Electric system question

[Uplander]

Before I buy and install a new battery in my travel trailer I'd like to check and confirm the fact that my converter is recharging my 12 volt battery.
I know all other systems work but don't know how to check the charging feature.
Last year I replace a very old tired battery with a new deep cycle battery..I got it at Walmart and it was very fresh based on the date on the battery. It came with a one year replacement warranty. Installed in the spring...it discharged once in late summer and again in the fall of the year. This happened when the trailer was parked for about 5 days with nothing "on" and no shore power attached.
I assumed the battery was bad and returned it to Walmart...not a happy camper so they gave me a complete refund...because it was the end of my camping season until spring I elected to wait and buy a better battery in the spring.
Spring is around the corner...buying a battery in a few weeks...the big question is ....How do I check my system to be sure it is charging the battery ?
Do I need a battery in the trailer to check the charging system?
I have a digital voltmeter if that will help.
Any knowledgeable folks out there who know about this stuff?

Thank You.

[Byron Kinnaman]

First it would be a good idea to try and understand what the converter does.
When the trailer is plugged into shore power the converter provides 12 Volts to the 12 volt system and charges the battery. If there is no shore power connected there's no charging. With no charging of any kind batteries will self discharge over time. If something like a propane detector and/or a fridge with electronic controls it will discharge faster.

[Jon Vermilye]

I'd first be sure "nothing on" is actually no current draw on the trailer. Propane detector, refrigerator (on gas) etc can draw enough current to drain a battery in 5 days. If you put an amp meter in series with the battery, that will give you your current draw. With nothing on, a cheap (or even free) Harbor Freight multimeter will measure anything under a 10 amp draw.

If you have a battery disconnect switch, use it. Even then it is worth checking to insure that EVERYTHING is disconnected when the switch it thrown. If not, during long storage periods disconnect one of the battery terminals.

Another solution is to add solar, which has many advantages. A small 15 - 25 watt panel will keep the battery charged while the trailer is not being used, a 100 watt panel will let you dry camp under most conditions. The 100 amp panel will require a controller, either built in to most folding portable panels, or installed in the trailer for a roof top panel.

Depending on the brand of converter & state of charge of the battery, a working converter will produce anything between 13.2 - 14.7 volts when connected to the battery & pedestal.

The lower voltage is what you should expect when the battery is close to fully charged (called float) and the higher voltage is when the battery is low (called absorption or bulk).

For good information on maintaining & using RV batteries, check Mark Nemeth's "12 Volt Side of Life, Parts 1 & 2. An excellent tutorial on the title.

[Uplander]

Jon Vermilye, Thanks for that link. It however do not have instructions how to test battery charging output on a trailer's converter.

Byron, The discharge was rapid and there were no heavy drains on the system. Nothing on...unit in storage.

I only want to know how to test charging feature on converter in trailer.

[Jon Vermilye]

Without knowing the condition of the battery connected to the converter, it is difficult to determine how well it works.

Assuming you have a good, fully charged battery, the converter is working properly if it produces 13.2 - 13.6 volts when plugged in & connected to the battery. If there is no load on the battery, it should be putting 1-2 amps into the battery, which can be checked with a multimeter set for DC amps & placed in series with a battery lead.

If the battery is heavily discharged (i.e. reads 11.5V or less with no load and disconnected from the converter), the converter when connected should show 14.5 - 14.7 volts, and, an amp meter in series show something like 20 - 25 amps going into the battery. It might be less, depending on the state of charge of the battery. If the converter only shows 13.2 - 13.6 volts with a heavily discharged battery, I would suspect it is not going into the bulk stage. It will still charge the battery, but it will take a long time, i.e. days.

A rapid discharge with no load on the battery indicates a defective battery. It has nothing to do with the converter assuming that the battery was fully charged when disconnected from the pedestal. If you still suspect there is something wrong with the converter (it is unlikely a modern converter will discharge a battery), disconnect it from the battery, and check the battery voltage after a couple of days.

Any kind of diagnosis at a distance is difficult; I hope this helps...

[Byron Kinnaman]

I still say you something discharging your battery.
Remember NO POWER CONNECTION (Shore Power) NO BATTERY CHARGING. The converter is NOT magic and can't pull electricity out of the air.

[ZachO]

Also, unless the battery is disconnected, as others have said, there is likely something drawing from it. If you have a co or propane detector wired in, that will absolutely drain the battery in a week. I know from experience. Any little "phantom draws" of power add up. Digital displays, any digital clocks (like your car clock/radio, which is not "on" when your car is off, but in order for the memory to keep track of the time and your preset stations, there is some draw on the battery), and carbon monoxide/smoke/propane alarm/detectors will draw down the battery unless the battery is disconnected.

Again, I know from experience that a CO/Propane detector will drain a battery in as little as a week.

If you can tell us for sure that you don't have anything like that, then I think we'll be happy to agree that it's just a bunk battery.

[redbarron55]

Maybe you could install an inverter to run a battery charger?
Just kidding.
A little Wednesday humor.


Sent from my SCH-I605 using Fiberglass RV mobile app

[ZachO]

Jon touched on all this stuff I'll just add a couple things: before buying your new battery, you could take your truck battery and hook it up to the trailer. Plug in the trailer and make sure the breaker for the charger is 'on', then test the voltage at the battery. If it's putting out more than, say 13.0V, then your charger is working.

When the charger is on, taking the voltage at the battery tells you the output of the charger. That's what the voltmeter is reading.

Getting the actual battery voltage requires taking the voltage when the battery is "at rest", which you can only get when there's been nothing charging or drawing from the battery for several hours.

People will try to get you to use the right terms which in some ways is not necessary, but it's a good thing. You don't want to mix your terms, you definitely want to understand the system as well as possible, and you'll get better answers if you use very clear terms.

A converter changes AC to DC. An inverter changes DC to AC. A charger takes the DC which the converter produced, and charges the battery with it. A converter doesn't charge your battery.

It gets confusing because most converters have a charger attached to them. But you could, and some trailers do, have a converter with no charger. Technically, what you have is a "power center". It's a place where you have a converter and battery charger and fuses for the 12V items pulling off the battery, and in some cases people might also have an inverter mixed in there, too.

It gets complicated really fast but those things are things you should really know as an RV owner, if you're going to do any trouble shooting or asking for help.

If you're always going to bring it straight to an RV shop, you don't need to understand the difference in any of those terms. But that's the only situation.

If you already know all this and were just being a little "loose" with your terminology, then I apologize!

[Uplander]

Extra thanks to both Jon Vermilye and ZachO for all the excellent information.

Too often on this and other boards there are many answers and comments that do not address the original question. Jon and ZachO stayed on point. I own a digital multimeter and have only used it to determine the charge level of a battery. After reading your detailed instructions I might actually know what I'm doing!
I will be transcribing the step by step instructions and adding them to my battery information sheet...thanks again.

I did order a new 100AH 12volt AGM group 27 battery through Amazon (amazing prices). I also decided to order a compact digital LED DC Voltmeter @ $7.50 it will allow me to monitor the status of my battery with some degree of accuracy. The control panel that came with my RV does have a battery status "bar light" charge level status display but it does not indicate actual voltage like the $7.50 meter will...very cost effective device for peace of mind.

[Glenn Baglo]

Originally Posted by Uplander

...very cost effective device for peace of mind.

I have one that plugs into a 12V outlet.
Doesn't produce peace of mind. It monitors battery voltage and your level of anxiety as you watch the voltage drop.

[Uplander]

Glenn, When we boondock it is good to know the status of the battery so you do not draw it down too much and do permanent damage. When it goes down to a certain point I start my generator and recharge the battery. I only use the generator when the battery is low or I want to use items like the microwave or the Air Conditioner.
Even though my generator is super quiet I do respect the peace and quiet and my neighbors...only run it when it is absolutely necessary.

Starting this season I'm adding a battery disconnect switch when my camper is back at home base once the battery is fully charged. Someone suggested it and I thought it was a great idea.

Happy Camping

[Timber Wolf]

Originally Posted by Uplander

Starting this season I'm adding a battery disconnect switch when my camper is back at home base once the battery is fully charged. Someone suggested it and I thought it was a great idea.

Happy Camping

Sounds like a good idea as you probably have a draw somewhere to kill the battery that quick. I have noticed with the new car batteries you get one, maybe two complete discharges then the battery is toast. In the "good old days" it seemed you could get away with drawing a battery down too far a few times, but no more. I went with two 6V Golf Cart batteries and good on-board monitor for my "peace of mind", or lack thereof.

[Glenn Baglo]

My point is that more knowledge as to the state of your battery will not bring peace of mind. More likely it will increase anxiety.
I have a voltmeter, and solar panels, and a Honda 1000 generator.
You may find you spend your camping day shifting solar panels, starting up the genset, monitoring your voltmeter and fretting about the lack of sun.
Sometimes ignorance really is bliss.

But Trojan offers a lot of good information at their site.
http://www.trojanbattery.com/tech-su...y-maintenance/

[Steve L.]

I'm going to go with the others that suspect you have "phantom" loads you don't know about that are draining your battery.

However, a questionable battery from Walmart isn't unheard of. Also, I believe they use the term "deep cycle" a little loosely, often referring to hybrid starting/deep cycle batteries. If the battery specs refer only to CCA (cold cranking amps) you probably don't have a true deep cycle and as many amp-hours as you might think.

I don't have much use for the plug in volt meters. However, if the trailer is plugged in and the meter reads in the range that Jon provided you then the converter is charging the battery.

If the trailer is not plugged in, the converter will not do anything. Just a lump of wiring.

If your inclined to buy tools at the slightest need (as I am) then a clamp-on digital ammeter that reads DC amps (not all do, check the specs) then you can clamp around one of the battery wires while the trailer is "resting" and it'll provide the total "phantom" amp load.

Sources of phantom loads:
Refrig control board
CO/CO2 alarms
Digital clock/alarm or TVs running on 12vDC. Even TV's turned off have a draw.
Volt meters (like the ones stuck into an accessory socket
Battery monitors
Assorted stray current, usally from improper grounds. (this is a real problem with fiberglass boats)
"idle" inverters

The best defense against any of these a battery switch in the positive battery cable. Needs to be pretty heavy duty.

[Uplander]

Thank you Steve L. Armed with all the info gathered from this inquiry I feel confident once my new real deep cycle battery arrives from Amazon all will be well.

Yes, most if not ALL the deep cycle batteries at Walmart are labeled " Marine/RV deep cycle" and list CCAs (a clear indication they are dual purpose and lack the thickness in their lead plates to preform as true deep cycle.

As with all things in life...the more you know the better the buying decision.

Thanks again to all.