AC to DC conversion - Fiberglass RV


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Old 08-05-2020, 09:50 AM   #1
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AC to DC conversion

Iím hoping someone can answer this question. I have recently had my trailer wired and am using Redarcís Battery Manager 30 to charge and monitor my batteries. Iím waiting for my batteries to arrive and be installed and canít use any 12volt fixtures even if plugged into 120v AC shore power. Is there a device that converts 120v to 12v without going through batteries?
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Old 08-05-2020, 09:56 AM   #2
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Any off-the-store-shelf battery charger. https://www.amazon.com/Best-Sellers-...otive/15707061
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Old 08-06-2020, 08:52 AM   #3
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Thanks. I guess my question more specifically should be is there a converter that changes 120 to 12 volts before it goes to the batteries? ie a converter that isnít a charger. Iím considering this to save the number of charge-discharge cycles on my batteries if I have 120v shore power available but still need to use my 12 volt fixtures (lights, fan, etc)
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Old 08-06-2020, 08:57 AM   #4
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Put in a battery disconnect switch, then wire the charger to the "OFF" side of that switch to isolate the 12V lines from the battery. All converters are just a charger with a whole lot of fuses and breakers inside. Semantics.
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Old 08-06-2020, 09:11 AM   #5
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Perfect! Thank you
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Old 08-06-2020, 09:21 AM   #6
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I would buy a 120 VAC to 12 VDC regulated power supply
A battery charger is designed to charge batteries and the charger output voltage is often too high for 12 VDC equipment ( LED Lights , furnace and roof fan control boards )
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Old 08-06-2020, 09:31 AM   #7
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Hi Steve, thanks for that info. Would it be possible for you to provide a link to an example of an appropriate one?
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Old 08-06-2020, 09:41 AM   #8
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It depends on your battery type. My LFP battery charger (Progressive Dynamics) is just a Constant Voltage Constant Current power supply set to 14.6 volts. A lead acid battery requires a considerably more complicated battery charger to optimize battery life. You didn't state the type of batteries you are installing making it more difficult to provide a solution. It looks like the Redarc charger supports LFP (Lithium Iron Phosphate batteries. I would recommend reading about the LFP charge characteristics and see if it mimics a CVCC power supply. If it does you could set the battery type to LFP and, if possible, set the voltage to 13-14 volts. You would not need a battery. One caveat, is the charger might look for a battery to be connected to operate. If this is the case you might be able to turn it off, if not you will need another solution. Trying it with all your loads turned off will not hurt anything.

Regarding your desire to reduce the number of cycles on the battery, If you are connected to AC power then the battery does nothing because all the power comes from the charger. The only time you incur a discharge cycle is when you use 12 devices and you are not connected to AC.
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Old 08-06-2020, 09:46 AM   #9
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Hi Carl, many thanks! As you can tell, I am not an expert in 12 volts. I will be using LFP batteries and will do a little more reading on the specifics. It seems that I needn’t worry about charge and discharge cycles so my question isn’t really relevant anymore! Put in batteries and no need to be concerned when hooked up to 120 v. Thanks for the education!
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Old 08-06-2020, 09:51 AM   #10
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Shannon,

If you are using LFP batteries they provide thousands of cycles of use. You will probably be looking for your next trailer long before they are worn out!
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Old 08-06-2020, 10:07 AM   #11
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Yes, thatís true! Was just considering maximizing this given the cost!!! Thanks again
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Old 08-06-2020, 12:08 PM   #12
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It depends on your battery type. My LFP battery charger (Progressive Dynamics) is just a Constant Voltage Constant Current power supply set to 14.6 volts. A lead acid battery requires a considerably more complicated battery charger to optimize battery life. You didn't state the type of batteries you are installing making it more difficult to provide a solution. It looks like the Redarc charger supports LFP (Lithium Iron Phosphate batteries. I would recommend reading about the LFP charge characteristics and see if it mimics a CVCC power supply. If it does you could set the battery type to LFP and, if possible, set the voltage to 13-14 volts. You would not need a battery. One caveat, is the charger might look for a battery to be connected to operate. If this is the case you might be able to turn it off, if not you will need another solution. Trying it with all your loads turned off will not hurt anything.

Regarding your desire to reduce the number of cycles on the battery, If you are connected to AC power then the battery does nothing because all the power comes from the charger. The only time you incur a discharge cycle is when you use 12 devices and you are not connected to AC.
Escape has had issues with their LED lights , roof fan control boards and furnace control boards due to too high a DC voltage being impressed on the various loads . I have had to replace 4 LED light fixtures and the furnace control board in my Escape
The voltage level necessary to charge a battery whether supplied by a battery charger or solar is often too high for many 12 VDC loads
Some batteries require a charge voltage in the high 14s to 15 VDC but that voltage when applied to 12VDC loads can spell failure
IMHO battery chargers or solar are designed to charge batteries

Some Escape owners have installed individual voltage regulators at each light fixture or appliance , which has solved the problem . I would prefer to regulate all the DC power at the source .
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Old 08-06-2020, 01:39 PM   #13
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I have not had any issues with any components in my trailer. I know some LED lights use a series resistor to limit the current in the circuit. These types will burn out easily if to high a voltage is supplied to them. The better quality LEDs use a linear current source, some use a switcher which is noisy. For example, I have an LED light in my Unique DC refrigerator that operates at 12-24 VDC. It uses a LM7809 linear regulator in a TO3 package for the ballast.

Chargers, regardless or input power are designed to charge batteries while connected to loads. A well designed DC system will not have problems with this. Battleborn says 14.6 VDC, lead acid is 14.4 in equalize, the loads must be designed to withstand those voltages.
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Old 08-06-2020, 01:41 PM   #14
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That’s good to know. I think I asked earlier but are you aware of a specific regulator that would do the trick?
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Old 08-06-2020, 01:44 PM   #15
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Some Escape owners have installed individual voltage regulators at each light fixture or appliance , which has solved the problem . I would prefer to regulate all the DC power at the source .
My solar controller has two outputs.
One is for charging the battery, and the other is a line output that can be regulated for maximum and minimum voltage.

One way around having appliances that don't accept the high charging voltages found in RVs would be to wire those items to the line output on the solar controller and set a voltage limit.

Those fans you mention are found on all industry campers, not just Escapes. Hopefully newer fans will be designed to accept a wider range of voltages, the voltage limit I saw mentioned in the past for the MAXXAIR fan was 13.8 volts maximum, which is not good for solar.
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Old 08-06-2020, 01:57 PM   #16
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If Maxxair designed there fans to operate at 13.8 volts max then they have a poor design. It's just not the real world. The must like selling controller boards. I think they need a new electrical design engineer.
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Old 08-06-2020, 02:19 PM   #17
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If Maxxair designed there fans to operate at 13.8 volts max then they have a poor design. It's just not the real world. The must like selling controller boards. I think they need a new electrical design engineer.
The problem is as I see it is that the wiring in FG trailers is not designed as an integrated system by a qualified Electrical Engineer but more in a piece meal approach using whatever parts are cheapest or readily available on the open market and installed by untrained / unqualified people.
The lights in our Escape have no built in voltage regulation and are designed for 12 VDC operation , so why is anyone surprised that when you apply 13.4 VDC to them they fail
If you add solar to a trailer and your only concern is getting the voltage high enough that you fully charge the battery and nothing else , itís a recipe for failure .
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Old 08-06-2020, 02:41 PM   #18
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Redarc’s Battery Manager 30
It would seem that a $1200 battery manager should run your lights without burning them out.
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Old 08-06-2020, 02:48 PM   #19
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"12 volts" really means somewhere between 11 and 14.5 volts. Everything listed as being for "12 volts" should be able to handle that difference.

The batteries may show 11 volts while fully charged and running a big inverter load, smart chargers bring batteries up to 14.5 volts while undergoing normal charging. Cars are commonly run at 14.2 to 14.5 all the time while the engine is running. Some reduce the voltage to 13 volts when the battery reaches full charge. Lead acid batteries are floated at approximately 13.2 volts to avoid sulfation. And batteries are commonly run down to 12.2 while rested at nearly 50% discharge. Inverters can be set to work down to 10.5 or 11.5 measured voltage before tripping out. Equalization can bring the voltage up to as high as 16.

12 volts, is a general term. It does not mean always, under every situation, exactly 12 volts. The load, state of charge and charging process all affect the indicated voltage. And we can't wait until that magic number of exactly 12 volts shows up on the volt meter to turn on the lights. A 12 volt battery is practically dead if it is only reading 12 volts while rested. And a fully charged battery can be reading 11.5 while fully charged and under load. A battery under absorption charge can read 14.5. The solar will take the battery to 14.5 every day if it has sufficient power to do so.

"12 volts" is a category that distinguishes it from 24 volts, or 120 volts.
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Old 08-06-2020, 03:43 PM   #20
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The maxxair issue is not with the system integrator. It is with Maxxair designing products intended for the 12 Volt recreational industry that will fail in normal use. POOR DESIGN - period. You can find LEDs on the internet designed for 12 volt operation and they even say not to exceed a specified voltage that is in the normal operating range of a RV. Here is an example:

https://www.amazon.com/Wedge-Trailer...xpY2s9dHJ1ZQ==
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