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Hellroaring Technologies, inc.

Polson, Montana  -  USA

Our No Moving Parts Page 

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The Hellroaring Battery Isolator/Combiners have no moving parts to arc or wear out.   They are designed with all solid state construction for long life reliability.  

Solenoid or Relay Installation

Due to the diode voltage drop inherent in diode isolators, many people prefer to use a solenoid or relay and wire it to the ignition circuit so that it is ON only when the motor is running.    This method overcomes the voltage drop problem, but it also introduces several other problems to consider.   They are listed below along with the Hellroaring BIC solution:


Drawbacks to Solenoid or Relay

Hellroaring's Solution

1 It is not fully automatic.    Batteries are combined when ignition is ON, or by manual switch.    If the alternator fails, both batteries will discharge.  

Fully automatic operation.    Batteries are combined only when voltage is appropriate for charging whether the engine is running or not.  The backup battery will not discharge as a result of alternator output loss!


2 They consume substantial power, drawing 1 to 3.5 amps (12 to 42 Watts) when ON.  This can drain a battery if left ON overnight.  

All solid state electronics consume less than 0.012 amps (0.14 Watts) when ON (most of this is for the LED indicator). This would take at least 6 months (with no charging operation) to drain a 60 AH battery if manually left ON!



When the mechanical contacts touch, they provide a very fast transition from open circuit to closed circuit resulting in short pulse high inrush current.    When switched open, the contacts spark and over time, the contacts will wear out and sometimes will not open due to sticking.  Some mechanical contacts also tend to bounce, causing this on/off condition multiple times in the first few milliseconds.


Again, with all solid state electronics, the ON and OFF transitions (although fast) are controlled and limit inrush current over the first 2 milli-seconds.   There is no sparking to cause degradation of the product.   The electronics provide a positive ON/OFF transition with no bounce characteristics.
4 Solenoids or relays tend to be bulky with a non-uniform size.   Connections tend to be in multiple orientations.   In some cases, this can hinder installation and protection from shorts.  

The Hellroaring BIC units are compact in size and all the connections are oriented in the same way for convenient installation and protection.



During extreme cold weather, solenoids or relays can fail to operate, especially if not environmentally sealed.


The colder the weather, the better the Hellroaring BIC units perform.   The already very low Resistance decreases further allowing even more current when you need it most!
6 A Solenoid's contact resistance is not very repeatable.  Over time, the contact resistance can vary substantially from one energize to the next.  Compare the diagram below. The resistance between the terminals are very repeatable and predictable.  This makes it ideal for parallel operation to share load currents equally.


The graph below depicts tests on five different units (2 solenoids and 3 BIC models).  The test was performed by switching a 0.5 amp load across the connections.  The voltage drop was measured and the resistance was calculated.   For each unit, it was switched on and off 18 times and the measurement recorded for each ON condition.  As you will notice, even the contact resistance varied substantially for a brand new solenoid and its resistance was higher than the BIC-75300 for all 18 measurements!   The plot for the old solenoid demonstrates the effect over time for the mechanical devices.  Also, you will notice that all BIC units show a consistent and low ON resistance.

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Old Solenoid


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Copyright 1998-2008 Hellroaring Technologies, inc.
Last modified: 1/5/2008