Elementary Question on basic charging - Fiberglass RV


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Old 07-10-2016, 08:40 AM   #1
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Name: Lyle
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Elementary Question on basic charging

My Scamp has a relatively simple electrical system. The 12 volt side powers only the lights, refrigerator, 12v outlets, and a couple of fans. It has no converter, and does not hook into the tow vehicle charging system. Previous owners have mounted a simple battery charger and a 400 watt inverter. These plug in to an AC outlet that is powered by shore power, and/or a 12v outlet that have been installed in the privacy room.

In order to use the charger I plug it into the shore power, and the output plugs into the 12v. To use the inverter, I must unplug the charger and plug the inverter into the 12v outlet. As I said, it is a simple, manual system for maintaining/using the electrical power and seems to work for the basics.

In my experience and testing, the inverter set-up does work, and will power a small wattage 120v light, other than that, I have not used it. The battery charger, however did not seem to work, I had it plugged in to shore power and the charger connected for a couple of days with "power" and "charging" lights illuminated - the battery never did fully charge. I assumed the charger was malfunctioning.

I have replaced it with a Die-Hard 4 cycle charger, that seems to work well when hooked up as described above - input to charger via the 120v land line outlet, output from charger plugged into the 12v outlet connected to battery. The charger reads the power level in the battery, quickly charges it, then switches to maintenance mode and maintains the battery at 12.6v or slightly higher. I monitor the battery levels via a plug-in battery monitor, which confirms that the battery charger is charging and maintaining the battery quite well.

My question is this: I have several 12v fans inside the trailer, including a new Endless Breeze that works quite well (I seldom have used the other fans). Is there any problem in running the fans/lights while the battery charger is hooked up and in "maintenance" mode?

While the voltage on the plug-in monitor drops to the low 12 or high 11 volt range, once the fan is turned off it returns virtually immediately to the 12. 6 range.

Operating in this manner seems to work well, but am I damaging the charger or battery by doing so?
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Old 07-10-2016, 10:30 AM   #2
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Originally Posted by LyleB View Post
My Scamp has a relatively simple electrical system. The 12 volt side powers only the lights, refrigerator, 12v outlets, and a couple of fans. It has no converter, and does not hook into the tow vehicle charging system. Previous owners have mounted a simple battery charger and a 400 watt inverter. These plug in to an AC outlet that is powered by shore power, and/or a 12v outlet that have been installed in the privacy room.

In order to use the charger I plug it into the shore power, and the output plugs into the 12v. To use the inverter, I must unplug the charger and plug the inverter into the 12v outlet. As I said, it is a simple, manual system for maintaining/using the electrical power and seems to work for the basics.

In my experience and testing, the inverter set-up does work, and will power a small wattage 120v light, other than that, I have not used it. The battery charger, however did not seem to work, I had it plugged in to shore power and the charger connected for a couple of days with "power" and "charging" lights illuminated - the battery never did fully charge. I assumed the charger was malfunctioning.

I have replaced it with a Die-Hard 4 cycle charger, that seems to work well when hooked up as described above - input to charger via the 120v land line outlet, output from charger plugged into the 12v outlet connected to battery. The charger reads the power level in the battery, quickly charges it, then switches to maintenance mode and maintains the battery at 12.6v or slightly higher. I monitor the battery levels via a plug-in battery monitor, which confirms that the battery charger is charging and maintaining the battery quite well.

My question is this: I have several 12v fans inside the trailer, including a new Endless Breeze that works quite well (I seldom have used the other fans). Is there any problem in running the fans/lights while the battery charger is hooked up and in "maintenance" mode?

While the voltage on the plug-in monitor drops to the low 12 or high 11 volt range, once the fan is turned off it returns virtually immediately to the 12. 6 range.

Operating in this manner seems to work well, but am I damaging the charger or battery by doing so?
I don't know the exact model charger or fans and the number of them your running while hooked up to the charger but what from what I found the charger is a 2-4 amp charger/maintainer and the Endless 12v fans can draw up to 3 amps ( I'm guessing fan speed, wired in vs plugged in etc). That being said the charger is working overtime to keep up. Your batteries will not ever reach a "full" charge and the longevity of both the charger and the battery will be shortened. Other than that and maybe excessive heat in the fan wiring I don't see a major issue.
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Old 07-10-2016, 11:00 AM   #3
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Thanks,

According to the packaging, the battery charger is the Platinum DieHard Charger/Maintainer. It is a 3A, 6V/12V Model # 28.71239.

The Endless Breeze fan draws 1.18 A, 1.62 A or 2.59 A respectively on low, med, and high. Again, according to manufacturer packaging.

Guess the best bet is to just unplug the charger when using any 12V appliances, plug it back in when done.

Another question, is it better to recharge the battery frequently, at say 85% or 95% or let it get down to 50% or 60% before re-charging?
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Old 07-10-2016, 11:30 AM   #4
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Thanks,

According to the packaging, the battery charger is the Platinum DieHard Charger/Maintainer. It is a 3A, 6V/12V Model # 28.71239.

The Endless Breeze fan draws 1.18 A, 1.62 A or 2.59 A respectively on low, med, and high. Again, according to manufacturer packaging.

Guess the best bet is to just unplug the charger when using any 12V appliances, plug it back in when done.

Another question, is it better to recharge the battery frequently, at say 85% or 95% or let it get down to 50% or 60% before re-charging?
Type of battery and overall condition as well as environmental issues all play a part but the end result is that the number of cycles (longevity again) is what will be affected. i wouldn't want to drop much below 80% and always stay above 10.5 volts. Keep in mind the battery will never honestly reach 100% again after a discharge.
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Old 07-10-2016, 02:39 PM   #5
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On the Trojan battery (if I recall correctly) site they have an FAQ that states that constant partial recharging shortens a lead acid battery's life. That's not exactly what you're asking about. Assuming that you always recharge back to fully recharged (and then stop the recharge) I don't think your battery durability would take much of a hit.

I've found the description I was thinking of:

Common Mistakes

1. What are common mistakes made by flooded battery owners?
Undercharging: Continually operating the battery in a partial state of charge, or storing the battery in a discharged state results in the formation of lead sulfate compounds on the plates. This condition is known as sulfation. Both of these conditions reduce the battery’s performance and may cause premature battery failure. Undercharging will also cause stratification.
  • Overcharging: Continuous charging causes accelerated corrosion of the positive plates, excessive water consumption, and in some cases, damaging temperatures within a lead acid battery.
  • Under watering: In flooded batteries water is lost during the charging process. If the electrolyte level drops below the tops of the plates, irreparable damage may occur. Water levels should be checked and maintained routinely.
  • Over-watering: Excessive watering of a battery results in additional dilution of the electrolyte, resulting in reduced battery performance. Additionally, watering the battery before charging may result in electrolyte overflow and unnecessary additional maintenance.
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Old 07-10-2016, 04:42 PM   #6
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My suggestion would be to run 120 volt fans from your shore power, with an extension cord. Let your battery charger maintain the battery and use it for lights, and for the control circuit of your fridge. I assume you have a fridge that operates on propane. The best plan, if you are hooked up to shore power, is to run as little as possible off of your battery. Also, if you have standard light bulbs, I would replace them with LED lights.
On the question of battery longevity, it is better, I believe, to keep the battery well charged rather than deplete it too far.
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Old 07-11-2016, 08:48 AM   #7
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You need a converter!! Get the Progressive Dynamics with the "Charge Wizard". It's plug-n-play and you can forget it all go camping and relax! The "Wizard" is designed so you can leave your RV plugged in 24/7 and it will NOT hurt the battery but will keep the battery properly charge (maintained) which will let it last MUCH longer.

Battery chargers are NOT intended to keep 12v items running...only to charge the battery. I believe you said the one you're using is a "maintainer". The converter along with the "Wizard" is designed to do ALL of this.

I know you call it "basic"...but reconsider this: The "converter" IS part of the most basic 12v system you will ever have on an RV. If you have an onboard 12v battery- in my opinion you need to do one of two things: You need a converter or get rid of the battery.
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Old 07-11-2016, 10:03 AM   #8
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Elementary Question on basic charging

It's arithmetic: if the load withdraws 4 amps and the charger puts in 3 amps, the battery supplies 1 amp. With a three stage charger ( bulk, absolution, float) there is no reason not to leave it operating all the time.

You unit has float mode so you are good.

Battery chargers generally won't power a 12v load without a battery between the charger and the load but who doesn't have a battery?


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Old 07-11-2016, 12:29 PM   #9
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Quote:
Originally Posted by MCDenny View Post
...With a three stage charger ( bulk, absolution, float) there is no reason not to leave it operating all the time.

You unit has float mode so you are good.

....

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Denny, I'm not following you around just to quibble with you but you are making some blanket statements for which I think there are some significant exceptions that ought to be noted.

In this case, the basic Parallax converter (or at least my older version) has a higher float voltage (a little less than 14v, no load) than the Progessive Dynamics converter with the Charge Wizard (~13.2v). A Parallax converter if left on continuously will boil away the water/acid. The Charge Wizard is kinder to the water/acid level.

So, what I'm saying is that not all float voltages are created equal, so to speak.
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Old 07-11-2016, 01:12 PM   #10
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We are agreeing here, you need a proper three stage charger to safely leave it on all the time.


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Old 07-11-2016, 02:27 PM   #11
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What I disagree with, is to NOT run the RV on the battery while the charger is hooked up...or anything of high-amp draw like fans etc. I use Deltran Battery Tenders but I still will not use pumps etc...except maybe a test "burp". If you read on the charger/maintainers, they tell you NOT use it to power devices. The BT I use is only .7A (700 mA). The Battery Minder I have will charge up to 8A but I will not use it in place of a "Converter"!!

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We are agreeing here, you need a proper three stage charger to safely leave it on all the time.


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Old 07-11-2016, 03:33 PM   #12
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Darryl, are you sure the don't mean 'do not connect a load directly to the charger'? That's not the same thing as connecting a charger to a battery and a load to the same battery.


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Old 07-11-2016, 04:30 PM   #13
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You may could get by with it more on a charger like my Battery Tender. I also have a Battery Minder that "desulfates"...(to be honest...I have NO clue if that REALLY works...I've just read it does). When the charger is desulfating, it's using a completely different charge method. I dont see how it could possibly work IF you're continually pulling a load with it.

But now that you mention it.... does the Progressive Dynamics "Charge Wizard" run continually with the battery in use? Dont see how it couldnt be running as it's wired in. That would be interesting to get their take on it...

Unless you have a higher amperage output charger (like my Battery Minder), I dont see how the battery could stay charged and it WOULDnt for long with these small BT's at 750 mA if you're trying to use the battery continual. Maybe it wont hurt the chargers, but still, I prefer the converter when the battery is in use at a campground. Otherwise, you're going to start losing 12v access if you're camping very long!

Interesting points...

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Originally Posted by MCDenny View Post
Darryl, are you sure the don't mean 'do not connect a load directly to the charger'? That's not the same thing as connecting a charger to a battery and a load to the same battery.


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Old 07-16-2016, 05:23 PM   #14
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The first thing is, you need a smart charger that will bulk charge, maintain a float charge and will condition if needed.
Second, it needs to put out more amps than the continuous load you plan to connect.
Third, the charger should remain connected always, with or without a load. The older ferro-resonant chargers will ruin batteries, but a smart charger won't. Intermittent high loads are fine, provided they are not there long enough to discharge the battery. This occurs while running the heater, or an inverter while running a microwave, etc. Short term.

Marine chargers are good because they can be hardwired in. You should be able to select if you have AGM or flooded cell batteries so the proper float voltage can be delivered to them. Once in float mode they will remain there until the charge drops to a predetermined level, because of a load, and then they will go back to bulk charging and eventually back to float. All automatically.

Never let your batteries sit and gradually discharge. This ruins them by allowing them to sulfate. That reduces their total amp hours to the point of being useless over time. Voltage is not linearly related to charge. A battery is virtually dead at about 11 volts or so and will become sulfated at that level. Proper float voltage is somewhere around 13.2 to 13.8. Bulk charge will pull it up to about 14.1 during charging. Conditioning, which is an attempt to fix sulfation, will pull the battery voltage to as high as 16 volts for a short time.

Smart chargers will not carry a load without a battery connected. They must sense battery voltage before they can turn on. This is how they know they are connected properly, how they prevent sparking and how they know what the battery needs. No battery connected means no output from a smart charger. Also, a dead battery will not charge from a smart charger if the voltage present is to low to turn on the charger. In this case you must jump the batteries to a car or some other charged battery to get the charger going, or use an old ferro charger that always puts out current. Then disconnect it when the smart charger is able to take over. Old style chargers (ferro-resonant) just put out current and will do it whether connected or not. They tend to not fully charge the batteries and at the same time cause them to loose water. Not good at all for continuous use.

A short term reduction in apparent voltage while a load is connected does not mean the battery is low, it is reading line loss, etc. Rested voltage is the measurement of true battery voltage. This is measured with a meter after the charging phase is complete and the batter has sat for a while. Not under load. So it's not accurate to think the battery is discharged because the voltage reads low while under load. This is also why it appears to pop right back up when the load is disconnected.
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