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RV Battery at 25%?


GVJeeper

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I'm hooked up to city power (have been for several weeks) and my control panel shows all 4 lights lit on the battery. The power just went out here and I checked my batteries level and it showed only one light lit which is about 25%. Shouldn't it have been at 100%? I'm in a 2013 Rockwood 35' TT with two house batteries. Don't my house batteries charge when I'm hooked up to city power?

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All lights showing on your led panel simply shows your converter is supplying charge. It has nothing to do with your batteries actual state of charge. There is no telling what their actual charge level is. They "should" be charging while hooked up to city power, but too many factors come in to play to give you any type of definitive answer.. ie.. what load are you drawing from your batteries during charge? Do you routinely check water levels? What size of converter do you have? And on and on....

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I check the water level but will check again to be sure it's ok. I don't know what size converter or how to check that. I don't know the load as I don't know when it's charging....just know I'm hooked to shore power unless the power in the area goes out. I have a volt meter...is that the only way to check if they are charged?

 

Thanks

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Since you have a volt meter, go to this website: http://www.marxrv.com/12volt/12volt.htm%C2'> scroll down to "Care of your Batteries" and start reading. Be sure to scroll down the section "Testing your Batteries".

 

In the Care of your batteries, he mentions measuring the voltage under load. A quick way to do this is, disconnect from shore power, turn on 4 to 6 of your light fixtures and then measure the battery voltage. Use the chart Mark provides. Now leave the lights on and check the voltage after 15 minutes, 30 minutes and an hour. If the voltage is dropping significantly you probably have one or both of the batteries, or one of the cells in one of the batteries is bad.

 

Each incandescent light bulb draws about 2 amps of battery power. So turning on fixtures a total of 6 bulbs will pull about 10-12 amps of power. With two house batteries you should have about 150-200 amps of capacity. So 6 lights being on for an hour should reduce your battery state of charge (SOC) no more than about 6-8% (or well over 90% charged).

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GV Jeeper, since you have a Voltmeter, I copied this from a Battery Voltage versus Percent of Charge table for a battery at rest once stabilized. I forget where I got the info from so no guarantee as to its accuracy. I don't like to let my house batteries draw down much over 20% or 30% Max discharge if at all possible so as to reduce the number of Life Cycles of which a battery only has x number available. It wont take you a minute to take your meter out there to check voltage.

 

Its very simple cheap and easy (2 wires + and - connected to batteries, NOT rocket science) to buy a miniature (mines like 1 inch) LED 3/4 digit digital readout panel voltmeter wired to your house batteries so when you're plugged up you can monitor their charge voltage level and also when dry camping keep an eye on their state of charge. If you want even more info, add an ammeter to also monitor current levels. If you happen to have an older or cheaper "dumb" (more like a constant 13.4 to 13.6 voltage source) Converter/Charger, I highly recommend you purchase a modern so called "Smart" 3 or 4 Stage Charger which has computer controlled progressive charge levels starting out at maybe 14.4 + volts if the battery is discharged, and eventually once fully charged maintains batteries at a float level maintenance charge of somewhere around 13.2+ volts. They aren't all that expensive and can increase battery life.

 

 

Voltage vs Percent Charge

Note that the voltages calculated are for an unloaded battery. This means that you shouldn't be charging or discharging while you take these readings. Always wait several minutes after disconnecting a load or at least one hour after charging before measuring the voltage. For specific gravity you do not need to lift the leads to the battery in order to be accurate enough for most RV use.

Temperature: 67 degrees Fahrenheit

Percent Hydrometer Unloaded
charge reading voltage
100 1.262 12.61
75 1.207 12.28
50 1.157 11.98
25 1.117 11.74
0 1.097 11.62



Temperature: 77 degrees Fahrenheit

Percent Hydrometer Unloaded
charge reading voltage
100 1.265 12.63
75 1.210 12.30
50 1.160 12.00
25 1.120 11.76
0 1.100 11.64


Temperature: 87 degrees Fahrenheit

Percent Hydrometer Unloaded
charge reading voltage
100 1.268 12.65
75 1.213 12.32
50 1.163 12.02
25 1.123 11.78
0 1.103 11.66


 

Should be a piece of cake for you

 

John T

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Al, no link above, but do you mean Mark's site, HERE??

I don't know if that was the link intended, but any RV owner who plans to do more than just take the RV to the shop each time something fails to work should read that link, The 12V Side of Life by Mark Nemeth. It is the best place I know of to start to learn what you have in your RV. It don't take all that long and knowledge is the best way to deal with challenges.

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Its very simple cheap and easy (2 wires + and - connected to batteries, NOT rocket science) to buy a miniature (mines like 1 inch) LED 3/4 digit digital readout panel voltmeter wired to your house batteries so when you're plugged

 

John T

please check you messages as I can't post a link to one that I think will work.

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GV, I replied. The small 3/4 digit 0 to 30 or 100 volt DC voltmeter I bought on E Bay was an idiot proof fool proof TWO WIRE + and - model. The one you linked has 3 wires but Im sure it will work. My buddy bought a Combination Voltmeter/Ammeter from E bay or Amazon but the directions were horrible, he liked to never figured it out lol and hes an electronic tech but got it working.

 

You got the basic idea of my recommendation it appears. As to which make model and brand and where to buy and following the directions YOURE ON YOUR OWN LOL

 

John T

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That happened to me, my wimpy stock converter (need to upgrade) will keep battery charged but if it gets to low (only happened once) manual states to hook up battery charger till charged. I guess my converter is not for full time use. It was when using furnace during a cold spell and the blower motor drained battery. When furnace was running blower motor was very slow, power went out and battery was almost dead.

Steve

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I installed this ( http://www.voltminder.com/ ) on my RV with a switch to check either house or chassis battery. Worked great, has an alarm to let you know if a battery is too low.

 

It told me that my converter was c**p so I upraded to a progressive dynamic with charge wizard (actually already had the PD) just added the charge wizard. had all batteries in shape in a few days.

 

Have fun.

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Since you didn't complain about all things 12V going dim before city power died, it would seem that the converter is doing it's job, somewhat.

 

But, get the meter and confirm a voltage of 13.X at the battery when the converter is powered. If it's a lot less, bad converter.

 

Assuming it's above 13 it would seem that the battery is toast.

 

The only other question I have is: Do you have an inverter?

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I got my mini meter in the mail but it's been raining so haven't hooked it up. Will be gone over Xmas so it might have to wait until then. Then I'll be drilling a hole in the bedroom floor to run two cables from the 12V (on the hitch "V") to the inside for my converter.

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Are you running cables for the converter itself of for the meter? Assuming you meant the meter, you don't need to install a meter just to establish whether the converter is working. (This was your original problem right?) A hand held multi meter is fine. Unless I missed something here......

 

Something like this: (also handy for other diagnostics, like continuity)

 

http://www.amazon.com/Etekcity-Digital-Multimeter-Tester-Measurement/dp/B00B7CS3UY/ref=sr_1_1?ie=UTF8&qid=1450615048&sr=8-1&keywords=multi+meter

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Assuming you meant the meter, you don't need to install a meter just to establish whether the converter is working. (This was your original problem right?)

I was wondering the same thing? Just measuring between the battery posts with a meter without doing anything else is really not going to tell you much more than you now know. In order to determine if the problem is the converter, the battery, or something else entirely, you are going to need to do some isolating of the questionable items. Just owning a meter will not tell you anything useful.

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Battery issue: Actually i don't have a problem - I was just wondering why the lights on the control panel were down to one when the power went out (and I had been connected to shore power) and you've answered that for me. I'm just adding the mini meter so I can know what the charge is on my batteries.

 

Power Outage issue: I was told I could wire my 1000 watt inverter (so I can have wifi/laptop etc when power goes out) to just one of my house batteries but I think it would be better to wire to the + on one battery and the - on the other battery. Can i connect the mini meter to the other + and - the same way?

 

Lou - I'll order them up right off and will have them to do the job after Xmas. thanks!!!!

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Hi again GV, to your questions " I was told I could wire my 1000 watt inverter (so I can have wifi/laptop etc when power goes out) to just one of my house batteries but I think it would be better to wire to the + on one battery and the - on the other battery.

 

Okay, from your wording I take it you must have two twelve volt batteries in parallel right???? That means you have a big parallel tie cable from + of one to + of the other, and likewise another big parallel tie cable from - of one to - of the other.

 

IF THATS INDEED THE CASE YES I agree, for better balance, connect your Inverter (I would use cables with 100 amp minimum or more ampacity, subject to distance) to the + of one battery and the - of the other.

 

LIKEWISE, for better balance, connect the + and - leads from a battery charger or solar charge controller the same, + of one battery - of the other. Sure, no problem in connecting your mini meter the same.

 

John T

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