Voltage Sensitive Relay Analogue Fixed Programme
Voltage sensitive relay analogue vs digital
There are 2 main types of voltage sensitive relays on the market, by far the most common is the lower cost analogue model (The Sterling analogue model has the added advantage of 8 mm stud connectors and IP68 rating), (fully waterproof), this type of device is very basic and simply switches on and off between two preset voltages with a 40 or so second time delay. This product works fine for the majority of installations where the second battery banks is only being charged when the engine is running and there is no real current drawn from the second battery set while the vehicle is on the move, ideal for most vehicle operation, however, things get more complex where there is current being drawn while the engine (on a boat or while a vehicle is not moving but the engine is running) or the batteries are the more exotic batteries such as AGM are being used (where different voltage switching is required) then the limitations of the analogue (no adjustable aspect) unit can be over come with the more expensive but much more controllable digital unit. The digital unit offers the operator a wide switching voltage range to chose from ensuring the open circuit voltage is above the discharge voltages of AGM, Gel and lithium, also the unit’s bi-directional features may be required, and last but by no means least a switching algorithms is used to prevent unnecessary switching of the relay. Also, because a digital unit is active all the time the quiescent current of the product is vital, i.e. the current it takes to run the product, in the case of the Sterling is less than 1 mA that’s 0.001A which is about 1A per week usage.
Why would I want to adjust a voltage sensitive relay?
1) Most Analogue VSRs come preset (for 24V x 2) to engage at 13.3V and disengage about 12.8V. Where as this is ok for normal lead acid batteries an AGM, Gel and Lithium battery have a much higher surface which will require adjustment voltages as high as 13V, this makes standard relay settings incorrect and will require the thresholds to be adjusted up. Batteries would be partially discharged at this voltage and would require switching off at about 13.2V. This could not be achieved with a fixed analogue model but there is no problem with the digital.
2) Directional control, Most analogue VSRs are preset as Bi-directional activation, i.e. if either the second battery or the first battery reaches the required trigger voltage the unit will work, however, there are times when the system wants to have the unit activated from the first battery but not activated from the secondary battery, this is called unidirectional, the digital version can do this.
The digital unit has a unique built in magnetic program ability, the lid of the unit has an in built magnet and the unit has an internal reed switch to pick up the magnets pulse generated by the user when the unit requires reprogramming this allows the product to be totally programmable by the lid but still maintained the waterproof integrity.
This unit is fitted with the latest on/off algorithms to prevent unnecessary switching, and has an extremely low quiescent current of less than 1 mA
What size of relay do I require?
To match a relay to your system the important things are
1) Ensure the amp ratings of the relay 10 - 20 % is larger than the largest charging source.
2) Ensure no load on the secondary battery bank exceeds the rating of the relay when on.
In the event of having a large load such as a 2000W + inverter, anchor winch or bow thruster then please look at our range of Current Limiting Voltage sensitive relays to deal with these high loads.
If the relay is to be used on a battery bank with a solar cell which is required to charge other batteries when the engine/battery charger is off then please look at the Latching Relay products, as this is more suitable for that operation.
Features of the Analogue VSR
|Fixed voltage switching
|Fixed time switching delay
|12 or 24V unit only
|Anti relay contact arching protection
|High quality brass connections
|Relay electrical override ability
|1 LED active information
|Bi directional operation only