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Filed under: Comfort at Camp, RV Maintenance, RV Modifications

Installing Your Auto Start Generator

May 30, 2014 by · Leave a Comment 

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Typical RV Generator

Typical RV Generator

Auto start generator controllers are a great feature.  But, like any other product, you have to understand it to get the most out of it.  We will look at the primary purpose of this machine and discuss setting up your auto start generator.

Basically, this device constantly monitors your house batteries to determine their state of charge.  At a given charge state, it will automatically start your generator to supply charge to the batteries.  When the battery charge state has reached a measured full charge, the controller will shut down the generator. This all sounds simple enough, but to do this efficiently requires correct parameters be preset.

To set up your auto start generator, this control device must be calibrated to exactly what voltage it should start the recharge sequence.  To know the correct cut-in voltage, we must know what the high and low voltages in the house bank are.  A fully charged battery in a rested state should be 12.7 volts or have a specific gravity of 1.265.  To get the most life from a wet cell battery, no more than 50% of the stored power should be used.  So, our lower limited will be 12.2 volts or a specific gravity of 1.190 measured at a rested state.

These numbers would indicate that you should set the generator start up at 12.2 volts. That is however, incorrect and would cause the generator to start and stop in too short a cycle.  The key phrase here is “Voltage at a rested state”.  A rested state is when the battery has not been charged or discharged for a period of some time. This is not going to occur while you are using your RV at any time. You have the refrigerator, idle TV circuits and other loads periodically drawing the voltage reading down. Depending on the amount of equipment drawing these loads, one can expect the low point setting to be 11.7 or 11.8 volts. This is because, until you get the operating load down to near these values, you will still be above the target of 12.2 volts when adjusted to a rested state.

The high settings or those commanding the controller to shut down the generator are usually factory set to about the right value and may only require setting the amp hour value of your battery bank.

A secondary feature available on many auto starts is air conditioner monitoring.  Basically, it monitors AC demand.  If the AC and the auto start are enabled, the generator will start when needed. This feature is great to use when boon docking on a hot night.  It will shut off automatically when the cooling need has been reached.

Note: Never check the generator oil or service it in any way while the auto start mode is enabled.  Always verify that exhaust from the engine of the generator is clear to vent away and not able to enter the living quarters of the RV.

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