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Old 01-31-2012, 05:39 PM   #1
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Battery Over Charging

I recently acquired a 2006 Wildcat RV and on my first time out I noticed smoke coming from the battery compartment vent. I disconnected shore power and the battery was very hot and 2 cells were dry. I suspected the converter but was not sure of the battery condition either. I put another battery in this weekend and after being connected for the weekend it failed when I started to hook up. This battery had one cell dry and the end of the battery was bulging out. This has to be the charging circuit but I am not sure how to test it. Suggestions please. Thanks.

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Old 01-31-2012, 05:49 PM   #2
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Was the second battery new, or at least known to be good?

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Old 01-31-2012, 06:30 PM   #3
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Sounds like the converter is overcharging. Measure the voltage on the battery, then connect to shore power and measure again. Should not ever be over 16 volts. After and hour or so, should be 14 volts, or less. Now this is with a good battery. You can still test for max voltage with a junk battery, as long as the battery has over 8 volts before you connect shore power.
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Old 01-31-2012, 09:02 PM   #4
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I had the battery for awhile but put it on a trickle charger early in the week and it held charge and seemed to be good when I checked it several days later.
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Old 02-01-2012, 06:28 AM   #5
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may be time to get the volt-meter out - be lost without mine

With a multimeter set up (ground to the metal cover screw) Positive probe, on the positive battery lead( look at the diagram on the lid on the converter. You should read about 13.5 volts. IF it does not, chances are real good that you have a fried converter. Here is the hidden purpose of a good battery that is so important. The battery actually acts as a filter, helping the converter circuitry straighten out the alternating current, allowing it to be used and regulated into 12 volts and general 15 amp, 20 amp, 30 amp, 35 amp, 40 amp, 50 and higher. The converter shown is 45 total output amps., with only 3 amps dedicated to charging the battery.
RV Services Online - Troubleshooting - Power Converters

So you ask: "what does all that mean?" It means that battery charging is a little more complicated than most people think. It's not really safe to assume that driving your motorhome will keep your house batteries up to par, or that plugging your trailer in to A/C power and letting the converter run will make everything hunky-dory. The truth is, most of the RVs on the road have very poorly designed battery charging systems courtesy of the factory. Why? Well, cost plays a key role in deciding what equipment a RV will have installed when it's sold. Most RVs depend on the 12volt converter to charge the house batteries. In most cases, that's a very poor compromise!

Converters vs. real battery chargers
As stated above, the converter in your RV really isn't designed to be a decent battery charger. It's main purpose in life is to provide 12 volt power for your rig while you are plugged in to an A/C outlet. Since the converter is designed to not exceed a voltage of about 13.5 volts, it will never fully charge your batteries. Also, after it has succeeded in partially charging your batteries, it will then commence to boil off electrolyte, as the "float" voltage is too high (should be about 13.2 volts max.). If you plug your rig into A/C power for months at a time, you MUST keep a close eye on your battery's electrolyte level. It is very common for a converter to boil a battery dry in a month or two. Don't let it happen to you! If you must live with your converter, it is a big help if you unplug it or switch it off when the rig is in storage and attached to A/C power. Just run the converter overnight once a month or so and it will be much easier on your batteries. Another significant disadvantage to the converter is that most units aren't capable of delivering their rated amperage to the batteries to charge them. Older converters will only manage about 10 or 15 amps and will put out significantly less when powered by a generator.
A much better choice is to replace your converter with a modern 3 stage battery charger. These units are fully automatic and can be left plugged in continuously without damaging your batteries. They provide much higher charging current than a converter and will fully charge your batteries in short order, even on generator power. Many better inverters include a 3 stage battery charger as part of the unit. You can also buy just the charger and replace your existing converter with it, as it will handle all the functions of the converter and keep your batteries in shape too! Unfortunately, these chargers aren't cheap... you can expect to pay from $50 to $400 for one, depending on ratings and features. Still, if you need to replace a failing converter or are considering getting an inverter, don't miss the chance to get a 3 stage charger. They really are worth the money if you use your batteries a lot.

Battery Charging. Many of the better inverters designed for RV use are also high quality battery chargers. This is an excellent option, as it allows you to get rid of that old, inefficient converter and enjoy faster, safer 3 stage charging. Most of the major inverter manufacturers offer this either as standard equipment or as an add-on accessory on their inverters. These chargers typically can deliver from 25 to 150 amps of charge current and run very well with generator power, allowing you to quickly recharge your batteries while out in the boonies. These 3 stage chargers will also not boil the water out of your batteries. Instead, they will bring them to full charge and then taper back to a true float charge... these units can safely be left plugged in continuously, unlike the standard converter found in most RVs. Costs. You can expect to pay about $50 to $100 for a small portable MSW unit. RV designed units start at about $500 for a 750 watt w/charger and go all the way up to units rated at more than 3000 watts and costing several thousand dollars. Price increases with wattage ratings and capabilities. The best thing I can suggest is to do some research. Check the links listed below for inverter manufacturers and remember to size the inverter based on your real needs.
The 12volt Side of Life (Part 1)

All batteries, regardless of their chemistry, will self-discharge. The rate of self-discharge for lead acid batteries depends on the storage or operating temperature. At a temperature of 80 degrees F. a lead acid battery will self-discharge at a rate of approximately 4% a week. A battery with a 125-amp hour rating would self-discharge at a rate of approximately five amps per week. Keeping this in mind if a 125 AH battery is stored for four months (16 weeks) winter without being charged, it will loose 80 amps of its 125-amp capacity. It will also have severe sulfation, which causes additional loss of capacity. Keep your batteries charged while not in use!
Do lead acid batteries develop a memory?
Lead acid batteries do not develop any type of memory.
Do I need to completely discharge my lead acid battery before recharging it?
No, in fact you should never discharge your lead acid battery below 80% of its rated capacity. Discharging it below this point or 10.5 volts can damage it.
When do I need to perform an equalization charge?
Equalizing should be performed when a battery is first purchased (called a freshening charge) and on a regular basis (every 10 discharge cycles or at least once a month). Reduced performance can also be an indicator that an equalizing charge is needed.
What is an equalizing charge?
An equalizing charge for a 12 volt battery requires that it be charged with a voltage of at least 14.4 volts for a period of at least one hour once a month, or every 10 discharge cycles. An equalizing charge prevents battery stratification and reduces sulfation, the leading cause of battery failure.
When should I add water to my batteries?
How often you use and recharge your batteries will determine the frequency of watering. Also, using batteries in a hot climate will require more frequent watering. It is best to check your battery water level frequently and add distilled water when needed. Never add tap water to your battery. Tap water contains minerals that will reduce battery capacity and increase their self-discharge rate.
A brand new battery may have a low electrolyte level. Charge the battery first and then add water if needed. Adding water to a battery before charging may result in overflow of the electrolyte.
What is the proper electrolyte level?
Battery electrolyte levels should be just below the bottom of the vent well, about - inch above the tops of the separators. Never let the electrolyte level to drop below the top of the plates.
Do I ever need to add acid to my battery?
Under normal operating conditions, you never need to add acid. Only distilled or deionized water should be added to achieve the recommended electrolyte levels.

now that the Mountainman has read this
I need to get my real charger out
I have been using my little topper off charger
and bringing the battery up to full charge
if I read this right every month or so
the bigger charger should be used ??
I still think distilled water level to be of most importance
never let water level get below the plates

regarding this post and my thoughts
battery is being over charged causing major breakdown of battery cells

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Old 02-01-2012, 07:04 AM   #6
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Dead batteries freeze.
Trying to charge a dead frozen battery looks like this.

At the bottom is the manual for the most common camper converter.
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Old 02-06-2012, 04:02 PM   #7
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Hey Herck,

Did that dead battery in the picture explode? Looks like the plastic is torn. Just curious.
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Old 02-06-2012, 06:36 PM   #8
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Originally Posted by MikeInColo View Post
Hey Herk,

Did that dead battery in the picture explode? Looks like the plastic is torn. Just curious.
It sure did Mike. I was at the campground when it happened.

We had just set up at the FAMCAMP at Little Creek Amphibious Base, Norfolk, VA and there was a Bounder across the road from us. He had the hood up and was trying to charge his battery. I had just pulled a cold one from the fridge when we heard a huge explosion (like a rifle shot).

I ran outside to see if someone was hurt and saw smoke coming from the Bounder. There was acid everywhere. (In fact I am wearing the same pants right now while painting the Living Room. There are many small holes in the pants from splashed acid while trying to decon the engine compartment.)

That is why I know that the story is true. The owner of the Bounder joined the Forum shortly afterwards, but I have not seen him on in quite a while.

This is a picture of the other house battery. The one on top (green top) is the starting battery.
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Old 02-06-2012, 07:41 PM   #9
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This is interesting, has a cause been found yet? It seems as though converters often fail and under charge or stop all together more often than over charging. This would also be consistent with the obvious design criteria of a "safe" failure mode. As previous posts indicate, it's almost as though converters are actually designed to under charge! Good Luck
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Old 02-13-2012, 10:24 AM   #10
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It must have been the battery. I checked the converter this weekend and it is outputting 13.75 volts at the panel and 13.72 at the battery. It did not very just a constant voltage. I have a brand new deep cycle battery in place and will keep my eye on it.

Thanks to everyone for your input.

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