Deep Cycle Battery Question

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  #1  
Old 04-20-15, 07:55 AM
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Deep Cycle Battery Question

Connected my rv to shore power for 2 days. Monitor panel in rv showed full charge on the battery. Disconnected shore power and waited 24 hours. Checked the deep cycle rv battery voltage. Reading was 10.72 volts.

Is my battery bad?
 
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  #2  
Old 04-20-15, 08:47 AM
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It's hard to say if your battery is bad. It sat there for 24 hours before you checked it but what is attached and running off the battery ? There can be many hidden and sneaky loads in an RV.

If it sat there for 24 hours with no load connected.... it's definitely bad.
 
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Old 04-20-15, 02:42 PM
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10.75 volts is dead as a door nail...

1, how old is the battery?
2, what level is the electrolyte at?
3, did you check the converter charger voltage. I assume the convertor is good since you said the below statement. But with a bad cell you should of heard the converter trying to run full tilt and the cooling fan on constantly.
Monitor panel in rv showed full charge on the battery.
4, Use a hydrometer to check the cells..
5, You may be able to equalize the battery if you can get a charge going on it..

I dont know what model convertor you have in the camper, whether smart charger or a one set voltage charger like mine..

Last some of the older convertors will take many days to charge a dead depleted battery...

Mine is a set voltage of 13.6 volts and charges at 12 amps max.. Most other type were 6 amp.

The modern converters charge at full rated amps and voltage varies...
 
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Old 04-20-15, 03:04 PM
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Did you take a voltage reading with a good meter after you charged the battery in the camper.
It is possible that the rv panel does not report the state of charge accurately.

You might want to plug in the camper so it charges the battery then disconnect battery from camper and measure the voltage a few hours later.
Should be about 12.8 volts fully charged.
If much more than that your charger could be overcharging it.

It should read very close to that after a few days.
It is recommended by most battery mfrs to not take a deep cycle lower than 30% of it's capacity which is about 11.8 volts.
11.5 volts will take the battery to 0% charge remaining and running lower than this will damage the cells.
 
  #5  
Old 04-21-15, 05:09 AM
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Voltage

did you check the converter charger voltage
No, I did not. How do I do that? I need to learn.
 
  #6  
Old 04-21-15, 10:12 AM
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In one instance you said "the rv showed full charge" then later said "the reading was 10.72 volts".
What did you use to get these readings.

You can get many different types of battery voltage testers if you don't have one.
A good type to get and learn to use is a multimeter that can be used for different measurements.

 
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  #7  
Old 04-21-15, 04:55 PM
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Battery

the rv showed full charge
The above was from the monitoring panel on the wall inside the rv.

"
the reading was 10.72 volts".
This was the reading using my multimeter 24 hours after disconnecting from shore power. The battery was disconnected and the meter probes were placed on the battery terminals.
 
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Old 04-21-15, 07:01 PM
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I would suggest that you charge the battery with the rv system then once the rv panel says the battery is charged, disconnect the battery from the camper.
After an hour or so measure the battery voltage with the multimeter.
The reading should be about 12.8 volts.
Leave it for 24 hrs then check voltage and see what you get.
 
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Old 05-01-15, 06:43 AM
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Update

Disconnected both battery cables. Connected rv to shore power. Checked voltage between ends of battery cables and reading was 12.7 volts. This tells me the rv charger is working correctly. I have removed the battery and am charging with an external charger. At this point, I suspect a bad battery or bad battery cable connections at the battery terminals.
 
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Old 05-01-15, 09:19 AM
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Do you have a load tester? if not you can take the battery to most any auto parts store and they will test it for free.
 
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Old 05-01-15, 10:15 AM
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Checked voltage between ends of battery cables and reading was 12.7 volts.
That dont sound right.. Most converters are pre set to 13.6 volts.. If its a 3 stage then its 14.3 bulk, 13.6 absorption, and 13,2 float..

You are saying 12.7 so its none of the #'s above...

I dont know what model convertor you have in the camper, whether smart charger or a one set voltage charger like mine..

Last some of the older convertors will take many days to charge a dead depleted battery...
Open the electrical panel in the RV and tell us the make and model...
 
  #12  
Old 05-01-15, 11:27 AM
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Voltage

That dont sound right.. Most converters are pre set to 13.6 volts.. If its a 3 stage then its 14.3 bulk, 13.6 absorption, and 13,2 float..

You are saying 12.7 so its none of the #'s above...
I stand corrected. You are correct. I just now checked again, and the voltage between the ends of the disconnected battery cables is 13.69 volts with shore power connected. Sorry for the mistake.

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  #13  
Old 05-01-15, 05:43 PM
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I would expect to see an open-circuit (battery not connected) voltage closer to 14.5 or maybe even 15 volts. Testing with the battery disconnected and connected should give some more information. If the battery charges okay with the external charger then the on-board charger is the problem. Unfortunately, if the on-board charger has been running a low voltage into the battery for some time it has probably been responsible for destroying the battery.
 
  #14  
Old 05-02-15, 05:19 AM
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Voltage

I would expect to see an open-circuit (battery not connected) voltage closer to 14.5 or maybe even 15 volts.
I finally found the owners manual and it says I should be getting 13.6 volts. I think the inverter is O.K.

The battery is not fully charging on an external charger, so I think it is time to replace the battery.
 
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Old 05-02-15, 11:33 AM
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Inverter? I thought the discussion was concerning the on-board battery charger in your RV?

An inverter is a device that takes battery power and "inverts" it to AC at normal line voltage, usually 120 volts. A fully charged lead-acid battery will have a voltage of 2.2 volts per cell or 13.2 volts on a 12 volt battery.

The charger MUST output a voltage higher than the battery in order to charge the battery. The "24 volt" charger for my electric lawnmower outputs a bit over 30 volts when the batteries (a pair of 12 volt deep cycle in series) are fully charged.

If your "charger" outputs only 13.6 volts then (in my opinion) it is not a charger but a maintainer. That low a voltage may be why the battery went bad as it never was able to receive a full charge.
 
  #16  
Old 05-02-15, 12:16 PM
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If your "charger" outputs only 13.6 volts then (in my opinion) it is not a charger but a maintainer. That low a voltage may be why the battery went bad as it never was able to receive a full charge.
AFAIK a maintainer charges at 13.2v Most older campers like mine charge at 13.6 volts. Mine has a max of 12 amps. While slow it will charge the batterys. In fact the problem is after the batterys charge you now have too much voltage and the battery's will boiler off water.

This is why its important to check batt water levels monthly.

With these types of RV convertor/chargers they should not be left plugged in.

They have upgrades you can install that are 3 or 4 stage chargers. These you can leave plugged in and will not boil the battery's as bad.

Here is my alternator charging thread if you want to see what I do boon docking..

( Im camping now and am using a pre paid hot spot I have )



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http://www.doityourself.com/forum/el...lternator.html

Here is a good article on RV battery's and charging.. Although as I stated the older and some manufacturers still only supply dumb convertor chargers that have a set voltage of 13.6 volts or so..

RV House Battery: How to keep it charged

And here is an excerpt from this article..


Charge RV Batteries



I'm going to limit my discussion to single stage chargers that are standard in most RV's. For our single stage charger we want the voltage high enough to charge quick as possible but not so high it will damage the battery if left charging for extended periods. I've been an advocate of the middle ground, 2.3 V/cell. For a 12V battery this is 13.8V. I've seen it mentioned that several charger mfgrs. also recommend this voltage setting. Set much higher than this and if the charger is left on for periods better described in days/weeks, it will over charge the battery will "boil" it dry. There is no actual boiling as with water but the chemical reaction looks like it is and this term is commonly used to describe what we observe during overcharging. The lower we set the voltage the longer it will take to fully charge and if set too low we will never fully charge the battery.


And post the make and model of your converter/charger. I can recommend and upgrade that will fit in the same spot with no modification. You will have the benefits of 3 or 4 stage charging.
 
  #17  
Old 05-02-15, 04:20 PM
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Converter

Inverter?
I should have said "converter". Sorry for the mixup.

WFCO Model WF-8955 PEC is what I have.

Here is the manual:

http://www.wfcoelectronics.com/Image...erDocs/9-3.pdf

I used the procedure on page 5(page 4 of pdf) to check the output.
 
  #18  
Old 05-04-15, 01:52 PM
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Battery

Purchased a new battery. The off-the-shelf voltage is 12.59 volts. Is this O.K., or do I need to put the new battery on a trickle charger before installing?
 
  #19  
Old 05-04-15, 04:51 PM
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Its ok voltage... What I did with my new batterys is took them down to 12.1 volts then recharged... It takes a few charge / discharge cycles to get the battery's to work close to 100%...
 
  #20  
Old 05-04-15, 05:02 PM
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Battery

O.K. Thanks for your help. We'll see how it goes.
 
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