what a stand-alone charger is and does! I was not planning to remove my battery from the travel trailer at any point, but figured that for now, I would just keep the travel trailer plugged in to our home outlet to maintain the battery charge. Is there any reason that this is not a good idea for long-term storage? Do you still need a stand-alone charger if you keep your travel trailer plugged in while not in use and/or use higher-capacity solar panels and a converter? If I understand you, it seems that the benefit of the stand-alone charger is that it is more efficient at charging and maintaining the battery, is that right?

Since we live in Arizona, we were leaning toward using solar panels as much as possible to keep the trailer battery charged and to use if we go dry docking. At the same time, we are on a budget, so want to keep things as simple and cost-effective (and lightweight) as possible. The travel trailer's current electrical system works great for our current needs, but based on what you are saying, we will definitely do more research before buying any solar panel system and converters (thank you for the additional links)!

Thanks for the great feedback and input!

Val & Kayla
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Old 03-18-2010, 12:21 PM   #9
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Hi Val & Kayla,

Unfortunately -- it depends. How much output does your converter/charger supply and the same with a solar set up? Remember, you need at least 14v. What ever you use, you need a setup that "reads" your battery and gives it what it needs. Get those two items taken care of and you sould be good. I don't know how often nor for how long you would need the full 14v, but I'm sure Frederick and Brian would have the right answer.

I've researched solar and it seems that in order to be 100% confident your solar arrary will keep your battery where it needs to be you would need minimally 150-200 watts of solar panels (off the top of my head). I'd guess this would cost $300-$400 just for the panels. You would also need to secure them to your camper or if you use stands on the ground you would need to sit there so they didn't sprout feet. Again, Frederick and Brian are much more in the know regarding the specs than I.

My solar is a "someday" project as the cost is too much for us right now. Especially considering that, for safety reasons, we have stuck with state campgrounds that provide us with more power than we need.

Great questions! You are a thinker!
Darnelle



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Old 03-18-2010, 01:06 PM   #10
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Hi,

Deep cycle flooded lead acid batteries have a self discharge rate of 8% to 40% per month.
For a 100AH Battery... this could as high as 40 AH per month or over 1 amp per day so panel
would have to supply about .2>.3 A [at] 13.4 (ideal float charge voltage for a fully charged battery)
assuming 5 hours/day bright sunshine exposure on the panel.

As to the problem of the propane detector - get a battery cut off switch so the battery will be
isolated from on board devices.

I use a simple battery maintainer on both my trailers that use a few cents of grid power per day
to keep up the batteries. http://batterytender.com/motorcycle/batter...v-at-1-25a.html
Seems I bought 3 of them about a year ago for $35 to $40 each on line? I checked the
float voltage they provide and it was right on at 13.3 VDC.

Hope this helps. Larry H
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Old 03-18-2010, 01:59 PM   #11
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Quote:
I was not planning to remove my battery from the travel trailer at any point, but figured that for now, I would just keep the travel trailer plugged in to our home outlet to maintain the battery charge.
Is there any reason that this is not a good idea for long-term storage?
Maybe. Leaving the trailer plugged in can be good or bad depending on the type of converter/charger your trailer has. Bigfoot probably installed a decent one. Do you have the instruction book for it, or can you determine it's make and model. The problem is older dumb converters just pushed 13.8 volts whether the battery needed it or not. This will harm the battery and shorten it's life. Unless you have a much newer smart converter/charger, leaving the trailer plugged in for a long time is not the best thing for the battery. The older converter/chargers frequently used a timer to start another charge cycle even if the battery doesn't really need it. These frequent charge cycles on a fully charged battery are not good for it.

{quote}Do you still need a stand-alone charger if you keep your travel trailer plugged in while not in use and/or use higher-capacity solar panels and a converter? {/quote}

No you do not need a stand-alone charger if you plug your trailer in periodically or have adequate solar panels and a charge controller for the panels. Or, if it will be awhile before you get to the solar panels you may want to use a Battery Tender when the trailer is going to be plugged in for a long period of time. This would eliminate having to remember to check the battery voltage weekly and plug in periodically. Depending on the weather and health of the batteries the time span could vary from a month to 6 months.

{quote}If I understand you, it seems that the benefit of the stand-alone charger is that it is more efficient at charging and maintaining the battery, is that right? {/quote}

Maybe. Stand-alone chargers come in many varieties. Some are better than your trailers converter/charger and some are not as good. I like Black and Decker brand. They bought out Vector which as one of the leaders in consumer battery chargers. A word of wisdom about these smart chargers. They will report a completely dead battery as having a bad cell when the battery may not. Those batteries can be recovered by using a dumb charger to get them recovered enough for the smart charger to accept them.

{quote}At the same time, we are on a budget, so want to keep things as simple and cost-effective (and lightweight) as possible. {/quote}

Being on a budget and changing to a solar system are mutually exclusive. It can cost a lot of money, upwards of $1,000.00, to get a good solar system working. You are probably talking about switching to 6 volt golf cart batteries (you need pairs of two to make 12 volts) for longevity of charge and battery life.

You have a lot of studying to do.

My suggestion is to learn how to efficiently use what you have, before spending money on a hi-tech solution that will require to you know how to efficiently manage your power consumption.

Curt
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Old 03-19-2010, 08:29 PM   #12
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Our travel trailer came with the owners manuals for all the appliances, but there is no separate manual for the charger. In the Bigfoot owners' manual we have, there is only a brief generic mention of the converter, with a notation that some models may be equipped with a converter/charger, so I may have to dig around under the dinette seat to see if I can tell what kind of charger it is.

For now, I just have the TT plugged in to an exterior outlet.

The solar panels project will be relegated to the back burner for now because of the cost and complexity. We usually stay places that have power, so I don't see spending $1K just for the occasional dry docking excursion. We are good at using lanterns with rechargeable batteries at night and using the water pump minimally to extend the battery power over a number of days without having to plug in the trailer, so we can just do that when necessary.

Thanks for all the great responses!
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