Frequently Asked Questions about Parallax "Switch mode" Converters.


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  1. Where can I find diagnostic or technical information?
  2. Can I get a Schematic for my Parallax Converter/Charger?
  3. Battery Charging and charging rates. Does my converter constantly charge my battery? How long should recharging take?
  4. Can I leave my Parallax converter system constantly connected to 120VAC power? Will this damage my batteries?
  5. My friend has a "smart charge controller" that plugs into his converter system. Why hasn't Parallax offered a "smart" charger option for my unit.
  6. Can I use Gel Cell or AGM batteries with my Parallax converter/charger? 
  7. Is it normal for the fan to cycle periodically in my Converter/Charger?
  8. Option Codes  My Model number references an option "A" or an option "T". What does this mean ?

Where can I find diagnostic or technical information on my converter?

Applies to all models.

Select this link. Technical Documents

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Can I get a Schematic for my Parallax Converter/Charger?

Applies to all models.

Schematics for Parallax electronic "switch mode" converter/chargers are proprietary and are not available for release. We appreciate your understanding.

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Battery Charging and charging rates.

Applies to 500,6700,7100,7300,and 7400 series Converter/Chargers.

These converter models deliver a nominal "float voltage" output of 13.2 -13.8 volts DC. These models basically supply a "pool" of available current for 12 volt loads and the batteries to draw "from" and do not "push" current into the batteries. Converter current is "shared" by the 12 volt system and the battery bank, so any converter DC current not being used by the 12 volt system in the RV is available to the battery bank for recharging if needed.

The battery bank determines what current it will accept from the converter/charger based on the effective resistance of the batteries and the float voltage applied. 

The effective resistance of a battery or battery bank is a result of several variables, these include a battery or battery bank's amp hour capacity, state of charge, age, condition, and ambient temperature. These variables make it very difficult to calculate what rate of current the battery bank should accept, or how long battery recharge will take. Our battery charge curve provides a reference for recharge time as well as battery current acceptance. When looking at the graph, please note that the voltage (yellow) remains constant, and that the amperage (lavender) drops as the battery reaches full charge. 

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Can I leave my Parallax converter system constantly connected to 120VAC power? Will this damage my batteries?

Applies to 500,6700,7100,7300,and 7400 series Converter/Chargers.

These converter models deliver a nominal "float voltage" output of 13.2 -13.8 volts DC. Leaving the RV connected to 120VAC and the converter output connected to the battery should present no problems as long as this "float voltage" is between 13.2 - 14.1 volts DC and recommended  battery maintenance is performed.

In order to keep the battery at 100%, the charging source (converter) must "stir" the electrolyte in the battery. This results in a normal amount of water vapor loss in non sealed batteries. This water must be routinely replaced. Failure to periodically "top off" the water level will expose battery plate surfaces to air. This leads to battery sulfation. The battery will develop internal "short circuits" as a result of the battery sulfating. A defective battery will "mimic" the symptoms of "over-charging" since the "effective" voltage and resistance of the battery system remains low and the defective battery or batteries will continue to accept a charge. Also see Battery Charging and charging rates.

Non-sealed batteries should be checked for fluid level at least once a month. Check the water level more often in hot weather.

All voltages generally referenced by battery manufacturers and converter manufacturers assume an ambient air temperature of 70 degrees F. When the battery temperature is above 70 degrees, the "rule of thumb" is for every 20 degrees of temperature rise, the float voltage should be lowered by .5 volts. Inversely, for every 20 degrees of temperature drop below 70 degrees the voltage should be raised by .5 volts. The problem is that no converter manufacturer, at present, controls voltage by temperature. Converter manufacturers currently provide the float voltage based at 70 degrees F as an output meant to "generally" cover most locations and conditions. This leads to the need to check water level more often if the battery is continually "seeing" temperatures above 70 degrees F.

If the RV provides charging from alternate sources, (ie alternator, generator, inverter, solar, etc.) voltages should be checked for recommended output. In many cases the voltages provided from these additional sources may be 14.5 volts or above. 

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My friend has a "smart charge controller" that plugs into his converter system. Why hasn't Parallax offered a "smart" charger option for my unit.

Applies to 500,6700,7100,7300,and 7400 series Converter/Chargers.

The issue we have with "smart charger technology" (when used in an RV) lies more with the application of the technology than the technology itself.  In a typical RV 12 volt electrical system, the converter/charger and the battery or battery bank is connected in parallel with the rest of the 12 volt distribution system. In "parallel" means where the charging source (converter/charger)  positive and negative output is electrically connected to both the battery bank positive and negative, and the 12-volt distribution system positive and negative, at the same time. The voltage output of the converter "smart charger" is based on a "detected" battery voltage. The converter "smart charger" claims to "monitor" and respond to battery condition while connected to the entire 12 volt system. Unless the charging source (converter) has a separate or isolated charging output, we do not agree that a converter or charger can effectively differentiate requirements of the batteries from other 12 volt loads while simultaneously connected to the rest of the 12 volt distribution system in the RV.

Detected use or voltage change on the RV 12-volt load system (i.e. lights, pumps, etc being turned on) generally keeps these devices at a 13.6 -13.8 "float" voltage. This raises the question whether any real additional benefit is being provided to the battery bank unless the coach remains in a "non-use" storage condition.  If a converter "smart charger" is only connected to the battery bank and can therefore monitor only battery voltage or current, and is not also connected "in parallel" with the 12 volt distribution system, we have no problem with the application of "smart charger technology".

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Can I use Gel Cell or AGM batteries with my Parallax converter/charger? 

Applies to all models.

There are many people using Gel Cell and AGM batteries with our converters/chargers. We do recommend that the battery manufacturers specifications be checked to ensure that the batteries chosen have "float voltage" requirements consistent with the converter output float voltage which is 13.2 - 14.1 VDC.

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Is it normal for the fan for to cycle periodically in my Parallax "switch mode" Converter/Charger?

Applies to all models.

The fan in your Parallax "switch mode" converter/charger has been designed to only run as much as is needed to keep the converter components cool. How often the fan comes on and the amount of time the fan operates is determined by primarily two factors, the amount of DC current the converter is supplying to the DC system (which also includes any battery charge current), and the air temperature inside the compartment where the converter is mounted. 

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Option Codes

Applies to 7300, 7400 series.

 

"A" Option

Currently only available on 7300 series units, the option "A"  indicates a factory installed 30 ampere Line/Generator Switch to handle automatic switching between 120VAC utility or "shore power" and 120VAC generator power.

 

 

"T" Option  (Timer options are not available on all models.)

 

Our converters (non option "T") typically deliver a constant voltage output of 13.2 - 13.8 VDC when the DC load amperage required from the converter is within the converter's stated DC amperage capacity. "Stepped Voltage" or "Timed Voltage" mode is not employed unless you have the "T" option listed in the option code block on the nameplate label. The nameplate label is located on the top of 7400 series units. (Look at bottom center of the label for the option block.) On the 7300 series the nameplate label is pasted to the inside surface of the access door.

 

"T" option units deliver an output voltage of 14.1 -14.2 VDC (referenced at no DC load current) for 13 hours each time the converter is connected to 120VAC. After the 13 hours has elapsed, output voltage is reduced to 13.6 VDC. 

 

"T" option units are only recommended for limited applications such as extended stay operation (Park models, storage mode, etc.) or when requiring faster recharging after "dry camping or boon docking" (when you have had no 120 VAC available from either utility/shore power or your generator). If you also have recharge capability from the alternator in your motor home or your tow vehicle, a "T" option would not generally be recommended since after towing or driving you would not want an already charged battery or battery bank supplied with 14.1 volts for another 13 hours.

Timer option components can not be added to your present unit.  The entire 7400 series converter or the 7300 series lower section would need to be replaced with a "T" option unit.

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[ Page will be updated as necessary.]

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Copyright 2007  Parallax Power Supply. All rights reserved.
Revised: October 30, 2009 .